But my humble opinion is that the bass will resonate long enough to be a little 'slow' for the rest of the music. So it kinda got left behind when the other notes had reached your ears. I've only tried making lenses out of sponge and nothing denser like felt, paper/fabric, or others, so I didn't get as much bass enhancement.
Sure changing pads is alright, but I wouldn't want to change the opening of the drivers. I believe the engineers have something in their heads when they created the vents in the outer layer of the inside plate.
Yes after I taped the ports I listened to them and noticed it didn't sound quite right but after I stuffed with the PTs it sounded perfect. I've noticed that if the cushions are stuffed a little off you may hear the difference. This is how I discovered the port interaction when one of the untapped ports became uncovered when the PT left it open. As for what the engineers had in mind I believe it was to reduce the impact to make them more long term listening. The sound signature sounds similar to stock but with a fuller balanced more powerful lower end that restores the balance with the AKG pads and reveals all the lower resolutions.