Originally Posted by HesterDW
Why/how do focus pads make such a difference? What on the inside is different from the stock pads?
Lots of things going on vs. stock pads. It feels like much more thought and engineering went into these. I posted a lot of impressions a couple of pages back. Coletrain104 and Mani ATH 87 have been posting lots of excellent impressions along with me. I've done lots of mods and pad swaps on lots of different cans, and this has been one of the most dramatic and impressive I've come across.
Mesh on inner side of earpad and softer/less dense fill are the most obvious differences. I believe these changes contribute to the lift in the upper mids I noted a few pages ago. These are much more neutral, present and aggressive vs. the stock pads.
The pads are also thinner on the front side, which angles the driver toward the ears. This improves imaging.
There is a softer velour on the top side at the contact point with the head and a cushier overall feel compared to the stock velours, which I always found to be hard and itchy. These are now among the most comfortable headphones I've worn. As good or better than Sennheiser, but not quite up to the level of the Beyerdynamic DT880/990.
If you want to learn more about the engineering behind these, read Jerg's excellent posts about his JergPads. That dude knows infinitely more about the damping and pad engineering than I do. The FocusPads are essentially HiFiMan's version of his design.