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Fostex T50RP Incremental Mods and Measurements

Jul 15, 2012 at 9:08 PM Thread Starter Post #1 of 2,874
bluemonkeyflyer

bluemonkeyflyer

Headphoneus Supremus
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Fostex T50RP Incremental Mods and Measurements (FIMM)​
 
Table of Contents​
 
  1. Introduction
  2. DIY Measurement Kit
  3. No Solder Phantom Power Supply and Mic
  4. Making Incremental Measurements
  5. REW .mdat files, ARTA Setup Pictorial, and Videos stored at Google Drive and Docs
  6. Audio Measurement Chain
  7. Begin Incremental Mods and Measurements
  8. Temporary Bass Ports
  9. Additional Requested Pictures and Graphs
10. DBV 1
11. DBV 2
12. My LCD2 Measurements
13. All Stock T50RP T40RP T20RP with Triflange and Foam Tip Mounted Mics
14. About Measurements and Tuning
15. Some Additional Photos of Mods and Kits
16. Preparing Rolled Cotton For Effective Damping
17. Pad Rolling
18. Shure 840 Pad Modification and Measurements
19. Implementing Tutorials and Pictorials
20. Simplified and Consolidated Tutorial for DBV 3
21. Simplified and Consolidated Pictorial for DBV 3
22. Rock Wool Mod - Improved
23. nick n Make-up Remover Memory Foam Mod
24. Paxmate Lattice Mod with Cotton or Grodan Rock Wool 
25. Balsa Wood Mod with Paxmate and Rock Wool 
26. Tuning Rules of Thumb
27. Repairing Stripped Cup Threads
28. Better Modified Bass Ports
29. Naked Driver Mod - Improved
30. T50RP Wave Guides AKA Phase Plugs DIY using basswood or balsa wood
31. T50RP Wave Guides - 3D Printed by SeEnCreaTive
32. T50RP Incrementally Mass Loading the Baffles with Dynamat Xtreme, Paxmate Plus, and Tungsten Putty
33. Crossfeed Filters
34. DIY Mods and Measurements Acknowledgements
 
 
Introduction
 
You bought a set of Fostex T50RP planar magnetic headphones to see what all the modding talk is about. If you are a beginner like I was when I started down the modification path two years ago, you probably don't know where to start. I initially tried some of the mods suggested in the T50RP modding thread with mixed results before branching out and trying different materials and configurations of my own. A year later in July 2012, I decided to evaluate the damping effects of various materials - individually and in combination. I made incremental mods and measurements using a "virgin" set of current production T50RP's. The set I used has the non-textured, translucent white driver dampening "paper" and the darker color - smoother finished metal hangers. I measured each mod using Room Equalization Wizard (REW), my MacBook Pro sound card, and a basic $50.00 DIY measurement kit comprised of a Phantom Power Supply and a Panasonic WM-61A Omnidirectional Electret microphone stuck in my ear.
 
 
FIMM graphs should be compared and interpreted relative to one another, only. 
FIMM measurements and graphs cannot be directly compared to others' measurements. 
The microphone used for incremental measurements failed after I completed DBV #2.
I built other microphones and a better phantom power supply designed by 'solderdude.'
Measurements with this new kit cannot be reliably compared to FIMM measurements. 
 
All information, photographs, and measurement graphs contained within this document are owned by me and represent my intellectual property. I have made this document available for anyone to use for DIY modification of their personal headphones. Use of any and all information, photographs, and measurement graphs in this document for publication, advertising, and profit is prohibited without my written consent
 
Use of the tutorials, pictorials, guides, measurement graphs, and all information within this document are provided for DIY modification of your headphones. Use this document at your own risk. Please understand that your results and opinions may differ from mine due to variations in: materials used, implementation of mod components, audio equipment chains, music file type and resolution, hearing acuity, personal preferences, and Positive and Negative confirmatory bias.
 
 
DIY Measurement Kit
 
A pictorial guide for making your own DIY measurement kit, REW links, REW Setup Pictorial, and more are located at the following link:
 
http://www.head-fi.org/t/452404/just-listened-to-some-fostex-t50rps-today-wow/8025#post_8354423
 
***Improved Phantom Power Supply by Solderdude - Recommended***   More information is available throughout Solderdude's thread...Thanks, Frans!  
 
***Panasonic WM-61A: Triflange-Mounted Mic In Your Ear Method vs DIY Dummy Head Method***  
Frans ran some experiments comparing Panasonic WM-61A mounted on a triflange IEM tip (sealed ear canal method) and WM-61-A mounted in a wooden dummy head. His results are interesting and his report is a Must Read for anyone using these methods. Frans' measurements of many headphones may be found HERE.
 
 
Frans' ('solderdude') Improved Phantom Power Supply (Mono)
 
Frans designed an improved Phantom Power Supply for use with the Panasonic WM-61A omni-directional electret microphone (or similar). Note the WM-61A was discontinued in late 2013. I bought 50 authentic WM-61A microphones from an eBay seller in Japan (pestman2012). Beware of many counterfeit WM-61A's from China, Hong Kong, and elsewhere. Some available from another eBay seller in Japan (bzf202022012) as of July 2014 look authentic but I cannot tell for certain without looking for the etched model number on the side of each one, under magnification. If anyone needs a couple at cost ($3.00), PM me.
 
Here's Frans' Phantom Power Supply schematic (Mono):
 


The upper schematic is for usage with non-polar capacitors. The bottom one is for usage with much cheaper electrolytic caps. Be aware of the polarity of the electrolytic capacitors, if used.

For the jack plug in the schematic the output is connected to the R channel (ring) but you can also connect it to the tip (Left channel) OR both channels (L + R). Some mic inputs have the R (ring) and ground connected. In that case the signal must go to the tip connection and the ground is the same.
 
Read more: http://diyah.boards.net/thread/361/?page=2#ixzz2pXvWvBrv

Phantom Notes: 
Februray 2015
 
1. The connectors shown in the schematic diagram show how to wire the most common connectors. You should use only the connector type you need, so not both types of connectors, shown. Substitute your preferred connectors and jacks. I chose 3.5 mm TRS jacks. 

2. 6k8 = 6.8k Ohm Resistor (just a different way of notation)
 
3. This design is for testing one channel at a time. REW requires Stereo jacks and plugs even when measuring in mono mode.
 
4. Using a 10.0 uF capacitor yields more extended bass FR than 4.7 uF capacitor.
 

 
Microphone Notes
July 2015
 
 
 
I searched previous Japanese sellers of authentic Panasonic WM-61A microphone capsules but none are currently available. Steer clear of fakes from China, Hong Kong, and Taiwan.
 
I bought some replacements on ebay but have not compared them to authentic Panasonic WM-61A. On ebay, search for seller mstrong1 and item Panasonic WM-61A Replacement Microphones currently $2.50 each.
 
Soldering these tiny mics is challenging. The Negative solder pad is connected to the microphone casing with a copper trace and the Positive solder pad is isolated from the capsule casing.
 
Step by Step Instructions Using the Re-flow Method
 
Mic End:
Place the mic in a Panavise.
Strip both ends of a 4' of Mogami W2490. I make the Red Positive and the White Negative. 
Pre-tin both wires at both ends.
Clean and pre-tin your iron.
Cut the ends of the Red and White Mogami wires to 1/16".
Pre-tin the solder pads.
Apply a bit of flux on the tinned wires and the the tinned solder pads. 
Place the pre-tinned and fluxed wire flat against the solder pad.
Touch the tinned and cleaned iron onto the wire and press down so the wire remains in place against the solder pad.
Get in and out fast...only ~ 2 seconds.
If it does not work, let the mic cool while you re-clean your iron, pre-tin the solder pad and wire if needed, and re-flux.
When it re-flows, remove the iron and keep the wire in place until the joint solidifies.
Repeat for the other solder pad.
Test continuity with a DMM.
Fill the entire circuit board and the soldered connections with a drop or two of super glue or J&B Weld...But, wait until you have successfully soldered the other ends of the Mogami to the TRS plug and confirmed continuity and no shorts.
 
TRS End:
Cut pieces of 3:1 heat shrink for the TRS plug and slide onto the Mogami cable.
Slide the TRS plastic shield onto the Mogami cable.
Slide the TRS jacket onto the Mogami cable.
Identify the Positive tab on the TRS = usually the shorter of the two is Positive...Confirm with your DMM.
Flux and pre-tin the TRS Positive tab and the Sleeve tab (Negative).
Pre-tin the wires and cut to ~ 1/2"
Tin and clean your iron.
Thread the wires into the TRS tab holes and make a firm mechanical connection by twisting the wires. 
If there are no holes in the tabs, you can drill holes with a 1/16" drill bit or hold the wires in place as you solder.
Check for continuity to insure you have not shorted the Positive and Negative wires...a single tiny strand can short circuit so use a magnifying glass or magnifying headset to visually inspect your work.
Clamp the wires onto the TRS plug by bending the tabs over and onto the wires making a strain relief.
Slide the TRS plastic shield over the soldered connections.
Slide the heat shrink in place as far as it will go.
Slide the TRS jacket in place and screw it onto the TRS plug. The heat shrink should fill the gap at the wire entry hole of the TRS jacket and extend about an inch outside the jacket.
Use a heat gun to shrink the shrink wrap.
 
Test:
Connect your mic to your measurement kit.
Open your measurement software and test the mic by talking or blowing on the mic.
The software dB meters should indicate whether or not you have a working mic.
 
Finish up:
Apply super glue on the mic circuit board and solder tabs. 
Spray with super glue accelerator for instant curing or wait until the super glue has fully cured
 
Here's what I use from markertek.com
 
2490Mogami W2490 Ultraflexible Miniature Microphone Cable - Gray PER FOOT52$0.22$11.44Shipped
NYS-231BGRean NYS231BG 3.5MM TRS Plug Black/Gold6$1.39$8.34Shipped
SHT116BK-4Heat Shrink Tubing 1/16inch Black 4 Foot1$0.88$0.88Shipped
 
 
 
 
Mono Phantom Power Supply
 

Back Right to Left: Red Positive Battery Lead > 6.8k R >2.2k R > Positive 100 uF Cap 
6.8k R > 2.2k R > Positive 10 uF Cap > 100k R and  Red wire to Left side Mic IN Jack (Ring tab)
Negative 100 uF Cap > Blue wire > 100k R
Negative 10 uF Cap >100k R
100k R > Both Blue wires to Negative tabs on Both Jacks; Negative Black Battery Lead; Green ground to metal tin
 

Back View
Closed cell foam glued to under surface to insulate the solder connections from the metal tin.
Front Left to Right: Red Positive Battery Lead to 6.8k R > 2.2k R > Positive 100 uF Cap > Negative 100 uF Cap > Blue wire
 

Side View
Negative 100 uF Cap > Blue wire > 100k R > 2 Blue Wires > Negative Jack tabs; Black Negative Battery Lead; Green to ground
 

Top View
 

Frans' aka 'solderdude's' Phantom Power Supply
 
I found using a 10.0 uF cap delivers better bass measurements.
 
 
Fran's Dual / Stereo Phantom Power Supply
February 2015
 
Two examples of the same circuit:
 

 

Large Form Factor
 
Notes:
 
1. Panasonic WM61-A microphone capsules Positive terminal must be wired to either the Tip (Left Channel) or the Ring (Right Channel) TRS tabs / lugs. For REW and ARTA, use the Tip (Left Channel).
 
2. For most measurements, you don't need a dual Phantom Power Supply. Simply place the mic in your preferred ear or onto your Dummy Head Jig, take a measurement of the Left Cup, then rotate the headphone and measure the Right Channel.
 
3. For Mono / single channel measurements of headphones with angled pads, rotate the pads 180 degrees for accurate results.
 
4. Your ear canals are not the same size. The mics may insert at slightly different depths, angles, and degrees of seal in Left vs Right ears. This will likely result in what appears to be channel imbalance but is actually measurement error. You will have to compensate for this type of error. Read about compensation in REW and ARTA user manuals or "Google it."
 
 
No Solder Phantom Power Supply
Feb. 2015
 
You don't have to know how to solder to make a Phantom Power Supply and Mic kit! Simply remove 3/4" of insulation from your hook-up wires, twist the wires and "legs" of the caps and resistors together, tightly. Compress with a mini-screwdriver or needle-nose pliers and secure in place with J&B Weld epoxy. Do the same for the TRS jacks and you're done, mount in a metal tin, and you're ready to measure using free software like REW and the free trial version of ARTA.
 
Mics: Score the mic solder tabs with a mini-file to make a groove for the hook-up wires. Place the tightly twisted hook-up wire in a groove and secure with tape. Apply some electrically conductive paint in 2 or 3 thin coats, letting it dry between coats. Dab a bit of epoxy onto the wire and fill the groove. Repeat for the other solder tab.
 

 

 

 

  

 

 

 
 

 

 
 
 
 
 
No solder was used making the Phantom Power Supply and the mic. All connections were made mechanically, only. J&B Weld holds everything in place and insulates the undersurface of the bread board so there's no shorting from the twisted wires to the tin. 
This kit was actually more difficult to build than using solder. The purpose was to determine if it's possible so anyone can build a kit, even without soldering skills. It works just as well as soldered kits. 
 
Magnification is necessary to make sure there are no shorts when making the mic and TRS connections. A single stray strand of wire can short at the mic and at the TRS.
 
 
CABLE CONNECTIONS
 

Blue 3.5mm male Stereo TRS to 3.5mm male Stereo plugs into Headphone OUT and Mic IN for the Calibration Loop. Alternatively, you can place the Phantom Power Supply into the chain by using Two of these cables.
 

White 3.5mm Stereo TRS cable plugs into my Mac's MIC In jack. The other end, also terminated with a 3.5 mm Stereo TRS plug goes into the Phantom Power Supply's Line OUT jack.  Beneath my Mac's Mic IN jack with the white cable, you see an optical cable plugged into my Mac's Headphone Out jack. The other end connects to my Dacmini's Optical IN. The headphone undergoing measurement is connected to my Dacmini's headphone jack.
 
 

 

These two photos show the rest of the connections:
 
White cable from Mac Line IN to Phantom Power Supply Line OUT.
Mic mounted on Etymotic triflange IEM ear tip terminated with a Female RCA plug connects to either of two Male RCA plugs.
Dual Male RCA Y-Splitter to 3.5 mm Stereo TRS plug goes in the Phantom Power Supply's Line IN.
 
Place the mic in your ear and be sure you position it the same way each time you measure = Same depth, Same angle, Same ear.
Place the headphones on your head and make sure you use your normal position and with same clamping force each time.
Use an earplug in your non-measuring ear to protect your hearing.
Turn down the volume, Select 'Measure' and then Select 'Check Levels.' Increase volume until you reach 'Check Level' =  -20 dB
Select 'Cancel'
Select 'Measure' and Select 'Start Measuring'
 
See Link to Tutorials with Screen Shots (Just Below) for details about configuring, calibrating, and setting-up and using REW. There are more photos of making your microphone near the bottom of this very long post.
 
Be patient. We're almost there...
 
I encourage everyone to consider building and using a measurement kit. I find it indispensable for L-R Channel balancing and tuning. It's also interesting, easy to use, fast (6 seconds per measurement), and fun.
 
 
MAKING INCREMENTAL MEASUREMENTS
 
I mounted the mic in an Etymotic triflange ear tip using hot glue. Next, I applied a ring of hot glue around the mic sitting on its perch at the IEM insertion hole. When making these measurements over two consecutive weekends, I made sure to use the same methodology. I placed the mic in my ear at the same angle and depth on both measurement days.  I did not remove the mic until all measurements were completed, each day. I SPL-matched the sweep level for each measurement. Various pads X mod(s) result in wide variability in sensitivity. Matching the sweep levels may not be necessary but I did so to control this variable.
 
I placed the headphones on my head based on my usual, most comfortable position whenever I use headphones. Considering the number of measurements and variables assessed, I made only 1 measurement for each. The baffles were secured to the cups with masking tape to avoid stripping the cup threads from multiple modding cycles done one at a time. I squeezed the baffle to the cup while taping and insured that all gaps and crevices were tightly sealed. Consider the data FWIW or a "snapshot" of each mod.
 
The small, sharp up/down "tics" in the SPL FR graphs and the very thin ridges in most of the waterfall plots are the result of "cable noise" from electromagnetic interference according to the REW Moderator. 
 
The FR graphs don't tell us anything about the speed or decay of each mod. I included Waterfall Plots to show the speed and decay on the 'z' axis, back to front. 
 
Anyone can download and use REW for free but please contribute (any amount) to support the site. You can use, view, and manipulate .mdat files without having to actually make any measurements of your own. Here's the link: http://www.hometheatershack.com/roomeq/
 
The default graph format is SPL FR. Tabs across the top of the measurement window allow you to 'Generate' waterfall plots and spectrograms. You must adjust the SPL FR display to 'Zero' before Generating waterfalls and spectrograms.  To do this, click the 'gear' icon at the top right of the measurement window. Type an offset value in the offset window - I typically use -155, then click 'Add to Data.' Go to the left side, vertical slider to pull the adjusted SPL FR graph down into the display window. Now, you can generate waterfalls and spectrograms along with decay and several other options, if interested. 
 
***Select 'Room Equalization Wizard (REW) Set-up Guide' (below) for a Google Doc that explains more about how to setup and use REW. I included some useful links and screen shots for clarity.***
 
 
You Can Learn How to Use REW Before You Begin Making Your Own Measurements
 
I uploaded the REW raw data .mdat files to Google Docs for all incremental measurements I made and listed in the links, below. First, download and install REW and then download and save the .mdat files from Google Docs into your computer's 'Downloads' file. Next, open REW and click on 'Open', go to your 'Download' files, double click the desired set of .mdat files, and the data files will load into REW.
 
Within REW's measurement window, and after you've 'Opened' a .mdat data file, you can delete all but the particular graphs you want to overlay with one another.  The individual data files are listed on the left side of the measurement window. Delete each file you want to remove by clicking the 'red X' to the right of one. This removes the file(s) from the list but does not permanently delete the file(s) stored in 'Downloads.' 
 
Next, click 'All SPL', located at the top tool bar of the measurement window, to display your chosen graphs as an overlay. You can change the resolution by clicking the '-' or '+' tabs at the top left of the SPL graph; i.e. 5 db or 10 dB SPL intervals. You can save this specific group of graphs by clicking 'Save All' at the top left of the window and type in a Group Name. When you're done comparing this set of measurements, close this file, after naming and saving it, by clicking the 'Remove All' tab. Re-open the complete .mdat file to repeat the process for a different group of comparisons. For example, you can delete all but the 3 graphs for "Stock Left Acoustipack Lite, Newplast, and type of pad (840, Stock, and FA-003 pads)" for comparing and overlaying these 3 graphs. Do the same for any other combination of incremental measurements from any of the .mdat files I uploaded to Google Docs.
 
 
Incremental Mods and Measurements, REW .mdat files, ARTA Setup Guuide, and Videos stored in Google Docs:
 
1. Room Equalization Wizard (REW) Set-up Guide
 
2. Main data set 1 .mdat data files for Incremental Mods and Measurements
 
3. Main data set 2 .mdat data files for Incremental Mods and Measurements
 
4. DBV #1 and #2 .mdat files:
 https://docs.google.com/open?id=0B5ZWXtWdNv9UYTBUZHRFTXZZSzQ
 
5. Stock T50RP, T40RP mk2, T20RP mk2 measurements with Etymotic Foam and Triflange mounted microphones .mdat files:
https://docs.google.com/open?id=0B5ZWXtWdNv9URmRSLW5mN0Vzblk
 
6.  DBV #2 with Taped on FA-003 Pads, T50RP Pads, and Inner Tube Modded FA-003 Pads .mdat files:
https://docs.google.com/open?id=0B5ZWXtWdNv9UWlcyeXVFbU1XblE
 
7. Disassembling Fostex T50RP/T40RP mkII/T20RP mkII For Repairs and Driver Modification - If this video does not open, try Right Clicking on the File Name and 'Open With Google Drive Viewer.'  Also available via dropbox.
 
[size=x-small]8. "Radical Russian Roulette" Driver Modification[/size][size=small] [/size][size=small]Video[/size] - If this video does not open, try Right Clicking on the File Name and 'Open With Google Drive Viewer.'[size=small]  Also available via dropbox.[/size]
 
[size=small]9. ARTA Setup Guide for Beginners uploaded to Google Drive January 2015[/size]
 
 
T50RP Incremental Mods and Measurements
 
Audio Measurement Chain 
 
Calibrated MacBook Pro Soundcard > REW Generated Sweep > Glass Toslink > Dacmini with 1 Ohm Output Impedance Mod > Headphones > Calibrated Panasonic WM-61A Microphone > Calibrated Phantom Power Supply > MacBook Pro > REW Analysis
 
 
General Interpretive Guidelines for REW Measurement Graphs
 
1. Frequency Response Graph (FR): Zero dB horizontal x-axis is the baseline.  The frequencies in Hertz (Hz)  are shown at the bottom in logrithmic format. The vertical y-axis is Sound Pressure Level (SPL) in decibels (dB) which indicates how "loud" the headphones measure. Positive numbers indicate louder than baseline. Negative numbers indicate less loudness than baseline.
 
+/- 2 dB above or below the baseline is acceptable and you probably would not be able to hear a significant difference. An ideal FR "curve" would actually be a flat line at zero dB extending all the way across the graph from sub-bass on the far Left to high treble on the far Right. 
 
FR graphs tell us nothing about resonances or ringing, speed of decay, impulse response, phase, or how the headphones will sound. You don't need to worry about any of these for now. Just understand that resonances, ringing, and slow decay speed are "Bad".... and, flat FR and fast decay are "Good."
 
2. Waterfall Graph: This is a 3D graph with 3 axes - SPL in dB on the vertical y-axis, Frequencies in Hz on the horizontal x-axis, and Decay Time on the Back to Front z-axis. Ideally, you want the x-axis to be as flat and uniform as possible across the top from left to right which indicates an even, or "flat" FR. The waterfall from the back of the z-axis extends forward and indicates the decay speed and whether or not there is ringing at particular frequencies. Generally, you're more likely to perceive a spike than a dip. A "suckout" is a wider (x-axis) range of frequencies that is more easily "heard."
 
3. Spectrogram: This graph shows speed of decay, ringing/resonances, dips, spikes, and suckouts. The vertical y-axis indicates speed of decay in milliseconds and the horizontal x-axis marks frequencies from sub-bass to treble (Left to Right). The Color Scale on the right side of the graph indicates SPL from 0 = Red to - 40 = Blue. Ideally, you want to see a wide, uniform beam of red with thin layers of yellow, green, and blue from far Left to far Right. Green and Blue "Flames" indicate low level ringing that may be difficult to hear. Yellow and Red Flames are more likely heard. Upward "Bulges" indicate humps. "Squeezed" areas indicate dips. "Pinched off" areas are suck-outs that are more easily heard.
 
Use all three graphs to better understand your headphones' performance and make more accurate predictions about how they might sound.  Start by looking at the "All Stock T50RP" FR and Waterfall graphs. Notice the big hump in the middle and the slopes to either side, especially on the left side. This indicates a mid-centric headphone with weak bass and weak treble that "rolls off." What the graphs do not show, however, is the resonance and standing waves heard from Stock T50RP's and described throughout the main T50RP mod forum. 
 
 
 
Begin Incremental Mods and Measurements
 
 
A.

 
Fostex T50RP - All Stock Left Side: Current production with smooth finished metal hangers and non-textured, translucent white driver dampener
 
1.

 
All Stock T50RP
 
 
2.

 
Stock with sealed cup vents
 
 
3.

 
Stock with sealed baffle port
 
 
4.

 
Stock with sealed cup vents and sealed baffle port
 
 
 
B.

 
Masking tape temporarily seals baffle to cup without risking stripping the cup threads. Shure 840 pads (Left) and FA-003 pads (Right-micmacmo's inner tube mod).
 
 
5.

 
Stock with Shure 840 pads
 
 
6.

 
Stock with Shure 840 pads and sealed cup vents
 
 
7.

 
Stock with Shure 840 pads, sealed cup vents, and sealed baffle port
 
 
8.

 
Stock with Shure 840 pads and sealed baffle port
 
 
C.

 
Temporary Bass Port using electrical tape or masking tape on the outside of the cup vents. Once the mod is completed, the bass port is moved to the inside of the cup unless you prefer the flexibility of re-tuning, on the fly. Masking tape makes the job easier because you first apply a piece that covers all 4 cup vents and then use an X-acto knife to cut the precise size bass port you want. This masking tape bass port is 3x1 mm. To prevent the tape from separating at the corners (Not Shown in the photo, above), use an X-acto knife to remove the excess tape from where it  overlaps onto the back of the cups and down the side walls flush with the cup vents. Once removed, smooth out and compress the tape flat onto the four cup vent slots. Use an X-acto knife to cut an opening over the center of one of the vent slots to make your modified bass port. Enlarge by 1 mm increments. If it's too wide, bass bloat will return. In this case, decrease the width of the bass port in 1 mm increments by placing a small piece of masking  tape over part of the bass port already opened.
 
When you have determined the size of the bass port needed for your mod configuration, you can make a permanent one by duplicating and placing it over the cup vents on the inside. Cut a piece of masking tape to cover all the stock black cup felt overlaying the cup vents. Place the tape over the vent felt on the inside of the cup. Use shirt pins pushed through from the outside to mark the limits of the bass port width on the inside. Use the "pin markers" to trace a rectangular opening on the masking tape. Remove the tape but leave the pins in place. Cut out the rectangle from the masking tape, re-apply the tape onto the vent felt on the inside by using the pins as your guide, and remove the pins. Glue all the way around the masking tape so it will remain in place and not "leak" around the edges.  The size of your bass ports from left to right may need to be different to balance the FR. In some cases, you may have, for example, a 3x1 mm bass port on one side and no bass port on the other side.
 
 
D.

 
 
9.

 
Stock with Shure 840 pads and 3 mm bass port
 
 
Grodan rock wool: 10x 60x70 mm with extra "fluff" around the rim. Thanks, JoelPearce and micmacmo.
 
10.

 
Stock with Grodan Rock Wool and Shure 840 Pads
 
 
11.

 
Stock with Grodan Rock Wool and Stock Pads
 
 
12.

 
Stock with Grodan Rock Wool and FA-003 Pads
 
Note: micmacmo's Inner Tube Modded FA-003 Pads were used throughout these measurements. 
 
 
E.

 
"Unobtanium" Rite Aid Natural Absorbent Cotton - approximately 15 cm wide and 4 cm thick out of the box and easily separated to the desired thickness. Other types of cotton may work but will likely require altering the amount and thickness used.
 
13.

 
Stock with Cotton and Shure 840 Pads
 
 
14.

 
Stock with Cotton and Stock Pads
 
 
15.

 
Stock with Cotton and FA-003 Pads
 
 
F.

 
50x60x70 mm Johns Manville fiberglass - uncompressed
 
G.

 
50x60x70 mm Johns Manville fiberglass compressed into cup with extra "fluff" around the rim. Note the rubber shock absorber caps showing through the fiberglass.
 
16.

 
Stock with Fiberglass and Shure 840 Pads
 
 
17.

 
Stock with Fiberglass and Stock Pads
 
 
18.

 
Stock with Fiberglass and FA-003 Pads
 
 
H.

 
1.5x35x35 mm Creatology Stiffened Craft Felt from Michaels' secured with strips of Transpore tape.
 
A better method uses 1.5x37x45 mm Creatology Stiffened Craft Felt secured by double sided tape strips cut to fit the outer edges of the driver grid. Thanks nick n.
 
19.

 
Stock with 1.5x35x35 mm Stiffened Craft Felt over the driver and Shure 840 Pads
 
 
20.

 
Stock with 1.5x35x35 mm Stiffened Craft Felt over the driver and Stock Pads
 
 
21.

 
Stock with 1.5x35x35 mm Stiffened Craft Felt over driver and FA-003 Pads
 
 
I.

 
12x35x35 mm open cell foam over the driver secured with Transpore tape.
 
22.

 
Stock with Open Cell Foam over driver and Shure 840 Pads
 
 
23.

 
Stock with Open Cell Foam over driver and Stock Pads
 
 
24.

 
Stock with Open Cell Foam over driver and FA-003 Pads
 
 
J.

 
4x35x35 mm 100% Wool Felt from Hobby Lobby, over the driver
 
25.

 
Stock with 4x35x35 mm Hobby Lobby 100% Wool Felt over driver and Shure 840 Pads
 
 
26.

 
Stock with 4x35x35 mm Hobby Lobby 100% Wool Felt over driver and Stock Pads
 
 
27.

 
Stock with 4x35x35 mm Hobby Lobby 100% Wool Felt over driver and FA-003 Pads
 
 
K.

 
Acoustipack Lite and Self-Adhesive Felt in the cup floor. The Acoustipack is in the left and right "floor wells" and the self-adhesive felt is at the top and bottom of the center area, above and below the headband hanger compartment.
 
 
28.

 
Stock with Acoustipack Lite and Felt in Cup Floors with Shure 840 Pads
 
 
29.

 
Stock with Acoustipack Lite and Felt in Cup Floors with Stock Pads
 
 
30.

 
Stock with Acoustipack Lite and Felt in Cup Floors with FA-003 Pads
 
 
L1.

 
20 grams of Newplast is less than 1 oz. 10 grams per side. Acoustipack Lite and self-adhesive felt in the cup. Newplast "Flush Mass Loaded" in the baffle compartments. A digital scale is not required. I used one to demonstrate just how little Newplast or plasticine is needed
                                                                                                                                                                                        
 
31.

 
Stock with Acoustipack Lite and Felt in Cup Floor, Newplast, and Shure 840 Pads
 
 
32.

 
Stock with Acoustipack Lite and Felt in Cup Floor, Newplast, and Stock Pads
 
 
33a.

 
Stock with Acoustipack Lite and Felt in Cup Floor, Newplast, and FA-003 Pads
 
 
L2.  This "Naked Driver" is associated with Graphs 33b, 33c, and 33d, Only. ALL preceding and subsequent graphs are based on modifications with the stock white driver dampening paper intact.

 
"Naked" Driver has had its stock white 'paper' removed, Acoustipack Lite and Felt in Cup Floors, and Newplast Flush Mass Loaded in the baffles. I do not recommend removing the stock white driver dampening "paper" from the back of the drivers. In my experience, this offers no benefits over keeping the stock white dampener intact.
 
 
33b.

 
Naked Driver, Acoustipack Lite and Felt in Cup Floor, Newplast, Shure 840 Pads
 
 
33c.

 
Naked Driver, Acoustipack Lite and Felt in Cup Floor, Newplast, and Stock Pads
 
 
33d.

 
Naked Driver, Acoustipack Lite and Felt in Cup Floor, Newplast, FA-003 Pads
 
 
M.

 
1.5x35x35 mm Creatology Stiffened Craft Felt has been added to the back of the driver, directly over the stock white driver dampening paper.
 
34.

 
Stock with Acoustipack Lite and Felt in Cup Floors, Newplast, Stiffened Craft Felt over the driver, and Shure 840 Pads
 
 
35.

 
Stock with Acoustipack Lite and Felt in the Cup Floors, Newplast, Stiffened Craft Felt over the driver, and Stock Pads
 
 
36.

 
Stock with Acoustipack Lite and Felt in the Cup Floors, Newplast, Stiffened Craft Felt over the driver, and FA-003 Pads
 
 
N.

 
25x60x70 mm cotton has been notched to fit around the shock absorbers and jack, placed over Acoustipack Lite in cup. Cutting off the shock absorbers is not required. Removing the rubber shock absorber caps gives you a bit more room to work but this is also optional. If you remove them, save them in case you want to go back to stock.
 
 
37.

 
Stock with Acoustipack Lite and Felt in the Cup Floors, Newplast, Stiffened Craft Felt over the driver, Cotton, and Shure 840 Pads
 
 
38.

 
Stock with Acoustipack Lite and Felt in the Cup Floors, Newplast, Stiffened Craft Felt over the driver, Cotton, and Stock Pads
 
 
39.

 
Stock with Acoustipack LIte and Felt in the Cup Floors, Newplast, Stiffened Craft Felt over the driver, Cotton, and FA-003 Pads
 
 
O.

 
For DBV #2, cut 10x60x70 mm fiberglass, similarly notched for the shock absorbers, and place over 20x60x70 mm cotton. You may need more/less of each for your mod, determined by tuning
 
40.

 
Stock with Acoustipack Lite and Felt in the Cup Floors, Newplast, Stiffened Craft Felt over the driver, Cotton over  Fiberglass, and Shure 840 Pads
 
 
41.

 
Stock with Acoustipack Lite and Felt in the Cup Floors, Newplast, Stiffened Craft Felt over the driver, Cotton over Fiberglass, and Stock Pads
 
 
42.

 
Stock with Acoustipack Lite and Felt in the Cup Floors, Newplast, Stiffened Craft Felt over the driver, Cotton over Fiberglass, and FA-003 Pads
 
 
43.

 
Stock with Acoustipack Lite and Felt in the Cup Floors, Newplast, Stiffened Craft Felt over the driver, Cotton over Fiberglass, Baffle Port Closed, and Shure 840 Pads
 
 
44.

 
Stock with Acoustipack Lite and Felt in the Cup Floors, Newplast, Stiffened Craft Felt over the driver, Cotton over Fiberglass, Baffle Port Closed, and Stock Pads
 
 
45.

 
Stock with Acoustipack Lite and Felt in the Cup Floors, Newplast, Stiffened Craft Felt over the driver, Cotton over Fiberglass, Baffle Port Closed, and FA-003 Pads
 
 
46.

 
This is the same FR Graph as the one just above but with 1/24 Smoothing.  This is the only FR Graph in this measurement database with any Smoothing applied.
 
 
 
Additional Requested Pictures and Graphs
 
1. BMF DBV #1: With Shure 840 pads compared with Stock and FA-003 pads
2. My LCD2
 
 
P.

 
DBV #1 and #2 Left Cup: 3x15 mm Paxmate "Ladder Rungs" over Acoustipack Lite in floor wells. 1.5x35x35 mm Creatology Stiffened Craft Felt over stock white driver dampener, Transpore overlay, and Newplast Flush Mass Loaded Baffle Compartments. Double Sided tape works best for securing stiff felt to the driver back for the permanent mod.
 
Q.

 
DBV#1 Left Cup: 20x60x70 mm (measured Uncompressed) Rite Aid Natural Absorbent Cotton with 10x60x70 mm (measured Compressed) Fiberglass overlaying Acoustipack Lite and Paxmate "Ladder Rungs." Baffle: Newplast Flush Mass Loaded baffle compartments, stiffened felt over stock white driver dampener and Transpore overlay. Note: Acid-free double sided tape applied to the driver grid perimeter works better than Transpore for securing the stiffened felt.
 
 
DBV 1
 
47.

 
 
48.

 
 
49.

 
Above:  BMF DBV #1 with Shure 840 Pads - SPL FR Graph, Waterfall Plot, and Spectrogram
 
The "DBV" designation in the Notes section of these graphs is simply my way of keeping track of various mods I'm working on. This mod configuration is a variation of BMF V8.1 described with pictures in "The Fostex T50RP Mods Summary Links" WIKI started by Ardilla. This mod is fast and neutral with excellent bass extension, texture, and definition. Mids are properly placed, clear, and lush, particularly for vocals and acoustic music. Treble extension, detail, and shimmer are very good without fatigue. Imaging is precise, channel balance is perfect, and soundstage is wide for a closed 'phone.
 
Note: I inadvertently failed to list four important mod components in the Notes Section of my DBV graphs, above: 
 
1. 3x1 mm bass ports over the black cup vent felt on the inside of the cups
2. Baffle ports are sealed with GE Silicone II
3. Dynamat (or FatMat) with self-adhesive felt overlay around the ear side of the drivers
4. Shure 840 pads
 
Note, also, that I typed in the wrong dimensions for the bass ports in the Notes section of these graphs. Instead of 2x2 mm bass ports for these DBV measurements, the actual bass ports are 3mm wide and ~1 mm high  -  and placed over the center of the lowest of the 4 cup vents.
 
I used a Dremel cutting tool to remove all 4 shock absorber posts inside each cup. This makes it easier to place the cotton and fiberglass overlay. I don't know if removing the shock absorbers improves the sound quality but it is possible because the cotton/fiberglass lays flatter and it's more uniformly distributed than when the shock absorbers remain in place. Removing the shock absorbers is not irreversible because they can be super glued back in place.
 
DBV #1 with T50RP Pads
 
50.

 
 
51.

 
 
52.

 
Above: DBV #1 with T50RP Pads - SPL FR Graph, Waterfall Plot, and Spectrogram
 
 
 
DBV #1 with FA-003 Pads
 
53.

 
 
54.

 
 
55.

 
Above: DBV #1 with FA-003 Pads - SPL FR Graph, Waterfall Plot, and Spectrogram
 
 
DBV 2
 
 
56.

 
DBV #2 Left with Shure 840 Pads Compared to All Stock T50RP Left
 
 
57.

 
DBV #2 Left with Shure 840 Pads Compared to All Stock T50RP Left.
 
 
58.

 
DBV #2 Left with Shure 840 Pads compared to All Stock T50RP Left.
 
 
59.

 
DBV #2 Right with Shure 840 Pads compared to All Stock T50RP Right.
 
 
60.

 
DBV #2 Right with Shure 840 Pads compared to All Stock T50RP.
 
 
61.

 
DBV #2 Right with Shure 840 compared to All Stock T50RP Right.
 
 
62.

 
DBV #2 Left with Stock Pads SPL FR
 
 
63.

 
DBV #2 Left Stock Pads Waterfall Plot
 
 
64.

 
DBV #2 Left Stock Pads Spectrogram
 
 
65.

 
DBV #2 Right with Stock Pads SPL FR
 
 
66.

 
DBV #2 Right with Stock Pads Waterfall Plot
 
 
67.

 
DBV #2 Right with Stock Pads Spectrogram
 
 
68.

 
DBV #2 Left with Inner Tube Modded FA-003 Pads SPL FR
 
 
69.

 
DBV #2 Left with Inner Tube Modded FA-003 Pads Waterfall Plot
 
 
70.

 
DBV #2 Left with Inner Tube Modded FA-003 Pads Spectrogram
 
 
71.

 
DBV #2 Right with Inner Tube Modded FA-003 Pads SPL FR
 
 
72. 

 
DBV #2 Right with Inner Tube Modded FA-003 Pads Waterfall Plot
 
 
73.

 
DBV #2 Right with Inner Tube Modded FA-003 Pads Spectrogram
 
 
74.

 
DBV #2 Left with Taped on FA-003 Pads SPL FR
 
 
75.

 
DBV #2 Left with Taped on FA-003 Pads Waterfall Plot
 
 
76.

 
DBV #2 Left with Taped on FA-003 Pads Spectrogram
 
 
77.

 
DBV #2 Right with Taped on FA-003 Pads SPL FR
 
 
78.

 
DBV #2 Right with Taped on FA-003 Pads Waterfall
 
 
79.

 
DBV #2 Right with Taped on FA-003 Pads Spectrogram
 
 
*****End of Incremental Mods and Measurements*****
 
 
My LCD2 Measurements
 
Triflange and Foam Tip Mounted Mic Comparisons
 
80.

 
LCD2 v.1 Left: Triflange Mic compared with Foam Mic
 
 
81.

 
LCD2 v.1 Left: Triflange Mic compared with Foam Mic
 
 
82.

 
LCD2 v.1 Left: Triflange Mic compared with Foam Mic
 
 
83.

 
Audeze's SPL FR Graph of my LCD2 v.1
 
 
 
All Stock T50RP T40RP T20RP Measurements with Triflange and Foam Tip Mounted Mics
 
Stock T50RP - Triflange and Foam Tip Mounted Measurement Comparisons 
 
84.

 
T50RP Left: with Triflange Mic compared with Foam Mic
 
 
85.

 
T50RP Left: Triflange Mic compared with Foam MIc
 
 
86.

 
T50RP Left: Triflange Mic compared with Foam Mic
 
 
87.

 
T50RP Right: Triflange Mic compared with Foam Mic
 
 
88.

 
T50RP Right: Triflange Mic compared with Foam Mic
 
 
89.

 
T50RP Right: Triflange Mic compared with Foam Mic
 
 
 
Stock T40RP compared to Stock T20RP with Foam Tip Mounted Mic
 
90.

 
T40RP Left compared to T20RP Left using Foam Mic
 
 
91.

 
T40RP Left compared to T20RP Left using Foam Mic
 
 
92.

 
T40RP Left compared to T20RP Left using Foam Mic
 
 
93.

 
T40RP Right compared to T20RP Right using Foam Mic
 
 
94.

 
T40RP Right compared to T20RP Right using Foam Mic
 
 
95.

 
T40RP Right compared to T20RP Right using Foam Mic
 
Note: All DIY measurements were made with the same methodology and measurement chain using a Triflange Mic unless stated otherwise below each graph.
 
About Measurements and Tuning
 
Consider the graphs, select the various components you want to try, and build your mod. Here is where the real work begins --> tweaking, tuning, and testing one component change at a time to improve and "dial in" the sound you want. You can tweak: cotton thickness, fiberglass thickness if used, bass port size vs stock, modified baffle port size vs stock, Grodan Rock Wool thickness if used, pads used, Dynamat or FatMat vs without, additional acoustic foam in the cup and/or on the ear side of the driver, cotton vs fiberglass vs felt of different types and layers over the ear side of the drivers, omitting any of these components, and adding anything else you're interested in trying. You can literally tune for bass, midrange, or treble emphasis or go for neutral which is what I try to achieve. Be aware that changing one component will likely effect others in your design. Based on my experiments, "the total (SQ) is greater than the sum of its parts."
 
Remember that FR graphs provide only an idea of how a mod may sound relative to another mod configuration. You cannot rely on others' opinions and you cannot know how a mod configuration will sound until you build, tune, and test for yourself. A mod's perceived SQ may be better, or worse, than suggested by its FR graph. This may result from an interaction of variables including your equipment and audio chain, source and file type, your personal SQ preferences, your hearing acuity and psychoacoustic factors such as Placebo Effect, Selective Perception Bias, Expectation Bias (positive and negative), Confirmatory Bias, the ephemeral nature of auditory memory, and Cognitive Dissonance.
 
You must take anyone's mod and "make it your own."
 
Tweaking, or tuning, is key.
 
There are no "slam dunks."
 
Consider and compare these measurements relative to one another. Do not directly compare these measurements with someone else's measurements.
 
Submitted FWIW & YMMV.
 
 
Some Additional Mod Photos
 
R.

 
Modified baffle port using masking tape. Glue around all 4 sides. Use a needle to pierce the center and enlarge to desired size. A smaller baffle port increases bass.
 
S.
 

 
The white and yellow felt is Creatology Stiffened Craft Felt 1.5 mm thick. The black material is a piece of the ear side dust cover that was not glued down properly at the factory. Its "thickness" is ~ 0.2 mm. How much effect can it have on the SQ?
 
 
T.

 
Dynamat (or FatMat) with self-adhesive felt overlay surrounds the driver. Note the notch for the baffle port which you can leave open, completely close, or modify the size. 
 
U.

 
1.5x37x45 mm stiffened craft felt held in place with double-adhesive tape around the outer perimeter of the driver grid. 22x28 mm Transpore overlays yellow felt for better treble. Try different sizes. DBV #2 uses 45x27 mm Transpore but you may need to use less for your mod. 8 grams of Newplast in the baffle compartments. Acoustipack Lite in L/R floor wells, adhesive felt on top and bottom of the central area, and Paxmate strips 90 degrees across Acoustipack Lite. 
 
 
V.

 
 
W.

 
 
X.

 
Re-flow soldering method makes soldering tiny wires to tiny terminals easy-er. Instructions are provided in the link at the top of this post.
 
 
 
Y.

 
Panasonic WM-61A in an Etymotic foam tip.
 
NOTE:  Etymotic Foam IEM ear tip Increases sub-bass measurements by ~ 2 dB and Decreases treble (9 kHz to 10 kHz) measurements by ~ 5 dB. Adjust graphs accordingly.
 
 
Z.

 
Panasonic WM-61A mic in Etymotic Triflange ear tip(micmacmo)
 
NOTE: Etymotic Triflange ear tip with a surrounding bead of hot glue Decreases sub-bass measurements by ~ 2 dB and Increases treble (9 kHz to 10 kHz) measurements by ~ 5 dB. Adjust graphs accordingly.
 
 
A2.
        
 
Phantom Power Supply: 2 caps, 2 resistors, 2 jacks, 1 9-volt battery snap, a PCB from Radio Shack, and some wire.
Original idea and design by symphonic; Design revision by wdahm519.
 
 
B2.

 
Top View of the Phantom Power Supply
 
 
C2.

 
Phantom Power Supply circuits mounted in tea tins
 
 
D2.

 
Wired mic, Ety foam tips, and extra Panasonic WM-61A microphones
 
 
E2.

 
Old driver dampener
 
F2.

 
New driver dampener
 
G2.

 
Old and New Driver Dampening Paper
 
H2.

 
T20RP Clear Mesh over the cup vents lets the light from my work table shine through.
 
 
I2.

 
T20RP: No screw compartment cover. Clear mesh dampener over cup vents shows work table light shining through.
 
Note the blue light shining through and showing unwanted ventilation around the jack, central screw compartment, and at the top where the wire enters the cup.
 
J2.

 
Johns Manville fiberglass from Lowe's
 
 
K2.

 
Aleene's "Fabric Fusion" peel & stick tape holds stretched pads on the cups and works great. It is semi-permanent but will pull loose from the cups, if necessary. It remains on the pad flap and may require another layer before re-installing onto the cups. Do not place this tape over the white thread around the pad flaps. Position the pad against the baffle and roll it over.
 
L2.
          
 
It works great as shown, above. The application on the left works best for sealing very stretched pad flaps. The application on the right works well and allows for easier removal should you decide to remove the pads.
 
 
M2.
          
 
Aleene's "Fabric Fusion" protective covering has been removed. Press it firmly onto the pad flap, then use your fingernail or tip of an X-acto knife to get it started and it peels right off.
 
 
N2.

 
Stretched-out Shure 840 pads now securely mounted with Aleene's "Fabric Fusion" double sided tape.
 
 

Sources for Modding Materials and Current Prices (July 2012)

 
Grodan Rock Wool
ir
 Get the slab or the 4x4x3 inch cubes (6-pack) Without holes. ~ $12.00 to $16.00.  Also: Dynamat, FatMat, Silverstone Acoustic Foam (Similar to Paxmate Plus).
 
Fiberglass: Johns Manville (JM) yellow fiberglass at Lowes or Owens-Corning (O-C) pink fiberglass at Home Depot.  Each comes in a small roll 2x16x48 inches for ~ $5.00.  I used JM Fiberglass, which is more resilient than O-C fiberglass, for all Incremental Mods and Measurements. Also:  3/4" Masking Tape, Super Glue, mini screwdrivers, etc.
 
Transpore Tape labeled: "3M clear flexible plastic tape" and available at most drug stores. A 3/4" width roll in a dispenser is more convenient for ~ $5.00. A 1" width roll is cheaper for ~ $3.00.
 
3/4" Masking Tape: Anywhere for ~ $2.00.
 
Stiff Craft Felt for ~ $1.00 per 8.5x11 inch sheet. Also: Acid-free double sided tape, 3/4" masking tape, plasticine, rubber cement (Acid-free), X-axto knife, Super Glue for repairing stripped cup threads, Hot Glue, Limp Felt, Self-adhesive Felt, etc. 
 
Aleene's "Fabric Fusion" peel & stick double sided tape from Michaels and from Amazon for $7.99.
 
100% Wool Felt:  Hobby Lobby for ~ $4.00. Density is Not uniform. May be available at fabric stores.
 
Acoustipack Lite for ~ $25.00  Also, Here for ~ $28.00.
 
Paxmate Plus for ~ $17.00.
 
Newplast Scroll down. ~ $21 for one, 500 gram bar includes shipping to USA. Cheaper per bar if you order 3 bars. 
 
Shure 840 Pads
ir
ir
 Currently for ~ $15.50 per pair.
 
Fischer FA-003 pads  Ask for Billy for ~ $25.00 per pair.
 
If you can find it, get Rite Aid "Natural Absorbent Cotton" that comes in a roll for ~ $5.00 which is what I used for all Incremental Mods and Measurements. Alternatives that may work include "Rite Aid First Aid Rolled Cotton" for ~ $5.00, "London Drugs Absorbent Cotton Roll" for ~ CAD $6.95, and "U.S. Cotton Absorbent Cotton Roll" 2-pack for ~ $12.00, each weighing one pound. Cotton makeup remover pads and ordinary cotton balls pulled lengthwise may also work but not as well as rolls of cotton, in my experience.
 
O2.

Available in stores and online November 2012.
 
P2.

 
Rite Aid "First Aid Rolled Cotton" when properly prepared works similarly compared to "Natural Absorbent Cotton."
 
 
Preparing "First Aid Rolled Cotton" for Effective Dampening
 
1. Separate the roll of dense cotton into 40 individual layers.
 
2. Divide into 2 parts of 15 layers, each.  15 layers = approximately 2 cm thick.
 
3. Cut 15 layers to fit the cups = 2x7x7 cm.
 
4. Cut 1x7x7 cm fiberglass and place over the top of the cotton.
 
This is my initial DBV #3 build with "First Aid Rolled Cotton" followed by tuning one or more of the following variables (individually) to achieve the desired frequency response:
 
* add/remove cotton
* add/remove fiberglass
* tweak the size and number of holes in the stiff felt over the rear driver grids
* tweak the size of the paper treble reflectors
 
 
Pad Rolling
April 2013
 
I thought it would be interesting to measure the effects of different pads on FR of an All Stock set of Fostex headphones. This should provide clues about the performance of various pads without making any other mods. I did not have an All Stock T50RP on hand so I used an All Stock T20RP mk2 for some pad rolling experiments. Pads measured included: Fischer FA-003 Pad taped onto the baffle, Fischer FA-003 Pad with 'micmacmo' Inner Tube Flap Mod, Shure Velour Pad, J$ Pad, MrSpeakers Dog Pad, MrSpeakers Alpha Pad, Shure 840 Pad, and Stock Fostex Pad.
 
I used a recently built and calibrated phantom power supply and mic. The new mic was mounted on an Etymotic Triflange Ear Tip in the same manner as the mic used for "Incremental Mods and Measurements." I placed the mic in my ear at the same depth and angle (as close as possible) as I did for the "Incremental Mods and Measurements." I did not remove or change the position of the mic during measurements.  The T20RP mk2 was placed on my head in the same position for each pads' measurement. Clamping force was constant across all measurements.
 
EDIT: I adjusted the "Check Levels" setting within REW to -15dB for the Left Channel of the All Stock T20RP mk2 with a Stock Fostex Pad.  I did not change the volume pot setting of my CEntrance Dacmini for any of the other 7 pads. Each pad has its own "efficiency factor" based upon its materials, dimensions, and construction. The "Notes" section for each graph indicates the SPL for each pad relative to the Stock Fostex Pad baseline of -15 dB. The SPL ranged from -15 dB (loudest) for the Stock Fostex Pad to -20.1 dB (least loudest) for the Shure Velour Pad. I matched the "amplitude" of all graphs referenced to the Stock Fostex Pad by adding the difference between each pads' REW "Check Levels" measurement and the Fostex Pad -15 dB baseline. For example, before generating graphs, I added +1.7 dB to the taped on Fischer FA-003 pad measurement and +5.1 dB to the Shure Velour pad measurement.
     ​
 
Q2.

 
Top Row: Fischer FA-003 Pad, Fischer FA-003 Pad with micmacmo inner tube flap mod, Shure Velour Pad, J$ Pad.
Bottom Row: MrSpeakers Dog Pad, MrSpeaker Alpha Pad, Shure 840 Pad, Stock Fostex Pad.
 
NOTE: As pointed out by micmacmo, the pleather of the Fischer pads (top row, 1st and 2nd pads) is different. The first one is a Fischer FA-003 pad with soft pleather all around and inside the ear hole. The second one may actually be an HM5 pad; its pleather is stiffer all around and inside the ear hole. 
 
R2.

 
 
 
S2.

 
Taped on Fishcer FA-003 Pad.  All others mounted with the pads' flaps.
 
 
96.
     
Stock Fostex Pad on Stock T20RP mk2
 
 
97.
     
FA-003 Pad taped on Stock T20RP mk2
 
 
98.
     
FA-003 Pad with inner tube flap mod on Stock T20RP mk2
 
 
99.
     
J$ Pad on Stock T20RP mk2
 
 
100.
     
MrSpeakers Alpha Pad on Stock T20RP mk2
 
 
101.
     
MrSpeakers Dog Pad on Stock T20RP mk2
 
 
102.
     
Shure Velour Pad on Stock T20RP mk2
 
 
103.
     
Shure 840 Pad on Stock T20RP mk2
 
 
Shure 840 Pad Modification and Measurements
October 2014
 
Shure 840 pads are known to improve sound quality beyond the T50RP series stock pads. They also produce a mid bass hump around 100 Hz than can cause bloat in the midrange frequencies. This is due to their construction = sealed pleather. Take an 840 pad and roll it inside out (the inner area where your ear goes). You will find 6, 6mm in diameter holes punched in the inner side of the pad walls. This was done to tune the pads for Shure SRH840 headphones. The problem persists, though, because the pleather on the outside of the pads prevents the pads from venting. 
 
Using an X-acto knife and a pair of sharp scissors, I cut 6, 4 mm holes along the outside edge of the pads aligned with the factory holes on the inside. Using a NIB T20RP mkII set of headphones, I made some measurements for your consideration.
 
The graphs tell the tale. The size, number, and placement of the modified external holes progressively modulate the amount of venting and the degree of midrange bloat attenuation. Fewer/smaller external pad wall vents = greater pad damping and greater midrange bloat....and vice versa. Conversely, sealing some/all of the factory punched holes on the inner pad walls should progressively increase the bass quantity but likely at the expense of bass quality, midrange clarity, and treble detail.
 
Another approach I've been thinking about, but not yet tried, may work without marring the pad appearance from cutting holes in the outside of the pads. Shure obviously punched 6 mm holes along the inner pad walls to tune the pads for best performance on SRH840. Here's the hypothesis --->  The factory holes allow controlled venting of the front wave's bass resonance and standing waves caused by sound waves reflecting off the otherwise sealed pleather pads. In addition to the type of foam used and its porosity-density- permeability quotient, there is also (blue) fabric mesh that appears to envelope the foam cushion inside the pleather. These two components may be able to absorb, disperse, and attenuate the 100 to 200 Hz bass hump. So, I plan to make more 6 mm holes along the interior pad walls, 1  at a time, then measure and listen to determine if my hypothesis is correct. A few pin-size holes in the outer pad wall may still be needed for fine-tuning.
 
If anyone tries these modifications, please post your impressions.
 
Pad Modification Measurements
 
The first 3 graphs are All Stock.
The next 3 are with stock 840 pads.
The last 3 are with modified 840 pads, as described.
 
104.

 
105.

 
106.

 
107.

 
108.

 
109.

 
110.

 
111.

 
112.

 
 
 
Implementing DBV #1, DBV #2, DBV #3, Grodan Rock Wool Mod, and Naked Driver Mods: Tutorials and Pictorials
 
Every Mod Is Different - Even When Built By The Same Person
 
 
DBV #1 - A Variant of BMF V8.1 
 
 
1. Seal the jack and wire entry points with GE Silicone II. Cover the jack hole with tape to prevent silicone from oozing into the jack.
 
2. Optional: Remove all four shock absorber posts using a Dremel cutting tool. Cut flush with the bottom of the cup and save the posts in case you want to super glue them back in place to return to stock form. Be careful to not cut the driver wires and headband hanger screw compartment.
 
3. Construct a 3x1 mm modified bass port centered over the lowest of the four cup vents. Cover all other cup vents and the remainder of the lowest vent, to either side of the modified bass port, with tape applied directly over the stock black cup vent on the inside. Seal the edges of the tape with glue. Alternatively, use masking tape on the outside of the cup vents during the tuning process. This makes it easier to try different sizes of modified bass ports vs fully open vs fully closed cup vents.
 
4. Install 20x70 mm Acoustipack Lite in the left and right cup floor "wells" trimmed to conform to the curvature of the cups. 
 
5. Install 3x10 mm Paxmate "Logs" over Acoustipack Lite as shown in the picture, above.
 
6. Install self-adhesive felt on the top and bottom areas of the central column, above the headband hanger screw compartment and below the stock black cup vent felt.
 
7. Install 10 grams of Newplast or plasticine Flush Mass Loaded in the baffle compartments.
 
8. Cut a 40x40 mm square of Creatology Stiffened Craft Felt and apply directly over the stock white driver dampener on the back of the drivers. Use strips of tape, double-sided tape, or glue to hold it in place.
 
9. Cut and apply a Transpore tape square of the desired size centered over the stiffened craft felt.
 
10. Measure (Uncompressed) and cut a 20x60x70 mm block of Rite Aid Natural Absorbent Cotton (or equivalent) placed and compressed in the cup. Snip the four corners to conform to the curvature of the cups. Snip all four sides to clear the shock absorbers (if not removed) so the cotton will lay flat in the cups.
 
11. Measure (Compressed) and cut a 10x60x70 mm block of fiberglass with corners and sides similarly snipped and place directly over the cotton. Optional: Add additional pieces of "fluff" around edges.
 
12. Use an X-acto knife or Dremel to remove the dust cover and its adhesive from around the ear side of the driver down to bare plastic.
 
13. Cut a ring of Dynamat or FatMat and apply to the bare baffle plastic. Use a triple A battery as a rolling pin to compress the butyl substrate firmly to the baffle. Cut a notch to expose the baffle port. 
 
14. Cut and notch a ring of self-adhesive felt to overlay the Dynamat or FatMat.
 
15. Shure 840 pads.
 
16. Tune, measure, and tweak to achieve your desired sound quality.
 
17. Seal the baffle ports and cup-to-baffle rims with tape (temporary) or GE Silicone II.
 
 
DBV #2 mod tweaks that are different than DBV #1  
 
1. Transpore over the stiff craft felt covering the back of the drivers measures 45x27 mm (length x width with length oriented in a North-South position ---> see BMF V8.1 pictures) instead of 22x28 mm Transpore used in DBV #1.
 
2. There are No modified bass ports in DBV #2. The stock black cup vent felt remains in place inside the cups, over the cup vents. The outside of the vents remain uncovered. (DBV #1 uses a modified bass port measuring 3x1 mm as described, above.)
 
3. The baffle ports are sealed in DBV #2. Be aware, however, that your mod may sound better with baffle ports Open so try it both ways.
 
4. All the other mod components are the same.
 
DBV #2 used to be my Current favorite mod configuration. Now, I prefer DBV #3...see, below. Sub-bass and bass are deep, musical, and textured. Midrange is clear, lush, and properly placed. Treble extension and clarity are improved over DBV #1. Imaging is very good.
 
My mic failed after collecting 100's of measurements during Incremental Mods and Measurement and I sent out my phantom power supply to another Head-fi DIY'er. DBV #3 is a slightly tweaked DBV #2. Refer to Graphs beginning at #56 and labeled "Dmitry's Mod" for a representation of DBV #3.
 
Note: Treble can be significantly extended by placing the Transpore Under the stiff craft felt. If you want even more treble, substitute paper from a glossy magazine cover in place of Transpore. Using a piece of non-porous paper the same size as the Transpore in this mod delivers more treble but may reduce sub-bass quantity. I find that magazine paper ranging from 20x20 mm (or 25x23 mm oriented East-West, size determined based upon the rest of the configuration) centered over the back of the driver's stock white dampener offers the best FR from bottom to top. 
 
I made several sets of DBV #2's. Each one differed slightly from one another for baffle ports opened vs. closed, amount/thickness of cotton and fiberglass, and amount of Transpore tape or size of magazine paper Under stiffened craft felt. Approximately 20 modding cycles, or individual tweaks, were required to achieve desired results but the first build of each one sounded awesome.
 
DBV #3 Cotton + Fiberglass Mod Notes
 
DBV #1 with DBV #2 changes but with baffle ports open. Instead of transpore under felt, I substituted 20x20 mm glossy magazine paper treble reflector taped over the center driver grid/stock white dampening material And Under the 40x40 mm stiffened craft felt Over the back of the driver = DBV #3. Tweak the amount of cotton, fiberglass, and size of paper under stiff craft felt to get the sound quality you want.
 
Rules of Thumb:  Generally, more cotton/fiberglass, larger paper treble reflector, and baffle ports open = more treble, less bass. Going the other way generally = less treble, more bass. Reducing the size of the cup vents by making a modified bass port (i.e. 3 mm width of one  of the four cup vent slots open and the rest sealed) = tighter bass, more treble. 
 
Good news: Rite Aid First Aid Rolled Cotton and London Drugs Absorbent Cotton Roll work almost as well as Rite Aid Natural Absorbent Cotton which is difficult to find. For Rite Aid First Aid Rolled Cotton, cut two 7x7 cm blocks, snip the corners, cut slits for to accomodate the four shock absorber posts, and then tease or pull the compressed layers apart to make it more fluffy. For London Drugs Absorbent Cotton Roll, cut and snip in the same manner; no teasing or pulling required. See below for links.
 
 
Simplified and Consolidated Tutorial for DBV 3  
 
Steps
 
Note: The stock white driver dampening paper and stock black felt over the inside of the cup vents are your modding "friends." Do not remove them for this mod configuration. Instead, work with them for great sound.
 
1. Seal the open area around and under the jack in the left cup with GE Silicone II. Cover the jack hole with tape to prevent silicone from oozing into the jack. Make sure it does not ooze around sides of the jack because this could interfere with seating the plug.
 
2. Install 19x70 mm Acoustipack Lite in the left and right cup floor "wells" trimmed to conform to the curvature of the cups. Use 19x55 mm in the left floor well of the left cup next to the jack.
 
3. Install 3x15 mm Paxmate (or Silverstone) "Ladder Rungs" over Acoustipack Lite laid at 90 degrees; 3 or 4 above and below the side shock absorber posts.
 
4. Install self-adhesive felt (from Michael's) on the top and bottom areas of the central column, above the headband hanger screw compartment and below the stock black cup vent felt. Do not  cover the stock black cup vent felt with self-adhesive felt.
 
5. Install 10 grams of Newplast (or non-drying plasticine) Flush Mass Loaded in the baffle compartments. Compressing the plasticine into the rear baffle compartments and flush with the top = 9 to 10 grams per baffle.
 
6. Use a dime as a template and cut 18 mm disks of shiny magazine cover paper (or thin card stock) and secure one to the back of each driver directly on the center grid of the stock white driver paper. Use 2x10 mm strips of 3M Removable double-sided Scrapbooking tape (from Michael's) applied to two sides of the center grid square. This serves as a treble reflector.
 
Alternatively, cut a 20 mm square of for each driver instead of disks.
 
Or, use a 27x52 mm strip of Transpore tape oriented North-South UNDER stiff craft felt with South at the bottom of the driver next to the solder points. Place the Transpore on the underside of the stiff craft felt, not on the stock white driver paper.
 
7. Cut a 45x52 mm square of Creatology Stiffened Craft Felt and apply directly over the stock white driver dampener on the back of the drivers, covering the treble reflector. To secure the stiff craft felt over the driver, use 6x45 mm strips of 3M Scotch Removable double-sided Scrapbooking tape, cut lengthwise from the roll, and apply to the wider North and South edges of the driver. Apply 3x52 mm strips of double-sided tape to the narrower East and West sides of the driver, overlapping the ends of the N-S strips. Make sure the double sided tape does not cover any of the grid spaces along their edges. See Tuning Tips, below, for "Bass Boost Holes."
 
8. Separate and cut ~ 20x60x70 mm of J&M Fiberglass (from Lowes). Snip the corners to fit the curvature of the cups. Cut 10 to 15 mm slits aligned with the 4 shock absorber posts so the fiberglass will lay flat in the cup floors. Firmly compress it against your work surface. It should retain the compressed thickness and measure ~ 10 mm thick after compressing. Add or remove fiberglass layers to achieve this thickness. Finished weight ~ 0.7 to 1.0 grams.
 
   Preparing J&M Fiberglass​
  
a. Measure and cut a 7x7 cm block from a roll of J&M fiberglass, 2 inches thick.
 
b. Divide into thirds.
 
c. Remove layers until you have equal blocks ~ 2 cm uncompressed.
 
d. Optional: Weigh each block. 0.9 to 1.2 grams is about right.
 
e. Remove/add tiny amounts to the blocks until weights/thicknesses are equal.
 
f. Compress each block, firmly. It should not "decompress."
 
g. Measure thickness of each, after compressing. You want ~ 1 cm, or slightly less, thickness after compressing.
 
h. Once you've confirmed equal weights and dimensions, snip the corners and slit the sides like you did with the cotton.
 
T2.

 
i. Weigh each block and record in your "Modding Registry." 0.7 to 1.0 grams finished weight is about right after snipping the corners to fit the cup curvature.
 
j. Install
 
Alternatively, omit the fiberglass and increase the Uncompressed cotton thickness by 5 to 10 mm OR omit the cotton and increase the fiberglass Compressed thickness by 10 to 20 mm. That said, I think the combination of cotton and fiberglass works best, most of the time.
 
9. Measure and cut ~ 20x60x70 mm of Rite Aid Natural Absorbent Cotton (or equivalent). Snip the four corners to conform to the curvature of the cups. Cut 10 to 15 mm slits aligned with all four sides to clear the shock absorbers so the cotton will lay flat over the fiberglass. 
 
Note: Rite Aid Natural Absorbent Cotton is no longer available. Rite Aid First Aid Rolled Cotton is an effective substitute IF properly prepared.  Here's how:
 
   Preparing Rite Aid "First Aid Rolled Cotton” For The Best Sound Quality
 
U2.

 
a. Measure and cut a 7 x 15 cm block from the First Aid Rolled Cotton roll. The roll is 15 cm wide so just measure and mark 7 cm Length from the roll and cut with very sharp scissors. It's easier to cut if you first divide the full thickness into two or three parts.
 
V2.

 
b. Begin by carefully separating a single, VERY thin layer of 7 x 15 cm cotton and it peels right off. This is 1 of 40 layers from a "full thickness" of Rite Aid First Aid Rolled Cotton. Often, 2 or 3 layers come off as one thicker layer. You may think you have one layer, but you don't. Separate each VERY thin layer. 
 
W2.

 
c. Lay the first layer on your work surface and peel off another layer.
 
X2.

 
d. Lay alternating layers "face up", "face down", "face up", "face down", etc. Also, alternate turning, or flipping, every other single layer, end to end. This makes the stack more uniform. You'll see why/how as you do it. This photo shows 1/2 prepared and 1/2 not yet prepared.
 
e. Stack 15 layers = approximately 2 cm thick, uncompressed.
 
f. Trim the edges evenly, all the way around, for a neat 2x7x14 cm block of fluffy cotton. Divide this in half. Use your ruler to measure your "cutting point" by placing your scissors at the middle of one long side. Don't cut yet. Hold your scissors in place and measure each side to make sure you actually have the center point.  Now cut straight across. You now have two, 2x7x7 cm blocks almost ready for your initial build. The photo, below, shows one 2x7x7 cm block weighed Before trimming the corners.
 
Y2.

 
 
g. Snip the corners of each cotton block to fit the curvature of the cups. Cut ~ twice as much from the corner that will be placed next to the jack, as shown in the photo, below.
 
Z2.

 
 
h. Mark and cut slits aligned with the four shock absorber posts so the coton will lay flat in the cup floor.
 
i. Optional:  Weigh each block using a digital scale that comes with a calibration weight. You can see the model I use and bought from Amazon for $20.00. Add or remove individual layers of cotton from one or the other 2x7x7 cm block of cotton to obtain equal weights. This will help insure L-R Channel Balance. Weigh and record the weight and dimensions of each cotton block = ~ 1.7 grams
 
 
j. Install
 
Preferred Installation: Place the 2x7x7 cotton blocks in the cup floors. Place the fiberglass over the cotton like "Dmitry's DBV #2 Mod" shown in Graphs #59 - #61, below.
 
10. Shure 840 pads.
 
[size=13.63636302947998px]Installing Shure 840 pads: Turn the flaps inside out. Place the pad against the baffle and fold the top of the flap over the cup at the 12 and 1 o’clock positions and hold in place.  Fold over the flap on the left side from 12 o'clock to the 7 o’clock position and hold that spot in place. Still holding the 1 o’clock and 7 o’clock positions in place, continue to fold the flap over the right side of the cup, working your way down while holding in place each segment as you progress. Now that you have the flap folded over the cup and holding the 5 o’clock and 7 o’clock positions in place, finish turning the flap over the bottom of the cup.[/size]
 
11. Tune and tweak to achieve your desired sound quality.
 
 
 
Simplified and Consolidated Pictorial for DBV 3 
 
 A3.

 
Just opened. Be careful with the wires attached to the solder connections. When closing, be sure the wires are not pinched between the cup and baffle rim.
 
B3.
  
 
The Good Stuff - Now Extinct - is on the left. The one on the right works great with preparation. See preparation instructions, above.                 
 
C3.

 
"Good cotton" separates easily to your desired thickness and is pleasingly "Fluffy." Start with 20x70x70 mm block and snip corners to fit the curvature of the cups. Rite Aid Natural Absorbent Cotton layers are very fine and uniform. Compress it and it pops back up. Other types of cotton I've tried have dense, non-uniform layering. They don't compress and are not as "springy" as Rite Aid Natural Absorbent Cotton. If you find some, buy it because it's hard to come by. Rite Aid First Aid Rolled Cotton works as a very good substitute, if you pull the dense layers apart as describe, above. London Drugs Absorbent Cotton and U.S. Absorbent cotton Roll may also work if similarly prepared. Note: These 3 types of cotton are too dense and matted to use right off the roll.
 
D3.

 
J&M Fiberglass from Lowes.
 
E3.

 
19x70 mm Acoustipack Lite, Paxmate Plus, OR Silverstone in the side floor wells except 19x55 mm in the left side of the left cup. Self-adhesive felt on the central floor Above the center compartment and Below the stock black cup vent felt at the bottom.
 
F3.

 
Newplast has been Flush Mass Loaded into the rear baffle compartments. 19x55 mm Acoustipack Lite (or similar acoustic foam) on the left side of the left cup floor next to the jack.
 
G3.
 
 
 
Left Photo: Double sided tape around perimeter of the driver has had its protective top removed. It will secure 45x52 mm stiff craft felt. Double sided tape strips in the center with protective covering not yet removed will secure the treble reflector.
 
Right Photo: 18 mm treble reflector is my "default" size for initial builds. 44x52 mm stiff craft felt goes over this treble reflector/back of the driver. Make it larger for more treble. Make it smaller for less treble. Fiberglass over cotton in the cup.
 
H3.
 
 
 
Left Photo: 20x20 mm treble reflector over stock white driver paper. Preferred: Use an 18 mm disk. Try different sizes, if needed.
 
Right Photo: 3x15 mm Silverstone "ladder rungs" set at 90 degrees over Acoustipack in cup floor wells. Self-adhesive felt above the central screw compartment and Below (Not covering) the stock black cup vent felt.
 
I3.
 
 
 
Acoustipack Lite with 3x15 mm Paxmate Plus “Ladder Rungs” 40x40 mm stiff craft felt (left photo) over stock white driver paper and treble reflector in the left photo. The photo on the right shows a better method using 45x52 mm stiff craft felt over stock white driver paper and treble reflector. Note 3 mm holes in the stiff felt overlaying the center of the 4 corner grids on the back of the driver which serve as "Bass Boost Holes."
 
J3.
 
 
 
Optional: Punch holes in the stiff craft felt over various driver grid spaces for More bass. More/Larger holes = more bass. Note another method of making a treble reflector, shown in the photo on the right. I used a 27 mm (width) strip of Transpore tape 52 mm in length and centered it onto the stiff felt. Holes were punched to increase bass. The stiff felt will be turned with Transpore "face down." Double sided tape holds the stiff felt in place. Try different Transpore widths or "coverage" patterns. The "half-circle" holes around the sides add nothing to the sound quality but are punched so the stiff felt lays flat against the back of the driver.
 
 K3.
                                                                             
 
Fiberglass cut and notched to fit around all 4 shock absorber posts and compressed into cup floors. Cotton ready to go over fiberglass.  You can try it with cotton in cup floors and fiberglass over the cotton (Preferred). Use double-sided tape around driver perimeter and under the 45x52 mm stiff craft felt, instead of Transpore tape, for a "cleaner" build.
 
This is a better method. Cotton (~ 20x60x70 mm; 1.75 g.) trimmed to fit curvature of the cups and notched to fit around the shock absorbers was placed in the cup over Acoustipack Lite and Silverstone "ladder rungs." The fiberglass (~ 10x60x70 mm; ~ 0.7 to 1.0 g.), similarly trimmed and notched, will go over the cotton. Stiff felt with holes is secured by double sided tape. There's an 18 mm disk of glossy magazine paper under the stiff felt and centered over the driver grid. Newplast "flush mass loaded" in the baffle compartments.
 
L3.

 
Cotton over fiberglass, both notched for the 4 shock absorber posts and corners trimmed to fit the curvature of the cups. Holes punched in stiff craft felt for more bass - This is optional and generally not necessary unless you want more bass. Newplast Flush Mass Loaded baffles. There is no need to fill the tiny oval compartments around the driver.
 
M3.

 
Acoustipack Lite in cup floor wells, 3x10 mm Paxmate "Ladder Rungs" at 90 degrees over Acoustipack LIte, and self-adhesive felt at top and bottom of the cup central floor area. 2.5 mm holes punched over the center of all grid spaces=Even more bass. Newplast in the baffles. Note the empty "square" at the bottom to receive the Jack in the left cup.
 
 
Cotton: ~ 2x7x7 cm (Measured Uncompressed)
FG:       ~ 1x6x7 cm (Measured Compressed)
Note: These measurements are your starting points. You must tune each cup to achieve the sound quality you like best. You may need a little more or a little less cotton and/or fiberglass in the cups and the amount may differ slightly from one side to the other. Use a calibrated digital scale for easier L-R Channel balancing.
 
N3.

 
1.7 g Cotton over 0.7 g Fiberglass with slits to accomodate the 4 shock absorber posts. 40x40 mm stiff craft felt with 2.5 mm holes over center of all grid spaces. Note: 45x52 mm stiff felt is preferred.
 
 
 
DBV #3 Update: Modding Made (A Little) Easier (March 15, 2013
 
Recently, I misplaced my last box of Rite Aid "Natural Absorbent Cotton." As described above, Rite Aid "First Aid Rolled Cotton" performs similarly but requires "preparation."
 
Over 1 year ago, mrspeakers posted a modification to his Rastapants Mod using cotton balls. I tried different brands, sizes, and numbers of cotton balls in whatever mod iteration I was working on at the time (Not DBV #3). Cotton balls did not work with that older mod so I kept looking for materials and happened to get good results with "Natural Absorbent Cotton." Several months ago, Rite Aid discontinued "Natural Absorbent Cotton."
 
Fast forward...I've been searching for an easier application than the preparation necessary when using "First Aid Rolled Cotton." I came across several boxes of Rite Aid "First Aid" cotton balls and decided to give them a try with DBV #3. 
 
I opened up one of my DBV #3's and removed the prepared cotton and prepared fiberglass. I placed 6 "First Aid" cotton balls, right out of the box and with No preparation in two columns, in the cup floors. I did not use any fiberglass. Everything else remained the same as described in my DBV #3 Pictorial/Tutorial. I closed them up and took a listen. The results? Cotton balls work, And they work really well with DBV #3 mod - with no preparation.
 
I have not yet tried teasing them apart (a little vs a lot). I have not tried altering the number of cotton balls + fiberglass. It is possible that doing so will further improve their performance. If you try this, please post your results.
 
O3.

 
P3.

 
6 unprepared cotton balls weigh 1.8 grams which is similar to the weight of "Natural Absorbent Cotton." Prepared "First Aid Rolled Cotton" weighs about the same.
 
Q3.

 
6 Rite Aid "First Aid" cotton balls = Unprepared/un-teased
 
 
 
BMF Rock Wool Mod - Improved (May 2013) 
 
Steps
 
Do Not remove the stock white driver damping material that covers the back of the drivers. Doing so creates "Naked Drivers" that significantly change the sound quality for the worse. The driver diaphragm excursion becomes too great because it is under-damped. The result is Boomy Bass Bloat that muffles the midrange frequencies and overwhelms the treble frequencies. The "fix" requires a different mod configuration --> "Naked Driver Mod" described at the end of this Post # 1 (with links to photos and graphs).
 
1. Apply hot glue or GE Silicone II to seal the jack as shown, previously. Do not allow oozing around the sides that could impede the stock cable locking mechanism or block the jack opening.
 
2. Cut 2x7 cm Paxmate Plus(Silverstone or Acoustipack Lite) acoustic foam, trim the ends to fit the curvature of the cups, notch for the side shock absorber posts, and place in the cup floor wells; 2x5.5 cm goes in the left cup on the jack side. (See photos in "Simplified and Consolidated Pictorial for DBV #3", below) Cut and place acoustic foam above the central compartment and below the stock black cup vent felt.  Make sure the black cup vent felt remains in place and uncovered unless you decide to make a modified bass port during the tuning process. 
 
For T40RP mk2: Remove and save the plastic rectangles that cover the inside of the cup vents. Glue a rectangle of felt over the opening.
 
For T20RP mk2: Glue a rectangle of felt over the stock clear mesh. Place a piece of masking tape over the open central compartment.
 
Note: 18 months ago, I tested the effects of completely filling the cups (floors and walls) using a single layer vs a "crosshatch" configuration using strips of Paxmate in 3 layers. The results were equivocal. I also tried encircling the ear side of the drivers with Paxmate Plus: 1 layer, 2 layers, and 2 layers on the back half but only 1 layer on the front half with mixed results. I tried the same with the present Grodan Rock Wool mod. I decided to omit Paxmate on the cup walls but use a single layer around the ear side of the driver which seems to improve clarity. Perhaps this reduces ear side reflections off cup walls and your head.
 
3. Custom cut Paxmate Plus (or Silverstone) pieces and install in the baffle compartments. Alternatively, install Newplast (or plasticine) flush mass loaded in the baffle compartments. Yes, I know. They have different functions. Use what you have or try both to determine which works better for you.
 
4. Buy Grodan Stone Wool (their new name for Rock Wool) in 3-inch or 4-inch cubes Without the "planting" holes. The "slabs" I bought are not the same density as the cubes. The cubes work much better. They are easier to cut and keep their shape better than the slabs. Use a Sharp Serrated knife, preferably with a cutting guide. I use a bread knife that works great. It cuts cleanly with very little crumbling. Cut a slice of Grodan your desired thickness. Make sure the slice the same thickness, throughout. Cut the slice to your desired dimensions (width x length).
 
I've tried all the following dimensions:  1.3 x4x4, 1x4x4 cm, 1.3x5x5 cm, 1x5x5 cm, 0.7x4x4 cm, 0.7x5x5 cm, 1x5x7 cm, and 1.3x5x7 cm. Each performs similarly but offers different "flavors" and ratios of Bass:Treble. Smaller/Thinner = More Bass/Less Treble. Larger/Thicker = Less Bass/More Treble. IMO using my "ears and gears," 1x4x4 cm and 1.3x5x7 cm "slices" work best. The best  will be determined by each DIY'er during tuning.
 
5. Cut gauze the necessary width x length needed to "wrap" your Grodan slices. If you use 1x4x4 cm (Default Configuration) or 1x5x5 cm squares, snip off the corners just enough for the corners to fit inside the 4 shock absorber posts. This creates a Diamond shape. Wrap with gauze and use Transpore or Micropore tape as if wrapping a gift for a friend. Snip off the excess gauze at the corners. Turn the "Grodan Diamond" so each of its 4 snipped corners align with a shock absorber and position it in the cup. Gently adjust the snipped corners so they do not cover the shock absorber rubber caps.
 
If you use 1.3x5x7 cm slices, you need to cut holes for the top and bottom shock absorbers. Use a drinking straw for a cleanly cut hole. Snip the corners to fit the curvature of the cups and to clear the jack. Wrap with gauze and tape. Cut openings in the gauze (on both sides) so the top and bottom shock absorbers can go all the way through the "Grodan Block." Cut a diagonal slit at the top right side of the "Grodan Block" for the driver wire. This will prevent strain on the diaphragm solder pads.
 
6. Position the baffle/driver over the cup and make sure your driver wires are correctly positioned. Lower the baffle/driver onto the cup and compress with even pressure on the back of the cup and ear side of the baffle. You will feel and hear the rock wool compressing - this is normal. Secure in place with masking tape for quick tuning cycles or use the 4 screws.
 
7. Make a template and cut a ring of Paxmate for the flat area on the ear side of the baffle. Cut an opening 40x40 mm to match the driver opening with an extra 2 mm width x length. Cut a notch for the ear side baffle port. Rub your finger along the driver perimeter to expose the outline of the driver under the super thin dust cover. Use a silver or white marker and trace the edges of the driver. This makes it easier to position the Paxmate Ring and ensure you do not accidentally cover any of the driver opening.
 
Alternatively, cut 4 strips of Paxmate ~ 2 cm wide to make a "picture frame" around the ear side of the driver. This is an easier method.
 
8. You can use any pads you like but this configuration was tuned only for Shure 840 pads. Using other pads may require tuning tweaks to the other components to achieve the sound you like.
 
9. This mod configuration does not need a modified bass port unless you want Less bass/Tighter bass. See above, near the top of this post, for a description of how to make a temporary and permanent modified bass port.
 
10. The baffle port remains open in this configuration unless you want More bass and More lower treble. In this case, seal the baffle port with masking tape for a temporary fix. For a permanent fix, use hot glue or silicone. Hot glue is more easily removed if you use only a small amount. 
 
11. This mod configuration does not need Dynamat (or FatMat) with self-adhesive felt overlay around the driver on the ear side of the baffle. This optional component, however, may help reduce vibration-induced distortion. If used, remove the very thin dust cover material from the baffle around the driver and remember to cut a 4x4 mm opening from the Dynamat (or FatMat) to expose the baffle port.
 
12. There is no need to remove the dust cover directly over the driver because it's Very thin. Measurements showed No improvement in treble response after removing the dust cover over the driver. YMMV. For more treble, damp more and/or add a square of magazine paper over the drivers' center grid space. 
 
13. Tuning: Your "Initial Build" may sound "just right" to you and require no tuning, at all. If you want more or less bass and treble, tweak the thickness, width, and length of Rock Wool. You could also try a 4 mm wide modified bass port, treble reflectors, stiff felt over the back of the driver, or snipping off more at the bottom to expose some/all of the cup vents. Try your build with the baffle port open vs. closed. Try different pads. Make only one tweak at a time to assess its results.
 
Personally, with my preferences and audio chain, I like the SQ best after adding an 18 mm stiff/thin card stock treble reflector Under a 45x52 mm rectangle of stiffened craft felt secured to the back of the drivers with double sided tape and, if modding T20RP mk2 or T40RP mk2, with a rectangle of stiffened felt over the inside cup vents (first remove the plastic rectangle over the inside of the T40RP mk2 cup vents).
 
 
BMF Grodan Rock Wool Mod Pictorial (May 2013)
 
 
R3.

1. A 4-inch cube of Grodan Rock Wool Without a planting hole in the center of the opposite side.
 
S3.

2. Serrated bread knife with adjustable width guide.
1x10x10 cm slice of Grodan Rock Wool.
 
T3.

3. A 1x4x4 cm Grodan Rock Wool "Diamond."
Use a drinking straw to "drill" a hole in the center. This optional and adds a bit more bass.
 
U3.

4. Optional center hole "drilled" with a drinking straw and a straw segment 1/2 as long as the Grodan thickness. In this picture, the Grodan "Diamonds" are 1x4x4 cm with corners snipped off to fit inside the 4 shock absorbers. The other one has been wrapped in gauze, taped with Transpore, and excess gauze has been snipped off and ready for installation.
 
V3.

5. Wrapping Grodan Rock Wool with gauze.
 
W3.

6. A 1x4x4 cm Grodan Rock Wool "Diamond" wrapped, taped, snipped, and ready to install.
 
X3.

 
 
7. Cup: Paxmate Plus in floor wells and 1x4x4 cm Grodan Rock Wool. Paxmate not yet installed at top center of the cup floor.
Baffle: Paxmate Plus custom fit pieces fill the baffle compartments. Optional: Use Newplast, instead. Stock white driver damping material in place. 
 
Y3.

 
 
 
 
8. Cup: Grodan "Diamond" has more snipped off at the bottom to expose 2 of 4 cup vents to increase bass.
Note that for this T20RP mk2, there is a single layer of craft felt over the stock clear mesh that covers the internal cup vents. This is optional = a little more damping for a bit more bass control
Baffle: Paxmate Plus instead of Newplast.
 
Z3.

 
 
9. Ear side of Baffle: Paxmate around driver with 4x4 cm opening. Note the white marker outline of the driver edges. Masking tape secures baffle to cup for quick turn-around during tuning.
 
 
 
nick n MemFoam Modification November 2013 - March 2014
 
nick n and I have been "riffing" off one another for the past couple of months as he developed a novel modification he calls "The MemFoam Mod." What follows is the culmination of our back and forth tuning experiments. I documented the final steps of my "take" on his original design and he asked me to post both, here.
 
The Memory Foam Mod uses no cotton, felt, fiberglass, polyfil, or wool. It's a little complicated but the guides make it easy to build. The results are well worth the time and effort. Following Nick's killer formula, you will see how I took his mod "and made it my own" by adjusting a few things. 
 
Note:  This configuration will work equally well with T50RP, T40RP, and T20RP MkII. If using T40RP, simply remove the plastic rectangles from the cup vents (on the inside). If using T20RP MkII, leave the clear mesh over the cup vents (also on the inside) and close off approximately 2.75 vent slots with tape or decals instead of 3.0 vent slots.
 
‘nick n’ (head-fi name) is an experienced Ortho modder with a very interesting T50RP mod configuration. He took his Memory Foam Mod from November 2013, and made significant improvements.  
 
Nick meticulously tested many config variations to nail down this terrific sounding mod. I built several of his “test configs” including this one, which is the best. This mod is complicated and labor-intensive but his guides are clear for easy implementation. The results are well worth the effort.
 
nick n's MemFoam Mod
 
Supplies Needed For Cups:
 
1. Silicone (GE Silicone II, for example) – To seal the cable entry points into the cups, baffle port (one per baffle), and TRS jack in Left Cup
 
2. Adhesive-backed Creatology felt (2 mm thick) – For lining cup walls and upper portion of the central cup floor area
 
3. PlastiDip Pourable rubber compound – For leveling the side cup floor “wells” and mechanically damping the cups
 
4. Felt furniture pad with thin foam adhesive back (Dollar Store item) – Overlays PlastiDip for acoustic absorption and leveling the side cup floor "wells"
 
5. Black vinyl decal of some kind/equivalent for sealing cup vents from inside more permanently than electrical - For modified bass ports
 
6. “Health and Beauty” round white memory foam makeup remover pads. All memory foam pads are different but try to use these, available from Dollar Store – For damping the drivers
 
7. Twaron Angel Hair (sample bags of 100 grams available- Solen.ca = will last you forever and a day) - Placed between the cup walls and Memory Foam for acoustic damping
 
 
 
Supplies Needed for Rear Side of Drivers:
 
8. Arctic Cotton (A.C.) fabric material (this specific material only) – For A.C. Damping Pad acoustic damping
 
9. 3M MICROPORE tape (A.K.A. 3M paper tape on the package. Look inside the roll tube for the ‘Micropore’ logo. – Overlays both sides of A.C. Damping Pad for acoustic damping
 
10. Double sided tape – For securing A.C. Damping Pad to back of drivers
 
11. Silicone to attach and stabilize the driver diaphragm protrusion (with the solder tabs) to the driver frame. NOTE: This is important in order to prevent unwanted mechanical "buzzing" from low frequencies.
 
 
Supplies Needed for Rear Side of Baffles:
 
12. Newplast – For the rear baffle compartments to mechanically dampen them and reduce resonance
 
13. Adhesive-backed Creatology Felt (2 mm thick) – Overlays Newplast
 
 
Supplies Needed for Ear Side of Baffles:
 
14. Dynamat around ear side of the driver for added mechanical damping
 
15. 3M electrical tape – For sealing baffles to cups and prevent the back wave from canceling the front wave
 
16. Shure 840 Pads - For better comfort and significantly improving sound quality
 
 
Tools Needed:
 
17. X-Acto Utility Knife
 
18. Scissors
 
19. Screwdrivers
 
20. Hole Punch (5 mm diameter)
 
 
Steps:
 
1. Open cups and seal the top left baffle port with silicone. You may wish to seal the top cable entry. Seal around the female jack area (on the inside) using a small strip of painters tape to prevent PlastiDip from oozing into the stock jack area. Allow silicone to dry up overnight.
 
2. PlastiDip - Do one cup at a time; it's easier. Open cups and lay rears securely on level surface (on rag pile helps     keep it balanced and steady as it sets up). Use wooden coffee stirring stick, or similar, to drizzle PlastiDip into the cup floor wells. Fill carefully so PlastiDip is flush with the raised central cup floor area. PlastiDip will shrink down as it dries.
 
*** Let PlastiDip dry for at least two days. If you do not allow the PlastiDip to fully dry, off gassing will warp your drivers. Be certain that the PlastiDip has completely cured before you close baffles to cups. Patience, here, is especially important. Work in a well VENTILATED WORK AREA. Do not breathe the fumes. ***
 
3. Cut two strips of the foam-backed furniture felt the same shape as each PlastiDip-filled cup well (19 x 70 mm.) Notch for side shock absorber post. Apply furniture felt on top of each cup well you filled with PlastiDip.
 
4. Pull off the stock black cup vent felt (on the inside) and save for later mods. Cover 3 of 4 openings with a vinyl decal on the inside. Leave the top vent Open.
 
5. Fill baffle rears with Newplast. Do not fill the TRS jack-receiving area in the Left Cup.
 
6. Cover all remaining exposed surfaces with thin Creatology self-adhesive felt: Cup walls, central area of Cup Floor, Elevated central screw compartment in the center of the cups, and the Newplast. Do not cover the single open vent.
 
7. Take Memory foam discs and mark hole centers to be punched using a centered 20x20mm square template. Mark at each corner of the template as well as between the upper corners for a total of 6 holes as shown in the picture. 
 
8. Use a 5 mm diameter hole punch centered over each of the 6 template marks to make holes in the memory foam over the corresponding rear driver grids. Use your fingers to pluck out foam to about half the thickness of the memory foam pads to accommodate the shape of the raised central screw compartment in the center of each cup floor.
 
9. Make 36 x 36 mm Arctic Cotton Damping pads with Arctic Cotton and 3M Micropore tape using the wider roll, if possible (see page #2 diagram).
 
10. Place A. C. Damping Pad side directly on driver. Secure at the top and bottom edges (wider sides of driver frame) using double-sided tape. Make sure the double-sided tape does not overlay the driver grids. 
 
11. Orient the A. C. Damping Pads as shown on page #3 diagram.
 
12. Place Memory Foam pad as shown on page #3 diagram, centered between the four driver assembly screws. You may need to notch the sides, top, and bottom of the Memory Foam pads to accommodate the 4 shock  absorber posts in the cups.
 
13. Weigh 0.4 grams of Twaron Angel Hair. Form into a ring and tuck in between cup walls and Memory Foam pads. It expands rapidly so just do your best.
 
14. You may need to use a tiny bit of double sided tape to keep the foam disc oriented while closing baffles to cups. If so, make sure none is on the A.C. Damping Pad and driver.
 
15. Hold a cup flat in your palm and then align and lower the baffle onto the cup. This should prevent the foam from shifting around which is important since the memory foam holes must align with their corresponding driver grids. A direct drop on top is what you want. Check and retry, if necessary.
 
16. Tuck in stray Angel Hair that peeks out and screw the baffles to cups.
 
17 .Apply black 3M electrical tape around the cup to baffle rim, slightly stretching it as you go for better adhesion.
 
18. Cut away stock felt covering over driver and baffle face on ear side, leaving only the thin stock mesh protection.  Dynamat requires a hard surface in order to function as designed to reduce resonance.
 
19. Cut and apply Dynamat over the “naked” ear side baffles. Be sure you do not cover the driver opening that measures 35 x35 mm.  If you want to experiment with open vs. closed baffle ports, notch an opening in the Dynamat to expose the baffle port and do not seal the baffle port in Step 1, above. 
 
20. Overlay Dynamat with Creatology thin adhesive felt to prevent reflections off the aluminum constrained layer.
 

             Materials needed
 

Cured PlastiDip in cup floor wells
 

Makeup Remover Memory Foam with Template showing where to mark and
Punch 5 mm holes
 

  • Six, 5 mm holes punched in Memory Foam.
 
     2. Note the center section has been plucked to about ½ it’s thickness in an oval shape to fit over the Central Screw Compartment.
 
     3. The Memory Foam is positioned on the back of the driver and held in place by small pieces of double-sided tape.
 
     4. Green Newplast in rear baffle compartments (around foam) and Blue Creatology self-adhesive felt overlays the Newplast.
 
     5. Angel Hair in cup
 

Diagram Page 1
Shows how to apply Micropore tape to the first side of the Arctic Cotton fabric
 

Diagram Page 2
Shows how to apply Micropore tape to the opposite side of the Arctic Cotton fabric
 

Diagram Page 3
Shows the proper orientation of the A.C. Damping Pad
 
Special thanks
After at least a hundred trials later:
 
  1. BMF for swapping ideas over the course of this project, putting up with ridiculous “finalized now, again” comments, incessant obsessing, and helping me dig myself out of many a corner, and for this thread. This mod is essentially a hybrid of both our ideas. Thanks for the Micropore without which NONE of this would have worked.
 
  1. Sfwalcer (A.K.A. “cardboard”) and waynes world for forcing me beyond my usual mod trials, putting me under pressure to pull something decent out of my hat, making me sweat and supremely stress over this which was what pushed it to the maximum.
 
  1. Everyone who has ever posted in here or the Ortho Roundup thread and helped along the way.
 
  1. The Planar Dimensional Audio beings that threw a few “random” chance occurrences towards this project.
 
If you dig this mod be sure to thanks these three guys.
 
~ Nick N
 
 
BMF's "Take" on Nick's MemFoam Mod
 
Internal Mods:
 

 
1. Self-adhesive Creatology Felt on Cup Walls, Central Screw Compartment, and on the cup floor above the Central Screw Compartment
 
2. The Bottom Cup Vents are still open in this photo. The stock black felt over the inside of the     vents will be removed and the top three vents sealed with tape.
 
3. Furniture Felt Pad cut to fit over PlastiDip in the cup floor wells measures 19 x 70 mm. They are notched to accommodate the side shock absorber posts.
 
 
4. A.C. Damping Pad measures 45 x 52 mm. The center is cut out according to Nick's guide so that 12 rear driver holes are exposed: 6 inside the center grid space and 3 each to either side. The A.C. Damping pad is secured with strips of double sided tape on all four sides of the driver frame. Make sure the double sided tape does not cover any of the stock white damping material on the back of the driver.
 
5. Custom-cut pieces of Paxmate fill the rear baffle compartment instead of Newplast and its self-adhesive felt overlay.                             
 

A sheet of white paper placed under the cup vents shows that only the bottom vent is open. The other three are sealed with electrical tape. Nick’s decals work best.
 

The bottom of the Memory Foam is cut off to expose the bottom Cup Vent. 0.4 g. of Angel Hair tucked between Foam and Cup Walls. Note: The blue dots indicate memory foam plugs that were added to a previous build that had 8 holes.
 
 
External Mods:
 

Paxmate “Earrings” instead of Dynamat and adhesive felt overlay.  Note, I have installed Dynamat with Paxmate Earring overlay on the ear side of the baffles in previous mods with good results.
 

Paxmate Earrings template
Paxmate Earring with 35 x 35 mm driver opening and notch for exposing Baffle Port
 

BlueMonkeyDots (BMD) are 12 x 14 mm rectangles of Paxmate Plus with center adhesive snipped off. Simply bend it between thumb and forefinger like a horseshoe and snip off the "rib" with scissors. Place one on each center driver grid on the ear side in the orientation shown, below.
 
I believe the dust cover is acoustically transparent so I don't remove it. You can press down over the driver to feel and mark the position of the center grid.
 

  • Paxmate “Earrings” surround the ear side of the drivers.
 
     2. Baffle Port is Open.
 
     3. BMD’s made from 10 x 12 mm Paxmate with 1/3 adhesive removed from the center.
 
     4. Masking tape is used only during tuning trials to avoid stripping the cup threads.
 
The sound quality of Nick’s mod is phenomenal.
 
~ BMF
 
 
Paxmate Lattice Mod with Cotton or Grodan Rock Wool
[size=medium]April 2014[/size]
 
Materials Needed
1. Paxmate Plus or Silverstone Acoustic Foam
2. Cotton Make-up Remover Pads OR Grodan Rock Wool + Gauze "Pillow Case"
3. Shure 840 Pads
 
Steps
1. Cut 19 x 70 mm pieces of acoustic foam for the cup floor wells and notch for side shock absorber posts.
2. Cut 4 mm strips of acoustic foam and build your lattice as shown in the pictures.
3. Cut 35 x 35 x 5 mm squares of cotton make-up pad OR 35 x 35 x 5 mm squares of Grodan rock wool for the recessed   cavity that aligns with the rear driver area. 
4. Shure 840 pads (OR try different pads with various tuning tweaks).
5. Dynamat on the ear side of the drivers (optional).
6. BMD's over the center ear side grid space, if needed.
7. Add a bit more cotton or increase the thickness of the rock wool to tighten bass and elevate treble.
8. Modify the cup vents to tighten the bass and increase the treble.
9. Paxmate "earrings" around ear side of drivers.
 

Paxmate in floor wells and 2 strips of Paxmate lengthwise = first 2 layers.
 

45 degree strips of Paxmate for third layer.
 

Third layer finished.
 

Long strips = 4th layer over smaller segments = 3rd layer
creates a recessed cavity for cotton or rock wool.
Custom cut pieces of Paxmate installed in the rear baffle compartments.
No plasticine or Newplast.
 

Cotton makeup remover pad installed.
Paxmate in rear baffle compartments.
 

Both sides
 

Template for "Paxmate Earrings" placed on ear side of the baffles
 

Here, I used an extra baffle with the dust cover cut out over the driver opening as a double check for the Paxmate Earring opening.
I outlined the ear side baffle port with a white marker.
 

This shows the rear side of the baffle with the baffle port outlined with a white marker.
The adhesive side of the Paxmate Earring.
 

Paxmate Earring with 5 mm hole punched to expose the baffle port.
 

Paxmate Earring installed on the ear side of the baffle. I removed the dust cover directly over the driver for easier alignment. Note the clear mesh is intact and serves as a debris cover. Shure 840 pads have dust covers. The 5 mm "hole" punched for the baffle port serves as the BMD, placed directly over the center of the driver on the ear side. Masking tape seals the baffles to cups during tuning trials to avoid stripping the cup threads.
 
The sound quality of this mod was good except for the bass that was loose. I added a 3 mm modified bass port using masking tape on the external cup vents. This tightened the bass nicely, cleaned up the mids, and revealed more treble details. An alternative approach would be to increase the thickness of the cotton which I will try next. If the modified bass ports sound better than extra cotton, I will transfer the temporary external bass ports to the inside using techniques described and shown in "Better Modified Bass Ports."
 

Temporary Modified Bass Ports using masking tape on the external cup vents. I used a sharp X-Acto blade to open 3 mm width in the center of the lower vent slot.
 
 
 
Beta Testing Various Modification Configurations:
 

 
 
Recently, I treated my main listening room with 48 x 24 x 4 inch panels of Owens-Corning 702 made from compressed fiberglass. 702 is designed for this specific acoustic damping application. The company recommends placing the panels a few inches away from reflecting surfaces instead of directly against ceiling and walls. Creating a gap between reflecting surfaces and the fiberglass panels effectively doubles their absorption. Sound waves pass through the panel, reflect off the wall, and pass back through the panel. 
 
I began experiments to create a "skeleton support grid" in 2012 using a variety of materials. I tried mini plastic coffee stirrers and wooden coffee stirrers from Starbucks, toothpicks, popsicle sticks, and Paxmate, among other materials. I never considered elevating the grid until treating my listening room with Owens-Corning 702. 
 
The following series of photos show some of my current experiments to test a similar application inside our "headphone listening room." I cut strips of 2.5 x 2.5 mm Balsa wood from Michael's Arts and Craft store. I glued them together to create a leveling frame with 2 to 4 mm spaces underneath. Paxmate strips laid on top of the balsa frame create a Paxmate Lattice. I laid the Paxmate such that a 35 x 35 mm recessed cavity aligns with the orientation of the driver when the baffle/driver is placed onto the cup. Within this cavity, I placed cotton cut from a makeup remover pad 35 x 35 mm and approximately 5mm thick. You will see in the following pictures that I also used 35 x 35 x 5 mm Grodan Rock Wool wrapped in gauze. Both materials work. Both mods sound good but not as good as DBV #3. 
 
This mod is still in development and testing. If you test this mod, yourself, please post your results.
 
I plan to change the balsa grid layout by removing the long strips in the cup floor wells, make the spaces between the horizontal balsa strips wider, and see what happens to the SQ.
 
 
More Beta Test Photos:
 

 

Two photos, above:
 
40 x 55 mm gauze-wrapped rock wool taped to driver frame.
Self-adhesive craft felt in the cup floor wells (19 x 70 mm; shorter on left side of left cup due to the jack).
2-layer balsa elevating frame.
Custom-cut pieces of Paxmate in the rear baffle compartments.
Stock felt over inside of cup vents.
No Newplast or plasticine.
No Paxmate Lattice.
 
 

Wrapping rock wool in gauze
 

2-layer balsa frame can be glued with tiny drops of super glue or dabs of hot glue. I've tried both. Hot glue is easier to apply but much more difficult to remove than super glue.
 
...and another:
 

 

 

 

4 photos, above:
19 x 70 mm Paxmate in cup floor wells.
2 layers of Paxmate strips laid at 45 degrees with a recessed cavity for rock wool (or cotton).
Paxmate in rear baffle compartments.
18 mm treble reflector.
Rock Wool.
 
 
Balsa Wood Mod with Paxmate and Rock Wool (Or Cotton)
April 2014
 
Materials Needed:
 
1. Self-adhesive craft felt = 19 x 70 mm for the cup floor wells
2. Balsa wood strips from Michael's Craft Store = 2.5 x 2.5 mm. You can substitute match sticks for craft balsa wood.
3. Grodan Rock Wool 48 x 48 x 5 mm OR Cotton Make-up Remover Pad 48 x48 x 5 mm (try 1 and then 2 layers of cotton)
4. Gauze for wrapping rock wool
5. Paxmate Plus or Silverstone acoustic foam
6. Shure 840 Pads
 
Steps:
 
1. Cut and install self-adhesive felt in the cup floor wells. Notch for clearance around the side shock absorber posts.
2. Build a Balsa Wood Lattice, as shown, to elevate the damping material used (Grodan Rock Wool, Cotton, etc.). The width of the two balsa strips immediately above and below the central compartment = 16 mm. The top space = 7 mm. The lower space = 6 mm. Use super glue or hot glue to connect all the balsa wood strips. This creates 5 to 6 mm spaces between the cup floor and the bottom of the rock wool.
3. Cut Rock Wool = 48 x 48 x 5 mm = 1 gram. Snip off the corner for the jack in the left cup and duplicate for the right cup. I use a sharp, serrated bread knife with a guide to cut slices with uniform thickness. Cotton may work.
4. Wrap Rock Wool with gauze. Trim excess gauze so the the rock wool fits inside the 4 shock absorber posts. 
5. Custom cut Paxmate to fit the rear baffle compartments.
6. Cut off the dust cover directly over the ear side of the drivers for accurate placement of Paxmate Earrings.
7. Make Paxmate Earrings for the ear side of the baffles. Punch out an opening to expose the ear side baffle port. 
8. Install Paxmate Earrings.
9. Install BMD over ear side of the center grid, if desired.
10. Shure 840 Pads.
11. Optional: Remove the entire baffle dust cover, cut and install Dynamat Earrings, and overlay with Paxmate or Self-adhesive Felt Earrings.
 
This mod sounds great, to me. Bass is tight, layered, and digs deep. Mids are clear with no Boomy Base Bloat. Very good treble details. Sound stage is wider than Paxmate Lattice Mod.
 

Self-adhesive craft felt in cup floor wells.
Paxmate in rear baffle compartments.
Stock black felt over internal cup vents remains in place. 
No Cotton. No Newplast or plasticine. No stiff felt. No treble reflectors. No Dynamat.
 

Left cup Balsa Lattice
 

Gauze-wrapped Grodan Rock Wool with corner snipped off to clear jack
 

Balsa Lattice in right cup
 

Gauze wrapped rock wool in right cup with corner snipped to match the left cup
 

Paxmate Earring on ear side of baffle surrounds the driver.
BMD over center grid. Hole punched at the top to expose the baffle port.
Masking tape is used to seal baffle to cup during tuning trials.
 
This mod required no tuning. EDIT: After more listening and comparison with other headphones, I concluded the bass was a bit loose. I made 4 mm wide temporary bass ports on the external cup vents using masking tape, similar to the photo in the Paxmate Lattice Mod, above. The sound is cleaner and bass is tighter while still extending deeply with good slam.
 
EDIT: Here's an elevating support grid made with 3.2 mm strips of balsa. Laying it out on a folded sheet of paper protects the work surface from super glue run off. You can leave out one section in case the wires from the jack to the right cup need to be routed through the grid. The single piece may be glued in place after the grid is positioned on the cup floor.
 
The lower horizontal strip of balsa overlays the second from the bottom cup vent slot. There is a little space between the undersurface of the balsa strip and the second vent slot so the grid will not interfere with venting from that slot. The lowest cup vent slot remains fully open and available for a modified bass port, if needed.
 
Note: The following photos show the balsa grid in a spare cup I use for a template.
 

Assembled balsa grid
 

Balsa grid in cup
 

Here, the 16 mm balsa segment has not been glued to the grid in order to provide an opening for routing the wires from the jack to the right cup. If there is enough slack in the wires, however, this is not necessary. When possible, lay the wires under the grid and around the left side of the central screw compartment. 
 
 
Tuning Rules of Thumb  
 
Various configurations may sound "just right" to you and require no tuning at all. If you decide to tune, make only one tuning tweak at a time to assess its effect on the sound quality. Understand that very small changes in mod components can result in significant changes in sound quality - for better or worse.
 
a. If you want more or less bass and treble, tweak the amount and size of Fiberglass, Cotton, and Treble Reflectors.  Generally: More/Larger/Thicker = more treble, less bass. Less/Smaller/Thinner = more bass, less treble.
 
b. Try your build with the baffle port open vs. closed. Open = less bass. Closed = more upper bass and a bit more lower treble. Making a modified baffle port (ear side of baffle) with masking tape and needle may assist with fine-tuning.
 
c. Punch 2.5 mm holes in the stiff craft felt using a hole punch similar to the ones sold at Michael's. More/Larger holes = more bass.
 
d. If bass is too boomy and bloats the midrange, you can fine tune it by making a modified bass port as described, above, in the DBV #1 Tutorial. Covering more of the cup vents/decreasing the size of the modified bass port reduces bass quantity and should improve bass quality and speed.
 
e. If treble is too "hot," add some cotton or fiberglass over the ear side of the driver, under the Shure 840 pads, to tone it down.
 
f. Adding cotton, foam, or other materials under the pad cushions may increase sound stage and/or angle the pads but at the expense of bass quantity.
 
 
Here are some additional tuning tweaks that may work:
 
g. Thicker stiff felt (or two layers/partial layers) = Less Bass, More Treble. Thinner felt = opposite effect.
 
h. Smaller Treble Reflectors = Less Treble. Larger = opposite effect. My default size for DBV #3 is 18 mm disks installed over the center of the driver (covering the center grid).
 
i. Greater cotton thickness = Less Bass, More Treble. Thinner thickness = opposite effect.
 
j. Fiberglass = Less Bass, More Treble. No Fiberglass = opposite effect.
 
k. Stock cup vents = More Bass. Cover some or all with tape = Less Bass.
 
l. Stock baffle port open = Less Bass. Closed with tape on ear side of baffle = More Bass and lower treble.
 
m. Buy some 3/4" masking tape. Cut 4 segments to go all the way around the cup/baffle rim. Use masking tape to seal baffles to rims during tuning. This prevents stripping the cup threads. Put the small screws in a medicine bottle for safekeeping. Here's how to apply the tape for best tuning: Position the baffle onto the cup. Adjust so it fits properly. Compress the back of the cup and the ear side of the baffle with one hand while you start taping. Put the tape aligned with the edge of the cup. Fold the tape over onto the ear side of the baffle (the rounded area). Repeat with tape slightly over-lapping as you work your way around. Done. Use fresh tape for each tuning tweak. You can expect a little more bass once you seal the baffles to the cups with the 4 screws.
 
n. Buy some GE Silicone II. Apply a bead around the cup/baffle rim.
 
o. Buy some Aleene's Fabric Fusion double-sided tape. Use it as described in Incremental Mods and Measurements. This semi-permanent and will give you a good seal and prevent the Shure 840 pads from slipping off. Use this Only after you are satisfied with your tuning. 
 
p. DBV #3 is tuned specifically for Shure 840 pads. You can use other pads but all bets are off with regard to sound quality. You can stuff cotton or tissue under the pads but at the expense of bass: see Incremental Mods and Measurements.
 
q. Fine Tune and reduce Bass Quantity with a Modified Bass Port at the cup vents = 3 mm opening of just one of the four cup vent slots and covering the other three completely with electrical tape over the inside stock cup vent dampening material. This is described in Incremental Mods and Measurements.
 
r. Increase Bass by reducing the internal dampening materials.
 
s. Increase Bass by punching holes in the stiff felt overlaying some of driver grids. My default for DBV #3 is “No holes” for flater FR and 3mm holes in the stiff felt overlaying the 4 corner grids for slight “bass boost.” Try holes of different sizes for more or less bass.
 
Repairing Stripped Cup Threads 
 
There is a solution for repairing your cup threads. You need a 2 mm (1/16 inch) drill bit and liquid super glue. Super glue gel will not work because it will not "flow" into the tiny holes.
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Drill the cup thread compartments to the depth of the screws. Be careful to Not drill all the way through! Blow out the plastic debris in the screw compartments. Use something to protect your work area from super glue and don't get any on you. It bonds skin to skin and skin to clothing instantly! Use silicone gloves unless you are comfortable working with super glue.
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Add a tiny drop of super glue in a screw compartment and "tamp down" to the bottom of the compartment using a paper clip. Add another drop and repeat tamping. You will need several paper clips because super glue will adhere to them an effectively increase their diameter. Eventually, the paper clip becomes too "thick" and forces the super glue from the compartment. Continue until you think super glue has made contact with the compartment wall, all the way around, and the super glue is filled flush with the top of the compartment. Repeat for each stripped screw compartment. Let it cure for 24 hours. [/size]
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If your super glue has "mounded" above the screw compartment, drilling straight down through the center of the dried super glue will be almost impossible. In this case, use a rotary tool or ordinary file to flatten the top of the dried super glue "mound" flush with the top of the screw compartment. Drill on slow speed with minimal pressure. Drill straight down to the depth of the screws. Don't drill all the way through the cup by accident! [/size]
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Place the baffle on the cup and begin tightening the screws. Go slowly with just enough pressure to cause the screw to "bite" into the cured super glue. You may need to back out 1/2 turn, tighten 1/2 turn, back out again, and repeat until the screw has tapped new threads and the baffle is tightly secured to the cup. [/size]
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Sometimes the super glue will crumble when tapping. If so, it did not fully cure, or dry. In this case, you will have to re-drill, re-fill with super glue, let it cure, and re-tap. When successfully implemented, however, new super glue threads are good for 30 or 40 "mod cycles" as long as you maintain positive pressure to the back of the cup and the front of the baffle whenever tightening or removing the baffle screws. [/size]
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If your large headband hanger screw has stripped the threads of the outer connector (Part #5 on the exploded view), use a plastic covered bread tie. Cut a piece twice the depth of the screw ( ~ 1 cm). Stick it inside Connector 'B' and fold the remainder over the outside of Connector 'B'. Push Connector 'B' into its normal position; it may take a bit of force but it will fit. Then tighten as usual. The screw will "bite" into the plastic/wire of the tie and take up space inside Connector B which will allow you to regain a tight fit.[/size]
[size=12.727272033691406px]
 [/size]
[size=12.727272033691406px]
 [/size]
[size=12.727272033691406px]
Better Modified Bass Ports [/size]
[size=12.727272033691406px] [/size]
[size=12.727272033691406px]If you need to tighten up the bass, make a Modified Bass Port. Here's a better way that is much easier to make and install permanent Modified Bass Ports :[/size]
[size=12.727272033691406px] [/size]
[size=12.727272033691406px]Find some thin, stiff card stock and cut out rectangles 20 x 25 mm. Punch holes for desired size.[/size]
[size=12.727272033691406px] [/size]
[size=12.727272033691406px]A4.[/size]
[size=12.727272033691406px]
 
Michael's Craft Store Variable Hole Punch and Standard Paper Hole Punch.
[/size]
[size=12.727272033691406px] [/size]
[size=12.727272033691406px]B4.[/size]
[size=12.727272033691406px]
 
4 x 1.5 mm Bass Port (L) and 5 x 1.5 mm Bass Port (R)
[/size]
[size=12.727272033691406px] [/size]
[size=12.727272033691406px]1. For 4 x 1.5 mm Bass Ports, measure 4 mm from the bottom and 10 mm from side to side.[/size]
[size=12.727272033691406px]2. Punch a 4 mm hole using a variable hole punch similar to the ones sold at Michael's Craft Store.[/size]
[size=12.727272033691406px]3. Glue over the stock black cup vent felt with the punched hole near the bottom of the vents.[/size]
[size=12.727272033691406px] [/size]
[size=12.727272033691406px]C4.[/size]
[size=12.727272033691406px]
 
4 x 1.5 mm Modified Bass Port over inside cup vent felt.
 
D4.

 
External view of 4 x 1.5 mm Modified Bass Port. The Stock black cup vent felt has been removed from the vents. Once installed, the Modified Bass Port will not show because it will be installed behind (over) the cup vent felt on the inside.
[/size]
[size=12.727272033691406px] [/size]
[size=12.727272033691406px]1. For 5 x 1.5 mm Bass Ports, measure 3 mm from the bottom and 9 mm from side to side.[/size]
[size=12.727272033691406px]2. Punch a 5 mm hole using a standard paper hole punch.[/size]
[size=12.727272033691406px]3. Glue over the stock cup vent felt with the punched hole near the bottom of the vents.[/size]
[size=12.727272033691406px] [/size]
[size=12.727272033691406px]E4.[/size]
[size=12.727272033691406px]
 
5 x 1.5 mm Modified Bass Port.
 
F4.

 
External view of 5 x 1.5 mm Modified Bass Port.
[/size]
[size=12.727272033691406px] [/size]
[size=12.727272033691406px] [/size]
 
Naked Driver Mod Improved
 
"Naked Drivers" have had their stock white damping material removed from the back of the drivers. Naked Drivers are too under-damped so bass is excessive, out of control, and so bloated it messes up the mids and covers up the treble frequencies. I posted the "Naked Driver" config, with graphs, that worked best for me in Post # 244 of this thread. I had to use two layers of stiffened craft felt without any holes to make the drivers behave. This mod configuration measures and performs very close to DBV #3. Here's the configuration: 
 
Initial Build Steps:
 
1. 2 layers of Michael's Craft Store stiffened craft felt, each measuring 45x52x1.5mm, notched for clearance of all 8 driver mounting screw heads, stacked, and secured with 3M Removable double-sided craft felt.
 
2. 20x25 rectangular thin card stock treble reflector centered over the back of the driver and secured under the stiffened craft felt with thin strips of 3M double-sided tape.
 
3. 1x7x7.5 cm compressed J&M fiberglass = 1.3 grams.
 
4. 1.5x7x7.5 cm Rite Aid Natural Absorbent Cotton = 1.4 grams, under the fiberglass. As a substitute, use "Prepared" layers of Rite Aid First Aid Rolled Cotton 2x7x7.5 cm = 1.8 grams OR 4 to 6 Rite Aid First Aid cotton balls as described near the bottom in Post #1 of this thread.
 
5. Acoustipack Lite (or Paxmate or Silverstone) 2x7 cm trimmed to fit the side cup floor "wells."
 
6. Newplast (or non-drying plasticine) flush loaded baffle compartments = 9 grams of Newplast.
 
7. Stock cup vent felt intact.
 
8. Stock Open baffle ports.
 
9. Shure 840 pads.
 
 
T50RP Wave Guides AKA Phase Plugs
December 2014
 
Go to your local art or craft store and look for 1/16" x 1/16" basswood strips and 1/16" x 1/8" basswood strips. Bass wood is more dense than balsa wood and easier to work.
 
Use an X-acto Knife to remove the ear side dust cover that overlays the driver. Set it aside because you will want to re-install it using rubber cement.
 
Score the driver cross-members on each side, as shown, and then snip them off with wire cutters. Apply maksing tape over the drivers to prevent plastic debris from fouling the inside of the driver compartment.
 
Cut lengths of each basswood width to span the driver frame, as shown. Use super glue to attach them, edge to edge, and clamp to cure. This creates perfect fit wave guides with equilateral sides. Sand the ends to fit within the driver frames with a little extra length to friction mount in place. Use E6000 glue to permantently secure them in place. Make sure the wave guides do not overlay the driver openings (2mm diameter holes). Also make sure none of the E6000 glue runs into the driver holes.
 
Cut pieces of 1/16" x 1/16" basswood for the two inner dividers and the far left and right sides of the driver frame. Secure them in place using E6000.
 
The wave guides increase efficiency by 2 dB. The sound is improved with better clarity and imaging. The treble is opened up a bit, too. 
 
Note: These wave guides are installed on the ear side of the drivers, only. The rear side damping paper interferes with installation of wave guides. IF you have removed the rear side stock damping paper, you can try installing wave guides in combination with your other mods. I have not tried this configuration.
 
 

Dimensions to consider when making your 3D Printed
or DIY Wave Guides.
 

Basswood pieces joined, edge to edge and glued in place.
 

2 Wave Guides
 

Wave Guides glued and clamped for curing.
 

Driver cross-members have been snipped off.
 

Finished wave guides mounted and glued in place.
 
 

Ear side dust cover re-installed.
 

Masking tape to prevent debris from entering the driver compartment when snipping off the cross-members.
 

Finished and installed wave guides.
 

 
 
T50RP 3D Printed Wave Guides by SeEnCreaTive
January 25, 2015
 
The Wave Guides fit after a little bit of sanding to the bottom of the main frame. Shapeways.com added 1.5 mm to the base in order to 3D Print them. Place a sheet of 200 grit sandpaper on your work bench surface. Lightly sand the undersurface of the main frame by ~ 1.5 mm. Finish with 320 grit sandpaper until the top of the main frame is level with the top of the 3 single guides mounted on the magnets.
 
I used an X-Acto knife with a fresh blade to separate the pieces. Be sure you don't accidentally slice into the Wave Guides. They are a bit rough so I sealed them with 2 thin coats of clear nail polish. I also sanded off the outer ends of the frame on the 2 narrow sides for a better fit.
 
Using my X-Acto knife, I scored and then snipped-off the ear side driver grids in the longitudinal orientation using crosscut soldering snips. Be careful of debris that may fall into the driver diaphragm compartment. I had to use a vacuum cleaner to suck out a couple of pieces of the snipped driver grids. If you score both sides of the grids, they come off easily when snipped.
 
Carefully place and center the 3 single Wave Guides directly onto the magnet frames and glue them in place. I used Bondic glue that’s activated by its ultra-violet LED. This works great for a clean, permanent attachment to the ear side of the drivers.
 
If you remove the dust cover and the mesh underlay material from the ear side of the driver with care, you can re-install the mesh over the Wave Guides once they are glued in place. This will prevent debris from getting into the driver diaphragm compartment.
 
Attached are Before and After ARTA graphs:
All Stock T50RP
All Stock T50RP with Shure 840 pads
With and Without Wave Guides
 
To my ears, Wave Guides improve imaging and they increase sensitivity by ~ 2 dB. Draw your own conclusions from the graphs but understand that graphs don’t tell the whole story. Let your ears be the judge. For about $10.00 including shipping, they’re worth a shot.
 
  
One Wave Guide. Use X-Acto Knife to separate 3 singles
from the main frame.
 

3 singles glued in place. I used Bondic Ultra-violet glue
but hot glue should work just fine.
 
  
Main frame glued in place
 

 
  
Finished with mesh dust cover glued in place
 

 
 
About the Graphs
 
The following graphs were made with ARTA, a professionally calibrated Dayton EMM-6 mic in a dummy head, Windows 7 PC, calibrated Steinberg UR-22 USB interface with Yamaha ASIO, and line out to Dacmini. 
 
These graphs are "raw" and uncompensated. The dip between 1 kHz and 6 kHz is an artifact of my measurement rig. While there is a natural and desirable dip in this area, the graphs do not reflect what is actually heard from those frequencies. Compensation would make them look better but is not necessary if you compare them to the "T50RP All Stock with Stock pad" graphs. The bump between 100 Hz to 250 Hz is unique to Shure 840 pads. Both of these frequency ranges can be improved with modification and tuning.
 
You cannot compare these graphs to anyone else's graphs. Compare them relative to one another, only, because each measurement rig and configuration, setup parameters, and methods vary.
 

All Stock T50RP with Stock Pad.
This is the baseline for interpreting the Wave Guide
 and Shure 840 pad graphs.
 

CSD of T50RP All Stock with Stock Pad 
 

T50RP All Stock with Shure 840 Pad
 

CSD for T50RP All Stock with Shure 840 pad 
 

T50RP All Stock with Wave Guides and Shure 840 pad
 

CSD for T50RP All Stock with Wave Guides and Shure 840 pad 
 
 
T50RP Incrementally Mass Loading the Baffles 
February 2015
 
Shure 840 Pads
Shure 840 Pads and Dynamat Xtreme on the Ear Side of Baffle
Shure 840 Pads and Dynamat Xtreme on the Ear Side of Baffle with Paxmate Plus Overlay
Shure 840 Pads, Dynamat Xtreme on the Ear Side of Baffle and Paxmate Plus Overlay, and Homemade Tungsten Putty in the Rear Baffle Compartments
 
  
Tungsten Putty
 
  
Tungsten Putty in Rear Baffle Compartments
 
 
Ear Side Baffle Dust Cover Sanded Off
 

Dynamat Xtreme on Ear Side of the Baffle. Firmly
roll it flat with an AA Battery "rolling pin."
 

Paxmate Plus Overlays Dynamat Xtreme on Baffle
 
 

 

 

 

 

 

 
 
These graphs suggest that distortion may be improved by mass loading the baffles. In this series of experiments, a combination of Dynamat Xtreme with Paxmate Plus overlay on the ear side and Tungsten Putty in the rear baffle compartments worked best. Similar results may be achieved with other materials such as Silverstone acoustic foam and Newplast or plasticine. 
 
Note that these measurements represent the effects of mass loading the baffles of an All Stock T50RP with SenEnCreaTive Wave Guides and Shure 840 pads. No tuning modifications were implemented. Add your favorite tuning mods for good sound and lower distortion.
 
 
Crossfeed Filters
 
Crossfeed circuits may improve the stereo imaging by modifying hard panned Left Channel and hard panned Right Channel recordings. Depending upon the caps and resistors used, a portion of the Left Channel is blended with the Right Channel main signal and vice versa. 
 
 
I made the Simple XFeed from rock grotto (Jan Meier's Bass Enhanced Lite version), added the 4PDT switch, and mounted it in a Hammond aluminum enclosure with ground from the circuit to the enclosure. It sounds weak...thin, closed-in, attenuated bass, and attenuated treble + much less efficient than in stereo mode but not surprising given its simplicity.
 
Next, I made CMoy's Modified Linkwitz XFeed in 4 variations:
 
1. Original design with 150 and 200 ohm switchable XFeed with Bypass
2. 100 and 150 ohms
3. 150 and 260 ohms
4. 100 and 200 ohms
 
#1 sounds best to me. Minimal efficiency loss, minimal treble loss, no bass loss, no detrimental effects in the mids. The overall effect is subtle but it's designed that way. It's really noticeable with tunes that have hard panned Left and Right tracks by moving the sound stage in, up, and a bit forward. There's not much difference between 150 and 200 ohm settings. I think I'd be happy with 200 omh resistors  and no need for a "Perspective" switch.
 
100 ohms effects is not discernible...just too little XFeed to perceive a difference so that knocks out #2 and #4, for me.
 
260 ohms is too narrow and the loss of treble and overall efficiency is more noticeable, so No Deal.
 
I think I will remove the 260 ohm R's in #3 and substitute 220 ohm R's.
 
I am interested in the Alternative XFeed Circuit and plan to compare them to Frans' XFeed and Meier's Corda Cross-1 XFeed; PCBs and components are on the way.
 
 
CMoy's Modified Linkwitz Crossfeed Filter Schematic (Click for link)
 
 
Here's my Low-Z Version:
 
 
The Right Channel is a "mirror image" of the Left Channel.
 
The Black Rectangle at the bottom shows the common ground for the 100 Ohm resistors (2) and the 1.2 uF caps (2), as well as the ground wires to the RCAs. 
 

Frans' and CMoy's XFeed Filters
 
 
 
 

Fran's Crossfeed Filter (Click for link)
 
 



 
 
 
 
Jan Meier's Corda Cross-1 Schematic (Click for link)
 

 
 
 
Jan Meier's Corda Cross-1 Diagram built on a Radio Shack 2 x 6 inch "Experimenter Printed Circuit Board"
 

 

 
*****************************************************************************************
 
 
"There are many paths leading to the same destination." 
 
 
*********************************************************************************************************************************
 
DIY Measurement Acknowledgements
 
All the credit goes to 'symphonic' and Room Equalization Wizard (REW) for bringing DIY measurements to the masses.
 
Contributions by micmacmo, Arleus, wdahm519, Ardilla, Cortlendt, geetarman, nick n, and wje - all active on the T50RP modding thread.
 
BMF
July 2012
 
Jul 15, 2012 at 9:12 PM Post #2 of 2,874
Wow. Awesome.
 
Jul 15, 2012 at 10:02 PM Post #5 of 2,874
If these are the same mods that was done to my BMFs  Then I must say WOOT  WOOT  they most definitely worked.  A tip of the hat goes out to Keith and all his hard work.  
 
Keith, I'm working on a write up now on some compressions I did over the weekend.  All I can say is the competition does not start until you get to the 1K range.
 
beerchug.gif

 
Jul 15, 2012 at 10:35 PM Post #6 of 2,874
Keith, You've done an astounding amount of work to collectively walk through the build process and test the various combinations of modifications to show the benefits and the perils of each.  This is really, really great stuff !!!  I loved the old thread because I could learn something each day.  Now, we have another T50RP thread that seems like it will be focused on the BMF recognized items for modifying the Fostex headphones.  I still need to slow down for a second myself and finish setting up the box so I can take some measurements and contribute, too.  
 
Jul 16, 2012 at 12:42 AM Post #8 of 2,874
Wow. This might be the single best contribution to the T50RP DIY modding community. It's a breathtaking amount of work. Thanks, BMF!

For us completists, could you include graphs for one of your gold-standard phones? And you seem to get respectable results without any cup filling. How did those sound?
 
Jul 16, 2012 at 8:52 PM Post #13 of 2,874
Thank you BMF for all your hard work on this.  You have taken the T50-RP thread, and just took this thing as far as anyone has taken.
 
Your enthusiasm and curiosity has made this T50-RP modding piece great for curious modders, as well as people looking for great sound quality for a reasonable price.
 
Thank you once again.
 
BTW, I have three sets of T50-RP.  One bass heavy, one bass-light, and one for my brother.
 
Jul 16, 2012 at 9:21 PM Post #14 of 2,874
My friends,
 
I'm happy to hear that my contribution to the community is helpful and interesting. Thank you all for your feedback, props, and suggestions. My intention, however, was not to start a new thread to toot my own horn or pull anyone away from the T50RP mod thread. I started this thread because I did not know how the headfi system would handle such a large file upload. I figured if it crashed, failed, or otherwise caused any problems at least it would not make problems for the "Mother Thread."
 
Several forum members have PM'd me and asked if I will include the associated waterfall plots. I will work on doing so over the next few days. I think this is a good idea because waterfalls add another dimension to understanding the effects of each mod in isolation and in combination with other components. Based on my experiments, "the sum is truly greater than its individual parts." I will, however, leave the interpretation, conclusions, and continuing mod experiments to each reader.
 
Please share what you learn and discover with the community. Doing so helps the forum thrive, keeps it interesting, and makes it fun for all.
 
BMF
 
Jul 16, 2012 at 9:24 PM Post #15 of 2,874
Quote:
ambchang said:
Thank you BMF for all your hard work on this.  You have taken the T50-RP thread, and just took this thing as far as anyone has taken.
 
Your enthusiasm and curiosity has made this T50-RP modding piece great for curious modders, as well as people looking for great sound quality for a reasonable price.
 
Thank you once again.
 
BTW, I have three sets of T50-RP.  One bass heavy, one bass-light, and one for my brother.
Click to expand...

 
Sweet! As you and many of us have discovered, these humble headphones can be easily modded and tuned to rival commercial products costing much, much more.
 
Thanks so much.
 
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