OK, let's see what AT say about them:
Technical data
Closed Dynamic type.
Driver: 40mm, Neodymmagnet, CCAW Voicecoil.
Sound pressure level: 100 dB/W
Impedance: 36 ohms
Interface: USB
Transfer speed: 12 Mbps (USB FULL SPEED standard)
Power voltage: 5V (USB Bus power)
Max power usage (?): 120 mA
Max output level: 23 mW + 23 mW (1kHz, Digital 0dB output)
Freq. range: 20-20 kHz.
Plug: USB A plug.
Cord: 2 m long, one sided.
Earpad: Soft leather.
Weight: appr. 210 g (without cord and plug).
Replacement earpad: HP-A4 1,300 yen.
Release date: 2002, April 21st.
Price: 12,000 yen.
Product description
First in the world! USB headphone with high performance D/A amp.
* High performance D/A amp, bla bla bla
* Use power directly from your PC, no external power source needed.
* Powerful magnets giving transparent sound, great highs, mids, lows (yeah, yeah...)
* Selfadjusting fit with "Wingsupport"
* Supposedly so comfortable you can wear them for a very long time.
Supports:
Win98, 98SE, Me, 2000, XP.
iMac, iBook, Power Mac G3/G4, Power Book G3/G4
* Equipped with D/A amp, high increase in music quality! (not my words)
Lots of bla bla bla, basically saying that because the digital signal is set to the phones before converted to analog sound signals, you'll avoid interference from the PC housing (like we don't knew that from before....)
SNR of 90dB (at max output)
That's pretty much it. Boring, boring stuff....