Two Subwoofers... Comb Effect

I think it's an advantage to place the subs as close to the mains as practical running in mono to minimize phase issues. There is going to be some overlap of frequency and you don't want the same frequency coming from sources several feet away from each other. Speaker makers go to alot of trouble to align drivers. Depending on the crossover slope it might also be beneficial to angle them within 15 degrees or so of the mains. Yes it's all room dependent and you could end up with something quite different but I would start with the sub drivers and the main drivers on the same plane as close together as possible with a similar angle. In a normal sized room treatments are likely to be needed - Jim

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

Phase matters alot

Interesting post Duke. What do you think about the concept expresed in the "subwoofer conundrum" under the subheading 'Timing is everything' at www.sound.westhost.com/subcon.htm It's not the greatest techno reference but it's quick and expresses what I was trying to get at with variable distances.It mirrors what I have experienced in my home and what the folks at jl audio preach. Thanks - Jim

Thanks for the thoughtful answer Duke. Your posts are always well resoned. Reguarding your 1/2 wavelength remark I agree that you need to compensate for second order crossovers by inverting phase( 180 degrees available on most subs). Once you have done that does the distance argument not hold ? You can attempt to compensate for various distance discrepancies by utilizing continuous phase adjustment on the sub but you have to pick a frequency to correlate this with.( adjusting to be in phase at one frequency will take you further away in another. Figure 1 I think is an exagerated 'sub in one corner placement'. Your dead on with the major deal being in room frequency response at all likely listening positions which far outways this one argument. I just think this is a simple practical place to start. -
jim