Ultra, not that I generally doubt your measurements much, but I guess I'm just surprised the PMx2 measured so similarly to the stock PM-1 or 2. Just seems a bit too homogeneous for me, and I subjectively hear a larger difference. Even compared to the HD600. Dunno. Also, what amps have you tried the OPPOs from? IME certain setups and amps make them sound more strained and grainy than others, but I believe that you heard what you heard when you listened to these.
Ok here is a few more measurements of different PM-1/2 pads from Tyll and then ones made today on my own rig using left driver of the brand new PM-2 positioned exactly the same with all the pads. The differences are quite dramatic and true for both mine and Tyll's rigs. We can also see that PM-2 pleather pad measures quite similar to the alternative leather one while both original leather and velour measure quite different with original PM-1 leather which in turn is closest to the alternative leather and PM-2 pleather pads. The differences are definitely there, don't know why not every rig and every ear captures them though
To finish up the measurement thingy I can say that my random measurements of different pads from few months ago do correlate perfectly (within 0.5db) to the ones done just recently when all four brand new pads arrived along with brand new PM-2s. This for me removes the rig variation concerns but I would certainly agree small variations should exist within reason just not something like 5db. Tyll's article and measurements of OPPO pads (http://www.innerfidelity.com/content/oppo-ear-pads-listening-and-measurements) clearly indicate significant, also up to 5db variations in frequency response for different pads. That is quite noteworthy considering some small differences had to be smoothed out by how he averages multiple takes and compensates for HATS. Though it would be really interesting to see how my PMx2s would measure on his rig. Once at it will say a few things from my own experience about in ear measurements similar to those Hans uses. Crucial points for those are the insertion depth, angle of the mike relatively to the driver, acoustical properties of the material used to secure the mike inside the ear canal ( different materials would create different pressure within the coupler, different materials will also exhibit different reflections with the tip of the mike, different distance for the tip of the mike related to the surround material will also play a huge role ). Only considering all of the above one could imagine how correct combination is probably incredibly difficult to strike. Then add a different shape and size of the pinna, hair on it, then properties of hair surrounding the ear itself and finally properties of the skin. Seriously complicated would be an understatement. Well either way Hans is correct, what really maters is how they sound to the listener and I can tell already they really don't seem to sound the same for all, that's a shame. Ideal set should sound great for all, just a dream for now but what could stop us from achieving such dream? My answer is nothing, we just have to keep on working!
BTW Alex, Tyll's plots exhibit a higher variation due to head coupler Vs a flat baffle coupler. What I read from those plots and commentary is that differences between pads exist. But these changes r not mind blowing.
AZ - can you let me know which set of pads you prefer subjectively with the stock PM-2 and why. My recollection is that Marv prefers the Alt PM1 pads and Tyll prefers the original Leather PM1 pads with the PM-2. I have the stock pads, but have heard the Alt pads which I do think I prefer (it being acknowledged that my audio memory is not the best). But I haven't had the chance to listen to them with the original PM-1 leather pads. Also, please keep me posted if/when you will start modding pre-owned PM-2s.
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