Just wanted to post an update on playing with polyfill. When I originally stuffed the cups, I tried to mimic the thick polyfill/acoustic material included in the th900s cups. To do that I took polyfill, layered and repeatedly flattened it. I tried to be consistent between both cups, initially making two sheets of flattened poly fill that were approximately the same size, then folding them twice, flattening them and stuffing it in the cups. The result? Deeper soundstage, likely due to a dampened bass response and upper mids (presence region).
After reading more about why polyfill is added to speakers (if done right, some say it can double the perceived cavity size of the speaker), and how only a small puffed out amount should be used in this application, I wanted to see if that approach would benefit the X00s more. To do this I removed about 1/2 of the polyfill that was originally in each cup and thoroughly kneaded it out to form a consistent texture and made sure both cups still had a near equal amount. The result was slightly better soundstage depth over stock but less depth than the previous configuration. The bass was noticeably more impactful now though, probably still lower than stock though. Again, levels of bass and presence region are suspected as those seem to contribute to soundstage depth here. But I do like them a lot now, still have that great impact they originally had but now make some sounds that are out of head. Note this was done in conjunction with hm5 pleather pads with a cotton filter added in front of the driver.
