The 4's never got gaskets as I was in a rush to get them assembled. A few days ago I finally picked up a few feet of shower pan liner and started cutting.
It makes a subtle difference. Sounds like it removed a bit of glare and/or added a bit of smoothness to the presentation.
I've added weatherstripping or rope caulk around the drivers of other speakers and experience similar results. And when the weatherstripping or rope caulk was removed the effects vanished.
A good $16 dollar upgrade. A VERY good $16 upgrade.