So I've not read through the vib sensor thread, but I have definitely found over the last few years that having subwoofers IMMEDIATELY behind the listening position pointing towards the listener adds intense tactile feel at the same overall SPL levels. I fire mine directly into the back of the chair.
I'm using just three UM18-22 firing directly into the back of my three primary listening positions. When I've been exposed to a perhaps more traditional mid bass module - specifically a HSU MBM - I personally didn't like it. It is missing all the low wobble effect that I personally find most desirable about the nearfield feel. It seemed a shallow trick. I tried a 10" Infinity Kappa driver directly behind my seats in my theater and while enjoyable - was not nearly as enjoyable as sitting in front of the 18".
I know there has been some discussion that a high excursion low sensitivity driver like the UM18-22 that I'm using can't deliver the same punch as a pro driver --- Frankly - unless I just don't know what I'm missing and not liking the HSU MBM --- I don't want whatever it is I am missing if it's like that HSU MBM.
To each his own I suppose.
For nearfield tactile feel I much prefer the drunken wobble feel of the low frequency stuff, to the teeth buzzing feel of the higher bass stuff. Perhaps that's simply a personal preference. I still run my nearfield subs balanced though - eq'ed flat -- as that seems to be preferable to me than just having high bass making my teeth vibrate. That feels weird (uncomfortable) to me.
I guess I won't know unless I try it - but personally I think the nearfield UM18-22's can deliver as much tactile feel as I need, if so inclined - even running them flat FR. I used to have mini buttkickers on each chair but I removed them as they were inferior to the nearfield 18"'s feel in pretty much every characteristic.
I think this hobby is cyclical. Mid Bass modules were all the rave a few years back, fell out of favor a bit for full extension subs, and now it appears they are coming back into fashion. I do know some people really crave that intense vibration effect of higher midbass --- and that's cool. I think, personally, I'm just fine skipping this round of 'upgrades'.
I like the full extension nearfield, because sitting on a concrete slab - having my sealed nearfield is the only way I feel the wobble of the deep ULF. Without the nearfield sealed, I' might as well not even bother trying to chase inaudible low frequency content. My eight 18" subs just can't deliver.
I've said it before, and I'd say it again. I started in my room with all eight 18" subs up front under the projector screen. I moved one sub back to my behind my listening position and quickly discovered that a single 18" nearfield - firing directly into my back could produce more subjective tactile feel than all eight up front. So if I had to chose for movie watching 1 sub behind me or the other 7 subs up front - I'd chose one of my subs directly behind me. (at least for cinema --- for music I like the subwoofer sound to originate from up front - and only the nearfield playing sounds like it's coming from behind me -- not ideal---- so I do 5 up front, and 3 behind, and I run the front subs usually about 1dB louder than the rear - and that seems to work out A-Ok for me for both music and movies.)
With nearfield - a single 18" sub delivers that deep tactile feel --- and delivers in spades. Maybe one of the local guys will install a quality MBM and I can give the midbass focused idea another try. Until then - I'm pleased with what I have.