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post #5086 of 10820
Quote:
Originally Posted by HDMan View Post

L/R balance issue seems to have comeback, really starting to annoy me, anybody here can say they don't have this problem? If not, how and what mods did you do.

 

They may become redundant soon, inexchange for LCD2. Pity though, because they really do have great drivers, just a bad design otherwise.

 

Something I noticed which I will try next, the screw holes on the left cup are worn and the baffle doesn't screw down tight like the right side, looks like its in need of some metal nuts on the inside instead of plastic screw holes, I mean to say, plastic screw holes,it's going to be a nightmare eventually.



This man is truly dedicated, I have not worn the screws out on my T50 yet, and have probably opened them 20+ timesbiggrin.gif

post #5087 of 10820
Assuming you have equal amounts of mod materials placed identically on both sides:

Guess 1. Only one baffle fails to fully close due to stripped plastic threads. Youve lost your seal and that side has reduced dB and no bass. I just ordered a product from Amazon to fix some stripped threads. A temporary fix is to use electrical tape to keep the baffle compressed against the cup and then seal all the way around with tape. Did you over fill the cup with dampening materials? If so, you may need to remove some from both sides.

Plastic-safe epoxy IF you get to the point where you are completely satisfied.

Guess 2: One ear pad has been stretched more than the other. Get new pads or seal with tape.

Guess 3: bad jack or plug. Clean with Deoxit or similar product.

Guess 4: Cable fault. Try another cable if you have one.

Guess 5: Source fault. Try a different headphone with the same audio chain and the same song.



Quote:
Originally Posted by HDMan View Post

L/R balance issue seems to have comeback, really starting to annoy me, anybody here can say they don't have this problem? If not, how and what mods did you do.

 

They may become redundant soon, inexchange for LCD2. Pity though, because they really do have great drivers, just a bad design otherwise.

 

Something I noticed which I will try next, the screw holes on the left cup are worn and the baffle doesn't screw down tight like the right side, looks like its in need of some metal nuts on the inside instead of plastic screw holes, I mean to say, plastic screw holes,it's going to be a nightmare eventually.

post #5088 of 10820


WoW! great work Arleus. I'm happy that it worked for you too. This is why I like this hobby biggrin.gif

Quote:
Originally Posted by Arleus View Post

So, I took a page from Twinster's book (you cunning fox, Twinster), and built a budget measurement rig from a cheapo SPL meter I got from amazon (probably too cheap - it's not great, and I'll go into why a little later). I was lazy though, and instead of mounting it in a box, I just duct taped a CD to the aperture, and covered the CD in paxmate. I've been measuring a couple of mods, and some of my other headphones over the past few evenings, and I thought I'd share, in case anyone's interested.

 

Forty test tones were produced in MATLAB, logarithmically spaced between 20Hz and 20kHz (code in the spoiler section below - in the interests in openess, I'm going to post my code in case anyone wants to use it to generate tones in Octave or MATLAB. I know nobody will, but I feel better posting it anyway). I played each tone in turn, with the 485Hz tone set to 90dB, and recorded the SPL measured on the meter, set to 'slow' speed, and C weighting. I then switched sides and went through the same process for the other cup.

 

 

Warning: Spoiler! (Click to show)

 

 

% Initialisation
close all;
clear all;
clc;

 

% Variables
Fs = 44100;     % Sample rate in Hz
maxt = 10;       % Maximum length of the tone in seconds
notones = 40;  % Number of tones
amp = 0.9;       % Amplitude of the tone

 

% Generate frequency vector
f = logspace(log10(20), log10(20000), notones);

 

% Generate time vector
t = [0:1/Fs:maxt];

 

% Loop through each frequency
for n = 1:length(f)
    y = amp*sin(2*pi*f(n).*t);
   
   
    if f(n) < 100
        name = ['000' num2str(f(n)) '_tone.wav'];
    elseif f(n) < 1000
        name = ['00' num2str(f(n)) '_tone.wav'];
    elseif f(n) < 10000
        name = ['0' num2str(f(n)) '_tone.wav'];
    else
        name = [num2str(f(n)) '_tone.wav'];  
    end
       
       
    wavwrite(y, Fs, name);
end

 

 

 

After this point, I 'correct' the data by setting 485Hz to zero, and removing the C weighting curve - this is one of the dodgiest bits I do, and if someone would like to tell me that I'm wrong to do so, please let me know. It is my understanding, however, that the meter will 'artificially' reduce the dB value at low and high frequencies to account for human hearing at those ranges. I wanted the raw numbers, not the weighted ones. I got the formula for the weighting curve from Wikipedia, and subtracted it from the recorded numbers.

 

I then put a cubic spline through the points (using MATLAB's spline function, upsampling by a factor of 10) to interpolate between the rather coarse 40 frequencies I recorded. My SPL meter does have an analogue output on it, so in future I might see if I can chav (read: steal) an oscilloscope, work out how the devil it works, and record a continuous sine sweep so I don't have such a coarse set of data points... but if I'm going that far, I might as well get a better meter too.

 

Then it's just a case of plotting. For reference, here are my results for my K702 and RS1i to give you some idea of how my graphs look. It's generally not a good idea to compare frequency responses from one person's measurement equipment to another person's results... especially if the equipment is home brew.

 

K702.png

RS1i.png

 

These look, I have to say, surprisingly good I think. Okay, so first thing to note - I don't think you can trust my results below 50Hz or so. All of the headphones I've measured show a very similar slope of roll-off below 50Hz, and I suspect that's the meter that's at fault (considering I've 'corrected' for the C-weighting). Compared to Tyll's results for the RS1, the RS1i looks incredibly flat through most of the midrange, and I don't see any 100Hz bump that he has for the older model headphone. At this point, I don't know if it's really there and I can't detect it, or if the RS1i doesn't have one. Upper midrange looks like classic Grado to me though, so that gives me some confidence. That channel imbalance at 2k? I didn't realise I had one, but it looks pretty big to me - I did double check it.

 

The K702 response again looks pretty reasonable, though a slightly different shape to Tyll's. Maybe I could chalk it up to the HRTF he uses, and my complete lack of one, but frankly it's probably because I bought cheap equipment and built it from gaffa tape and dreams.

 

Given those two results as a baseline, what do the T50RPs look like that I've modded? Well, I have to admit at this point that I don't have a stock pair to measure, so take these results with an ever growing pinch of salt.

 

 

 

Mod 1:

Plasticine on back and walls of cup (I'm too cheap for dynamat), paxmate covering it all, including the centre screw post. Stock bass port felt in place, 3 slots covered by electrical tape. A square of floppy craft felt, maybe 2mm thick, resting on the back of the cup (not glued in place). Stock white fabric on the cup side of the driver square, 3 sausages of tungsten putty (18g per cup) surrounding 3 sides of the driver housing. Plasticine in the seal between the baffle and the cup. On the ear side, the felt over the driver has been removed, and a paxmate lifter added under the rear-side of the pads (no other paxmate or putty on this side). Shure 840 pads with the centre foam removed.

 

T50RP_mod_1.png

 

Holy channel imbalance Batman! I would describe the sound as a bit confused, quite dark, somewhat congested in the upper bass / low midrange. The 1k resonance that's been plaguing my builds is also clearly visible, and quite annoying on certain songs, especially some female vocals that hit this note. At least the sound is fairly open, and the midrange, though imbalanced and a bit bumpy, has that amazing liquid quality that I can only assume is what everyone raves about when they talk about orthos (I don't own any other orthos). To my ears, the bass lacks extension - remember that you can't trust my graphs down there though.

 

 

 

Mod 2:

No plasticine in the cups. Paxmate on the bottom of the cups. Bass port felt removed entirely, and the ports left uncovered by paxmate on the inside of the cup. On the outside, electrical tape covers 3 slots. Half of a UK sized cotton ball in each cup, teased into a square the size of the bottom of the cup. The same tungsten putty surrounds the driver housing as in Mod 1, still got the plasticine seal between the baffle and the cup. Ear-side is identical.

 

T50RP_mod_2.png

 

Oh man, much much better. Firstly, I sorted the channel imbalance - that makes a big difference to the cohesiveness of the sound, I think. The mods have also really smoothed over the midrange, making it  fairly flat now. The sound is tighter, significantly faster too, partly due to there being less mid-bass bloat, and partly due to the lifted high frequency response (this one is only down at -10dB at 5kHz, whereas Mod 1 was down at -20dB. There's a dip immediately after 5k on this mod, but it doesn't go lower than Mod 1 does).  I've not noticed a sibilance problem with the 8k peak yet, but I think I'm fairly tolerant to sibilance compared to some people on these forums. The bass sounds to be better extended too - if I play my test tones, I would say things are pretty good down to about 30Hz, then take a bit of a dive after that, but nevermind.

 

 

 

In conclusion, I'm pretty happy with Mod 2 (most of the ideas for which came from bmf of course). If I do any more mods, I'll make sure to measure them, and if I think the mod is worth something, I'll post my measurements here. Whilst I would love to take a systematic approach, and measure each mod individually, I frankly don't have the time to be able to do this, plus I doubt that the mods are linear, in that if you stick two mods together, I doubt that the results will simply be the same as the sum of the individual parts, if that makes sense. If anyone else is toying with the idea, I encourage you to go and get your own SPL meter and give it a go - it's easy, and it seems to work surprisingly well. Was a great idea Twinster!



 

 


Edited by Twinster - 11/26/11 at 6:20am
post #5089 of 10820

Quote:

Originally Posted by bluemonkeyflyer View Post

If your source has a mono option, send identical signals to both channels. Then mute one side compared with the other side. This might be a useful alternative for those without a stock comparison set.


That's exactly what I did.  

post #5090 of 10820

I ordered some of this to repair stripped threads:

 

 http://www.amazon.com/Woodmate-2498-Grip-Screw-Repair/dp/B001B38ALG/ref=sr_1_1?ie=UTF8&qid=1322327728&sr=8-1

 

I'll post the results sometime next week.

 

Quote:
Originally Posted by drez View Post



This man is truly dedicated, I have not worn the screws out on my T50 yet, and have probably opened them 20+ timesbiggrin.gif



 

post #5091 of 10820

I dynamatted and acoustic foamed the inside of both cups but I'm hearing some extreme graininess.  Anyone know why that is?  The resonance issues have been killed and the result is a blacker background for subtle details to stand out against but the grain/fuzz is quire irritating.  It seems to be associated with a particular frequency, mostly in the vocal region.  

post #5092 of 10820

Okay you guys are really starting to get to me with these headphones. Im heavily contemplating them now just to see how good i could make them. Could someone link the main page for modding again? Gunna do some heavy reading. 

post #5093 of 10820
you guys are crazy. you seriously don't need much to get these to sing properly. just some mineral wool/fiberglass and cotton/polyfill. just have to measure it out correctly for each cup cause once you start hitting down to 100hz and below you can run into channel imbalances. i had very difficult time trying to get 25hz even out on each side of the cups but little patience and lots of manhandling(lol,yes cause i needed use some force to get them to shut from crap load of mineral wool and cotton i stuffed inside). only took me few tries of opening and closing,then testing to get these even out in the sub-bass area. it's much easier to absorb midrange to air frequencies on these to even out cause wave lengths of them are very short and don't take much dampening at all to be absorbed. bass and sub-bass frequencies is the only frequency ranges that's pain in the a55 for me(not only headphones but rooms as well).
post #5094 of 10820

referring to this?

 

http://www.head-fi.org/a/fostex-t50rp-modification-summary-links-wiki
 

Quote:
Originally Posted by Deathdeisel View Post

Okay you guys are really starting to get to me with these headphones. Im heavily contemplating them now just to see how good i could make them. Could someone link the main page for modding again? Gunna do some heavy reading. 



 

post #5095 of 10820

Less is more smile.gif Why don't you describe more in detail?

 

Quote:
Originally Posted by RexAeterna View Post

you guys are crazy. you seriously don't need much to get these to sing properly. just some mineral wool/fiberglass and cotton/polyfill. just have to measure it out correctly for each cup cause once you start hitting down to 100hz and below you can run into channel imbalances. i had very difficult time trying to get 25hz even out on each side of the cups but little patience and lots of manhandling(lol,yes cause i needed use some force to get them to shut from crap load of mineral wool and cotton i stuffed inside). only took me few tries of opening and closing,then testing to get these even out in the sub-bass area. it's much easier to absorb midrange to air frequencies on these to even out cause wave lengths of them are very short and don't take much dampening at all to be absorbed. bass and sub-bass frequencies is the only frequency ranges that's pain in the a55 for me(not only headphones but rooms as well).


 

post #5096 of 10820

As I suspected it was a seal issue on the left side, the screws were worn and no longer clamped the cup tight, resulting in the left side sounding kinda hollow, was very annoying. Thanks to bluemonkey for suggesting the electrical tape.

 

I got some screws from my PC Motherboard kit, slightly larger than the T50RP ones and screwed them in tight, worked out alright and applied electrical tape for extra seal.

 

So far so good, balance seems to be much better now.

 

No doubt I will be back in there again once I get some acoustic material tongue_smile.gif

post #5097 of 10820
Quote:
Originally Posted by sphinxvc View Post

I dynamatted and acoustic foamed the inside of both cups but I'm hearing some extreme graininess.  Anyone know why that is?  The resonance issues have been killed and the result is a blacker background for subtle details to stand out against but the grain/fuzz is quire irritating.  It seems to be associated with a particular frequency, mostly in the vocal region.  
Try inspecting for peaks in the 8KHz- 11KHz area.
post #5098 of 10820

This article might be interesting for those of you who hasn't seen it already

 

Tyll Hertsens explains Orthos

 

http://www.innerfidelity.com/content/how-planar-magnetic-headphones-work

 


 

Especially this (quote)

 

 

Damping --- With electostatic drivers, the charge carrying stators on either side of the diaphragm can be very thin and sonically transparent. Planar magnetic driver diaphragms are surrounded on either side by relatively large structures. The magnets are fairly large, and the opposing force they exert on each other is significant, so sturdy metal structures hold the magnets in place. There is a significant amount of trapped air in volumes of various sizes that must be moved before sound is radiated out of the driver. The springiness and resonances that may exist in this trapped air volume can cause problems. Quite a bit of the design effort with planar magnetic headphones seems to be spent on getting just the right damping. The vintage Orthodynamic headphone scene is filled with various damping modifications done by enthusiasts.

 
110511_planar_photo_damping.jpg

 

 

 


Edited by ardilla - 11/26/11 at 2:24pm
post #5099 of 10820
Quote:
Originally Posted by HDMan View Post

L/R balance issue seems to have comeback, really starting to annoy me, anybody here can say they don't have this problem? If not, how and what mods did you do.

 

They may become redundant soon, inexchange for LCD2. Pity though, because they really do have great drivers, just a bad design otherwise.

 

Something I noticed which I will try next, the screw holes on the left cup are worn and the baffle doesn't screw down tight like the right side, looks like its in need of some metal nuts on the inside instead of plastic screw holes, I mean to say, plastic screw holes,it's going to be a nightmare eventually.

I never really had an issue with balance. What you should do is rip out 3.5mm adapter in the left ear cup, fill that area up and top it dynomat and plaxmate. Make sure the amount is as close to each other as possible on both ear cups. Then do a re-cable and your L/R balance should be fixed.
I know this is not a reversible mod, but the T50RP is only $74 and I plan on keeping it. If you plan on keeping yours and the L/R balance issue bothers you that much, you might as well try it.

 


Edited by snakeeater69 - 11/26/11 at 2:40pm
post #5100 of 10820
Quote:
Originally Posted by sphinxvc View Post

I dynamatted and acoustic foamed the inside of both cups but I'm hearing some extreme graininess.  Anyone know why that is?  The resonance issues have been killed and the result is a blacker background for subtle details to stand out against but the grain/fuzz is quire irritating.  It seems to be associated with a particular frequency, mostly in the vocal region.  


Check to see if the solder that connect to the drivers have proper contact and not loose internally. Also make make sure the solder is clean. Same thing happen to mine and it was either a result of improper contact or the solder having some plasticsine on it.

 

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