Sennheiser unipolar 2000
Flagship electrostatic (electret) headphones by Sennheiser; released in the late 1970s. Original price, adjusted for inflation: about an HD 800.
Based on the single pair I've heard and currently own, the driver holds an immense potential relative to the price this model sells for nowadays. This potential isn't evident out of the box, however, necessitating mods to bring out what you paid for. (Your safety not guaranteed while modding electrostatic headphones, proceed at your own risk.)
Some comparisons of the modded Unipolar 2000 to other quality phones.
- Unipolar 2000 vs. Beyer DT 990 (1980s, 600-ohm)
- Unipolar 2000 vs. Yamaha HP-50S
- Unipolar 2000 vs. AKG K 250
- Unipolar 2000 vs. AKG K 240 DF
- Unipolar 2000 vs. AKG K 701
- Unipolar 2000 vs. Sennheiser HD 530
Below are five basic Unipolar mods to get started. In addition to these, there are now several other mods proposed throughout this thread, many of which may or may not supersede the five mods below. Have a browse, man.
1. Got rid of the slotted side grille (see this image) and original pads; put on some AKG pleather pads.
- Tonality improved,
- though soundstage reduced in size.
2. Removed the baffle filter material to make a direct path for the sound from driver to ear.
- I measured the frequency response with and without the filters - didn't see much of a difference, so you may or may not want to remove the filters.
- A future follow-up mod might increase the size of the baffle holes.
3. The driver itself is wrapped up on both front and back in a moisture protector (very thin mylar?). While it does protect the driver, it also gives an uneven response in the mids. I removed the stock moisture guard and attached a layer of thicker mylar (roasting bag material) onto the front of the driver only.
- A smoother response in the mids.
- (I removed the stock moisture guard from both front and back of the driver before measuring the response - it's possible that taking off the guard from the back only, not replacing the front, could smoothen the response just as well.)
4. There is a reflex disc at the back of the driver, under the moisture guard. It punches up the treble, but since my pair had a piercing treble to begin with, I got rid of it.
- The piercing, ringing highs were subdued by a few decibels.
5. Finally, I got rid of the cup. I attached the naked driver directly to the baffle, onto which the headband assembly could be attached as usual. I added a large foam disc to the back of the driver to (a) protect it from dust, and (b) dampen the driver.
- Frequency response gained neutrality,
- soundstage widened,
- and the driver ringing was brought to levels more typical of good electrostatics.
(Given the high voltages involved in operating electrostatic headphones, I make no promise that these mods are safe to perform. In other words, you may be at risk of injury or damaged property by: attempting to mod the Unipolar 2000; and operating a modded Unipolar 2000.)
Edited by vid - 7/22/13 at 8:39am