Considering a Second Subwoofer for the Front

Hasn't Salk closed?

With a four sub array I can't imagine your shooting for stereo. The mono room lock should be amazing. I did it using three different asymmetrically positioned subs and it worked just fine.

If the master sub has remote control volume and the connectivity to daisy chain the other three the system would be conveniently controllable. Good luck with it.

Since my last post was removed, let’s try this again. What in the H E double toothpicks is a bucket sub? Can we see an example of this beast?

Your OP was very vague and cryptic. You should provide more details if it’s really advice you are after.

I called my friend who recommended trying the bucket sub. The formula is on Bruce's website-Transcendent Sound.  The Bass picture is spot on.  The sub is essentially the bucket with concrete in the bottom and a woofer on the top.  I control mine with an amplifier that can cut off at various levels.  They augment the sound.  They are not meant for heavy bass.