As much as I want the 712 to be a difference from the Q701, the main difference really is just the pads. And yes, I compared directly, and swapped the pads. The differences are so minute, it really isn't worth getting the 712 for sound alone. Its worth it for the new headband, and the pads already coming on the headphone which gives the 712 the better sound over the others. Someone who is happy with their Q701 and wants the 712 for testing can just easily get the 712 pads. They may be ever so slightly different, but its so close that unless you had them side by side, you wouldnt know.
I have owned
K701
Q701
K702 Anniversary
and have been sent a 712 and another Q701 for comparison.
Besides my old K701 (7 bumps not 8), they all sounded pretty much the same when using a specific pair of pads.
I would still spend the extra for the 712 over the others due to the better headband. Even the new standard K702 headband isn't as comfy despite being flat.
Don't know if this is true or not and hard to say (IMO).
When I removed the K712 pads on the K712 and installed NEW Q701 pads it sounded more like a plain K702 and NOT a stock Q701. Note: The K712 doesn't have any outer grill foam.
K702 is probably "technically" better and has a better measuring driver perhaps (compared to Q701). The Q701 sounds warmer to me than any K702 and could be due a worse measuring driver along with a combination of the outer grill foam and many other things.
The K712 + Q701 pads was definitely thinner/brighter than my old stock Q701. Could be because it was newer.
Want to know what's amusing? Bass port modded Q701 with K712 pads is warmth overdose. WAY too much and it makes everything sound way too congested, but it was kind of nice for some music. You'd probably need to move the outer/inner foam to tune to sound to make it listenable. Some may like it.
K712 is worth it for some of course, but I didn't buy it because Modded Q701 was close enough in sound. I'd say there is only a 5% difference between them. Most might prefer the K712. It depends on music preferences too. I could live with either of them. The difference between the K702 and Q701 is actually larger to me(!).
If I did not have a modded Q701 (and just stock) i'd probably own the K712.
BTW I think out of all versions of K702 variations the K712 probably does have the best measuring driver. It did sound noticeably clearer with some well recorded music. This extra clarity was almost not heard on my Q701, which makes no sense. I don't think it was due to changes in frequency response.
I bet a stock Q701 with K712 pads is actually warmer sounding and smoother than a K712 (more musical and closer to the HD-650 in sound..not as good for studio use). Just slight differences of course.
Oh and I want to forget those flat "doughnut pads" on the old Annie ever existed. Not sure what AKG was thinking.
One thing I couldn't figure out is that some music on the K712 was harsher than on my modded Q701. This was crappy Jpop with peaky upper mids and treble. My guess is that the K712 is just less forgiving of garbage and that is all (just being accurate). I can't say the modded Q701 smooths over this stuff, but maybe a tiny bit in comparison.
I like the K712 but I don't really think it's a smoother sounding version of the Q701 at all.
Disclaimer: My Q701 has 10,000+ hours of use and the K712 I heard probably had less than 1000. Maybe this causes some differences. My Q701 has never had harsh treble unless it's a REALLY bad recording. Even then it's not so bad.
Haha, I bet AKG wishes nobody heard about the Q701 bass port mod. Could be getting less K712 sales. Then again, the Q701 is stupid cheap now and very easy to mod. They probably sell a ton of Q701s. $150 for a Q701 is a ridiculous price. I paid $237 for mine back in 2010 I think it was.
I also wonder what happens to a K712 when you open it's bass port? I bet it would be OK unlike the bass port modded Q701 + K712 pads. I just feel that the K712 probably has more treble than my Q701. There's actually quite a few out there that think the K712 definitely has no lack of treble and can be kind of bright!!