I have an older pair of MDR-V600 headphones (a predecessor to this model) which I like a lot - they are extremely comfortable, even after hours of use, they sound good, and they do a decent job reducing ambient noise. So when I wanted another headphone I got the MDR-V900, which I thought would be an improvement over the V600. At nearly twice the price ($170 versus $90), I had high hopes.
Recommend this product?
Well, the results are mixed.
First, the good stuff - aesthetics, ambient noise attenuation:
Right out of the box, these phones look beautiful. The "SONY" logo is not painted as in cheaper phones, but is embossed into the shiny black plastic. Functionally unnecessary, but beautiful nonetheless.
"Closed" headphones like this one (and the V600) prevent ambient noise getting in, and music from getting out. The V900 does this even better than the V600, perhaps because of its deeper, stiffer earcups. This muffles my noisy air conditioner quite well. Although there are other closed phones that attenuate ambient noise even more, like the Sennheiser HD280 Pro, I find that to be overkill - the Sennheiser blocks so much noise that it feels like wearing an Igloo cooler.
The V900s are as comfortable as the V600. Both Sony models feel much softer than the Sennheiser HD280, which starts to hurt after about an hour.
According to the specs, the V900s can handle 3 times the input power as the V600s (3 watts vs 1 watt). I never turn up my headphones that loud, but I suppose this could be useful for some people.
The construction quality of the V900 is very similar to the V600, which I consider above average. Both have a sturdy coiled cord, which on my V600 has lasted for 3 years of heavy usage, much better than the flimsy cords on cheaper phones. The only flaw is that the V600 earpads have a thin vinyl covering that wore out after a couple of years, and I expect the V900 to do the same. Replacement earpads can be had for about $20, but even with the vinyl covering gone, the underlying foam still functions fine.
Sound quality is mixed:
Right away, I noticed these headphones have a peculiar property. When listening to recorded pop music, they sound great - at least as good as the V600 and Sennheiser HD280. The V900 sounds stronger in the treble range than the other phones, which helps bring out percussion details. It seems to have better bass than the Sennheiser HD280 as well.
But when using the V900 with my digital piano (a Yamaha P70), they sound terrible compared to my other two phones. The reason is the V900's prominent resonant frequencies, which cause specific note ranges to sound disproportionately loud. For example, notes around 3 octaves above middle "C" (roughly 2 kHz) sound absolutely piercing, relative to the rest of the keyboard. And the notes "E", "F" and "G" in the octave above middle "C" (roughly 300-400Hz) are also disproportionately loud. Notes outside of these ranges also sound muddy, because of the extra emphasis of certain harmonics over others.
By comparison, the HD280 and V600 had fewer resonant bumps, so the solo piano notes sound more even in intensity.
As long as I stuck with pop music, the V900s sounded great, but I often use headphones with my keyboard, where the tonality is obviously peculiar. The V900's frequency irregularities occur in two distinct narrow bands, making them difficult to compensate with an electronic equalizer.
Many people swear that new speakers need time to "break in", but the dogma doesn't seem to apply to headphone. Just in case, I waited until I'd used the V900s for a week before rendering judgment. The "breaking in" didn't reduce the annoying resonances.
If you're looking for a flat frequency response, you will be disappointed with the V900. If you're looking for an improvement over the cheaper Sony V600 or Sennheiser HD280, that won't be clear-cut - the V900 has decent bass, and accentuates treble frequencies, which can make pop music sound very good. But solo instrumental stuff sounds terrible to me, as certain note ranges just don't sound right.
These phones are comfortable and decent for some kinds of music, but I can't recommend them unequivocally, given their high price and non-flat frequency response. While they block ambient noise better than the V600, their resonances are actually worse than the cheaper models costing $100 less, and are distributed in a way that is hard to equalize electronically. The V900's resonant peaks are especially noticeable and distracting with a solo instrument like the piano. Although the V900's accentuated bass and treble make pop music sound good, I can get a similar effect by turning up the bass and treble knobs on my amplifier. I don't need to pay an extra $100 for that.
If I had known about the Sony's frequency response, I would not have bought these headphones. Unfortunately, Sony does not make this data available, and very few headphone review sites measure frequency responses. I could only find one review site that systematically measures frequency responses (http://www.headphone.com) and they don't include any Sony models. But they have excellent reviews of almost every other high-end brand, like Sennheiser, Grado, AKG, etc. So I would recommend giving them a look for further info in your headphone shopping.