Pros: Amazing, lush, liquid mids, vocals that are so rich and palpable you can taste them
Cons: Bass can be muddy without really good amplification, highs can sound wrong to some ears.
These were my first foray into high end, high fidelity sound. They were a true revelation. These headphones were built for my ears, laid back, rich warm mids, deep but controlled bass, the de-facto ultimate headphones of their time.
Treble: Laid back, airy, great sound stage, contrary to popular belief, bigger is not always better with regards to sound staging, some things weren't recorded on a giant sound stage afterall. Liquid cool and never fatiguing, the treble was far from analytical but still revealing of source quality, a transparent headphone to be sure.
Mids: Wow. Rich palpable midrange to die for. This is what you dream of. Perfect vocals, anyone could hear the sound of a singing voice coming from these and be instantly transported. The mids on the HD 600's are capable of amazing things on the right music with the right amp. Still punchy and musical on almost all music types. My only complaint was with symphonic music, which always felt a little strained to my ears. In the end, I loved these most with the xcan v2, perfect, perfect vocals, any singing voice shone through on that setup like the voice of angels.
Lows: Rich enveloping bass cradles the music in a seamless landscape of liquid sound. Can be boomy on some tracks. Not the best headphones for rap or other excessively bass heavy music.
High build quality.
An excellent headphone which with the proper amplification (tubes) has a unique sonic signature, that if it works for you, is nearly impossible to beat at any price.