Subwoofer advice sought

Truly deep, accurate bass does indeed improve imaging, midrange, and treble, and contribute to a sense of envelopment. It improves midrange and treble because of the way the ear senses volume balance. Two speakers can easily produce enough midrange and treble, its deep bass they can’t do. Low bass improves the sense of envelopement, feeling like you are in the soundstage instead of it being just in front of you. This happens because our sense of space is tied in to very low frequency sound. At very low bass frequencies the wave lengths are much longer than any room you will find in any normal home. 40 feet or longer. So we hear that, our brains assume we are some place big. 

Okay so that explains the why.

Now, how to get this. The good news is its easy. The bad news is it can’t be done with one.

Every speaker no matter what is in the room which as mentioned above is smaller than the lowest bass wavelengths. Because of this they reflect and bounce back and cancel and reinforce. The areas where they cancel and reinforce change depending on the frequency, and where the sub is, and where you are. But they are always there. For every sub. No matter what.

This is why with one sub you have all these problems moving it around trying to get the best smoothest most even bass. You never can get there because all you can really do is move the modes around. You never can get rid of them. Its impossible.

So what you do instead is use a lot of subs. The more the better. Four is pretty good. Then you put them in different locations. This spreads the modes around. Lots of very small modes is way better than a few really big ones.

Its called a Distributed Bass Array. DBA. Do a search. Audiokinesis makes one called the Swarm. Doesn’t have to be a Swarm. Any four subs will work just fine. DBA. Totally the way to go.
https://systems.audiogon.com/systems/8367

I see the DBA cult has already arrived.  I've posted my thoughts here so I don't have to keep repeating myself here:

https://speakermakersjourney.blogspot.com/2020/04/how-to-not-buy-subwoofer.html

Please message me directly if you have any questions as the DBA cult has worn me down. 

There is also Vandersteen.
His subs use a high pass filter between the amp and preamp and offloads all the power draining lower frequencies from the amp to the sub. The newest model, Sub 3, offers an equalizer to compensate for room aberations.
Mr. V also sees the beauty of using multiple subs in achieving natural sound.
Bob

why stop with DBA?  Might as well just go ahead with full-on 3D immersive surround sound and go for the full monty of sound envelopment, right?  Afterall, if you aren't setting a reference at producing a live acoustic music sound stage then just immerse yourself for the experience.  We all like music presented in various way and there's no wrong answer....but being immersed in the music in an unnatural way isn't for me.  All venues have their unique acoustics and associated challenges...I don't often see 4-6 double bass players scattered throughout the venue to immerse you in their bass.

I tend to agree with @erik_squires on this one (but I wouldn't call it a cult - we all have a preference for how we enjoy experiencing sound and music).  Are we trying to envelope ourselves within a soundstage instead of having it presented front of us?  I actually thought the biggest merits of a DBA approach was not necessarily to envelope yourself in the sound (like you may want in a movie) but rather to combat problematic room nodes....so it's really a form of acoustic treatment and not creating a fake soundstage that envelopes you in it.