Placement of Single Subwoofer Affecting Sound of Main Speakers

I don't know anything about your sub but I'd still try to set the crossover low like you have been. I really enjoyed one REL Britannia B1 sub set deep in a corner away from both speakers but crossed at 30Hz or so.

My main speakers go way low (not high passed yet) but B1 sub made the bottom two octaves fill in for a solid foundation that was very enjoyable from my singular listening position. I even achieved a +- 2dB from 31-200hz in the 'seat'. It was smooth and deep.

I've since moved to three sealed SVS subs for a distributed bass array and need to get one more sometime soon so as to have four total. (I still have to explain what the two old RELs and single DefTech subs are for... (TV and home theater rooms, 2).

I'd try in between the mains. I did that twenty years ago and it worked well in another home.  Good luck!

I can echo others in stating that integrating a sub or subs can be a big challenge. I’ve fought many rooms and many single sub setups over the years trying to get things to sound right.

My advice is to keep trying since that sub you have seems to be a very nice piece and should add quite a bit of enjoyment. Move things, change settings, etc. as you have been doing until your ears tell you it’s right.

I’m a firm believer in a dedicated outboard crossover too where you can just assign low frequencies to the sub (low pass filter) and roll off the low end to your main speakers (via high pass filters). As stated a million times on these boards, getting those low frequencies out of your main / satellite speakers really reduces intermodulation distortion and makes a world of difference.  For me (but other persons experiences may vary), having that dedicated crossover makes integration of low frequency cabinets much easier.  I've never had too much sucess with running the main speakers full range, then adding in a sub with just a low pass crossover (which is typically built into self powered subs).  24 db per octave minimal slope helps too on both high pass and low pass.

I have 4 systems in my home ranging from decent stuff to stuff that’s in the garage. Three of the systems have subs and I don’t think I could live without subs, especially on the two critical listening systems I have set up.

Hello,

Besides all of the good things to try above I would also check the Phase of the sub. If it’s out of phase it can really mess with the sound if it’s in a bad location. Sometimes there is a switch on the sub itself. If you don’t mind spending $150+ IsoAcoustic makes a sub platform that come with spikes. I think it’s called Alperta Sub. It works great as long as you subs don’t have a driver on the bottom of the sub like a REL T9. I think putting the sub in the listening position and crawling around is your best option. People sometimes turn the sub too loud. Turn up the crossover to 60 hz and turn down the volume until it disappears from its location. 
If you are in the Chicagoland area this store is an IsoAcoustics dealer and they can help with the sub placement. Maybe a wireless kit is the trick. 
holmaudio.com

They let you try before you buy something in your home. Very easy to deal with. I hope you can get the sub to work. It really made my system great. 

Hello Ryan!  The sub will absorb energy since its cone is moved by the sound in the room (especially bass) and since its cone moves, it generates sound itself even though its just sitting there not connected to anything. That's the problem with listening rooms with multiple speakers at a dealer's showroom. You could just put a pillow in front of it, connect the two terminals together, move it out of the room, or throw a rug over it. If you decide t use it, be sure it's in phase with the main speakers. Listening and then switching the leads listening some more will tell you what's right. Good Luck.

Have the sub to the left of your left floor standing speaker or to the right of your right floor standing speaker. The sub parallel in line with either. And at 0 phase. With the best crossover chosen(60 Hz? 40Hz? 80Hz?) for your room....I dial between 50Hz and 70Hz. And the volume low but just enough. 

That will give you the best chance with 1 sub as that is what I have currently.