But some of 318 couplers or Gras artificial head dont have any damping material on it.
I feel damping material is necessary to simulate effects of skin, fat, muscle, blood, which seem to have some absorbing properties. I've had access to artificial ears, shoved a microphone through a large piece of pork belly, coated surfaces with sriracha sauce, etc. until I came up with this V2 version (small ear size piece of felt over a sheet of high-density construction foam).
Without damping material, I feel that peaks and ringing in CSD tend to be overemphasized, at least with what I was working with. Finally, my V2 rig as seen here, uses absolutely no compensation. The whole thing was about doing it fast / uncompensated jointly on an unbiased device for evaluating headphones.
