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Fostex T50RP Incremental Mods and Measurements - Page 42

post #616 of 1215

Lateralus is a phenomenal album. Maynard is an amazing artist.

post #617 of 1215
Thread Starter 
Quote:
Originally Posted by jasonb View Post

How much would you say it costs?

 

I'm not sure it would benefit me any at this point though. I have them dialed in to where I want them, and I doubt seeing a measurement would make me change anything about them.

 

I really should be sleeping right now, I have work early in the AM, but I don't want to stop listening. L3000.gif 

All information for building a measurement kit and setting up REW is available in Incremental Mods and Measurements.

 

Mic: 

$4 for Panasonic WM-61A electret mic capsule (available on ebay) or $2.28 for its replacement - POM 3535L-3-R from Digi-key. Their perfomance is a little different but it's all relative.

$2 for Radio Shack Female RCA plug

$1 (approx) for some 19-strand silver coated 26 gage hookup wire (2 colors needed and must buy 25 feet of each for $6 each; or use what you have on hand)

$1.50 for Etymotic triflange IEM tip

$? for helping hands clamp or vise

$? for J&B epoxy to seal the back of the mic solder joints; just need a tiny bit

 

Phantom Power Supply (may not be needed if your sound card provides 2 to 10 volts of phantom power:

Schematic See Post 101. Substitute 3.5 mm TRS (Stereo, only, for REW) jacks for the RCA and 1/4" TRS plug shown)

$6 for 2, 3.5 mm TRS jacks from Digi-key

$4 (approx) for resistors and capacitors (Digi-key, Mouser, or Radio Shack)

$3 for Radio Shack universal PCB; less for bread board; nothing for point to point

$? Radio Shack 24 gage hookup wire (3 colors)

$? for solder

$? for soldering iron

$? for tin box for mounting and grounding the phantom power supply

 

Interconnects (Radio Shack or Amazon):

$? for 2, 3.5 mm TRS to 3.5 mm TRS cables; 2 used for calibration; 1 used for phantom OUT to Sound Card IN

$? for a 3.5 mm TRS to Male RCA splitter cable; only on Male RCA used to connect Female RCA from the mic and the 3.5 TRS to Phantom IN

 

Software:

REW - Free

FuzzMeasure - Try for free, buy for $150

Others available - Google it

post #618 of 1215
Quote:
Originally Posted by bluemonkeyflyer View Post

Beautiful!

 

Mind sharing your BOM?

 

Sent you an email, will be doing the next round of mods and if I'm satisfied, I'll post the BOM and see if I can get them measured. 

post #619 of 1215
Thread Starter 
Quote:
Originally Posted by Armaegis View Post

Didn't I send you baffles with it? I thought I put them along with all the screws in a ziploc bag. 

Yep! LOL I found them in one of my T50RP boxes with a bunch of other parts. I'll transplant them back into my "Naked Driver" T50RP's.

 

In other news, the "CopperHeads" you sent me now have new T20RP mk2 drivers installed. They look slick. Thank you!

 

I had a heck of a time getting the stock copper wire "pigtails" to take up Kester eutectic solder. In case anyone is interested, here's how I was able to make the connections:

 

I tinned each end of 4-cm lengths of 26 gage 19-strand silver coated copper wire (from navships on ebay).

Made a loop, or hook, at each tinned end using small needle-nose pliers.

Tinned the stock copper wires from the jack in the left cup and the wire in the right cup the best I could (which was not much!).

Linked the hooks and compressed them with needle-nose pliers for a firm mechanical connection.

Cleaned and pre-tinned my iron.

Soldered the mechanical connections.

Insulated with liquid electrical tape (from Amazon).

 

BTW, I accidentally severed the wires from the solder pads on one of the drivers. I had no trouble soldering pre-tinned 19-strand wire directly to the solder pads using Kester eutectic solder. I put a tiny dab of Radio Shack flux (didn't have the good stuff but this works) on each pad and the tinned wire. I taped the wire in position on the pads, pre-tinned my solder iron, and set the temp at 550 degrees F. It took about 2 seconds. Anyone trying this should be careful to get in and get out Fast or risk burning a hole through the diaphragm at the solder pads.

 

I'm modding them with a Grodan Rock Wool variation. The initial build has a lot of bass and it's good quality bass, to boot. The mids are where I want them. I will tune for a little more treble emphasis.

 

Pictures to follow.


Edited by bluemonkeyflyer - 5/24/13 at 8:57am
post #620 of 1215

For those curious, here are the "Copperheads" before I sent them to BMF...

 

Warning: Spoiler! (Click to show)

 

copper hammertone paint

 

1000

 

the colour looks different depending on the light

1000

 

and sprayed rubber inside and on the baffles

1000

 

 

It took almost a week for the thing to dry properly, but I did put on a ridiculously thick coat of paint to get that textured look. Here's hoping it doesn't chip off blink.gif

post #621 of 1215
Quote:
Originally Posted by bluemonkeyflyer View Post

Yep! LOL I found them in one of my T50RP boxes with a bunch of other parts. I'll transplant them back into my "Naked Driver" T50RP's.

 

In other news, the "CopperHeads" you sent me now have new T20RP mk2 drivers installed. They look slick. Thank you!

 

I had a heck of a time getting the stock copper wire "pigtails" to take up Kester eutectic solder. In case anyone is interested, here's how I was able to make the connections:

 

I tinned each end of 4-cm lengths of 26 gage 19-strand silver coated copper wire (from navships on ebay).

Made a loop, or hook, at each tinned end using small needle-nose pliers.

Tinned the stock copper wires from the jack in the left cup and the wire in the right cup the best I could (which was not much!).

Linked the hooks and compressed them with needle-nose pliers for a firm mechanical connection.

Cleaned and pre-tinned my iron.

Soldered the mechanical connections.

Insulated with liquid electrical tape (from Amazon).

 

BTW, I accidentally severed the wires from the solder pads on one of the drivers. I had no trouble soldering pre-tinned 19-strand wire directly to the solder pads using Kester eutectic solder. I put a tiny dab of Radio Shack flux (didn't have the good stuff but this works) on each pad and the tinned wire. I taped the wire in position on the pads, pre-tinned my solder iron, and set the temp at 550 degrees F. It took about 2 seconds. Anyone trying this should be careful to get in and get out Fast or risk burning a hole through the diaphragm at the solder pads.

 

I'm modding them with a Grodan Rock Wool variation. The initial build has a lot of bass and it's good quality bass, to boot. The mids are where I want them. I will tune for a little more treble emphasis.

 

Pictures to follow.

 

Just a thought or two. Has anyone ever tried using the silver powder imgregnated conductive epoxy for driver solder pad repairs? Or match solder for that matter?

post #622 of 1215
Thread Starter 
Quote:
Originally Posted by Hutnicks View Post

Just a thought or two. Has anyone ever tried using the silver powder imgregnated conductive epoxy for driver solder pad repairs? Or match solder for that matter?

I haven't tried silver powder epoxy. I have successfully used window defogger conductive paint wje described.
post #623 of 1215

Version 2 finished, going to hold off on further work until I get the exterior sanded and painted. Will do some further tuning and hopefully measurements afterwards. It's similar in many ways to core of what BMF has so much hard work into perfecting.

 

==

 

Build is as follows:

 

1. Dynamat (or GTMAT, etc.) on ear side of baffle and entire interior of cups (covered all of the vents), including the outside "rings" of both to decouple interactions

2. Custom machined "braces" glued on to stiffen baffles and cups

3. Dremeled out all of the asymmetrical posts, shock absorbers, etc. for a more uniform smooth cup interior; filled in all of the holes with wood putty

4. Paxmate (or Silverstone, etc.) lining driver side of baffle and over the Dynamat in the cups

5. Drilled a new bass port in bottom of each of the cups (also added mono jacks for detachable, dual-entry cables, but this isn't sound-related)

6. Uniformly "fluffed" cotton behind the driver (currently testing how much cotton is desirable for tuning, if any at all; this will be dependent on individual tastes)

Other: Using Shure 840 pads at the moment, but will hopefully have a pair of Dog Pads to test (and retune for) shortly, as they look like fatter, bigger 840 pads. Also using a Paradox-inspired suspension headband made from a luggage strap. 

 

==

 

Fairly simple in theory, with a heavy emphasis on vibrational damping. I wonder if cotton (or fiberglass, rock wool, etc.) will actually even be necessary depending on how I want it tuned. Perhaps unrealistically, I am trying to extract a bigger soundstage out of these, something closer to what I'm getting with my Magnums.

 

I think with the extraordinary progress BMF has made on testing and documenting the mods, we're at a point where the minor changes in damping material implementation and choice are roughly equal in performance and substitutable based on taste, so the biggest limiting factor now is just the cups themselves, the relatively crappy material choice, and resonances. For now, I've stopped short of machining new cups entirely, so hopefully the braces will have some kind of measurable effect. Now to get that measurement rig set up...


Edited by tintin220 - 5/26/13 at 7:54am
post #624 of 1215

Promising results with the use of additional bracing, but since that is neither trivial to make nor practical to do for most DIYers, I'm looking into another approach that can give similar (or hopefully, much better) benefits and can also be easily replicated by anyone who wants to try it. Just ordered another pair (uh oh, I think I've been sucked in to this madness!) and some parts, and I'll report back on the methods/build if the new approach works well. 

post #625 of 1215
I just finished my modand they sound amazing. But I have two question. It seems like there are less midrange and I'd like to increase it, and I want to know whst's the effect of the felt over the driver on the cup side. I'll glad if someone help me to lnow about this questions.
post #626 of 1215
Thread Starter 

Armaegis kindly sent me T50RP cups painted in hammered copper. I transplanted a set of T20RP mk2 drivers, cabled them with a detachable mini-single-sided stereo jack, and taped on FA-003 pads.  I call them "CopperHeads."

 

 

  

post #627 of 1215

Looking Good! was hoping those would find some use! I really dig that hammered paint.


Edited by nick n - 5/27/13 at 10:18pm
post #628 of 1215
Thread Starter 
Quote:
Originally Posted by tintin220 View Post

Version 2 finished, going to hold off on further work until I get the exterior sanded and painted. Will do some further tuning and hopefully measurements afterwards. It's similar in many ways to core of what BMF has so much hard work into perfecting.

 

==

 

Build is as follows:

 

1. Dynamat (or GTMAT, etc.) on ear side of baffle and entire interior of cups (covered all of the vents), including the outside "rings" of both to decouple interactions

2. Custom machined "braces" glued on to stiffen baffles and cups

3. Dremeled out all of the asymmetrical posts, shock absorbers, etc. for a more uniform smooth cup interior; filled in all of the holes with wood putty

4. Paxmate (or Silverstone, etc.) lining driver side of baffle and over the Dynamat in the cups

5. Drilled a new bass port in bottom of each of the cups (also added mono jacks for detachable, dual-entry cables, but this isn't sound-related)

6. Uniformly "fluffed" cotton behind the driver (currently testing how much cotton is desirable for tuning, if any at all; this will be dependent on individual tastes)

Other: Using Shure 840 pads at the moment, but will hopefully have a pair of Dog Pads to test (and retune for) shortly, as they look like fatter, bigger 840 pads. Also using a Paradox-inspired suspension headband made from a luggage strap. 

 

==

 

Fairly simple in theory, with a heavy emphasis on vibrational damping. I wonder if cotton (or fiberglass, rock wool, etc.) will actually even be necessary depending on how I want it tuned. Perhaps unrealistically, I am trying to extract a bigger soundstage out of these, something closer to what I'm getting with my Magnums.

 

I think with the extraordinary progress BMF has made on testing and documenting the mods, we're at a point where the minor changes in damping material implementation and choice are roughly equal in performance and substitutable based on taste, so the biggest limiting factor now is just the cups themselves, the relatively crappy material choice, and resonances. For now, I've stopped short of machining new cups entirely, so hopefully the braces will have some kind of measurable effect. Now to get that measurement rig set up...

The minor changes you mention? "Take anyone's mod configuration and make your own" by tuning to suit your preferences and audio chain. 

 

After removing the shock absorbers, I think you'll have to devise another method for de-coupling the cups from the baffles. I suspect decoupling is important to control resonance from "shared mechanical vibration" while maintaining a complete cup-to-baffle seal.

 

I'm really curious about your bracing technique and glad to see you're building a measurement rig. 'solderdude' recommends ARTA over REW. I think I'll buy Crossover windows emulator recommended by ARTA and give it a try. Take a look at solderdude's  Phantom Power amp schematic. It's much quieter than the one I originally used. His circuit does not pick up heart beats as does the other. The link to his schematic is in Post #1 of this thread, near the top, I think.

post #629 of 1215

On decoupling baffle from cups:

I basically filled the cups and baffle outer rings with GTMAT butyl rubber, but removed the aluminum foil so it's basically a mess of black goop. The best thing about this is that it adds vibrational damping and decoupling of the two, while at the same time, providing a complete and total hermetic seal (fancy terminology LFF used that basically just means air tight). The bad thing is when you try to remove the baffle for additional modding, you're in for a fight... this stuff holds tight and is sticky/stretchy. 

 

==

 

On DIY-friendly cup/baffle stiffening:

In short, my new idea is that instead of using the braces, to apply a thinnish layer of some kind of steel reinforced epoxy putty over all of the Dynamat on the cup interiors. This would form an extremely rigid (more stiff than aluminum in fact) inner cup, which is sandwiching the Dynamat as well. In theory, the two cup shells (epoxy inner, stock plastic outer) with vibrational dampener in between should be extremely effective, probably more than the bracing I used. It would also be accessible to anyone to try for all of the $8 it costs for a bar of QuikSteel (from memory, SteelStik doesn't adhere to plastic so that's a no-no). 

 

Baffles could benefit as well by placing some Dynamat in the wells, and then filling in the rest of the holes with QuikSteel. After this, cover all the QuikSteel with Pax/Silverstone. I've got a bar coming in from Amazon tomorrow, but I probably won't have time to give this a try until the weekend at the earliest. If anyone wants to give this a shot before I do, please feel free to post.

 

==

 

On bass port sizing:

Somewhat unrelated, I tried to calculate what would be the optimal bass port size. While everyone's tastes will vary, what doesn't vary is the system's "optimal" port tuning frequency and resonances and there is a mathematically "ideal" size/design for the port to properly tune the system (to avoid too little or too much "one-note" bass). Since my design variation calls for a new port drilled and a complete closing of the rear vents, I approached this as I would when building a vented speaker; of course, this happens to be.... totally unconventional from the volume of the enclosure to the shape, material, and driver type. 

 

Ultimately, I came up with a respectable range being two to five 1/16" holes (fewer = less bass)... Yes, that is a large range, but it shows how difficult my guesstimation had to be to try and adapt speaker building principles. I am definitely NOT a basshead, but I do appreciate a good amount of it, and more importantly, clarity and tightness, and so I'm pleased that I can't hear any obvious port resonance or notes overpowering the rest. Again, in theory, it doesn't really matter where the ports are located, so I put them "down-firing". 

 

 

EDIT: Reorganized for ease of reading. 


Edited by tintin220 - 5/28/13 at 11:07am
post #630 of 1215

Hopefully I can build the measurement rig within the next two weeks, but with my apartment lease still delayed due to unexpected renovation issues, that'll have to wait until I get settled in. I am curious myself to see the FR of how I tuned them, but I'm more interested in seeing the spectral decay.

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