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Fostex T50RP Incremental Mods and Measurements - Page 4

post #46 of 1874
Thread Starter 

I uploaded 6 new graphs to the database: BMF DBV #2, a slight variation to BMF DBV #1.

post #47 of 1874

The greatest source of info on modding T50s for sure. Big thanks to you BMF!

 

Insane extension on the DBV 2!

The only thing I did not really get about the mod is about cup bass ports: Are they completely closed or completely open (only felt cover)?


Edited by Nevod - 7/31/12 at 1:58am
post #48 of 1874
Thread Starter 
Quote:
Originally Posted by Nevod View Post

The greatest source of info on modding T50s for sure. Big thanks to you BMF!

 

Insane extension on the DBV 2!

The only thing I did not really get about the mod is about cup bass ports: Are they completely closed or completely open (only felt cover)?

 

Thanks, everyone. I'm happy to hear this database is helpful.

 

DBV #2 does not have a modified bass port. Instead, the stock black cup vent felt remains in place inside the cups, covering the four cup vent slots. The small stock baffle ports are sealed with tape, or you could use silicone, on the ear side of the baffles. Transpore covers more of the stiff craft felt over the back of the driver in DBV #2 compared to DBV #1.

 

The differences in these two mods demonstrate that every mod must be individually tuned - even when following the same mod configuration, using the same materials, by the same person. That's why I say, "You must take anyone's mod configuration, implement it, and 'make it your own' by tuning to achieve the sound quality you like best."

post #49 of 1874

Those DBV2 measurements are insane! That's about the flattest FR graph I've seen -- Kudos! I'm going to have to crack mine open again and give this a shot. What kind of fiberglass are you using -- just standard home insulation? Hopefully this new version will be added to the wiki soon though you've detailed here quite well. Thanks Keith!!

post #50 of 1874
Thread Starter 
Quote:
Originally Posted by AnotherN00b View Post

Those DBV2 measurements are insane! That's about the flattest FR graph I've seen -- Kudos! I'm going to have to crack mine open again and give this a shot. What kind of fiberglass are you using -- just standard home insulation? Hopefully this new version will be added to the wiki soon though you've detailed here quite well. Thanks Keith!!

 

 

700

 

I bought this fiberglass at Lowe's for $4.00. This is what I used in the DBV #1 and #2 mods.

 

I bought some Owens-Corning Pink fiberglass in a similar size roll for $6.00. 

 

Comparing the two, the JM fiberglass expands to its full 2 inches once taken out the bag. The Owens-Corning fiberglass expands between 1 inch and 1.5 inches. I have not tried the Owens-Corning. It may work, but I know the JM fiberglass works.

 

Note that after I built both mods, I tweaked 30 or 40 mod cycles to find the SQ I wanted. "There are no slam dunks" even if you follow the mod configuration "to the letter."  A reference headphone (I use my LCD2 v1) and a measurement kit are essential *for me* since I am an amateur with no mastering or technical training.

 

Best wishes to all for a successful mod!

post #51 of 1874

Man, This Thread ROCKS...

 

Thank you sooooooo much.

 

Jim

post #52 of 1874
Thread Starter 
Quote:
Originally Posted by AstroTurf View Post

Man, This Thread ROCKS...

 

Thank you sooooooo much.

 

Jim

L3000.gif + beerchug.gif   to all.

post #53 of 1874
Cheers mate!
post #54 of 1874
Thread Starter 

I uploaded 18 new graphs to the database. Go to Post #1 of this thread and scroll down to the bottom.

 

DBV #2 with Stock T50RP Pads, Left and Right Channels: SPL FR, Waterfall Plots, and Spectrograms

 

DBV #2 with Inner Tube Modded FA-003 Pads, Left and Right Channels: SPL FR, Waterfall Plots, and Spectrograms

 

DBV #2 with Taped on FA-003 Pads, Left and Right Channels: SPL FR, Waterfall Plots, and Spectrograms

 

Party On,

 

BMF


Edited by bluemonkeyflyer - 8/1/12 at 5:45pm
post #55 of 1874
Thread Starter 

Everyone, Thank you for your comments, feedback, and "Thumbs UP's."

 

This is a "Labor of Fun" for me. If the database is helpful to anyone, Bonus!

 

BMF

post #56 of 1874
Thread Starter 

You can learn to use REW without making any measurements by downloading REW and various .mdat data files. For those without a measurement kit who want to view and compare selected mods/measurements using REW, I uploaded three new Google Documents (REW .mdat files 3, 4, and 5) to the database:

 

 

1.Main data set 1 .mdat data files:

https://docs.google.com/open?id=0B5ZWXtWdNv9UczQtX3lxUW1CWnM

 

2. Main data set 2 .mdat data files:  

https://docs.google.com/open?id=0B5ZWXtWdNv9UblZtWjlISjYxSm8

 

3.  DBV #1 and #2 .mdat files:

 https://docs.google.com/open?id=0B5ZWXtWdNv9UYTBUZHRFTXZZSzQ

 

4.  Stock T50RP - T40RP - T20RP measurements with Etymotic Foam and Triflange mounted microphones .mdat files:

https://docs.google.com/open?id=0B5ZWXtWdNv9URmRSLW5mN0Vzblk

 

5.  DBV #2 with Taped on FA-003 Pads - T50RP Pads - Inner Tube Modded Pads .mdat files:

https://docs.google.com/open?id=0B5ZWXtWdNv9UWlcyeXVFbU1XblE

post #57 of 1874

BMF,

If i understand correctly, your measurements show the blocked ear canal response for your ears. Are you using any compensation EQ in these measurement (to account for a free-field or diffuse-field type of response at your ear)? Can you explain your reasoning for using or not using a specific compensation scheme?

post #58 of 1874
Thread Starter 
Quote:
Originally Posted by thune View Post

BMF,

If i understand correctly, your measurements show the blocked ear canal response for your ears. Are you using any compensation EQ in these measurement (to account for a free-field or diffuse-field type of response at your ear)? Can you explain your reasoning for using or not using a specific compensation scheme?

 

These measurements were made with a basic DIY kit that costs no more than $50.00 to make comprised of a phantom power supply and an omnidirectional mic. It was designed by a friend who shared it with me. It's not intended to compete or compare with anyone else's measurement system. I find it interesting, fun, and useful for tweaking my mods. I thought I'd share this information with the community with the goal of perhaps helping others with their mods.  Consider the measurements "FWIW."

 

I included measurements of a stock set of T50RP's and my LCD2's which serve as reference points for all the other measurements. Anyone interested can go to Tyll's site, download his measurements of LCD2 v.1 and T50RP, compare them to my measurements, do the math, and make their own "adjustments" to all the other graphs.

 

Cheers

post #59 of 1874
Quote:
Originally Posted by thune View Post

BMF,

If i understand correctly, your measurements show the blocked ear canal response for your ears. Are you using any compensation EQ in these measurement (to account for a free-field or diffuse-field type of response at your ear)? Can you explain your reasoning for using or not using a specific compensation scheme?

 

What BMF is trying to do is basically achieve a flat response from headphones (T50RP's) for his own ears. His work does not try and mimic speakers in a room. Both free field and diffuse field equalization try and mimic what a speaker would sound like in an anechoic room (well more free field on that one). The diffuse field equalization tries to mimic speakers in a reverberant room.

 

The work BMF is doing differs from that because he is saying, "I know I don't have a pair of speakers on my head, so I won't pretend they are speakers". He is trying to remove the T50RP sound signature from the audio chain by allowing its response to be virtually flat as the sound enters his specific ear shape. That way, with a perfectly flat DAC and Amp, his audio chain will be free from alterations and deviations of the Master recording, and hence be "as the pro's wanted it" -- free from other sound signatures.


Edited by wdahm519 - 8/3/12 at 7:02pm
post #60 of 1874

Hey thune,

 

As far as compensation goes, the first thing to note is that below about 1 KHz HRTFs are unimportant. We have an objective measure of flatness. (Acoustically at least. Some may like a bass boost to compensate for the absence of bass felt in the body.) This is where the mods make the biggest difference, too.

 

Even with HRTFs available it is tricky decide on the relative direct vs diffuse levels, since it depends on a reference to sound in a real room including direction. Still, diffuse curves are fairly generic since they include averaging over the interaural time and amplitude differences and so reduce individuality a little bit. Relative to the overall response there should be a bit of a bump between 2-4 kHz before dropping to the pinnae notch which will be quite individual (and also direction dependent in real life). a
 
I think the best logic to apply, without measuring your HRTFs, is to aim for flatness below 1 kHz. When you look at someone's in ear measurements, you need to keep an eye out for the generic HRTF features above and know that the treble needs to be adjusted for your own ears/brain so that FR sweeps aren't peaky. 
 
As for blocked/open ear canal measurements, researchers have found that blocked measurements are more repeatable. That is my experience too. You can take the mics in and out of your ears and get very consistent curves. The ear canal is naturally added on playback without a problem so long as the acoustic load in the headphone-head chamber doesn't change much.
 
My own overall plan is to measure my HRTFs at various angles and use them to construct various EQ schemes. I have a good idea of my direct field curves for straight ahead, but need to finish building a rig to do accurate angular measurements. 

 

Quote:
Originally Posted by thune View Post

BMF,

If i understand correctly, your measurements show the blocked ear canal response for your ears. Are you using any compensation EQ in these measurement (to account for a free-field or diffuse-field type of response at your ear)? Can you explain your reasoning for using or not using a specific compensation scheme?

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