http://www6.head-fi.org/forums/showthread.php?t=230
MDR-7506 / MDR-V6 -- Have Them Both. Are They The Same?
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Okay, okay....this really wan't much of a mystery anymore. But just to confirm: they're the same headphones.
I now own them both. I assumed they were the same going into this. The only differences? MDR-7506's say "MDR-7506" on each earpiece instead of "MDR-V6." MDR-7506's come with blue stickers that say "Professional" on them -- V6's come with red stickers that said something like "Digital Ready" (I can't remember exactly what they said, as I took them off a while ago). MDR-7506 has what looks like a black anodized metal housing leading to a gold-plated mini plug with a gold 1/4" adapter. The MDR-V6 has a silver-colored anodized metal housing (otherwise exactly the same shape as the 7506's) leading to a silver/chrome-colored mini plug with a silver/chrome-colored 1/4" adapter. Also, the MDR-7506's come with an expoded parts diagram (if any of you with V6's is looking for replacement part numbers, let me know, and I may be able to help).
I slapped my extra pair of Beyer velour pads on the 7506's and gave both a listen. They are indeed the exact same pair of headphones (other than the differences already noted). Here's an interesting thing though -- there are slight but noticeable differences in sound, but I attribute this as likely being break-in effect (the V6's have seen a lot of hours of use). And, yes, I prefer the V6's at this time because of that break-in. I'd be willing to bet that the 7506's will sound exactly like the V6's at some point (assuming breaking in levels off with both at some point, which I expect).
Same phenomenal and absolutely unmatched deep deep bass (that I've heard so far from headphones). I've got very good hearing going into the upper registers, and I'm still puzzled by those who consider the V6/7506's overly bright, as I find the overall sound to be on the warmer side. Admittedly, the treble isn't as refined as with my Sennheiser HD-600's (actually, overall the sound isn't quite as refined as the HD-600's), but it doesn't strike me as harsh at all.
The V6/7506 still remains one of my very favorite pairs of headphones -- a 15+ year sonic love affair. Two pairs of these and two pairs of HD-600's, and I've got what, to me right now, is a darned near perfect set o'cans for the music I listen to -- one set of both, each, at home and at the office.
As expected, the HD-600's can be found on my ears when my system is cranking out most jazz or classical. And the V6/7506's can be found covering my ears when rock, pop, or any very bass-demanding music (even classical or jazz) is playing.
Thus endeth the mystery that wasn't really a mystery anymore anyway.
NOTE: If you're interested in buying the MDR-V6/MDR-7506, try to find the V6's first (in my opinion). Why? Because it's the same headphone as the 7506, only it's usually sold for $10.00 to $20.00 less. I think I paid $69.95 plus shipping for my V6's. And I paid $89.95 + 6% sales tax for the 7506's (which I now know for sure is $10.00 to $20.00 too much).