Differences in sound quality/performance between the LV12R and LVX12/FVX15

[N Boros]

You want to keep the subs in phase to get the cancellation of the standing waves when you are placing them symmetrically across the room from one another. Just imagine the one frequency (and its harmonics) where the wave perfectly fits in the room. If you place a sub across the room from that symmetrically, then the wave coming out on the other side is inverted and the two cancel each other out. This is important in most rooms, where with just one sub, the frequency bounces back and forth and adds to the previous, creating huge peaks, or huge nulls depending on where you sit in the room. If the subs are 180 degrees out of phase and placed symmetrically across the room, I think that the standing waves would add together, making things worse. It is only predicable like this in a sealed rectangular room, which is why shooting for that is nice. Otherwise one is left playing with placement and the phase on one to get good seat to seat variation.

[sludgeogre]

You want to keep the subs in phase to get the cancellation of the standing waves when you are placing them symmetrically across the room from one another. Just imagine the one frequency (and its harmonics) where the wave perfectly fits in the room. If you place a sub across the room from that symmetrically, then the wave coming out on the other side is inverted and the two cancel each other out. This is important in most rooms, where with just one sub, the frequency bounces back and forth and adds to the previous, creating huge peaks, or huge nulls depending on where you sit in the room. If the subs are 180 degrees out of phase and placed symmetrically across the room, I think that the standing waves would add together, making things worse. It is only predicable like this in a sealed rectangular room, which is why shooting for that is nice. Otherwise one is left playing with placement and the phase on one to get good seat to seat variation.

Indeed that is true. I just set mine both at 0 and let the receiver/processor do the phase adjustment through the distance measurement. Has worked well for me. In a normal 2 channel system without room correction/automatic measurement you have to be a lot more rigorous about it and do all of the dialing in yourself since there is no distance adjustment to account for phase, so yes, you're absolutely right for a 2 channel system.

[N Boros]

What makes the 12 by 12 foot room such a challenge is that you get these standing waves building up in both directions at the same frequencies. The frequency that has a wavelength of about 12 feet is 95 Hz. This means that with one sub you will get massive peaks or nulls with a frequency close to 95 Hz, depending on where you sit in the room. The same will be true with multiples of 95 Hz. Anything that can be done in a square room to knock down these standing waves, like correctly placing 2 or 4 subs in the room and bass traps and corners traps, etc. will go a long way.

The nice thing about a square room is that the standing waves are very predictable. You don't get them happening at two different frequencies from front to back and left to right. As long as you address them in some way, you can still get good sound in a square room.

[sludgeogre]

What makes the 12 by 12 foot room such a challenge is that you get these standing waves building up in both directions at the same frequencies. The frequency that has a wavelength of about 12 feet is 95 Hz. This means that with one sub you will get massive peaks or nulls with a frequency close to 95 Hz, depending on where you sit in the room. The same will be true with multiples of 95 Hz. Anything that can be done in a square room to knock down these standing waves, like correctly placing 2 or 4 subs in the room and bass traps and corners traps, etc. will go a long way.

The nice thing about a square room is that the standing waves are very predictable. You don't get them happening at two different frequencies from front to back and left to right. As long as you address them in some way, you can still get good sound in a square room.

Could not have said it better myself. 100% agree.