Subwoofer

I used successfully use a single sub for about 15 years.

With only one sub, it's important to remove the sub range from the mains. AND have sufficient drive from the sub.

Most subs have inadequate controls to integrate properly. You must have variable crossover frequency and slopes, continuous phase and polarity inversion.

You can get away with a less capable sub by setting the controls to minimal, e.g. highest crossover and using miniDSP or other capable crossover. I do not recommend using the miniDSP internal A/D so either feed it digitally or only use it for the low end only, feeding the mains with a passive analog XO to roll the bottom octave @ 6dB/octave.

See ieLogical SubterraneanHomesickBlues. There useful links for room analysis and other information.

Thanks for your kindness ...

 My very best to you....

@mahgister 

Glad to see you are here again seemingly healthy. At our ages, you never know when one may have passed.

Hi I just purchased and installed two subs tonight!  They are Pyle 8" down firing that I got off Amazon for $125/each.  I used two because my mentor has two at his place that are on at a very low volume and cross over but what they add is a deep soundstage. I think having bass behind the speakers creates this.  I used male to female spliters and line out of my pre.  It makes holographic deeper sound stage. It is amazing. JH

Added an SVS micro 3000 (for dimensional reasons) to khorn-tube integrated system and, at lower volumes, it made a tremendous difference.

I intend to add a second one and hope the SVS app will be up to seamlessly integrating 2 subwoofers.

Baloney...I used one REL Q150 for years and it sounded great, and still use that one now along with a Q108MK2...still...one properly adjusted sub can work beautifully in any room.