Well, I've been using the 3590 for quite some time now, and I thought that I'd make some comments, not because my sound eval is better or significantly different than others, but because I think that although they are somewhat v-shaped in sound signature, this signature is not so strongly marked in sound as it is remarked in reviewsand there are some special notes about the bass on these headphones. Also, the somewhat harsh treble (only noticeable with some kinds of music) can be tamed with a little very simple and obvious mod.
My Headphones Background and History
My headphones history go through basically several Sennheiser, Philips, JVC, Panasonic, and some other that I'm forgetting. Sennheisers I've been using (and use, depending my mood and situation) include the PX 100 (version I -now called PX 80- and current PX 100-II), HD25-I-II, HD650, in-ears from the CX series -250, 300-, and Momentum In Ear-. I've used IE series but only for a short time, so I'm not gonna compare them. I also have the JVC HAS160 (known as Flats), Aiaiai Tracks, and been testing the Panasonic RP-HJX5E (I think it's also known as Drops 360°) lately. Also I have to say that lately my favorite sound signature comes from a Philips Fidelio L1, which I found to be extremely nice, but some other find them somewhat dark. I think that's why I also prefer Sennheiser's sound signature, which some find dark and veiled (generally Grado fans).
Music used for testing
Basically metal and jazz. Metal includes bands like Fear Factory, Disturbed, Faith No More, Tool, Machine Head, Slayer, Trivium, Device, Mnemic, etc. Relating jazz, I'm particularly inclined to trios composed by drums/piano/double bass, and that includes Esbjorn Svensson Trio, Vijay Iyer Trio, Avishai Cohen Trio, GoGo Penguin, Tingvall Trio, Phronesis, Trioscence, Portico Quartet, Helge Lien Trio, Fox Capture Plan, The Bad Plus, Alexi Tuomarila Trio, Jacob Karlzon 3, etc. Almost all musc is high quality FLAC.
Sound
I think that the most remarkable achievement of the 3590 is the impact in sub bass (below 60Hz). Usually, on these low notes (most notable on Drop D tunings, or five strung basses, or specially strung double basses like Renaud Garcia-Fons), the note change on sub bass frequencies can be felt because of a shift in thirds and fifths of the fundamental note (which are on a higher frequency than the fundamental and in a field where the headphone has a better response and much lower drop in dB). Hence, usually (and more on cheap headphones) these very low frequencies have little differentiation between them on the fundamental note, and changes are noted because what most noticeably change are the highest frequency thirds and fifths of the sub bass fundamental.
The 3590 manages to maintain very good impact and resolution on these very low notes, making the change in fundamental note very noticeable, and not only because of the resonating thirds, fifths and other harmonics -which resonate at higher frequencies and help to differentiate these low sounds- but because indeed it can resolve with adequate power notes below 60Hz. This can be noted specially with jazz music, where you can feel the rumble of the double bass and not only a slight change below 60hz and a noticeable change in the harmonics above the fundamental (these low frequencies is where the double bass growls).
On other aspects of sound, they are not flat but not aggressive neither in bass nor mids, nevertheless perhaps a little aggressive with treble depending on music and recording. They have a deep bass, which is still very audible below 40hz, very little bleed into the mids, more or less flat mids, and indeed a little harsh on the highs, which with some recordings can be bothersome. With jazz music it is almost non existant, but with some metal music it can be fatiguing.
Treble Mod
In order to reduce the treble harshness, I simply inserted a little piece of foam in the "nozzle" that is created by the silicone tip. The idea behind was to achieve a similar result as with those IEM that feature interchangeable filters in the nozzle to achieve a certain sound signature (like Trinity Atlas IEM). With this mod, and depending on the foam used and the compression of the material, the treble can be tamed a little or a lot, without affecting significantly the bass and mids. I have found that the best results are achieved with low density foam compressed to fit and stay in place inside this artificial "nozzle" in the silicone tip.
With the mod, the sound signature is very similar to the Philips Fidelio L1, a little darker than the HD25-1-II (less bass impact, but deeper bass, more tamed treble, less bass speed), much better than the Panasonic Drops 360° -or RP HJX5E- which below 60hz become "one note bass", and more resolving than the PX 100-II but similar in sound signature. Since they are IEMs, sub bass is clearly felt.
Overall
Incredible bang for the buck. And as they are so small, can be worn around the ear, thus eliminating most of the microphonics (which these do have, though not as strong as other IEMs). For the price, they are awesome. The 3590 can make some other much expensive headphone a run for their money.
As a closing statement, pardon my english since it is not my mother tongue, and I hope the explanation about bass signature in these headphones and what I think is remarkable about them is understandable.
