wink said:

  Torn Leg, Didn't Run.

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Ugh, I'm due for a run this morning and have a sore tendon. Don't say that!

Duplicate post (see below)

Duplicate post (see below)

Duplicate post, see below.

Interesting thread on mechanical damping issues in audio by a mechanical engineer. He supports the use of sorbothane footers rather than solid items such a cones. I would have though solid spikes would at least work better for speakers although you can still reduce vibrations with sorbothane.  This has some bearing on the damping of heapdphone ear cups.
 
"09-02-06: Rotarius The last time I replied to a similar post it never made it past the moderators for some reason. Placing different materials like wood or brass under a cd player or tube equipment will alter the sound slightly at times for better or worse but are not very effective in isolating the component from the mechanical vibrations via the rack. If you look up isolation or vibration damping devices you will find that materials like polyurethane are used often. Sorbothane is just ultra soft polyurethane. As a mechanical engineer with access to vibration analysers it is easy for me to see which materials dampen vibrations and which don't but I doubt I can convince any of the serious audiophiles to give up their high dollar cones and ball bearings for something that cost a few bucks. Rotarius (Threads | Answers | This Thread) "
 
Here is the thread:
 
http://forum.audiogon.com/cgi-bin/fr.pl?aamps&1146508660&read&keyw&zzsorbothane

A technical advisor at Sorbothane  told me today that damping occurs on a basis of about 40 dB per cm of thickness at 50 Hz and above.  So essentially the thicker the sorb, the more damping which will occur. He did not however have any data on the linearity of the damping or advise on how to damp the lower frequencies or how this varied with duro (softness of the sorbothane). Unfortunately this means a lot of trial and error is still called for here to get uniform damping across the frequency spectrum.
 
Low frequency boominess has been more of a problem with the 007A than any other of the phones I have tried so far but I may have part of a solution. Following a tip from a seller of sorb that smaller pieces were more effective than large pieces, I cut the ring of 1/4 inch sorb into 4 sections, whereas it had originally been a solid ring. This seems to improve performance by reducing the bassiness of the phones and making the other frequenciess more dynamic. Thus I now am getting  dynamics and bounce to individual instruments more like I have been getting with the modified Lambdas. I tried a partial segmenting on the 007 phones I displayed at Canjam in March and finally did the last sectioning and like the result very much.
 
I don't understand why segmenting works though. However the information from the Sorbothane technical support may explain why there is a bass problem after damping with sorb. If the sorb is mainly supressing resonances above 50 Hz, the frequencies below 50 Hz are still there, at their original volume and thus the system may sound bassy. Sorb is subtracting sound from the mix you hear from your phones, it has been pretty obvious to me from the beginning of this experiment that I have to turn the volume up after applying sorb. 
 
Of course what you are losing by damping the earcups is not really music, it is resonant rubbish, which sometimes sound "airy." This is not just a Stax problem, but as best I can tell no phones other than the Sennheiser Hd800 have made any effort to get rid of  these resonances.

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

edstrelow said:

  I have been a stat fan most of my life,  first with Koss, then Stax and even Jaecklin. I appreciate the sense of reality they provide and their tonal accuracy.  I take it you hear a lot of acoustic music that gives a reference to decide if a sound is accurate. People who only know amplified sound lack this reference and mainly seem to judge on the basis of bass slam, as in a rock concert. And if that's what you like and will be listening to and don't mind damaging your hearing, that's fine.

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earspeakers said:

  We're of the same mind on this exactly. I only listen to acoustic music. Classical, about 8 hours a day while I work at the computer these days mainly. I agree with what you say about amplified music. It starts off as an electronic signal, then is sent through compressors and all sorts of stuff, and out a dynamic speaker at 130 SPL. What's the obsession with reproducing that?

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I have to say I disagree with this.  I'm fully "converted" to 'stats and my primary genre is metal.  IMO, short of the HE1000 or possibly a properly modded HD800 (haven't actually heard one, but the measurements I've seen look promising) nothing comes close to the speed and separation of stock SRS-2170 system.  I prefer my Lambdas for any genre of music for that reason.
 
Thanks for the heads up on the sorbothane though.  I just ordered one of the self stick sheets and I'm going to compare and contrast it with the dynamat that I used in modding orthos before I got into 'stats.

maverickronin said:

   
Thanks for the heads up on the sorbothane though.  I just ordered one of the self stick sheets and I'm going to compare and contrast it with the dynamat that I used in modding orthos before I got into 'stats.

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That'll be interesting because dynamat evidently works much like sorbothane.  I haven't tried it myself although as I google it various people have used it with a number of phones and I know of one modding company that will install it.
 
One good thing about sorb is that it comes in various thicknesses and hardnesses (what they call "duro.")  I assume that softer is better for absorbing energy but I could be wrong and am not sure whether different duro absorb different frequencies.  My impression so far is that it is better to use  samller pieces than large sections, even if the total amount of sorb is the same.
 
Of one thing I am sure though, that virtually all headphones have resonance problems and that this problem has been mostly overlooked by the industry.

So, I've tried it on my SR-303. Actually, after removing the 4 screws, I couldn't for the life of me separate the baffle from the grey outer shell (is earcup the right word?). Therefore, I got another idea. Since I just had to replace my earpads and I hadn't stick them to the baffle yet, I placed some thin (about 5mm) strips of sorbothane right on the inner edge of the baffle, even touching a bit the metallic mesh that protects the driver. I used 2 strips for each headphone first, about 5 cm each, placed on opposite parts of the oval window of the baffle, then I cut them shorter and even completely removed one of them. Still experimenting, trying to find the right amount.
 
I was pretty sure I will hear a difference, but I wasn't expecting such an obvious one. The sound is cleaner, less hazy, with less air and milder upper mids / highs, fuller, bassier; in complex passages, it's easier to hear what's going on in the lower mids area. Pretty much in line with what has already been posted. On the negative side, too much sorbothane made the bass a bit boomy in my system (which was tweaked to sound pretty balanced to my ears). Also, I had a feeling that the mids, perhaps around 800-1000Hz, I'm not sure, had a tendency to become a tiny little bit... shouty, I should say. Perhaps this is how these headphones sound in my system anyway, but the extra energy above this frequency area was masking a bit this shouty-ness?! Not a strong phenomenon, and dependent on the amount of sorbothane, of course, but it made Garbarek's saxophone on the 4th track of his Visible World album (ECM), for example, a bit too upfront, a bit unpleasant sometimes. Perhaps the most important, the diminished air made the sound somehow less free, expansive, sometimes even less expressive in a way - to my ears and in my system. The cymbals in particular were less metallic than they should have been now. When applying an excessive amount of sorbothane, the sound became dead, perhaps similar to speakers in an overdamped room. This made me think that 'hearing only the driver" was not the goal to be aimed at here, and made me remember the thin, underdamped speaker walls concept of Harbeth (some speakers I would really like to hear, but I haven't had the chance yet). I found myself wishing I could somehow retain the better clarity of the modded headphones and the airy quality of the stock ones at the same time.
 
So, jury is still out. I'm pretty sure I will end up with some amount of damping, but how much, this I will determine over long term listening. As a side note, I have also tried damping the outer part of the headphone by placing a short (~3cm), thin strip of sorbothane just under the plastic fork, on top of the headphone so to speak, where there is a small darker piece of plastic with "STAX SR-303" written on it. To my astonishment, I could hear a small difference even with such a small amount of damping applied in such an innocuous location! (the baffle was not damped when I tried this) I didn't expect it would matter at all and I don't understand why it did, but I heard what I heard.
 
Many thanks to edstrelow and the other fellows for inventing and refining this tweak, and I encourage all the other Stax afficionados to try it.

don quichotte said:

  So, I've tried it on my SR-303. Actually, after removing the 4 screws, I couldn't for the life of me separate the baffle from the grey outer shell (is earcup the right word?). Therefore, I got another idea. Since I just had to replace my earpads and I hadn't stick them to the baffle yet, I placed some thin (about 5mm) strips of sorbothane right on the inner edge of the baffle, even touching a bit the metallic mesh that protects the driver. I used 2 strips for each headphone first, about 5 cm each, placed on opposite parts of the oval window of the baffle, then I cut them shorter and even completely removed one of them. Still experimenting, trying to find the right amount.
 
I was pretty sure I will hear a difference, but I wasn't expecting such an obvious one. The sound is cleaner, less hazy, with less air and milder upper mids / highs, fuller, bassier; in complex passages, it's easier to hear what's going on in the lower mids area. Pretty much in line with what has already been posted. On the negative side, too much sorbothane made the bass a bit boomy in my system (which was tweaked to sound pretty balanced to my ears). Also, I had a feeling that the mids, perhaps around 800-1000Hz, I'm not sure, had a tendency to become a tiny little bit... shouty, I should say. Perhaps this is how these headphones sound in my system anyway, but the extra energy above this frequency area was masking a bit this shouty-ness?! Not a strong phenomenon, and dependent on the amount of sorbothane, of course, but it made Garbarek's saxophone on the 4th track of his Visible World album (ECM), for example, a bit too upfront, a bit unpleasant sometimes. Perhaps the most important, the diminished air made the sound somehow less free, expansive, sometimes even less expressive in a way - to my ears and in my system. The cymbals in particular were less metallic than they should have been now. When applying an excessive amount of sorbothane, the sound became dead, perhaps similar to speakers in an overdamped room. This made me think that 'hearing only the driver" was not the goal to be aimed at here, and made me remember the thin, underdamped speaker walls concept of Harbeth (some speakers I would really like to hear, but I haven't had the chance yet). I found myself wishing I could somehow retain the better clarity of the modded headphones and the airy quality of the stock ones at the same time.
 
So, jury is still out. I'm pretty sure I will end up with some amount of damping, but how much, this I will determine over long term listening. As a side note, I have also tried damping the outer part of the headphone by placing a short (~3cm), thin strip of sorbothane just under the plastic fork, on top of the headphone so to speak, where there is a small darker piece of plastic with "STAX SR-303" written on it. To my astonishment, I could hear a small difference even with such a small amount of damping applied in such an innocuous location! (the baffle was not damped when I tried this) I didn't expect it would matter at all and I don't understand why it did, but I heard what I heard.
 
Many thanks to edstrelow and the other fellows for inventing and refining this tweak, and I encourage all the other Stax afficionados to try it.
 

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As you note, the effects are not subtle even though you weren't able to place the srobothane where soren_brix and I think it is most effective. Still, this sounds like progress.  Too bad you couldn't get the baffle off the Lambdas.  They get stuck in the cup, especially if they haven't been removed in a decade or more.  I have sometimes used a sharp knife to gently pry under the edge. between the baffle and the outer earcup.  I undestand your hesitation about breaking something though.
 
Regarding the "air" that seems to be reduced.  I have noticed this as well, but believe what you are hearing is not actual ambience but rather earcup resonance.  When I turn the volume up a notch I often find that I am hearing the hall ambience for the first time on many recordings.
 
I found that the arrangement I first applied to the lambdas worked very well on both an LNS and 404 Lambda. I got no sonic anomalies ,have left it alone and have been very happy with the sound.   Frnaky, it was os good that it took a lot of experimenting before I could get my 007A to sound better.
 
I have had some of the problems you note with other phones however, and have had to proceed by trial and error to get rid of especially bass boominess.  One thing I am finding is that putting the sorb into smaller segments seems to keep the bass from getting boomy.  You might try this, but still I hope you are able to succeed in opening your Lambda and putting the sorb on the inside baffle.  As you can see however, this is a fun activity, cheap to get into and with a big payoff when you get it right.

Have you considered sending a sorb-modded phone to Tyll for measurements?
 
I'd like to echo Don Quichotte's observations, wrapping the driver with cling film decreased the "air", but also made it easier to hear things in the lower mid area, so I'm guessing that its also helping to dampen driver vibrations.
 
The reason I wrapped the driver originally, was to seal the baffle properly. The glue Stax used either deteriorates over time or simply wasn't good enough, so the baffle is often leaky in older Lambdas. If the driver doesn't fart when pushed against the ears, its leaky.
 
On my LNS, I used a spatula to push the baffle out, but you could probably do the same with a plastic knife.

tachikoma said:

  Have you considered sending a sorb-modded phone to Tyll for measurements?
 
 

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Not a bad idea. I am using my SRXIII pro for experimentation but  I should contact Tyll to see if he would be prepared to do some measurements. Most of it's sorb is on the outer casing, so it can be removed for a before and after measurement.

I am pretty sure that I have made the world's best headphone with the most recent mods to the 007A.   The latest mod is something I have tried with success on other phones too,  basically cutting the larger pieces of sorbothane into smaller pieces.  It was originally suggested by a sorb seller on ebay and he was definitely on to something. I have made some edits in earlier posts to explain these, where I have described how I have damped different phones.
 
"World's best?"  That's quite a claim, but I spent some time comparing my modded 007A with an 009 at the last Canjam in SoCal and while I concede that unmodded, the 009 is probably better than the 007A,  even  with the more limited mods, the 007A was in the same league  as the 009 if not better.  The 009 seemed to have  a smoother  frequency response and more extension in both bass and treble.    But the 007A had dynamics and  more realistic tonal characteristics. I have now  reduced the size of the sorb pieces inside the earcup twice since then and each time the 007A has got noticeably better.  Now the inner ring of 1/4 inch sorb is in 8 sections.  At Canjam it was three. I have owned Stax phones for over 30 years and that experience gives me a familiarty with the nuances of sound.  "Golden ears" if you like.  Even after that long experience with about a dozen Stax, it is clear that the sorb mods make these phones a lot better.  
 
zolkis  claims that his mods to the 007 and 009 using different foam and earpads also give big improvements, and since I have not heard these I can't say.  However, the sorb mods are simpler and much cheaper and it seems more obvious why they work. Sorb is simply a damping material.  It gets rid of audible mechanical resonance in the phones. I suspect some of his mods work for the same reason.
 
I am pretty sure that a properly modded 009 would be even better  than my 007A  but I am not going there.  Possibly after my last kid graduates college (as I sit here I am paying on 4 apartment leases in Berkeley, which is next door to  San Francisco the most expensive city in the US) I may put out the bucks for an 009 but the sorb mod only costs a few bucks, not  a few thousand and gives more sonic improvement anyway. Even my modded Lambda 404 is remarkably good and its performance has been the model for judging whether the mods on the other phones are as good as they should be.
 
When I started this work I did not have much more to go on other than that I had found that under some circumstances the application of sorbothane to the earcups or other parts of some headphones could make a remarkable change in their sound. Now I realize that as important as that finding may be, more significant is the fact that doing anything to the body of the phones could markedly change their sound. I now believe this means that there is a large amount of mechanical energy floating around most phones, which is insufficiently damped and which is messing up the sound of even the best phones. Even more remarkable is that  this phenomenon has either not been observed before or has been ignored by even the top headphone makers, although not by speaker makers who seem to go to much more effort to reduce mechanical resonance.
 
I do not claim to fully understand what is going here but briefly what I think is going on is based on simple Newtonian laws of physics.  When a headphone is running, as much energy is going back into the earcups as is making the drivers move  (equal and opposite principle). This energy has to go somewhere since it cannot be "created or destroyed."  It shakes the earcups and possibly the driver again and thus you end up hearing it along with what the drivers are doing. Sorbothane reduces this energy by converting it to heat.  What I hear in an undamped phone is a sort of ambience which goes away when the phone is damped. There is generally a marked drop in volume when sorb is added.  But turn up the volume a notch and now you hear better tonality and definition.  The triangles ring better, there is more bite to the double bass and less overall harshness. ( Yes Stax can sound harsh)   More often now I am hearing the recording ambience which I would have sworn was not there.  And I am swinging and swaying more  to the music.   
 
 I will develop this argument at  a later time, although portions of it are scattered throughout this thread and the earlier one http://www.head-fi.org/t/671314/stax-sr007-resonance-problems  However  I am keeping the current thread for discussions of what may be the more effective types of sorb mods for various Stax phones.  I have also played with some dynamic phones and they also show the same effects of adding sorb, but that is for others to work on.

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).