A number of users try to give headphones and full range drivers which drop off at the normal ~~40hz range a huge boost here, such that tones all the way down to <20 hz sound the same volume - you must sharply increase gain such that you have literally a 20-30db boost at 20hz. While this works out to be flat with sine testing or music/movie reproduction, sounding like there is a separate subwoofer filling that gap, it seems to mud up the higher faster sounds when the driver is performing such an excursion at the very LF.
It would seem that when deviated far from resting position, the surround is much tougher mechanically and has less give, at least in one direction, which does not allow a much lower powered high frequency to sound as loud or accurately as it should be.
I added 10-20hz to my eq at +20db or so, and using a spectrograph you can see that most music, even while you can't hear it or it isn't intentionally placed there, has in fact lots of content at 10, 20, 30 etc hz at considerable levels, sometimes approaching 2/3 the level as the rest of the frequencies (After correction) when you can't even hear them, spiking of course when there is really a cannon-fire or something of the sort. You can barely hear it, but it probably adds the realistic ground-shaking that may be present during or in the recording/live environment, but the overall SQ seems to decrease. Just a note for anyone looking to flatten this LF drop-off out, or somewhat model response after any equal-loudness curve. If there is a seperate LF driver, it likely can't affect the rest of the sound much, but putting the HF and LF on the same driver with LF at such a high power definitely should smudge the mid and high up by some amount.
Edited by k00zk0 - 11/24/11 at 2:47pm