[cucera]

I can report a clearer sound and dryer bass with the Stax 4070.

 

[edstrelow]

Where did you put the sorbethane and how much did you use?

 

[cucera]

I damped the Headband like your 007 and put one aditional stripe at the bottom of the cup.

 

[edstrelow]

I get a nice dry, punchy bass with the Lambdas and the SRXIII pro too.  In fact I was just listening to a recent DG recording of Tchaikovksy's  5'th symphony on  my damped lambda LNS and the 3'rd movement was dazzling with  the pizicato, drums and solo instruments. Very much the sound you expect to hear in the concert hall. However I have yet to get this effect properly with the Sigmas and 007A.  I am getting an occasional booming deep bass with the 007A. Although adjusting the clamping force of the clamped sorb helped.  However, I want to start all over again with them because I think that if you can work out the optimal damping of the 007's they could be incredibly good.
 
One of the more interesting experiences I have had with sorbothane damping is getting boomy and distorted bass, first with a Sigma and then with an 003. The Sigma's problem went away when I re-glued the sorb and the 003 required me to reduce the amount of sorb I was using.  At a guess, I would say that the sorb was storing some of the bass energy and feeding it back to the drivers. So it can be tricky getting it right.

 

[edstrelow]

Eureka! The 007A comes alive with the right damping.  While I first started to explore the use of sorbothane on Stax phones with the 007A, in the last few months  my 2 damped Lambdas, LNS and 404, have been getting more listening, along with the damped SRXIII pro.  So  I removed all my previous damping efforts on the 7 and started over. One of the reasons I suspect that the damped Lambdas sounded so good was that the sorbothane was placed right on the  baffles next to the drivers. I.e. you can't get it any closer to the drivers than that.  Unfortunately the 7 defeats you on that score, I just couldn't see where to put sorb next to the drivers unless I was willing to put it one the dust covers. So instead I put 1/8 inch sorb on the plate that holds the phones together, still pretty close to the drivers.
 
IMPORTANT EDITS
 
(Edit Feb 20/15 - now using 1/4 in 30 duro sorbothane which seems better. )
 
( I spoke to a technical person at Sorbothane on April 27, 2015 who advised me that damping occurs on a basis of about 40 dB/cm of thickness at 50 Hz and above.  He did not however have any data on the linearity of the damping)
 
( Edit April 27, 2015 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 duro 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 a 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.)
 
EDIT 5/28/2015  Cutting the ring into 8 segments was even better.  Even better dynamics and less bass boominess.   I think this is now the world's best headphone!

 
This sounded very much better than my last effort with these phones.  The previous sorb effort, (see pictures in earlier posts)  while generally sounding better than the basic phone, had a somewhat recessed midrange and an occasional deep bass boom.  Now the sound was much better balanced.  However, still, it was arguably no better than the damped Lambda LNS .
 
I looked at the headband arcs again, which is what got me started in the first place. When I tap them, they still ring.  So if any energy is getting from the ear cup, it could resonate here and even get over to the other cup, giving crossfeed.    So I took the old arc dampers and placed them at the base of the arcs, and also over the top metal and plastic portions of the earcups and then screwed them in place.
 
Each damper consists of two rigid plastic sections about 3 inches  by 1 1/2 inches and each has 4 1/8 in sorb pads about 1 in square, 2 on the top and 2 on the bottom plastic sections.  They are placed on the inside and outside of the arc band and screwed together  with one screw and nut .  Another advantage of this system is that you can tweak the sound to some degree by tightening and loosening the screws. Generally if these are fairly loose you will get more bass, as you tighten them, the bass decreases and the treble comes up.  However I have not checked these effects over all ranges of tightness.  If you tighten them too much I suspect they don't do much other than add some mass to the phones.
 

 
The sound is now very, very nice. Great definition of all frequencies, individual voices and instruments tend to jump out at you and finally an 007 which sounds better than the damped Lambdas.   As I have noted above on some other phones,  I believe the overall volume becomes lower after the damping is applied  and I seem to be turning the amp, a 717, up higher than on undamped phones.   This is possibly not surprising given that we are talking about "damping."
 
So what exactly is going on here?  I believe the damping is getting rid of a lot of energy in the earcups of the headphones, which is coloring the sound (and increasing the volume.)  In this respect what I am doing is like damping speaker boxes or putting spikes under them to stop the boxes from coloring the sound. Of course a full explanation  may not be that simple, but hopefully this will get figured out in due course.
 
Anyway, for the moment I just want to spend some time enjoying these, and then hopefully on to the Sigmas.
 
I hope to bring several of these phones to the SoCal CanJam in March.

 

[edstrelow]

Technical/promotional material from the sorbothane people about this material. Among other interesting points, they contend that the energy which gets absorbed is turned to heat. http://www.sorbothane.com/blog/what-material-is-best-for-damping/

 

[soren_brix]

very interesting read Edstrlow. Thnx a bunch for sharing.
In rgrds to the Sigma's, have you considered placing the sorbotane on top of the driver? (the side that faces towards the inside of the housing, and on the inside of the side facing the head (or hole to the ear)?
As far as I remember from doing the 404 upgrade, there are some space around the driver that is stuffed with glass wool. (I might remember wrong though)
Another thing is the 007 ... have you considered damping the top mess? the part that is covered by the earpads ... or would it just be crying for trouble?

 

[edstrelow]

  very interesting read Edstrlow. Thnx a bunch for sharing.
In rgrds to the Sigma's, have you considered placing the sorbotane on top of the driver? (the side that faces towards the inside of the housing, and on the inside of the side facing the head (or hole to the ear)?
As far as I remember from doing the 404 upgrade, there are some space around the driver that is stuffed with glass wool. (I might remember wrong though)
Another thing is the 007 ... have you considered damping the top mess? the part that is covered by the earpads ... or would it just be crying for trouble?

Actually there is almost no space left here.  Even though the  Sigmas are the predecessor of the Lambda, the Lambda has far more space here.  However, I have just finished work on the Sigma/404, see below.

 

[edstrelow]

Finally I got a sorbothane mod for the Sigmas which I like.  As I noted above, the problem with them is finding space on these phones, which is flat and preferably close to the driver on which to put some sorbothane.   So far, I think the best I have done is with the lambdas (404 and LNS)  where the sorb is placed on the baffle that holds the driver. (See first photo below)
 
 
 
.
 
Unfortunately, there is very little room on the baffle of the Sigma.  However, when I opened up my Sigma/404, I realized for the first time that the baffle extends around to the ear side of the earcup. 
 

The baffle is a piece of metal, bent to about 90 degrees.  The earpads are then fastened to what is, in this photo, the vertical section.  And there is a reasonable amount of flat space here.  (Even though there looks like open space around the driver it ends up being pretty much taken up when the rest of the earcup is assembled to the baffle.)
 
Also I have now got a new supply of sorb,  1/4 in. thick, and 30 duro hardness (i.e. pretty soft, smaller duro is lest rigid  and I assume, better for damping).  So I cut a number of pieces of 1/4 sorb to go on the top and bottom of the vertical section around the earhole opening. (new edit)  I am now using a total of 6 pieces of 1/4 inch sorb on the baffle, away from the driver 3 each on the top and bottom. I have since stopped using any sorb  on the back edge for the Sigma Pro and  the Sigma/404  so the picture is a  off in that regard.  To be clear, now there is none behind the ear. The benefits are a marked reduction in the bass boominess of the Sigmas, and a much more balanced sound.)  .
 
 

 
The 1/4 in.sorb was not self-stick so I had to use adhesive, 3M Rubber and Vinyl 80.  I would not want to use this on an exterior part put this is a metal part and on the interior so if I have to remove the sorb, not real harm should ensue.
 
On the other hand the wiring is pretty tight here, this is the original Sigma/404 that I had made by Yamasinc several years ago http://www.head-fi.org/t/175556/the-sigma-404-a-new-stax-headphone and they didn't leave much room to work.   In fact I had to resolder one of the stator leads.  This is the only damage I have done to any headphone during this exercise.
 
The sound is the best I have heard from the Sigma yet.  After I had realized you could damp the 007 by putting sorb on the metal arcs
http://www.head-fi.org/t/671314/stax-sr007-resonance-problems  I started on the Sigmas but had some really odd effects including. at one time. bass distortion.   However, this current arrangement seems to give very clean sound.  I spent some time listening to the naked Sigma/404 i.e. without sorb, before I did this mod.  After getting it modded and back together ( and after I fixed the broken lead) my first impression was of a reduction in harshness, greater separation of instruments and voices, better dynamics and a wider spatial field.    The bass is good, probably a bit better than before, but I wish it were a bit drier.  For my first listening,  I put on  the first recording of Lucia di Lammermoor by the great Australian soprano, Joan Sutherland, and was blown away by how good she sounded when she was young.
 
I do not know if what I have done is the best you can do with these phones, but I am prepared to put this out on Head-fi because I think it is at least good.  I now realize, for example, that you can add sorb to the back edge of the earcups near the head, since this is almost part of the metal baffle.  Anyone who wants to play with sorbothane  on the Sigma without opening them up might want to put a strip here as a first experiment.  I may yet myself.
 
I intend to bring these to the Canjam in March.

 

[soren_brix]

Hi Edstrelow
 
Again thnx for sharing your work and impression.
I have taken the liberty to work a bit on one of your photo's in order to visualize what I had in mind (it still may not work, or simply being pursuing other kinds of problems)

 
I can't figure out from your description whether you have already done damping the BLUE area on the 'vertical' part using the stickers you have designet.
The BLUE and GREEN area on the driver itself could make a difference?
Finally the RED will involve diassembling the protection filter and damp the stator ... there might not be enough space, or it is simply crying for trouble doing so ... was just inspired by some folks experimenting with full size ESL's where they do something like that.
 
Anyway I just wanted to share my thoughts on your brilliant work, and look forward to hear comments

 

[edstrelow]

  Hi Edstrelow
 
Again thnx for sharing your work and impression.
I have taken the liberty to work a bit on one of your photo's in order to visualize what I had in mind (it still may not work, or simply being pursuing other kinds of problems)

 
I can't figure out from your description whether you have already done damping the BLUE area on the 'vertical' part using the stickers you have designet.
The BLUE and GREEN area on the driver itself could make a difference?
Finally the RED will involve diassembling the protection filter and damp the stator ... there might not be enough space, or it is simply crying for trouble doing so ... was just inspired by some folks experimenting with full size ESL's where they do something like that.
 
Anyway I just wanted to share my thoughts on your brilliant work, and look forward to hear comments

Yes I put sorb on the blue, vertical sections. Sorry if that's not clear  in my description. The green and possibly the other blue sections might work too.   I would be loath to do the red just because I wouldn't want to mess with the dust covers, but who knows?   I  do not contend that I have exhausted examination of this topic.  There are potentially a lot of parameters to play with here: location, hardness of sorbothane, attachment and clamping.  I still like my first clamp on the 007 headband because it allowed some tonal adjustment.   Plus, based on my experience of bad bass on some attempts, you apparently can also screw the sound up, suggesting  positive feedback messing up the sound.
 
So you say someone has tried damping electrostatic speakers with sorbothane?  No reason why not, I have put some on my conventional speakers.

 

[soren_brix]

 
Yes I put sorb on the blue, vertical sections. Sorry if that's not clear  in my description. The green and possibly the other blue sections might work too.   I would be loath to do the red just because I wouldn't want to mess with the dust covers, but who knows?   I  do not contend that I have exhausted examination of this topic.  There are potentially a lot of parameters to play with here: location, hardness of sorbothane, attachment and clamping.  I still like my first clamp on the 007 headband because it allowed some tonal adjustment.   Plus, based on my experience of bad bass on some attempts, you apparently can also screw the sound up, suggesting  positive feedback messing up the sound.
 
So you say someone has tried damping electrostatic speakers with sorbothane?  No reason why not, I have put some on my conventional speakers.

Just to be absolutely clear: I really appreciate your effort and work in this area, and that you are sharing - it is a great inspiration, at least to me )
 
In rgrds to damping ELS's with sorbothane; I am not sure about the use of sorbothane, although I have read a few places that damping the stators makes a difference.
[url=http://www.eraudio.com.au/Loud...speaker_Kits/Acorn_ESL_kit/acorn_esl_kit.html[/url]
Stator Damping

Thin metal stators tend to “ring” when producing sound so it was important to provide some damping to the grid to deaden the colouration that would occur. This is especially important where large areas of unsupported stator are exposed.​

Fortunately, our experience with the ESL III and the use of a polyurethane material, which gave superb damping in this speaker, was very successful in stopping ringing. We have therefore adopted the same material and method in this design.​

 ​

Never tried it, so I cannot comment on the effects.​

 ​

I guess doing it on the Lambda drives will need a spacer between the driver and the protection film and it might incure other problems due to the surface the damping occupies.​

 ​

 ​

I have ordered some sorbothane from: [url[https://www.divineaudio.co.uk/audioquest-sorbothane-self-stick-sheet [/url] ...I will try damping my Sigma/404 and see what happens and report back afterwards.​

 

[edstrelow]

 
Just to be absolutely clear: I really appreciate your effort and work in this area, and that you are sharing - it is a great inspiration, at least to me )
 
In rgrds to damping ELS's with sorbothane; I am not sure about the use of sorbothane, although I have read a few places that damping the stators makes a difference.
[url=http://www.eraudio.com.au/Loud...speaker_Kits/Acorn_ESL_kit/acorn_esl_kit.html[/url]
Stator Damping

Thin metal stators tend to “ring” when producing sound so it was important to provide some damping to the grid to deaden the colouration that would occur. This is especially important where large areas of unsupported stator are exposed.​

Fortunately, our experience with the ESL III and the use of a polyurethane material, which gave superb damping in this speaker, was very successful in stopping ringing. We have therefore adopted the same material and method in this design.​

 ​

Never tried it, so I cannot comment on the effects.​

 ​

I guess doing it on the Lambda drives will need a spacer between the driver and the protection film and it might incure other problems due to the surface the damping occupies.​

 ​

 ​

I have ordered some sorbothane from: [url[https://www.divineaudio.co.uk/audioquest-sorbothane-self-stick-sheet [/url] ...I will try damping my Sigma/404 and see what happens and report back afterwards.​

And I appreciate your discussion because I don't think it is very clear  what is going on here and it's an interesting topic, which is I think quite important in headphone design.
 
I am uncertain as to what type of damping was used by the makers of the electrostatic speakers you link to.  I am sure there are other substances which can provide damping. They refer to "polyurethane material" but sorbothane just happens to be well-known and it has been used heavily in audio applications for footers and the like.
 
I got this definition of damping from Wikepedia:
 
"Damping is an influence within or upon an oscillatory system that has the effect of reducing, restricting or preventing its oscillations. In physical systems, damping is produced by processes that dissipate the energy stored in the oscillation. Examples include viscous drag in mechanical systems, resistance in electronic oscillators, and absorption and scattering of light in optical oscillators"
 
The key seems to be "dissipate the energy."  The sorbothane people claim their material does this by converting it to heat  which I guess falls under the category of "viscous drag.".   The speaker people you link to seem to be concerned as much with ringing of the stators.  However it seems to me  that this may be  slightly different issue.  You could make the stators extremely rigid and attach them to some major amount of mass to lower the frequency of ringing.  But you would still have energy passing into the rest of the "system"  which could be damped with sorbothane.
 
Previously you suggested putting damping directly on the stators.  That might get rid of both the ringing and the energy passing through.   However, thinking that electrostatic drivers are fairly delicate, I am reluctant to mess with them, although this in the end could be the best location to start damping.
 
I did one brief test applying sorb to some dynamic phones  and found the sound improving, so I think it's not just a stat issue.

 

[edstrelow]

I am staying up too late listening to the newly damped Sigma/404  and 007.  The 007 has more punch, more detail in the treble and deeper bass.  However the Sigma/404 has that great openness of sound and out of head projection.  Listening to The Book of Mormon ( the musical not the actual book - once described by Mark Twain as "chloroform in print")) I am hearing the recorded ambience clearly for the first time.  Previously I had thought of this as a good recording, but somewhat dry.  I don't get much sense that the sorb differentially affects any set of frequencies.  On the other hand, I seem to be finding the treble almost spectacular in places, especially sopranos.  The bass is generally better on both phones now, no bass distortion as I got on my first damping effort on the Sigmas,  but I still would like a drier bass with the 007, like I get with the damped  LNS Lambda,

 

[edstrelow]

I made a change to the 007's which seems to have brought them to a higher level. This involved removing the 1/8 in sorbothane from the metal plates over the drivers and replacing it with 1/4 in sorb. This sorb is also softer and solid because it consists of rings cut from a large sheet. Previously the rings were assembled from several smaller pieces. So essentially I have doubled the amount of sorb.  The sound is so good just with these new rings that  I have yet to use any clamping on the arcs, even though  I am sure they are causing ringing.(Edit I am now using the damping clamps where the arc meets the earcup as is shown in the previous picture of these phones. I am using 1/4 in at the arc and 1/8  over the top of the earcups)
 
On the other hand adding more sorb to the Sigma/404 just made the sound boomy so  I am sticking with what I reported above for these phones.