[weirded]

I bought these in Germany, circa 1991-1993.They cost 240 Deutsch Marks In those 20 years, I've had to replace the cable (original was coiled), ear pads (originals were black) and head strap (original was leatherette). Can somebody help me identify which version this is and what impedance they have?
 

 

[planx]

Aren't all of them 250ohms? This is the DT990 PRO. I have no idea if they older one is any different than the newer ones, but from what I'm aware they are 250ohms

 

[weirded]

Presently, Beyerdynamic offers 32, 250 and 600 ohm versions. Not sure they always have. These seem pretty hard to drive compared to the Senn 595 and Denon D2000 I've got, so my guess is they may be 600 ohm - wondering if somebody can confirm. 

 

[jupitreas]

The modern DT990 Pro uses the cups from the old ordinary DT990 (ie. the one you have). As far as I know, there are only 600 Ohm versions of this headphone available, Beyer did not offer lower impedance versions at this point.

 

[Calypso]

Quote:

As far as I know, there are only 600 Ohm versions of this headphone available, Beyer did not offer lower impedance versions at this point. 

The original version of the DT990 from the mid eighties is indeed 600 ohm

.
http://www.head-fi.org/t/429204/just-dug-out-my-old-beyerdynamic-dt990s-holy-frak

 

[weirded]

Thanks, mystery solved. I contacted Beyerdynamic support and sent them the picture, as well, here is their response (translation mine):
 
 

Thank you for your inquiry about the DT 990. The DT 990 was originally manufactured with 600 ohms. In the early 1990s we switched to 250 ohms and offered a conversion kit from 600 to 250 ohms.  
 
If you want to be sure, you can measure the 1/4 inch connector with a digital multi meter.
tip - shaft - left speaker
ring - shaft - right speaker
 
The multi meter measures DC resistance, which differs from AC resistance:
value > 350 ohms = 600 ohms impedance
value < 300 ohms = 250 ohms impedance

 
Just measured mine, the DMM showed about 550 on both sides. Looks like I have the 600 ohm version, as other posters said.