Two Subwoofers... Comb Effect

4 th order crossovers just never sound quite right to me despite the obvious theoretic advantages of 24db LR. Less overlap and summing to zero at the crossover as well as being able to crossover higher and not localize them. As a result I'm crossing over lower than I might otherwise. As far as the subs being a BIT closer or further away than the mains Duke is right in most real world situations but audible/non localizable frequencies ( 20hz-100hz) if they are in the crossover range will be arriving from two different sources at two different times. This of course may not make a pennies worth of difference in any given situation with any given listener - Jim

Most subs have a 12 dB per octave lowpass filter, and so will give away their presence and not blend well because they allow too much lower midrange energy to pass through.

That is what I have - 12 db/octave. That may explain why I prefer it up front.

Ok, points are definitely noted from those here responding about phase on the subs.
So here's some questions that even a novice might ask then. Which is, If phase doesn't matter on the subwoofers, in relations to each listner and the speakers, then why do subwoofers and even some processor offer phase adjustment in the first place? I mean, if you have one subwoower 3 feet from your listening position, and another 10 feet away, and maybe another 14 feet away from you, doesn't the phase get all confused and out of sync with the rest of your system?
I mean why does a full range speaker's woofer even have to be in phase with the rest of the drivers then? You mean it doesn't matter as long as you have relatively flat response from your sub-woofers, and proper volume level?
Maybe someone can address these questions concisely. Cause otherwise I think all the speaker engineers maybe put too much thought into making their large full range speakers so coherent in the first place. And not only that, but all the pre/pro's out there that have you specifying sub to listener position distance were just adding unnecessary steps to the process...

That's why I x-over as low as possible...40->45hz. And while my Sub IS fairly close to the LH speaker, it is still pretty seamless. Don't forget that recordings. ..with the possible exception of the Telarc recording of Wellingtons Victory are MONO below about 80hz.
The Telarc disk has very localized CanonShots which are a real system test.
SMALL point...using 1ms/ft is probably OK, but sound is actually a little quicker....maybe 14"/ms....like a said, a very small point......

Phase matters alot