Conclusion: Mod does jack shit in terms of measurements and probably does jack shit in terms of perceived sound (given how close the three measurements, FR, HD, CSD are). Although admittedly I have not tried listening tests yet.

Overlay of the two (foam removed and stock below):

Any changes I noticed here indeed could be tossed up as measurement variation and not actual changes: http://www.changstar.com/index.php/topic,1902.msg58222.html#msg58222

I suppose I could also take a lot of measurements to verify, but I suppose it would end up showing basically no difference in the end.

So the question remains...why is that foam there then anyway?

Tried same thing.

So yellow is stock, blue is w/o back foam (only), and red is w/o front foam ring (only). Differences I get are in the order of 1 to 1.5 dB.




With out the back foam 2 kHz decreases by about 1 dB or so. I think Marv's measurements show that smallish change there as well if you look closely.

With out the front foam ring 700 Hz decreases by about 1 dB or so.

I think I found this to be somewhat repeatable, but who knows, could be measurement variance. I didn't perfectly align things and > 15 kHz might be compromised since I re positioned cans.

If you want a really functional x7xx modification, then try this one:

Use 2-4 felt rings depending on your preference (4 used in the picture):


Comparison of stock K712 Pro (blue) with 2-4 felt rings used:


Other measurements and info: http://headaudio.weebly.com/clanky/modifikujeme-akg-k712-pro