[Bill13]

I was more than pleasantly surprised by doing a ‘mod’ of my old Stax Signatures.  IMO, this mod has much promise, and even sounds very good without adding EQ (yet).   Easier to listen to than my Stax Omega SR-007 --- dare I say ‘better’ in some respects. Because of the close proximity to the ear, the bass output doesn’t seem to be much less - if at all.  Of course, more listening is required before writing more. 
Some members might think I’m throwing a ‘curve ball’ here, and trying a crazy thing, but thought that I would share preliminary results of an experiment (mod) that I did with an old pair of Stax Lambda Signature phones. The Signature’s earpads and foam were totally deteriorated, so I decided to listen truly “open air” without earpads  -- like the Sony MDR-F1.  The resulting open phones minus pads are very lightweight, and IMO, now much more comfortable than my Omega SR-007, or even my other Lambdas. 
I was motivated to do this experiment for the following reasons:[size=10pt][/size]

• I’ve got an intuitive feeling that mounting an electrostatic transducer (‘sound element’) in any sealed cavity (e.g. Lambdas and Omegas) will usually present acoustic response problems (resonant cavity frequency response peaks and valleys, etc).  For loudspeakers, advantages have been demonstrated  using ‘open baffle’ mounting, provided the proper frequency response equalization is applied (so far, this equalization requirement seems to repel many potential adopters of an open baffle approach.
• Growing tired of the annoying “Stax Farts” and uncomfortable hot “sweaty ears” – So, like the Sony MDR-F1 open phones, I decided to let the Stax wire mesh/plastic mount rest upon my ears (can add a thin tape layer over the plastic case edges) – if nothing else, allows great air circulation … an open baffle.  [size=10pt][/size]
• The big Jecklin Float Electrostatic was comfortable for long term listing[size=10pt][/size]
• The Sennheiser Orpheus is diffuse field equalized. So, proper equalization is not inherently a bad thing.  {Perhaps Stax has a hard act to follow, because the Orpheus reportedly used a 1 µm diaphragm that was gold-plated using vapor-deposition technique, & electrodes made from special glass, etc.} [size=small][/size]
• BTW, earphone equalization can be automatically ‘profiled’ when using the Smyth Realiser. [size=small][/size]
• An example of earphone EQ:  There’s a typical EQ circuit, with technical discussion at http://www.linkwitzlab.com/reference earphones.htm  regarding the Sennheiser HD 414 open-air, supra-aural headphones {414 sufficiently well behaved for equalization}.[size=small][/size]

More latter -- if there’s interest.[size=small][/size]
Bill13

 

[Ikarios]

Isn't this basically turning them into Sigmas?
 
Nevertheless, I'm quite interested! I'm bothered by the same problems you had - the Stax fart and the warmth of the pleather pads. This might be worthwhile to try on a cheaper Lambda basic model, the original normal bias.

 

[Bill13]

I did the mod on my old Stax Signatures because apparently I had nothing to loose - the earpads and foam were totally shot - so 'why not'. 
 
So far, the mod's sound is clear and much more open compared to the original Lambda Signature .. there is still the typical slight high frequency 'etch' which can be alleviated by EQ, or perhaps moding a newer SR-407 which reportedly doesn't have this slight "etch" sound (?).  To me it's all worth it just for the open-air comfort, and 'fart' relief (just my opinion, for my ears)
 
The Sigmas place the sound element some distance away from the ear at an angle to ake the sound seem like it arrives from in front & outside the wearer's head.  
However, the mod to the Lambda phones has the sound element's wire mesh cover essentially in contact with the ear - like the Sony MDR-F1 which is open air, or open-baffle, if you will.
 
If you Google a picture of the Sony MDR-F1, you can see what I mean by the ear contacting the phone's wire mesh.
 
I think that Stax somehow missed the boat regarding opportunity to develop and market a comfortable open-air electrostatic ear-speaker with proper EQ frequency response.
 
BTW, IMO a smaller, lighter version of the Jecklin Float Electrostatic should be available to listeners who don't need to listen at ridicuously loud volume at bass frequencies. 
 
 Incidentally, I have decades-old 'normal bias' Stax Sigma -- & I may someday try to replace the original sound element with a 'pro' 580 V bias element from an old Lamba (I have accumulated several pairs of Stax over the years).   I like the Sigma's out-of-head soundstage.
 
Bill13

 

[edstrelow]

How do they stay on your head without earpads to hold them in place?
 
No this is not what a Sigma does. the Sigma is mounted in front of the ear firing back and there is a large earcup which acts as a resonating chamber and blocks some backwave sound. 

 

[Bill13]

The modified Lambda Sigatures stay in place OK, no problem. - The Lambda wire mesh cover with plastic frame contact the ear/head area to help prevent slippage (for my ears/head, anyway).
 
OK, the Sigma transducer is front mounted ("firing back", as you say) at about a 90 degree angIe to the ear -  it's still an 'angle' mounting - isn't it?  No big deal.
 
OK, maybe my description wasn't clear enough, with the best wording, but it was essentially correct.
 
Anyway, I have Sigmas, and know very well what they are, and what they do.  Incidently, these old Sigmas have fiberglas lining in the chamber presumably for some resonance suppression.  If there was also foam in the earcup at one time, the foam disappeared (rotted out ?) a long time ago. 
 
In a way' I'm surprised that these Sigmas still work.  They withstood the test of time much better than my oldest Lambdas.
 
BTW, I still have the new Stax SR-009 on order, which, hopefully, will far surpass what modified Lamdas can do. 
Based on several early reports, the SR-009 sounds fantastic, and many audiophiles expect it to be the new reference headphone.