There actually is quite a bit of damping going on in the SR-007, you just can't see it.
Have you tried to adjust the arcs on the SR-007 to better fit your head? The lack of bass might be caused by the loose fit besides the amp not supplying enough current for the lower registers. I recently tried a completely untouched SR-007mk1 and they sounded like poo compared to my set. Now I have a gigantic head so a stock set will never fit me properly but it was a useful experiment wrt to the importance of a proper fit.