Less than a year ago I replaced my Koss H60 (?) headphones with a new pair or Sennheiser HD 455's. The Sennheiser HD 455's are right in the middle of the Sennheiser lineup, I found that shocking (at the time) seeing as they cost me $100+ cnd, before that I never paid more than $30 for a pair of headphones. I've learned my lesson. The HD 455's are crystal clear from the bottom 18Hz all the way up to 22kHz. Because they're an open design, the bass isn't quite as powerful as most headphones (in the price range), but the bass does go very _LOW_ and that's what really counts. When I first got them I noticed a vibrating sound eminating from within at not-too-loud listening levels, I'm assuming this was on account of their being new. However, after a few weeks of loud play the vibrations have dissapeared (or I've gone a little deaf). Some forms of distortion/vibrations can be produced if I turn the music up to uncomfortable levels with the bass cranked to a bizzarre and unreasonable level though.
The 455's can take all the power you would ever want to give them (Unless you're just plain crazy) without any distortion. CLAIRITY, Precsicion, and efficiency are three words that go hand in hand with these headphones.
I must add that using a cheap headphone extension cord (as I usually do - don't worry, I'm replacing it) will colour the music, I didn't think my new Sennheisers were all that special until I used them without the exension cord. It really made an audible difference in the precision.
With the detachable and replaceable parts, these headphones could last a lifetime (unlike most other brands). The 455's was one of the best _investments_ I have ever made. Sennheiser has gained another happy and loyal customer.

Mike s. v7q2@unb.ca