Yeah, some of those guys are running 15's or 18's bolted to the back of the sofa/couches.
The HoverEzE inner tube actually creates a small sealed chamber, not an open baffle.
For it to work as intended, that is, shake what it is attached to, requires a leak free seal.
Unlike an open baffle, the small chamber volume raises the box resonant frequency (Fc) to many times that of the driver's Fs, resulting in ~12dB per octave drop below Fc:
The small variable volume chamber limits driver excursion, and increases the impedance to around double it's Re (DC resistance).
The simulation above is using a LAB12C with a Re of 3.11 (4 ohm nominal impedance), Fs of 22.85Hz, 13mm Xmax, rated for 500watts (EIA 426A free-air) or 1000watts "Music Program".
120 volts into 6.22 ohms is ~2300 watts, below 40Hz excursion would be limited to ~2.5mm even given that power:
That said, if the "Hover" chamber would (or could) expand to double (from 5 to 10 liters) on the compression stroke, excursion would also double, but at that point the seat would be thrown up 50mm (2inches), which would be a real tactile experience
Art
No question this is the best way:
To the question of hearing 20hz, I have to ask what you mean by "hear"? "Perceptable" and "Audible" are two different things.
My experience is that with a subwoofer that plays a clean 20hz tone, with minimal distortion and port noise, the 20hz tone is inaudible. Playing a 20hz tone is actually an excellent way to test for distortion and port noise, because both harmonic distortion and port noise are in a range you can clearly hear...while the 20hz isn't going to mask it even if the noise is much softer than the fundamental tone.
A simple test of how well your subwoofer performs is to use a tone generator and incrementally step down the frequency 1 hz at a time. I have had subs that would make an audible octave jump somewhere below 30hz. So you continue to hear a decreasing tone, but the dominant audible tone is an octave higher than the fundamental. And then, if things in the room start vibrating, it may be hard to separate the sub's output from the excited vibrations.
So I say start by making sure you are actually getting clean 20hz from your subs. And install the powersoft motor on your couch for subsonics?
Whole body vibration might be a novel experience for home cinema, actually reproducing ELF creates audible modulation which can be heard as in, say, a church organ. I have never heard any loudspeaker system which can come close to a 32' organ pipe 'sound', even if it's capable of reproducing the note. To my knowledge, no churches have yet experimented with vibrating pews...
Fun subject.
When I play something like this there's sub 20Hz a fair way in.
It shows when I measure it as 16 - 18Hz.
This can be pretty powerful when cranked up.
Also on Qobuz mOrgan Sonata No. 1 in D minor, Op. 42: II. Pastorale by Felix Hell on Qobuz https://open.qobuz.com/track/5164651
It's more of an oscillation or flutter in the air than a sound.
I use 2 X 15" Kappa Pro LFIIs in tapped horn subs.
Amp has a quoted damping factor of >250.
The exits for these are some 17ft away from where we listen.
It's a cool effect.
Other than that music is rarely down to 20Hz. Most being 30Hz and some 25Hz.
When I play something like this there's sub 20Hz a fair way in.
It shows when I measure it as 16 - 18Hz.
This can be pretty powerful when cranked up.
Also on Qobuz mOrgan Sonata No. 1 in D minor, Op. 42: II. Pastorale by Felix Hell on Qobuz https://open.qobuz.com/track/5164651
It's more of an oscillation or flutter in the air than a sound.
I use 2 X 15" Kappa Pro LFIIs in tapped horn subs.
Amp has a quoted damping factor of >250.
The exits for these are some 17ft away from where we listen.
It's a cool effect.
Other than that music is rarely down to 20Hz. Most being 30Hz and some 25Hz.
Here is my audio room still being constructed with my audio system set up in it. You can see the large, tall, tapped pipe subwoofer in the center back side of the room. I mounted the subwoofer drivers near the ceiling to make more floor space. There are two subwoofer drivers, a pair of 18 inch Avalanche woofers (27mm xmax) mounted in push-pull arrangement and the pathway from the backside of the driver to the front side is 22 feet, although my plan is to add an extension to the mouth of the opening extending the path length to 30 and potentially even 38 feet. This subwoofer is intended for a home movie theater and of course can handle any lower frequencies for music with ease. I have a frequency peak at 20 hz, which is not surprising given the length of the room (26 feet), and by adding the extension and venting the subwoofer into the middle of the room, I hope to achieve a flatter frequency response.
I chose a tapped pipe arrangement because tapped horns are really for high efficiency, emphasizing bass in the 60 to 100 hz range, while tapped pipe subwoofers are less for the upper bass frequencies, and more for creating a flatter frequency response. These Avalanche drivers have an FS of 16 hz, so designed for very low bass frequencies. I have a 1000 watt Hafler amp driving them so quite capable of loud, deep bass - its impressive!!!!
This tapped pipe subwoofer handles below 60 hz and I use Karlson speakers for 60 hz to 500 hz, and Lowthers in front waveguides for above 500 hz, and supertweeters for above 8khz.
Retsel
I chose a tapped pipe arrangement because tapped horns are really for high efficiency, emphasizing bass in the 60 to 100 hz range, while tapped pipe subwoofers are less for the upper bass frequencies, and more for creating a flatter frequency response. These Avalanche drivers have an FS of 16 hz, so designed for very low bass frequencies. I have a 1000 watt Hafler amp driving them so quite capable of loud, deep bass - its impressive!!!!
This tapped pipe subwoofer handles below 60 hz and I use Karlson speakers for 60 hz to 500 hz, and Lowthers in front waveguides for above 500 hz, and supertweeters for above 8khz.
Retsel
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