I bought the Senn 435 two days ago.
Listened to the phones for about 4 hours, so these are my initial findings: unamped vs. amped.
I have a Euro-limited PCDP from Aiwa, so it doesn't go loud enough to power these headphones, even though it's 35 Ohms.
Anyway, without amp, I found these to be a letdown. Bass was not in control, mids were recessed and highs too shrill.
On the contrary, with an amp (my own MTY I), these things do come to life
Proparly driven, they deliver very descent sound for their price, which is 70 dollars. Bass was in control this time, and the quantity was as much as compared to the UM2. Quality wise, I found the Westones to be clearer, though not punchier.
The thing is, I never really owned a full sized headphone, expect for a very old AKG. I'm impressed by how I felt engaged by the sound, by the overal experience of these Sennheisers.
Dynamics are superb, it keeps you right on the spot. Soundstage was great, as was the imaging of the instruments. Any IEM I've tried in the past, and right now the ER4S, fails to fill in the first aspect. It's hard to describe the difference in sound between an IEM and full sized headphone, but the sound is just way more engaging in every way compared to an IEM. I know IEM's have dynamics, imaging & soundstage, but on a full sized it's a completely different way of describing these terms imho.
On to the mids. They come to life, simple as that. More pronounced, a very little shrill and itchy, but depends on the recording in the end. And of course, the amplification.
Highs. Very sprakly (symbals), right on the spot.
About the looks and feel: it's supra-aural, so it just 'sits' on your ears. There are no earpads whatsoever. Very soft material, no pain afterwards. Cable length is a bit long for portable use (3m.), but you can wrap it up in portable bag, together with your amp and PCDP or MP3.
They do isolate quit well when songs are being played. About 20 dB I guess.
So overall:
- Without amp: 5/10
- With amp: 8/10
All of this is IMHO
