I'm not sure what I expected to see when I got up.
I hope we can all have fun with this. Even worst case scenario I still learn something.
After a bit of talking with Bill, the general conclusion was that the HD700 would be a difficult headphone to fix. I agree with this wholeheartedly. That being said, there still has to be
something that can be done. In these few days before I receive it, I'm doing some research on the headphone, damping materials, and determining a primary target.
The first thing I looked into was the construction of the earcup. It took a while to find but I'm already seeing a lot of red flags. I suspect the main problem here is the nature of the HD700's baffle plate. The entire mount for the HD700 driver is made of plastic. It looks pretty fucking cheap, and there's nothing between the driver and baffle. Just hard plastic on hard plastic. Bad. My prediction is that something will end up in here by the time this mod is done.
Soundwise, there's obviously a major problem at about 6kHz. This appears to be what people have the most trouble with when it comes to this headphone. The resounding peaks aren't particularly comforting to look at either, but the 6kHz appears to be the most prominent.
http://www.innerfidelity.com/images/SennheiserHD700.pdf
Using EQ and the SS-100, which is perceptibly the flattest headphone I own, I've tried to prepare myself for what I'm about to receive and approximated the FR of the HD700. I compensated for the SS-100's perceived FR, which rolls off progressively from 3kHz to about -6dB at 16kHz. This gave me a headache, quite quickly:
After getting "used" to that, I played around with the sliders a lot and determined a realistic target FR, something that sounds better while still being within the realm of possibility. Here's the target I came up with (again compensating for the SS-100's FR above 3kHz):
My suspicion is that the 6kHz peak is being accentuated by the ringing on marv's CSDs. Hopefully, this ringing is coming from the enclosure, and not the driver (which is notoriously much harder to fix). However, given the very clean distortion characteristics of the HD700 (above 200Hz), I don't suspect the driver to be the culprit here.
Now onto damping material selection...
