So I did a little tinkering with the cascades. First I closed the vent holes. I thought I heard some reduction in bass and some change in the soundstage. Changes were quite small and my measurements show only a tiny change so it migh have been my expectation bias that I was hearing.
Then I tried removing the white filter. What a change! Mids and highs are more present now. Midbass is not that much reduced relative to lower midrange but changes in other frequencies kind of achieve the same goal as me and most other people adjust the listening volume more by mids and highs. Unfortunately some subbass extension is lost but it's not a big deal for me. Most of the music I listen to is made with real instruments so there is not that much going for in the lower frequencies anyway.
Besides Cascade I have three other headphones that have beryllium coated drivers, Msur N550, MTV Evos (rebranded RBH HP-2) and Master & Dynamic MW50. Despite different sound signatures they all have common traits that I think are characteriscs of a Be coated driver. Most notable are the fast transitions, leading edges of notes are very distinct resulting in a detailed and clear sound even if the headphones are rather dark or bass heavy. Bass on stock Cascade is just way out there that I really could not hear the beryllium capabilities even though the hints where there. Now without the felt things fall into place. Theres zero veil and more than enough details. Best thing is that it's not because of emhasized treble but more because the amazing imaging capabilities and speed of the driver. Every sound has it's own place in the soundfield so that nothing get's cluttered. Of course bad recordings do no services here but with well recorded stuff listening to these is a bliss. I've been listening to a lot of Dire Straits and all the distant guitars sing beatifully over the scape, synths appear out of nothing, sax has all the emotion and body it should have and even though these are no longer the basscannons they were kick drums have a real kick to them! I just can't help but to marvel the soundstage and layering. It's just that good, not just for a closed headphone but any headphone.
It's not just the technicalities that impress me but the way how these connect me with the music. I actually got goose bumps and even shed a tiny man tear at one point. It's shame how rare that is. It must be mentioned that I wasn't particularly focused and trying to get connected... I was mopping floors.
Needles to say my cascades are no longer for sale. I need to compare these to Fostex TH900 which has been by main headphone lately. I really was not expecting that. I know that Cascades can't touch the bass quality of TH900 but besides that all the bets are off.
Thanks
@Nostoi for recommind this mod!