Unfortunately the majority of people think you select the xover frequency based on your speakers, in truth you should select your speakers, based on the correct frequency
: 80 Hz
, or so.
If your speakers don't cleanly go down to that frequency, (or a tad lower, just to be safe), you bought inadequate speakers. Conversely, if you buy speakers that go markedly lower than that, yet you plan to use a sub, you've bought larger speakers than you needed to, overkill, and most likely spent too much money.
There are so many of you though, and the audio industry doesn't want to bruise your egos, so they've even invented a special mode just for your poor understanding of why we use bass management and dedicated sub EQ. It's called "LFE + Main" on the AV7005, or generically as "double bass", and for those of you who foolishly "set 'till it sounds right, because you should always trust your ears as to what's accurate",[see my signature if you can handle the truth], I think your gonna just love it. Check it out!
Before the use of Audyssey based room EQ, we used to pick frequencies other than 80Hz, on occasion, to achieve either overlapping or "underlapping" as a way to address, for instance, a peak in the transition range. Now that we have a more sophisticated system to EQ such concerns, that issue goes out the window.
In fact, since Audyssey has many more control points dedicated just to the sub frequencies, if anything we want the sub ch. to handle as much as it possibly can, at least before becoming localizable [what many people incorrectly refer to as "directional"]. What's that frequency, one might ask? 80 Hz!
[In laboratory conditions, using special, dedicated test tones, some can even localize down to 40 Hz, but for music and movies, 80 Hz is safe.]
Tom Nousaine, technical editor and chief sub tester at Sound and Vision Magazine for over a decade, agrees with 80 Hz in most applications (and the ones where he doesn't is usually to tame a peak/dip, i.e. EQ, which, remember, we no longer need to do, thanks to RC EQ). He sums it up nicely in the final sentence of this [written before we had Audyssey, etc, RC EQ systems]:
And also a little company called THX agrees 80 Hz is the correct, go to frequency. All certified designs, including professional, commercial cinemas, must employ it as the default value. Perhaps some of you have heard of them?Edited by m. zillch - 4/15/13 at 8:31pm