Damping Mechanical Energy Distortion of STAX and other phones with SORBOTHANE and other materials.

[edstrelow]

 
The issue of aerodynamics comes into play as well. Baffle grills, coverings, reflected sounds all play a part in the sig.
 
I think you can probably use a small mic and put it in contact with cups, headband, and other parts to get a fair determination of what the largest culprits would be.

My concern with some measurements is that they may be inaccurate or not even relevant to the key issues.   Also the equipment needed to do this well is quite costly.  I have worked in or around  engineering or acoustics labs and the equipment costs are huge.  Certainly I expect companies like Sennheiser, Phillips and possibly even Grado to have some of this.  As I have mentioned, Sorbothane doesn't seem to offer much data on their products or do much measurement related to these issues.
 
In the end you are concerned with the sonic product the ear or microphone actually picks up but you need to tease out what the mechanical vibrations are doing to this sonic product as distinct from the airborne reflections coming from the parts you mentioned.  As well there are resonances in the air chambers of the headphones and physical characteristics of the drive to consider.
 
Another  technique which might help is what I think are called "waterfall" graphs. I have seen some, which looked at the decay of impulse sounds over a few milliseconds.  I think zolkis was referring to these.earlier.  These don't directly tell you what is going on due to vibrational issues since they pick up all the delayed signals. However if you compared plots from damped vs undamped systems you might get some clues as to what’s going on although it wouldn’t give you definitive answers.
 
Ultimately, I think you need a different kind of sensor than a regular microphone to tell what sort of vibrations any part of the earcup is undergoing. And even then, if you had a sensor which you could directly attach to portions of the earcups it would need to be heavily insulated to keep airborne signals from getting to it and contaminating the results.
 
All in all, I don’t think this is an easy problem to understand or solve and it seems to fall more into the realm of mechanical rather than electrical engineering. However most of the people working in audio, seem to have an EE background. I recall reading a post from a mechanical engineer in another forum who was quite caustic about theories put forward by audiophiles and EE types about mechanical type issues in audio. He was saying that they had come up with their own version of science unmoored from the real thing. In my opinion, much the same could be said about the psychoacoustic discussions on these forums.

 

[Tyll Hertsens]

Such is the lot of the enthusiast...but this directed play can still be a whole lot of fun. Plenty of learning to do for all.

 

[zolkis]

Not completely convinced that the measurement junkies have it right at the best of times.

Using materials to damp out mechanical vibrations would tell me that the logical way to proceed would be to measure the phone to see where it is vibrating and at what frequencies. That means the outside, the headband, etc. Simply stuffing materials in and on a phone and measuring the resultant change in sound sig  strikes me more and more as a crude shotgun type approach.

Still better than doing the same and just listening without measuring. Measurements do help guiding or at least sanity-checking the process. Of course you have to know the given application, that goes without saying. For instance the TH900 seems to be a type of Onken loading and it's more likely to be fixed by port tuning than controlling resonances, but the latter may play a role as well. If big enough to show up in measurements, certainly needs to be handled. The Lawton mods do result in measurement changes, as do any mods tgat put whatever small piece of material in the way of sound waves. Consistent correlation between measurements and listening is where the art begins. If enthusiasts do nothing else than noticing issues and show some results, it's good enough contribution. Perhaps the pros will pay more attention next time.

 

[Hutnicks]

   
All in all, I don’t think this is an easy problem to understand or solve and it seems to fall more into the realm of mechanical rather than electrical engineering. However most of the people working in audio, seem to have an EE background. I recall reading a post from a mechanical engineer in another forum who was quite caustic about theories put forward by audiophiles and EE types about mechanical type issues in audio. He was saying that they had come up with their own version of science unmoored from the real thing. In my opinion, much the same could be said about the psychoacoustic discussions on these forums.

Thisis quite a good summary IMHO. I think foremost one of the largest issues is one you addressed partially about the accuracy of measurements. When dealing with uncalibrated rigs from myriads of users the results you see fall well into the realm of Subjective observations. Just because something is measured does not by definition mean it is objective. In essence what we wind up with are "opinions" with some decent graphed interpretations. That is not necessarily a bad thing, until someone starts working with it as empirical truth.
I have worked both ends of the gig with EE's and ME's. Some interesting conversations are to be observed when they get together to solve some inherent problem with an electro acoustic device

 
The whole psycho acoustics thing as is currently understood and under review, if given the due it deserves on this and any other Headphone forum would shock most. There is a large movement studying concert halls and making recommendations to revamp them worldwide. The way we hear is now better understood and in all truth headphones could not possibly capture all the input needed for our brains to trully perceive a recording.
I would strongly urge anyone with an interest to read up on or look up the TED talk with Evelyn Glennie. She is the most successful percussionist in history, and happens to be deaf. She was one of the first people to be recruited into evaluating concert venues as her insight into hearing is tremendous.
Another recent issue is more in regards to ancient venues a fascinating little blurb is to be found here.http://www.theatlantic.com/technology/archive/2016/02/byzantine-angel-wings/470076/
This type of research if married into a playback device may well be a step in creating realistic soundstaging that is not just a gimmick.
 
So yes, in short the mechanical end of the spectrum offers a lot of hope, and I am sure a lot of red herrings as well.
 
 
 

  Such is the lot of the enthusiast...but this directed play can still be a whole lot of fun. Plenty of learning to do for all.

You have a search bot running to report whenever you're mentioned

 
Great little article on the HD800S, thanks for that. It is definitely food for thought for modders and gives a hint into what you need to have in the bag to implement the elegant solution.
Katz's Oppopotamus article was great as well.
 
PS. If by any chance you have em around and are bored some time. Try sticking a couple of strips of Sorbothane across the rear of the cups of the Tascam TH02's. I have been working with those for a while and the results to be had out of that 20 dollar wonderphone are pretty impressive. If everyone could standardize on that and test mods out on it and publish results we would be a long way toward all getting on the same page.

 

[richard51]

if it is a purely  mechanical engineering problem only, why sorbothanizing my Sansui amplifier, with the sorb. between the 2 granite plates, or with sorbothane under my Stax energizer,  translate immediately  in a new  perception of the sound from  the mechanical vibrating  membrane of my speakers or headphone, when in my amplifier or in the energizer the sound is only  an electrical impulse without supposedly any interaction with the mechanical aspect of the amp. or of the energizer ? 

 
i think it is because the problem is in the interactive frontier  between electrical and mechanical problem... a complex resonance problem not a simple one located only at the membrane and chamber-cup site...My 5 cents...My remark is more a question than an affirmation however, because i am more in the genus dumb poet than  in the species nobel science prize ...

 

 

[zolkis]

I tried 1/2" and 1/4" self-adhesive Sorbothane Duro 30 on my modded Fostex TH900, first too much, then removing some, in order to settle with a subjective optimum.
 
I measured the same driver before and after. The repeatability of my rig is pretty good, even through removing and replacing the headphones. Depending where I applied the Sorb, impulse response improved or stayed, but not much change. Distortion figures improved in all cases. Frequency response has slightly changed, but it's not significant either. So as far as measurements go, it seems that Sorb tends to reduce distortions (depending on the place, it can be 2 times reduction). In the figure, green line is with no Sorb, THD=0.602%, red line is with the best Sorb configuration, THD=0.335%, both with 1/6 octave smoothing. Note that this is my modded version. The stock one measures even worse.
 

 
 
Subjectively it sounds a tad darker but smoother, and with a more constricted/confined sound stage in the case of the TH900. The difference is quantitatively small, but quite noticeable.
 
Sorb seems to be the same material I used in certain speakers in the end of 90's called Deflex, which looks like 30 Duro Sorb with a special ragged surface, designed to be put on the back panel of a speaker to deflect, attenuate and scatter the primary backwaves. I noticed that time that when Deflex is in the direct path of the sound waves, it tends to make things darker and muddier. However, it worked much better when I used them on vibrating panels but on the other side, i.e. not hit by sound waves. 
 
I have found that in the case of the Fostex TH900, since the Sorb was placed on the driver's magnet, and/or driver assembly, and/or driver support plate, and/or cup - it was in the way of the sound waves and caused issues, the biggest issue being reducing sound stage. The least intrusive application (in the picture above) was 1/4" strips around the driver frame, and 4 short pieces of 1/4" on the driver support plate. However, after 8-10 hours of subjective listening, I have ended up removing all Sorb from the TH900. Also, without Sorb it works better with the original Fostex dampers (made of foam rather than felt, for obvious reasons: QC). That is darker sounding and more bassy to start with (goes flat to 20 Hz 6 dB higher than the green line), and didn't sound good with Sorb.
 
All in all, the sorbothane mods seem to be non-intrusive, low risk and cheap mods, both in money and time, but you need to find the right place to apply it and the right amount.
I assume Sorb would work better on open headphones when applied to the frame externally (not in the direct way of the sound waves). My Stax 007 will be the next target.
 
Don't take the above for granted, even if I measured things - of course they have not much more authority than subjective opinions.

 

[richard51]

  I tried 1/2" and 1/4" self-adhesive Sorbothane Duro 30 on my modded Fostex TH900, first too much, then removing some, in order to settle with a subjective optimum.
 
I measured the same driver before and after. The repeatability of my rig is pretty good, even through removing and replacing the headphones. Depending where I applied the Sorb, impulse response improved or stayed, but not much change. Distortion figures improved in all cases. Frequency response has slightly changed, but it's not significant either. So as far as measurements go, it seems that Sorb tends to reduce distortions (depending on the place, it can be 2 times reduction). In the figure, green line is with no Sorb, THD=0.602%, red line is with the best Sorb configuration, THD=0.335%, both with 1/6 octave smoothing. Note that this is my modded version. The stock one measures even worse.
 

 
 
Subjectively it sounds a tad darker but smoother, and with a more constricted/confined sound stage in the case of the TH900. The difference is quantitatively small, but quite noticeable.
 
Sorb seems to be the same material I used in certain speakers in the end of 90's called Deflex, which looks like 30 Duro Sorb with a special ragged surface, designed to be put on the back panel of a speaker to deflect, attenuate and scatter the primary backwaves. I noticed that time that when Deflex is in the direct path of the sound waves, it tends to make things darker and muddier. However, it worked much better when I used them on vibrating panels but on the other side, i.e. not hit by sound waves. 
 
I have found that in the case of the Fostex TH900, since the Sorb was placed on the driver's magnet, and/or driver assembly, and/or driver support plate, and/or cup - it was in the way of the sound waves and caused issues, the biggest issue being reducing sound stage. The least intrusive application (in the picture above) was 1/4" strips around the driver frame, and 4 short pieces of 1/4" on the driver support plate. However, after 8-10 hours of subjective listening, I have ended up removing all Sorb from the TH900. Also, without Sorb it works better with the original Fostex dampers (made of foam rather than felt, for obvious reasons: QC). That is darker sounding and more bassy to start with (goes flat to 20 Hz 6 dB higher than the green line), and didn't sound good with Sorb.
 
All in all, the sorbothane mods seem to be non-intrusive, low risk and cheap mods, both in money and time, but you need to find the right place to apply it and the right amount.
I assume Sorb would work better on open headphones when applied to the frame externally (not in the direct way of the sound waves). My Stax 007 will be the next target.
 
Don't take the above for granted, even if I measured things - of course they have not much more authority than subjective opinions.

my experience is when there is too much sorb. the soundstage is constricted with my speakers or headphone...Very interesting remarks and analysis... thanks very much ...
 
By the way i am sure that your remark about applying the sorb. externally and not too close to the driver is right on the spot ....
 
And i must say that with my Stax sr-5 and hybrid planar speakers, the application of the sorb. give more tonal and timbre accuracy, a better 3-d imaging,  hence certainly not a more bassy and darker headphone or speakers, hence i think that the application of sorb. is a case by case experiment with no general rule for all headphone or speakers, except not too much sorb, right duro, right thickness, and right form and right place for the sorb.  for each particular case of study

 
 
the Headphone is the most difficult piece of gear to sorbothanize....For an amplifier with near 30 pounds like mine, the best method is the sorb. between 2 granite plates, the same with my 30 pounds woofer.... i will not repeat all i had already said here, just one thing : all sorbothanization of each piece of my gear, surge protector, dac,energizer, amplifier, woofer, speakers, each time converge towards a more better tonal timbre, and 3-d imaging, and  sorbothanizing only the  headphone was already  an extraordinary result to obtain, the most difficult to rightly implement, but the final extraordinary result i listen to now  is the cumulative  effect of  the sorbothanization of all the  gear....

 

[edstrelow]

I tried 1/2" and 1/4" self-adhesive Sorbothane Duro 30 on my modded Fostex TH900, first too much, then removing some, in order to settle with a subjective optimum.

I measured the same driver before and after. The repeatability of my rig is pretty good, even through removing and replacing the headphones. Depending where I applied the Sorb, impulse response improved or stayed, but not much change. Distortion figures improved in all cases. Frequency response has slightly changed, but it's not significant either. So as far as measurements go, it seems that Sorb tends to reduce distortions (depending on the place, it can be 2 times reduction). In the figure, green line is with no Sorb, THD=0.602%, red line is with the best Sorb configuration, THD=0.335%, both with 1/6 octave smoothing. Note that this is my modded version. The stock one measures even worse.







Subjectively it sounds a tad darker but smoother, and with a more constricted/confined sound stage in the case of the TH900. The difference is quantitatively small, but quite noticeable.

Sorb seems to be the same material I used in certain speakers in the end of 90's called Deflex, which looks like 30 Duro Sorb with a special ragged surface, designed to be put on the back panel of a speaker to deflect, attenuate and scatter the primary backwaves. I noticed that time that when Deflex is in the direct path of the sound waves, it tends to make things darker and muddier. However, it worked much better when I used them on vibrating panels but on the other side, i.e. not hit by sound waves. 

I have found that in the case of the Fostex TH900, since the Sorb was placed on the driver's magnet, and/or driver assembly, and/or driver support plate, and/or cup - it was in the way of the sound waves and caused issues, the biggest issue being reducing sound stage. The least intrusive application (in the picture above) was 1/4" strips around the driver frame, and 4 short pieces of 1/4" on the driver support plate. However, after 8-10 hours of subjective listening, I have ended up removing all Sorb from the TH900. Also, without Sorb it works better with the original Fostex dampers (made of foam rather than felt, for obvious reasons: QC). That is darker sounding and more bassy to start with (goes flat to 20 Hz 6 dB higher than the green line), and didn't sound good with Sorb.

All in all, the sorbothane mods seem to be non-intrusive, low risk and cheap mods, both in money and time, but you need to find the right place to apply it and the right amount.
I assume Sorb would work better on open headphones when applied to the frame externally (not in the direct way of the sound waves). My Stax 007 will be the next target.

Don't take the above for granted, even if I measured things - of course they have not much more authority than subjective opinions.

Wow, actual frequencies response and distortion measurements even with a caveat. Not something we see too often in these forums. Very interesting indeed.

 

[zolkis]

Don't take these measurements for anything yet: I am still learning my way with Sorbothane . I think I've got the taste of it: it should indeed "calm down" the sound and make background blacker, 3D more defined, and attacks/decays cleaner. Of course it won't make the same magnitude change in each application, especially when the opportunity for improvement is masked by other, bigger problems, but indeed every equipment should deserve some time of Sorb applicability testing .

 

[wink]

I put some sorbathane in my shoes, and now when I walk around listening to my headphones - I don't rock as much.....   

 

[edstrelow]

I put some sorbathane in my shoes, and now when I walk around listening to my headphones - I don't rock as much.....    :blink:

Glad it works for you mate. Should keep the old brain from rattling around in an empty skull.

 

[bnsb]

  I put some sorbathane in my shoes, and now when I walk around listening to my headphones - I don't rock as much.....   

Wont try that, I love Rock and Roll 

  Seriously one of the best use of Sorbs are as shoe inlays for rehabilitation or correction.

 

[edstrelow]

Wont try that, I love Rock and Roll    Seriously one of the best use of Sorbs are as shoe inlays for rehabilitation or correction.

While things like sorbothane footers have been sold in audio for probably a couple of decades now, if you check the Sorbothane company website you will see that there is a wide range of sorbothane products that have nothing to do with audio. Sorb or similar products get used to dampen vibrations of factory machines, jet engines and a range of biological applications such as insoles. I often wonder if the concussion problem in American football isn't partly due to the use of the wrong padding in football helmets and whether better chosen damping material might reduce these injuries.

 

[Hutnicks]

While things like sorbothane footers have been sold in audio for probably a couple of decades now, if you check the Sorbothane company website you will see that there is a wide range of sorbothane products that have nothing to do with audio. Sorb or similar products get used to dampen vibrations of factory machines, jet engines and a range of biological applications such as insoles. I often wonder if the concussion problem in American football isn't partly due to the use of the wrong padding in football helmets and whether better chosen damping material might reduce these injuries.

I do not think Sorb would be the ideal for helmets.  It is usually the second impact (Brain hitting Skull) that causes the most damage
 
For super damping Alpha Gel is the only way to go.
 

 

[edstrelow]

 
I do not think Sorb would be the ideal for helmets.  It is usually the second impact (Brain hitting Skull) that causes the most damage
 
For super damping Alpha Gel is the only way to go.
 

That's impressive. Maybe we need to look into this material for headphones. I was aware that there are other materials out there but haven't seen any claims yet for audio usage other than dynamat which is sold for soundproofing but gets some use as a damping material in headphones too. It could be that very soft (low duro) sorbothane could do what is shown in the video too.  Sorb is used in some helmets but I  don't know if the NFL is seriously working on the most effective shock absorbing/damping material.