[nick n]

I should have been more clear I think it is for breaking up standing waves/that type of thing but who knows. Curious though no matter  what

 

[DefQon]

I'm gonna post some pics of a pair of dud weird looking drivers ripped from a vintage Pioneer headphone (probably the only person on headfi to own it) for you guys to identify later today.

 

[vid]

The AKG K 160 has one dot, right in the middle.

 

[MassiveTurboLag]

It's disconcerting how alike drivers from different manufacturers look.

 

[DefQon]

Pictures as promised, the top pair are duds, if anyone can ID any other headphone that have used them (weird construction too, 45mm diameter 32ohm, 96db /mW max 100mW), please PM me.
 

 

 

 

 

 

[GREQ]

I thought the dots might be used as an identifier - perhaps the more dots the better quality the driver.
As far fetched as it sounds, it's not far from the actual truth.

 

[nick n]

Koss TD85 55mm ~ 50 ohm, before driver vent mod, before it's new Stax home.

 
Yamaha YHE-50A
 
Tiny little thing ~ 38 - 40mm.

 

[GREQ]

Beyerdynamic DT75 Special Edition
 

 

 
As you can see in the first pic, the drivers are glued to the baffles, so I couldn't get a proper photo of the diaphragm.
I would have posted these photos sooner, but this is the 2nd set of DT75's I've owned, and my first set was in pristine condition, so I didn't want to pry around inside and risk any damage. 
This one had TOTALLY flat rotten pads, so I gutted out the rotten foam, cleaned off the gunk with spirits, put in some new foam and took these photos in between.
 
I'm actually surprised at how little of the diaphragm is exposed because these actually sound pretty good. 

 

[takato14]

  It's disconcerting how alike drivers from different manufacturers look.

Well dynamics may look a lot alike, but there are a LOT of factors design wise that look trivial/miniscule and cause massive differences sonically. 
 
And remember this rule; a headphone's sound is about 20% driver and 80% implementation; there's no reason for them to look much different. Put an HD800 driver in another housing and I guarantee it'll sound horrible.

 

[takato14]

Here's something gorgeous: A gold plated dynamic from the Sony DR-M5:
 

 
50mm diameter, with an odd petroleum jelly like lubricant around the edges of the driver.
 

 
Interestingly, this was the first foldable portable headphone from Sony and it actually has damping and latticing in the cups (!!!), presumably to make the headphone isolate better. Unfortunately, not only is the headphone rarer than hen's teeth and kind of meh sounding but it was also sold to me recabled, missing pieces, with the headband on backwards and with one diaphragm completely ripped out of the cup. Delightful.

 

[Acix]

  Here's something gorgeous: A gold plated dynamic from the Sony DR-M5:
 

 
50mm diameter, with an odd petroleum jelly like lubricant around the edges of the driver.
 

 
Interestingly, this was the first foldable portable headphone from Sony and it actually has damping and latticing in the cups (!!!), presumably to make the headphone isolate better. Unfortunately, not only is the headphone rarer than hen's teeth and kind of meh sounding but it was also sold to me recabled, missing pieces, with the headband on backwards and with one diaphragm completely ripped out of the cup. Delightful.

 
 
I have those hps for a few years now and they sounds great, remind me of the HD-25 but more balanced. 

 

[GREQ]

 

 
 

*_*   those drivers are mezmerizing!

 

[Wilashort]

  Here's something gorgeous: A gold plated dynamic from the Sony DR-M5:
 

 
Interestingly, this was the first foldable portable headphone from Sony and it actually has damping and latticing in the cups (!!!), presumably to make the headphone isolate better. Unfortunately, not only is the headphone rarer than hen's teeth and kind of meh sounding but it was also sold to me recabled, missing pieces, with the headband on backwards and with one diaphragm completely ripped out of the cup. Delightful.

Beautiful Drivers

 

[takato14]

 
 

 
The left one from the current Koss pro4 Series with Titanium coating. The right one from the HV/1A series from 1974. Booth have the same diameter size about 57mm and a fully compatible design. 
The left picture of the backsight of the pro4 shows above the dampening venting material.
The HV driver has a huge magnetic structure and weight a bit more.The plastic frame is also better quality made. From the sound the HV outperforms the pro4 in every aspect.
 

Strange, my 4AAAT's diaphragm looks far different than that, its a very bright and vibrant silver with a subtle rainbow tint. It also sounds superior to the vintage KOSS Pro drivers in every aspect...
 

 

 
I'd take pictures of the bare drivers but I literally CANT get these pads off for some reason.
 
Which headphone did yours come out of? A modern 4AA? A 4AAT? Either that or KOSS changed them, likely for the better...
 
EDIT: Here's some better pictures.
 

 
The rainbow tint is difficult to capture on camera, unfortunately.
 

 
From right to left, KOSS Pro drivers series 1-4.

 

[pkshan]

sennheiser hd560