[edstrelow]

  Very interesting thread. As an engineer, I have a little understanding of resonance (from the structural perspective) and how masses and their damping properties can affect response. I must say that it is interesting to read through this thread, because as noted previously, placement, amount, and size of dampers are all very important. For example, cutting up the same size of sorb into smaller pieces and then applying it may work better because of the fundamental frequencies of the smaller pieces may be more in tune with the frequencies you are trying to correct, instead of the bigger piece. Unfortunately, these things are always system-dependent to a large extent, so what works for one headphone may not work for the next. But I would be interested in knowing what size/thickness/amount of sorb would be particularly effective for 1500 Hz and 5200 Hz, for my TH900 headphones. This could also be the key to damping the treble peaks of the HD800s (without going all anax mod, etc).

I tried to get some technical specs form Sorbothane but I didn' t get the feeling that they had much to hand out. I talked with one engineer at Canjam who casually mentioned that his electronics firm used a custom ordered sorb, so I should keep after Sorbothane to give me more info. At the moment all  I can say is that it's a trial and error proposition.
 
I have accumulated a fair stock of various sorbs that exceed my likely needs. If you or anyone else wants to pm me, exchange addresses and send me an SSA with a dollar postage I would send a sample of enough to get going on most phones. 1/8 in  30 duro self-stick seems to work with a lot of phones, although my 007A  is mostly using 1/4 in.
 
As regards the HD 800 this is the only phone I know about which claims to be trying to solve this problem by damping. Whether they have done enough  I don't know.

 

[edstrelow]

  So I ran out of PTFE (teflon) tape for wrapping around my headphones, so I grabbed some cling film, rolled it up a bit and used that instead. I immediately heard a decrease in high frequency "air" on the side that had the cling film on, which sounds a lot like the effect you guys are getting from attaching sorbothane to parts of the headphone.
 
Here's a picture of what I did if you're interested:
http://imgur.com/nT63bkU

I am sure that many materials can dampen mechanical vibrations, even cling film.  The question is which does the best job and/or gives you the sound you want.  I haven't experimented with putting damping right on the edge of driver as you appear to have done, but soren_brix has.  In general  I would think you want to stop as much vibration getting out  as you can at the source (i.e. the driver) but if you can't stop it all you would still need to dampen other places on the phones.  With the Stax SR007 and the Sennheiser HD 800, the metal headbands appear to be a particular problem.

 

[preproman]

 

[wink]

   Ooops.... Pass me the Alka Seltzer    

   Too much popcorn..........   

 

[edstrelow]

I repeat my previous offer to provide sorb to anyone interested enought to try it themselves.  I have accumulated a stock of various sorbs that exceed my likely needs. Pm me, exchange addresses and send me an SSA with a dollar postage ( or more if outside the US. The envelope would probably not exceed 3 oz)  I would send a sample of enough to get going on most phones. 1/8 in 30 duro self-stick seems to work with a lot of phones, although my 007A is mostly using 1/4 in.

 

[edstrelow]

Looks like crap, sounds amazing.  While I satisfied my initial quest to find good damping arrangements for most of my Stax phones, I suspect that I have not found the ideal damping set-ups.  At the moment I am playing with the SRXIII Pro to see how much sorb you can add before sonic improvements end or the sound goes bad.  If I am correct and sorbothane is simply  damping the resonance in the earcups, the more you add, the less resonance there should be, and the closer the sound will be to what the drivers produce, because. you are simply getting rid of mechanical resonance distortion.
 
The problem with this theory  is that several times with various Stax phones, I have been forced to cut back on the amount of sorb, because I started to get audible anomalies, usually boomy bass. However, recently I have found that if you cut the sorb into small pieces, you can add more sorb with no boom and a still notable improvement in overall sound. Why this happens, I do not know but I am guessing that larger sizes of sorb resonate at low frequencies.    
 
The photo shows the SRXIII pro with an extreme amount of sorbothane on the outside of the earcups, but applied in smallish pieces.  In particular I have added more to the plastic section thinking that because it is directly connected to the driver, damping will be more effective if sorb is applied here. (The metal portion and the earpads are part of cup-like arrangement which is simply pressed onto the plastic section and is not in direct contact)
 
The results are very good indeed. The best attack and transients I have ever heard, beautiful tonal qualities and an ability to play louder than before.  It's still an SRX however, no bass monster and a bit peaky around about, I would guess 2 kHz.
 
The next step will be applying thicker, 1/4 inch sorb, vs the 1/8 I am currently using.  But  I am enjoying the sound of these so much I am in no real hurry.

 

[Don Quichotte]

I have tried this mod on my AKG K1000. I didn't have the time to experiment a lot, but placing 2 strips of sorbothane on the white wire mesh on each side (inner and outer side, both left and right, so 8 strips in total) resulted in a similar effect. Here the tonal balance change was the most obvious and important, as my bass-light K1000 coupled with my bass-light T-amp really benefit from a bass boost. Just a confirmation that some dynamic cans can indeed benefit from this mod too.

 

[edstrelow]

  I have tried this mod on my AKG K1000. I didn't have the time to experiment a lot, but placing 2 strips of sorbothane on the white wire mesh on each side (inner and outer side, both left and right, so 8 strips in total) resulted in a similar effect. Here the tonal balance change was the most obvious and important, as my bass-light K1000 coupled with my bass-light T-amp really benefit from a bass boost. Just a confirmation that some dynamic cans can indeed benefit from this mod too.

Photos of your modded AKG K1000 would be useful to other owners. It is interesting that the effects of sorbothane damping seem to apply to all manner of headphones.  At the outset because I dealt solely with Staxen, it seemed  possible that the effects would be limited to electrostatics. But instead, the resonance problems that sorbothane reduces seem almost universal among headphones.
 
I think it shows a fundamental problem with the design of phones, whether high or low cost. Fortunately sorbing helps but it seems clear to me that it would be better if the resonances could be prevented at the outset. Exactly how, I am not sure since everything resonates. Possibly  driver design in which a cancellation signal goes into the earcups, rather like the way noise cancelling headphones work. Then you would just get the a pure sound from the drivers without the resonance overlay.

 

[Don Quichotte]

I'll take a few photos at some point, I just want to experiment a bit more before offering a more elaborate personal conclusion. Unlike you, I perceive the result as more of a trade-off because the "air" /HF "shimmer" that gets lost due to the sorbothane sounds more like music to me, rather than "noise". Somehow, the sound is more relaxed / natural with it, despite being hazier (I don't know if this make sense to anyone but me...). Of course, being a trade-off doesn't mean you can't win more than you lose, overall it seems to be rather beneficial, but it still depends a lot on the rest of the system.  In my system, the 303's simply got a bit too dark for my tastes in most occasions, so now I only damp the outer case occasionally, when the recording seems to be particularly in the need of such a mod. The K1000's on the other hand really need this bass boost - if it only got a little deeper too! (apparently it didn't, or not very significantly).
 
I have a very unscientific theory. Just a wild (and not so educated) guess. Perhaps all the physical parts of the various headphones that sit between the membrane of the driver and the ear (including the perforated plate that is part of the driver "sandwich" of the electrostatic headphones) create a certain muffling of the sound, just as when you partially cover a tweeter with your hand. This is mitigated by the (mostly high frequency) resonances in the earcups and other parts of the headphone. So it's an act of balancing two shortcomings which impact the sound in opposite ways. And of course the tonal tuning, so to speak, of the actual driver is also part of this equation. In the K1000's case, I guess the best sound would be obtained by completely removing the white wire mesh parts, combined with damping the baffle.
 
Does this sound totally crazy, or there might be something true in all this "theory"?

 

[edstrelow]

  I'll take a few photos at some point, I just want to experiment a bit more before offering a more elaborate personal conclusion. Unlike you, I perceive the result as more of a trade-off because the "air" /HF "shimmer" that gets lost due to the sorbothane sounds more like music to me, rather than "noise". Somehow, the sound is more relaxed / natural with it, despite being hazier (I don't know if this make sense to anyone but me...). Of course, being a trade-off doesn't mean you can't win more than you lose, overall it seems to be rather beneficial, but it still depends a lot on the rest of the system.  In my system, the 303's simply got a bit too dark for my tastes in most occasions, so now I only damp the outer case occasionally, when the recording seems to be particularly in the need of such a mod. The K1000's on the other hand really need this bass boost - if it only got a little deeper too! (apparently it didn't, or not very significantly).
 
I have a very unscientific theory. Just a wild (and not so educated) guess. Perhaps all the physical parts of the various headphones that sit between the membrane of the driver and the ear (including the perforated plate that is part of the driver "sandwich" of the electrostatic headphones) create a certain muffling of the sound, just as when you partially cover a tweeter with your hand. This is mitigated by the (mostly high frequency) resonances in the earcups and other parts of the headphone. So it's an act of balancing two shortcomings which impact the sound in opposite ways. And of course the tonal tuning, so to speak, of the actual driver is also part of this equation. In the K1000's case, I guess the best sound would be obtained by completely removing the white wire mesh parts, combined with damping the baffle.
 
Does this sound totally crazy, or there might be something true in all this "theory"?

 
It doesn't seem that you have yet been able to open up the Lambda 303 to place sorb pieces on the driver baffle as I suggested.  Certainly  you can get some damping of the resonance of most phones by sticking sorb on the outside of the earcups.  However with the plastic lattice-type case or even the tab of the Lambdas but there is very little flat surface  for the sorb to actually stick to.    I had fairly poor results with the Sigmas, which have a similar design, trying to stick sorb on the outer case. Finally I opened them up and put the sorb on the baffle around the drivers as I do with the 404 and LNS Lambda.

I have the 404's with me in my office and the difference between them and the untreated 404 is night and day.  You will hear music with dynamics and tonal accuracy you never realized was possible.  These are very similar to the 303, I think they only differ in their cabling.  I hope you will continue to experiment.
 
As regards the improved bass on  AKG K1000,  a good outcome with most phones.  I may have a partial explanation.  When I contacted the tech people at sorbothane I was told that sorb damps  best above 50 Hz.  So if you are damping the higher frequencies, you are lowering the output of those frequencies and will probably find yourself turning up the volume more. to compensate.  The below 50 Hz signals are however not damped, thus I would expect to hear more bass.
 
I have had a few problems sorbing some phones,  Sigmas, Sr003 and SR007A,  getting excessive  and distorted bass.  Cutting the sorb into smaller pieces got rid of most of the problems.  Why, I am not sure.
 
As regards your theory about high frequency resonance replacing the treble which is lost by various things in the earcup which can muffle sound, I think that is true.  And that is why I consider virtually all current headphone designs to be obsolete.  You don't want your earcups contributing to the sound you hear from your phones any more than you want cabinet resonances contributing to the sound of your speakers.   High fidelity is all about neutral playback, not euphonic coloration.   I have come to the conclusion that there is no easy way to control headphone coloration and that is why we have had so much more coloration even in the best phones, compared to the best speakers.  Fortunately there is sorbothane.

 

[edstrelow]

My mod of the 007 does not create much risk to the phones, because you are only taking off the earpads to apply the sorb. I received a question about this the other day and here  was my reply:
 
"I would say that the risk to damaging the 007 phones doing my sorb mod is minimal.  This is because unlike many of the other phones I have worked with, you don't actually open up the earcups and the drivers remain protected from damage by a very strong perforated metal  cover.  The sorb is simply stuck to the perforated cover.  Normally I would try place sorb closer to the drivers but with the 007,  I couldn't see any place to put the sorb nearer the driver.
 
What you are doing then is: Firstly, pull the earpads off the earcup,  they are held in place by having their leather bottoms, (kind of a skirt) tucked into a groove that runs around the earcup, next to the metal support that holds the earcups to the headband.  Just pull them off gently and they will come fairly easily.
 
Secondly you will see a round  plastic/leather mesh which has a metal spring which fits into a rubber mount in the center of the metal cover.  This you just lift off and then thirdly, you are ready to apply the sorb.  I use small pieces of 1/4"  soft  sorb (40 duro I think) stuck to the perforated metal cover so as to make a ring around the edge.  I have not been able to find self stick 1/4 inch on Amazon or Ebay so I have stuck it on with 3M 80 adhesive.
 
Frankly the hardest thing is getting the earcups back on.  What I do is, after I have figured out the correct orientation of the earpad ( you want the thickest part towards the rear bottom - most people just say orient the pad stitching at the level of the eyes) just tuck the leather skirt into the groove using a blunt kitchen knife.  It's quite easy and usually takes about 1 minute to go all the way around the earcup.
 
I also dampen the two metal arcs of  headband since I am convinced that because it is firmly attached to the metal earcups, it passes vibrations between the cups.   I just cut 2 short pieces of plastic (metal or wood could work too) and stick a bit of sorb where it will contact the 2 metal arcs and hold this together with a bolt and nut.  I use 2 of these dampers, partially covering the top of the earcup, to get more damping, but  a single one will work reasonably well.  One interesting thing is that you can tune the sound by adjusting the tightness of the nut and bolt."

 

[crazychile]

Maybe this was covered somewhere previously in this thread. If so, my apologies.
 
Is it possible to mod the SR-507 with sorbothane and bring the performance even remotely close to the stock SR-007Mk2?
 
I have Koss ESP-950s and am looking at buying a pair of Stax to complement (not replace) the Koss', but If I can spend less than half the price of the 007 and get something that is smooth yet has better top end detail than the ESPs, I may consider the 507s.
 
Thanks.

 

[edstrelow]

  Maybe this was covered somewhere previously in this thread. If so, my apologies.
 
Is it possible to mod the SR-507 with sorbothane and bring the performance even remotely close to the stock SR-007Mk2?
 
I have Koss ESP-950s and am looking at buying a pair of Stax to complement (not replace) the Koss', but If I can spend less than half the price of the 007 and get something that is smooth yet has better top end detail than the ESPs, I may consider the 507s.
 
Thanks.

 
The 507 is a Lambda and the mods I showed for the LNS and 404 Lambda should work. Those used 1/8 inch sorb on the inside baffle.  I haven't opened  up a 507 but I
assume it is essentially the same as other Lambdas.  Soren_blix even suggested attaching the sorb directly to the edge of the driver.  I used self-stick 1/8 in 30-40 duro sorb on these phones, and think it gives  a major improvement.
 
Is it as good as an umodded 007?  In some ways better since you  are getting rid of a type of distortion, that as best I can telll, bedevils all current headphone designs of whatever make or cost. When I modded my Lambdas, I stopped listening to my 007, and listened entirely to the Lambdas. However, I do think that my currently modded 007 is a better phone than my modded Lambdas and now I listen to it exclusively, except at work where I have my modded 404.    Having listened to some big amps for Staxes at the recent Canjam  I also think that these mods do more for musicality than a superamp and at a negligible cost, versus the  $5K which seems to be the starting price for super amps.
 
There is one change that I would make to the above mod, I would cut the pieces of sorb in half and the re-apply them.  So far I have found that reducing the size of the pieces of sorb, while using the same total amount, gives  a better result, certainly it did with with the 007 and Sigma/404.
 
Another change  that I am contemplating is to replace 1/8 inch sorb with 1/4 inch in the Lambdas and Sigmas but so far I just haven't had time to play with this. Going from 1/8 to 1/4 really helped the 007 although part of it was that the 1/8 just didn't do as much for the 007 as it did for the Lambdas, possibly because the 007 is a very heavy phone compared to a Lambda and needed more damping material.

 

[crazychile]

Thanks Edstrelow. Very informative.
 
On the subject of using smaller pieces yet same quantity of sorb....
 
I can confirm that this concept does work. I discovered this myself back in the 90's when using Dynamat in vehicles with high end audio systems. Spreading 1 inch squares around the inside of a door panel worked as well and sometimes better than just plastering the whole 1 ft piece in the center of the door. I did this initially for customers that wanted to stretch their budget, but quickly suggested it for customers with big budget systems once I realized the benefits.

 

[edstrelow]

  Thanks Edstrelow. Very informative.
 
On the subject of using smaller pieces yet same quantity of sorb....
 
I can confirm that this concept does work. I discovered this myself back in the 90's when using Dynamat in vehicles with high end audio systems. Spreading 1 inch squares around the inside of a door panel worked as well and sometimes better than just plastering the whole 1 ft piece in the center of the door. I did this initially for customers that wanted to stretch their budget, but quickly suggested it for customers with big budget systems once I realized the benefits.

 I have seen that there are some professional modders out there who apply dynamat to headphones (and charge exorbitant amounts for this)   As far as I understand, dynamat is designed to block external sound, such as road noise, getting into cars.  To the extent that it also dampens vibrations it is doing the same thing as sorbothane. I, or someone else  ought to try it with headphones and compare it to sorb. There really is a lot of research that needs to be done here.