As requested, here are the results of measuring the HE500 with stock pleather (Red) and Alpha Pads (Blue). It's easy to get the pads onto the HF500 mounting rings, but it takes a few tries to get the rings onto the headphone. I'll post a video on how to put the pads on tomorrow for the curious.
The Alpha Pad smooths the peak from 800-1.5K, ads some energy to the upper mids and lower highs, and has a less output around 8-10K, perhaps owners who play with EQ could comment on these changes
I won't comment on the sonic changes, as I don't wish to present a biased message and will leave commentary on the sonic affects to any users who do the pad swap. The pads did have the Alpha feel, but the overall experience of the fit and sound of the phone is quite different from the Mad Dog.
Am I wrong to think it's a safe assumption that the regions affected here can also be reflected on other HE series models? My ear is not nearly as trained as some, but specifically regarding a stock HE-400 chart, comparing it to this seems to make sense to what I hear and has what I'd consider positive results. I know Clem is not a fan of the HE-400, but he has also cited positive results for the HE-4 and HE-5LE and I wonder if he experienced similar changes in those regions. Having using the Alphas for a few weeks now, it doesn't seem to dramatically change the presentation of the HE-400. It does seem reduce the mid/upper treble spike a bit, so I've not felt the need to EQ that region anymore...plus comfort is stellar compared to any other pads I've used. Also, the MD 3.2 FR looks fantastic *drools* kudos again Dan for releasing all these charts!