As I mentioned earlier I am currently working with Mitch at Accurate Sound to fine tune a FilterSet for my (quite heavily furnished but lightly treated) room. The more I listen the more I realise that Mitch almost hit the bullseye with his first attempt. The tonal clarity you get when the room modes are eliminated and certain octaves “emerge from the shadow” of a bloated neighbour are revelatory, as are the improvements to stereo imaging from corrected time alignment (my room is quite asymmetrical from a furnishing and therefore absorption/defratcion perspective). I can happily say without a hint of audiophile shame that “bit perfect” holds no sex appeal whatsoever for me any more.
Comparisons with pass-through are largely meaningless for me, as you say @Anupc the magnitude of the improvement is just so huge that it dwarfs any downsides. But interestingly one of the only areas I could fault with FilterSet 1 was a loss of “air”. So high up that no notes are actually played there, but where only overtones live. Strangely even my middle-aged quite average hearing was perfectly able to detect it. After a bit of detective work Mitch figured out that the filter was rolling off just a little bit lower (ca 15kHz) than my tweeter’s natural roll-off. He has just sent over a new version (see below) which I have not had a chance to test yet. Just mention this in case it could be relevant to your use case.
Red is untreated, blue is FS1, orange is FS3 (1/12 octave smoothing).
