Ha ha. You're welcome for the link, but you deserved it!
There is a lot of debate about <20hz. Here is my take on it from what I have read and it is FREE OPINIONATED ADVICE. It is worth every
penny! Yes, you can hear <20hz. If you have sufficient volume, you'll hear 15hz and probably even 10hz. The thing is that very few systems will play loud enough to play 10hz. Not only do you need more decibels to hear low frequencies, it become exponentially more difficult to play at the same decibels as higher frequencies.
At some frequency, I agree that you switch from hearing to feeling. Mind you that you can feel 50hz quite well and it gives you that chest "thump". The ULF stuff still adds something to the experience. From what I have read about other's experience of the Thigpen rotary sub is that they certainly do know when it is turned on and off.
I like to tell people that ULF gives a sense of dread. It does not exist in nature unless something really bad is about to happen like an earthquake or volcanic eruption. Actually, that is not true...it occurs it a lot of stuff from slamming a door to any instantaneous sound like the plucking of a string.
Now, whether it is worth $25k....that depends on how much money you have and your priorities....like a LOT of what is on these forums. A $1000 projector??? That is CRAZY. I just bought a perfectly good 45" TV at Walmart for $300. These people will buy a $30K car to commute in. I don't think the rotary sub is worth $25K and that is why I'm building one. If I didn't want to build something so crazy, I'd put in $1000 of IB subs or $5k of sealed subs and call it a day and have an amazing system.
....but the rotary sub is the "ultimate" and so I would like to try it. I think it will only cost me around $500 with the driver that Penngray donated to the project.