Stereo Subwoofer Pairing

willemj,

I'm new to subs and just about to integrate a couple in my system.

A commonly recommended crossover point for subs is 80Hz, which means the sub will also be still putting out sound above 80Hz.

That seems to be getting into the directional territory.  I've read numerous people say they can localize their subs when crossing over at that frequency.

80 Hz is common for HT. For music I prefer to use them below the main speaker's roll off frequency, i.e. rather lower, such as 35-50 Hz. That is also the advice from REL: set the low pass filter quite low, and the volume relatively high.

willemj

Deep bass is not directional, and that has been shown by a lot of research. Yet, as some have argued here, it may sound as if these deep bass notes do indeed emanate from different speakers. The explanation is that the human brain uses the upper harmonics from the main speakers to locate the deep bass tones.

It is absolutely true that harmonics can suggest that the bass you’re hearing is directional and often, when bass sounds directional, that’s the explanation. But it is not absolutely true that all bass is non-directional; differing phase between bass signals can create the impression of direction. That might be obvious if you really think about it, but it’s also been proven through research, including in work done on multichannel audio by Microsoft.

" Deep bass is not directional, and that has been shown by a lot of research. Yet, as some have argued here, it may sound as if these deep bass notes do indeed emanate from different speakers. The explanation is that the human brain uses the upper harmonics from the main speakers to locate the deep bass tones."

Hi willemj,

     Excellent post that really clarifies the forces at work.  I was starting to think that deep bass may be directional because I'm able to perceive the locations of deep bass instruments within my sound stage illusion in a very consistent and convincing manner. 
     Your explanation, that the human brain uses the upper harmonics of the deep bass emanating from my main speakers to locate the deep bass tones within the sound stage illusion, really helped me understand the forces at work and the reasons for my confusion. All 4 of my subs are run as mono signals and mentally making sense of the deep bass localization that I am perceiving was getting difficult.  Our brains may be the most valuable component in all our systems.   It's all clear to me now,  Thank you.
      I'm not aware of the OP's, rjb1101's, room size and budget so I'm not sure if he even has the space or funds for the ideal solution of a 4 sub distributed bass array system but agree that 2 subs are better than 1 as many have already stated.  
     Assuming he wants to use just 2 subs , I think it's more important for good bass response that there are 2 subs instead of 1 than it is that they match. 
     If  he's mainly concerned with good bass response at his listening position,  I'd suggest he run them as mono and position them in the following manner:

1. Position sub#1 at his listening position and play music with good and repetitive bass.
2. Slowly walk across your front wall from right to left and find the exact location that the bass on the music sounds best to you and place sub#1 at this spot. If you prefer accurate and natural bass, avoid placing sub#1 in a corner.
3. Place sub#2 at your listening position and play the music with the good and repetitive bass again
4. Slowly walk along your left wall, from front to back, and find the exact location that the bass on the music sounds best to you.  Place sub#2 at this spot again avoiding corner placement if possible.
5.  Sit at your listening position and play the same music again.  If the bass response is not very good, start again from the beginning.  Remember, even small adjustments in positioning can affect bass performance at your listening position.

    In most rooms, 2 subs perform best with an asymmetrical positioning scheme; that is, with one along the front wall and one along a side wall rather than symmetrically with both placed along the front wall with one placed behind each speaker. 
    If you really prefer both subs along your front wall behind your speakers, however, you could try this by substituting the following for step #4 above: 
   Slowly walk along your front wall, from sub#1 to the left, and find the exact location that the bass on the music sounds best to you. Place sub#2 at this spot again avoiding corner placement if possible.
     The only way you'll discover which positioning scheme sounds best to you in your room is to try them both. 
     I'm almost certain that you'd get better bass response in your room, and certainly better bass response throughout your entire room and not just at your listening position,if you utilized 4 subs in your room rather than 2,  but you may have constraints I'm unaware of.  I hope this post was helpful to you.
  
Best wishes,
   Tim

FWIW
I employ a pair of inexpensive Andrew Jones powered subs with either my Sonus Faber Cremona Auditor M Monitors or Magnepan .7 speakers.

One sub is in the right corner of the front wall, the other in the left corner of the rear wall. I experimented with numerous placement arrangements and after a great expenditure of time I decided that this basic configuration yielded the best results. It works quite well.

Sometimes satisfying home audio is not beholden to the number of angels which theoretically can fit on the head of a pin. Simple is often best.