Best subwoofer below 40Hz for Magnepan .7?

Cracked the home's foundation! Hopefully that didn't damage your hearing somehow...

Running military grade sub bass system its about 1000lbs and it doesn't crack concrete but it can bend the steel door to room when running tests. Since I know a bit amount about material science I would say expansion contraction due to thermal stress or earth movement most likely cracked the concrete foundation.  Infrasound is less damaging to hearing since it is mostly conducted by the human body it can damage eyes by retina detachment or may cause other issues our human whole body resonance is from 2-10hz  the human diaphragm about 40-60hz eyes about 16hz.

My Schiit Loki is usually in its bypass mode, but if a recording lacks treble energy (or "Fletcher Munson Curve" based late night low volume tweaking is necessary) the highest frequency (8kHz) adjuster will bring sparkle in, and really get the cymbals highlighted smoothly, and the same with the reduction or addition of bass. I rarely use the midrange bands. It might be the best 150 bucks I’ve spent on any hifi gadget as it’s really useful and I haven’t had tone controls on a preamp for a long time. My current trepidation regarding an Antimode box regards my hesitation of adding another thing in the line to the amp, and the fact that I don’t seem to need it in my listening room. But if I find one cheap enough I may still give it a shot for fun.

This is what The Absolute Sound had to say about the Audiokinesis Swarm (and it seems to make sense): https://webcache.googleusercontent.com/search?q=cache:vtIuKJVOkCoJ:https://www.nrc.nl/nieuws/2018/02...

So JohnK, has weaponized sub's. You must REALLY not like your neighbor's! My hearing is still fine. I just wish "Allstate" had thought like JohnK. In that case I wouldn't have had to pay "out of pocket", to fix the foundation. 
       The initial hook up for the first Descent I purchased really surprised me. I had the front grill off to tweak the controls and was watching the transducer as the song playing was quite sub-sonically challenging. As I watched the high excursion on the driver facing me, the frequency passed below my hearing threshold. And in total silence to me, that's when the excursion took a turn to the violent. It was moving so much in fact, that as I jumped up and ran over to adjust the level I just knew that I was going to have three ruined woofers. Amazingly the sub has never shown itself to be any worse for the wear! Still more articulate than any other I personally have heard.
   I would try a "Weaponized", sub system though. It sounds neat. And definitely a "guy" thing. But it seems I am fresh out of enemies.