[wakibaki]

Quote:

Maybe a cheap DT880 clone ? something like a Superlux HD-330 ? No idea if it would work alright.

But if you do get the CNC you could build everything from scratch

 
Hadn't thought of that...
 
The Superlux look like they might be a good bet though.
 
w

 

[spritzer]

I'd be worried about that band in the middle of the earcups.  Backwave reflection is a pain and does a lot of harm. 

 

[wakibaki]

So an open back is essential? That's something I wondered about, but never having had my hands on any electrostatics, I just didn't know, and nobody has said explicitly in the thread (I think). I've read most of it, but skimmed a few pages.
 
Maybe the phones would survive having the band cut off. Or maybe a layer of absorbent material stuck on. Sheepskin? They look useful for the price.
 
w

 

[spritzer]

Electrostatics are true dipoles so equal radiation front and back.  If anything reflects the backwave towards the front then there are numerous issues.  That is not to say it can't be done but the only good closed electrostatic is the Stax 4070.  There they used a clever bass reflex system to minimize the effect plus the neat chassis design.  Koss went a different route, they grounded the back stator or drove it at a diminished level to minimize the backwave.  Essentially single ended but the effect is minimized with the grounded back stator. 

 

[wakibaki]

Interesting. I wonder what happens if you don't perforate the rear stator, except for a small hole to allow equalization of atmospheric pressure, like an acoustic suspension speaker. Half a millimeter is a wavelength at 640.58kHz. Or a delay of 1.5 uSec. Something to try when I get moving with this. 
 
First CNC guy came back with a counteroffer 1.5% down on original price, second place I tried still hasn't responded to my best offer. At this rate I might as well pay the full asking price.

 

[AmarokCZ]

Do you hate bass and mids? No? ...then don't even try it. 

 

[arnaud]

Acoustic reflections occur with both an open and close back design (against popular belief) but the reflections are much worse in case of a closed back / affecting all frequencies and need to be handled by some acoustic sound absorbers.

In estat, there's another implication: the acoustic load the configuration presents to the diaphragm. A quasi non-perforated rear stator would certainly do something, not sure it'd be of any advantage though...

And another implication: the damping of the diaphragm motion through viscous effects in the DS gap / through the perforations / through the nearby felt or foam. Arguably, the foam/felt being the most influencial on the damping, with a closed back stator you'd loose the opportunity to damp the diaphragm from the rear stator.

About the delay for reflections, you should also consider those from the pinna.

 

[chinsettawong]

Quote:

Do you hate bass and mids? No? ...then don't even try it. 

 

[wakibaki]

I've never been put off an experiment by the fact that it might produce a negative result. A negative result is still a result.

 
If you're saying you've tried it...
 
2u mylar arrived today. I bought the CNC mill.
 
w

 

[chinsettawong]

Quote:

If you're saying you've tried it...
 

 
Oh yes, I have. 

 

[wakibaki]

So you must have thought it was a good idea at one time?
 
w

 

[spritzer]

I've tried it as well.  Not a good idea but it had to be tested.  Same as applying bias to the stators and drive the diaphragm SE, reduced operation on one stator etc. etc. 
 
Personally I'd just stick with the classic setup. 

 

[chinsettawong]

I'm sure W will try it somehow. 

 

[bidoux]

I have a question about the type of glue that can be used to attach the diaphragm on the stator. I have been using epoxy glue but it is hard to do something clean. I was thinking of trying super glue, which is more liquid but I am not sure if it is a good idea. Any input ?
 
Quote:

2u mylar arrived today. I bought the CNC mill.
 
w

I think you will be drilling lots of tiny round holes in the near future

Congrats

 

[chinsettawong]

The best glue that I've found so far is contact cement (yellow rubber glue). 

 
Wachara C.