People are mentioning the golds here. Well the Golds are miles more bassy and unbalanced than the copper.........
For the Copper, I'd say it's more bassy than being perfectly balanced but I won't say that's unbalanced.......and I'm an ER4 guy. Extremely coherent throughout the spectrum, not without peaks but tiny ones only (virtually every high-end earphones got peaks, including the SE535, whose peaks I found quite irritating). Extremely well-defined midrange and amazing sparkle in classical tracks - I was just amazed this morning by its ability to reproduce the sound of bells in Khachaturian's Symphone #2. Sends a chill down the spine. It's THAT good. Its bass is also well-defined BUT, and this is one caveat to its otherwise pretty flawless performance, is its miss in reproducing the timbre of the bass instruments. Bass guitar is ok, but for accoustic instruments such as double bass or pedalled organ the timbre is slightly distorted. But that's not a big issue - if I'm after that kind of absolute accuracy I'd go back to my ER4.
The coppers are becoming the ONLY earphones I'd use besides the ER4 and it literally shows my SE535 to the door.
Just like the ER4, I'd say the correct fit is of utmost importance since u'd get a completely different sound otherwise. BUT DO NOT TRUST THE SUPERTIPS for a evaluation of an IEM's SQ. I uses the supertips on almost every IEM I still have (including the SE535) - it's good isolation-wise and comfy and looks good - but it is by no means easy to fit. The sweet spot is very difficult to get - any other position than the sweet spot position would produce peaky, quirky sound with no bass, L/R imbalance, recessed mids etc., somehow down to pressure issues i believe.