Rel wrote me back. They do have a point I have wondered about with a SWARM
Thank you for providing this information. For strictly 2-channel systems, we recommend using a stereo pair of subwoofers with one dedicated to each main speaker channel. In our experience adding additional subwoofers placed throughout the room for a 2-channel system can negatively impact the timing of the system, and can result in a less seamless blend with the main loudspeakers
Even though people say bass is not directional, its waves are interacting with other waves. Couldn't this create timing and blending errors?
As an interesting point, Rel, JL Audio, SVS and others are all smart people wanting to sell equipment. You would think they would be testing their gear in different configurations to find what works best. Heck, if they could sell 4 subwoofers instead of 2, wouldn't they be saying "YES" to a swarm. Put 4 of our woofers in a room to create the greatest return? Why do you think they are leaving all that money on the table and saying it does not work. Use 2. Or stack them
Some of our subwoofer models allow for stacking, which will result in up to six subwoofers being used in the system, though this is somewhat different than the swarm approach since the three subwoofers on each side will be daisy-chained and will still be essentially functioning as left and right channel subwoofers.
Here they are trying to sell more, but they are not advocating to spread them around the room. Yet with the Longbow and other wifi options, it would be easy to pitch to consumers.
I'm not at all saying a SWARM does not work. I am just wondering why the industry leaders seem to have tried the approach but non are advertising it as an option and the one I reached out to said they did not find it to work satisfactorily.