Have you heard of sound dampening? Which is applied in the environment such as walls to dampen or prevent reflection of sounds for speaker systems. Shinier the surface, the more sound reflective it is. There are also diffusers to break up the sound as well. This is what i mean by reflective and something of dampening nature like the Velour. But yes, seal does have effect on the bass response. When they use spots, dots, or hole looking things in the pads, I think it has more to do with surface tuning of the pads. It's just adding some dampening dots to a leather surface without completely dampening surface. Isn't it a form of control of the surface? Or perhaps, it's a form of a diffuser? The seal has more to do with how cushony the pads are. For example, stock pads are stiff in shape, and won't shape to your facial contours. Whereas, something like Velpads or the new Focus pads will shape to the contours better. And of course adds comfort.