The fibrous paper filter is indeed glued on pretty well & seems very fragile (removing it in one piece is quite challenging & it can be easily punctured/torn). This makes re-installation difficult, if not impossible. Never fear though, as I decided to "take one from the team" and proceed with the non-reversible filter replacement anyways. I tried my best to carefully remove the paper filter but I ended up puncturing it fairly quickly.. once this damage had been done, I hastily ripped the remnants of the filter off the nozzle and installed a couple of spare RE262 filters I had..
The resulting sound? It's very much to my liking! These sounded fantastic in stock form (though I found the midbass a little too dominating).. by replacing the filters, I feel I've tailored the sound more to my taste. With the RE262 filters, the CKS77 sounds more balanced in terms of the ratio of "bass:mids:treble." I immediately noticed the midbass hump is noticeably tamed. Taming that midbass allows me to better hear the nuances & texturing across all the bass frequencies. The bass is still very powerful, punchy, & muscular.. but the low frequencies sound more cohesive and natural to my ears.
The midrange is brought much more in line with (if not forward of) the bass frequencies. The tonality of the CKS77 remains very much in tact, but it's tilted less towards the bassy side and more towards the midrange. With the mids coming to the forefront of the presentation, the liveliness and depth these phones possess is truly on display. Listen to some well recorded acoustic jazz-guitar by Earl Klugh and you can almost feel the string flourishes with these phones.
I feel I get a better sense of the AT house sound with this mod, too. The unique midrange coloration, in particular, is more clearly heard. Treble remains crisp & smooth.. but it gains presence & sparkle as the bass gets toned down. I really like how well the treble is integrated into the overall sound of these phones.. it was a little difficult to get a handle on pre-filter mod.. but now it's got a very nice airiness to it.
I haven't heard the CKM55, but I get the sense it's a more balanced, albeit less refined, version of the CKS77. I'd venture a guess in saying that by replacing the CKS77 filter, you will get the best of both worlds in terms of refinement & balance. I highly recommend this filter mod to those who want to bring a bit more of an 'audiophile' touch/balance to the bassy, warm sound.
Obviously going forward, my impressions of these phones will be with the the filters installed.. For brevity, I'll call my filter-modded ATs the:
CKS77-B ('b' for balanced).
