Imagine the flattest IEM that ever existed, take it and add a roll off to make it less clinical and more musical. You have the ER-4P.

The ER-4P is never harsh sounding, or even clinical... I would classify it as slightly dark sounding despite what many think. The bass hits hard with no noticeable roll off. One of its weaknesses is probably the lack of soundstage, however the pinpoint imaging is very good.

Its major weakness is the treble roll off, but I'm not sure whether I'd call that a weakness as it was somewhat intentional I believe. When compared to the ER-4S, the ER-4P has more body in the sound and a recession in the upper treble... think cymbals and stuff. The ER-4S is also more detailed and the bass is perceived to be less.

I really expected to like this as it seemed to be an audiophile favorite here. I listened to it for a few days to ensure that burn-in could occur, whether it be my brain of the headphones themselves.

The problem with this headphone is that it's super harsh, harsher than the DT990. And interestingly it sounds dark.

I don't know how they pulled that one off. At least the bass is fantastic, typical of orthos, but at this point, that bass extension and slam is pretty much useless due to that massive treble spike I'm hearing around the 10K+ region.

This headphone is quite V-shaped, I never quite understood why it stood evenly with the K701 and HD650. I dislike the HD650 but that didn't prevent me from giving me it a bad review, because it's quite impressive.

Now this, no matter how I try to listen to this. It's too bright and sibilant. Even its siblings, the DT770 and DT990 gave me problems.

The bass was the only thing that was enjoyable, it extends very deep and is good for a dynamic headphone. When listening to acoustic music it's harsh, but rock and such is less harsh as the bass somewhat masks the highs a bit. I could see this being nice for rock.

But the detailing is not good as the K701 or HD650 or HD600. Even with that abundance of treble, it does not render low level information as I expected it to. Also the soundstage is pretty normal, not much different from the average closed back headphone. I guess being semi-open doesn't give you the best of both worlds as the HD600/650 and K701 have much better soundstages.

It's built quite nicely and quite comfortable though. But I don't like how it sounds.

Similar sounding to the HD600, but is a bit brighter.

Not as bright as the DT880.

One thing that I like about these headphones is the out-of-head experience that it provides. It's like hearing the music in 3D and you can easily pick apart the instruments.

I think the weakness is the lack of bass (similar to the HD600) and maybe that it can get a bit harsh in the 2-3kHz region at times leading to a somewhat honky sound.

But the soundstage is fantastic, very similar to the HD800 in terms of presentation of sounds.

Oh and those headband bumps... glad they got rid of them in the limited edition 65th edition K702s. Maybe the K703's or whatever the next variation in the line-up will have the new headband. I wish AKG would make a new flagship.

VERY flat. Now this is a headphone I enjoy.

Except for that bass roll off. Forget the HD800, forget the HD700, find some way to get deep sub bass out of these and you have a winner.

It sounds quite clean and is never veiled (HD650, HD598) nor is ever harsh (HD700, HD800). That is all.

I don't like this headphone. Or rather I don't enjoy this headphone. But I can't deny it's impressive.

Plagued with the typical Sennheiser problems of being built cheaply and being overpriced, yet it's really the only in its class, the audiophile's favorite.

That warm and dark sound, that you can never get tired of. That impedance curve that makes it scalable. This is the audiophile's dream, it may not be relevant today with all the FOTMs but it still remains a classic. Grab one used from the classifieds if you're into this kind of sound.

As someone who is into accuracy, it was natural that I prefer the HD600... the HD650 was too thick in the mid-bass and lower midrange and the highs was rolled off, but the roll off wasn't really bad as the clarity is there, but the veiled like sound comes from the mid-bass and lower midrange.

Some complain that it's slow, I disagree, it's pretty clean and fast, but not harsh. Technically impressive, very low distortion.

Recommended!

Firstly, this headphone is the prime example of something I'd love to hate.

I did like the HD595 as a non fatiguing headphone... and yeah the HD598 is better. But that ugly design and MAP restriction left a sour taste.

I'm still saddened they didn't switch to a 1/8 inch connector as most devices use that nowadays. Another problem is the impedance varies among the frequency greatly, especially in the mid-bass. Don't plug these into some receivers, they will get really muddy.

It sounds like the HD595 with better clarity, and more treble. But again much better can be found for the money.

Supposedly Sennheiser fixed the build quality issues, but we'll see...