Rotary Woofer (2006)

Random observations:<p>* I heard the Thigpen Rotary Subwoofer when Thigpen premiered it at the Rocky Mountain Audio Fest in 2005. Something that&#x27;s not obvious from most of the published pics is that the rotary subwoofer was using an entire hotel room to serve as an enclosure. IE, you&#x27;re not going to easily get loud bass at 10Hz without an enclosure, and the Thigpen sub used an entire room.<p>* Tom Danley is a national treasure and designed something similar at Sound Physics Labs, about 22 years ago. Tom also licensed the technology to Phoenix Gold for use in their &quot;Cyclone&quot; car subwoofer. I&#x27;ve only met Tom once, but as I understand it, he abandoned the technology because subwoofers from companies like Faital, 18 Sound, MTX and Eminence offered comparable performance with improved reliability. Basically the subs he made for Sound Physics Labs were crazy, but reliability was an issue, especially since they used a lot of custom parts.<p>If anyone is curious about these designs, let me know, I love this stuff.

Skimming through the site, the magic behind this is that the fan spins at a constant speed, but the pitch of the blades can be modulated at very low frequencies - positively and negatively. I had to look carefully at the .GIF on this page to have the ah-ha moment when it made sense. <a href="http:&#x2F;&#x2F;www.rotarywoofer.com&#x2F;howitworks.htm" rel="nofollow noreferrer">http:&#x2F;&#x2F;www.rotarywoofer.com&#x2F;howitworks.htm</a>

Here&#x27;s a recent build by a hobbyist. An interesting watch and an impressive outcome, it vibrates the entire house.<p><a href="https:&#x2F;&#x2F;youtu.be&#x2F;NZKCxIuJ-5M?si=C545ivmg8TvhKhYg" rel="nofollow noreferrer">https:&#x2F;&#x2F;youtu.be&#x2F;NZKCxIuJ-5M?si=C545ivmg8TvhKhYg</a>

Reminded me of the Leslie speaker, used with the Hammond B-3:<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Leslie_speaker" rel="nofollow noreferrer">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Leslie_speaker</a><p>Although its rotation was for tremolo, not bass.<p><a href="https:&#x2F;&#x2F;youtube.com&#x2F;watch?v=G5fI3X9BdrQ">https:&#x2F;&#x2F;youtube.com&#x2F;watch?v=G5fI3X9BdrQ</a>

&gt; However nothing existed to produce significant enough output to change this belief.<p>I thought it was more accurate to say that the lowest frequency a human can perceive as sound is also the threshold between determining if a sequence of pulses is a sequence of distinct events and one continuous sound, whose period is around 5ms (or 20Hz) and this is pretty easy to verify experimentally, even with woofers that can&#x27;t produce a pure sine below 20Hz.<p>That said there is another factor which is that we don&#x27;t just experience pressure waves in air with our ears, but with our full body of senses. And if you can definitely be impacted by infrasound even if it isn&#x27;t just vibrating your ears, since it will absolutely vibrate your chest cavity and the rest of your body and you can feel that in your bones (or so to speak).<p>There&#x27;s also a long history of scientific&#x2F;pseudo scientific and almost apocryphal stories about infrasound. Off the top of my head I&#x27;ve heard of fans in a building causing subsonic vibrations that disoriented people, subsequent research into weaponizing it, whistles that were designed to vibrate below the threshold of hearing, the legendary &quot;brown note&quot; (a sound low enough and powerful enough to cause evacuation, of a building or a person) and even Havana syndrome was allegedly attributed to infrasound.<p>It&#x27;s very interesting to use a fan to create such waves when an electromagnetic piston might fail. But I wonder how useful it is since making a piston vibrate at low frequencies isn&#x27;t that hard, it&#x27;s enclosing it that is the problem. I suspect a large enough enclosure with a big enough woofer and enough power in an amplifier (eg, a commercial subwoofer) can do just as well without being so exotic as to require custom electronics.

A YouTuber did this recently and turned his house into a subwoofer:<p><a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=NZKCxIuJ-5M">https:&#x2F;&#x2F;www.youtube.com&#x2F;watch?v=NZKCxIuJ-5M</a>

Was I the only one who imagined a dog chasing its tail when reading the post title?

&gt; The air density is much too low to be a good impedance match with a cone loudspeaker. Take your hand and try and grab some air or flatten your hand and try and push some air as fast as you can. This illustrates the futility of trying to move air to create a small amount of pressure at low frequencies with a cone speaker. You can barely feel the resistance of the air to the motion of your hand, the air molecules simply slip around.<p>&gt; Now take your hand while driving down the road and stick it outside the window of a car. The faster you go the thicker the air feels.<p>So could you have a normal fan blowing air into a normal subwoofer to increase the pressure, and get more bass?

This sounds very cool!<p>Also very expensive.. which makes sense, it&#x27;s mechanically complex product (variable-pitch propeller) with strict requirements (don&#x27;t want things to rattle or while) which is marketed to rich people (hi-fi fans).<p>I wonder if modern power electronics and brushless motors can achieve the same effect with a fixed-pitch propellers. This could be much cheaper and more accessible to hobbyist.

Is the musical equipment in this music video operating on the same principles? <a href="https:&#x2F;&#x2F;youtu.be&#x2F;ZdJ5e70Q8mw?feature=shared&amp;t=128" rel="nofollow noreferrer">https:&#x2F;&#x2F;youtu.be&#x2F;ZdJ5e70Q8mw?feature=shared&amp;t=128</a><p>It&#x27;s the tall cabinet behind Money Mark in the Beastie Boys video for &quot;Gratitude&quot; at around 2:19.

Home owners in New England would refer to this as a &#x27;whole house fan&#x27;.

&gt; TRW-17 transducer $12,900.00<p>I mean, if we could find something that knocks off a zero at least this might make an interesting project but at this price point, it&#x27;s for die-hards only.

So what can you play on it? Any recordings or hardware available that go low enough?<p>Looks like they have a demo DVD. Was hoping for more.

It&#x27;s neat but dusting it would be tricky and kids would destroy it.