Why aren't rotary subs more popular? 

just watched some polish kid create his own rotary sub woofer and now i'm here

I heard Mazda stopped producing them because of reliability and emissions problems........oh wait

I used to attend electronic music shows at a concert venue with a single TRW-17 rotary subwoofer. That place would take your breath away when the bass hit. Years later, another venue was structurally reinforced, and had 3 of those same systems installed. When the bass hit, a friend and I had to hang onto the stair rails, so we didn't fall down. If the outside door to the smoking area opened, then the bass would knock cigarettes right out of people's hands/mouths. Truly feeling sub bass is a whole different animal than hearing notes within our range 😁

I attended a demonstration of a rotary sub at the 2008 AES conference in San Francisco. It was amazing. The fan is about 2 feet across. It was mounted in the doorway between to adjoining hotel rooms using the second room as a compression chamber. One benefit of rotary sub-woofers is that they have very tight, punchy low bass. The fan can grab a lot of air and shake it with very little distortion. A complete unit is about a cubic yard and can replace tens of sub-woofers. High pressure subsonic waves below 10 Hz are very disorienting. I found they induced mild virtigo. It was fun watching the CD cases migrate across the coffee table. The inventor said it was very hard finding recordings that had any meaningful signal below 10 Hz. Mostly movie sound effects. The other big problem is that it is very difficult to contain high pressure infrasonic sound. I could hear the fan from the other end of the hotel floor. I walked down the stairs and out on to different floors. I could hear it clearly one floor down. I could still hear it two floors down. I recall three floors down it finally started blending into the background noise. I suspect that movie theaters don't want the infrasonic sound of one screen to be heard in theaters two or three screens away. BTW, my personal experience is that infrasonics have to be loud to be heard (experienced). Low volumes just become part of air pressure changes that surround us every day. That is my experience, YMMV.

There is a fan in the ceiling of my bathroom. I've been known to "pressurize" the air in there. My wife, however, routinely fails to appreciate the musicality of these pressure waves.

I met Bruce Thigpen at Rocky Mountain Audio Fest and heard his rotary subwoofer. What he did for the demo was install a temporary baffle in the passthrough door between two rooms, creating an infinite baffle. It was an amazing experience. My friend who was present for the demo had to leave the room because the ultra low frequency made him queasy.

Most places that have rotary subs installed first have to be inspected by a structural engineer to see if the building and foundation can handle it. If you have double or triple paned windows in your house, prepare to have the seals blown. So, they can literally have your home falling apart if not installed correctly. I'll have to be happy with my Delcoid and Monoilith subs.

This is fascinating I've never heard of these before.

I actually made one of these based off the design of the guy in the channel you got that picture from. It’s quite an intricate piece. It still works without a box. It’s less efficient, but it works. I wasn’t able to run it properly above 20 hz, because the forces involved will cause it to shake itself apart. That’s also why thigpen’s design includes a very expensive dampening system. I don’t remember exactly what I paid, but I bought parts new since I was following a design rather than going from scratch. I ended up with maybe $600 in it, and the base was fabricated for free.

I would really love to experience one. I find them fascinating however the cost, the space requirements and the fact it could literally shake my house apart is keeping me on the sidelines

This is one of the best ever videos, I learned something new

I saw the title and i was like "Yeah! how come, right?? Great video. Youre a great speaker. Its impressive how well you can explain and articulate things so naturally without stopping or editing the dead space out like most youtubers do.

Paul you are a legend, thank you for your channel.

This is the best explanation of a rotary sub I have heard yet thanks!

Hi Paul, my name is Jean Michaud I'm from Québec, Canada. I love sounds systems for many years. I got my first stereo at the age of 10 and now I'm over 50. I realy love your videos, l learn a lot. I like the way you do your videos, a mix of technic, fun stories and respect. Keep the good work! 👍👍👍

That would be great in organ applications where there wasn't room for 32' pitch (about 16 Hz) organ pipes. Or in the case recording reproduction of the Atlantic City Convention Hall organ 64' pitch.

Bruce and his company Eminent Technology are very much still around! In addition to the TRW 17 rotary woofer, he still makes the ET 2.5 linear air bearing tonearm, and his LFT speakers, which are planar magnetic not electrostatic.

Paul, you kill me with your analogies, “Fart in a windstorm”😂😂😂

This old guy is a legend 🙌

infinite baffle is the best way to get the best results for a rotary sub. aka put it in a window. your house is where you listen and the planet is your speaker box. i JUST watched an awesome youtube video on this subject a couple days ago. even at 1 hertz there was very noticeable air movement. even watching it in a video where you cant hear it. everything in his house was rattling and his doors were opening and closing slightly with the air movement. amazing project. I thought it was gonna be some rigged together garbage but it actually came out extremely good. i wish i could find the video to post a link so people could get a better understanding on how they work.

Fantastic video. Tom Danley makes a lot of unbelievable sub bass systems(live sound) They made a subwoofer out of a shipping container called the matterhorn and they show it being built on youtube. This thing can actually modulate a mountain and be used for non explosive avalanche control. I have 2 of their TH118(tapped horn design) subs and they will choke you they hit so hard with a bass drum kik. Super efficient too. These guys are scary smart.

I have a couple of ContraBass ServoDrive subwoofers. Very interesting design that gets around the efficiency drop that occurs with voice coils on large cone excursion by using a low inertia DC servo motor to drive the cones. Apparently very big back in the 1980's and used by theme parks. 17-80Hz, +/-6.5dB which is pretty low. Mine came to me through a pipe organ repair and I ended up on a journey that took me back to the creator, a gentleman called Tom Danley. I was able to get them working. The reason they disappeared is the motor that was used was commonly used in large tape drive in those very old computers. Once that market died, the price of the motor skyrocketed making them unmarketable. Still, a very interesting cabinet that used two 15" pistons, and two 18" passive radiators in a "somewhat" compact cabinet. I should mention that sometimes pipe organs cheat on that last 32 foot stop due to building size limitations.

I remember back in 2006 seeing something like this on hackaday.

Quite fascinating! Thanks!

I’ve never heard of one, and it sounds intriguing!

Before watching the video, here are my impressions. I'm aware of four types of rotary subwoofer - subwoofers that convert rotary motion to air motion. The first is the Phoenix Gold Cyclone, where a rotating vane is coupled on either side to a curved waveguide that redirects the airflow forward and backward. The second is the Bruce Thigpen Rotary Woofer, which is like a fan where the blade pitch is adjusted by a voice coil motor. The third is the Servodrive method used in the Contrabass, BassTech 7, and SDL5, where a rotary servomotor is coupled through a rotary-to-linear motion converter using belts to a pair of opposing cone diaphragms. The last is the Intersonics Servo-Valve loudspeaker used in the Sonic Boom Generator, where an airflow source is coupled to a pair of output openings operating in opposite acoustic polarity through a valve where a rotating vane is driven by a servomotor. The one approach above that doesn't involve Tom Danley is the Thigpen Rotary Woofer by Eminent Technology. All the rotary woofers involving a servomotor driving a vane must rotate back and forth, so they have to fight the rotational inertia of the vane, and as a result they have limited upper frequency. The servomotor in the rotary-to-linear systems must also rotate multiple times to go through the full range of excursion (which is still mechanically limited by packaging and suspension geometry), so there is a lot of rotary inertia in the armature of the servomotor itself. Linear motor systems have similar inertia which must be overcome at high frequencies to avoid a decrease in amplitude as frequency increases. The Bruce Thigpen Rotary Woofer, being a fan, doesn't have to stop rotating and rotate in the other direction (AC rotation) - the rotation is continuous, enabling the fan to produce a "DC" air current. Its problem is its bladepass frequency, which comes from having five blades rotating at some speed. An acoustic lowpass filter is needed to absorb the bladepass frequency, and this is actually helped by having the motor spin as quickly as possible, but the motor is an AC induction motor which are commonly available in 1700-ish RPM (4 pole) and 3400-ish RPM (2 pole) variants, and higher speeds than that can't be achieved without increasing the line frequency from 60 Hz to some other value using an inverter drive. Multiply that by 5 and then divide by the number of seconds in a minute, and you have the bladepass frequency. If the bladepass frequency can be maximized, it can be effectively filtered by a smaller acoustic filter, but the size of the acoustic filter needs to be large to be effective at the bladepass frequency, and it will necessarily have a low corner frequency that also limits its upper frequency bandwidth. The advantage of moving-coil, linear-motion speakers is their very low mass, thanks to the columnar rigidity that comes from being comprised of shapes that are revolved around a central axis (the cone, voice coil former, surround, and spider), so they can have a very wide effective bandwidth, and they are not prohibitive in cost. If you think of acoustic systems as having a gain-bandwidth product (similar to ICs), you can also use acoustic filters that narrow bandwidth of your cone type drivers in order to obtain resonant gain, at the expense of bandwidth and rise time, and horn loading can be used to combine bandwidth reduction and acoustic impedance transformation to greatly increase system gain. For now, the dynamic driver with linear, permanent-magnet motor has the edge in simplicity and low cost, even when subsonic output (below the range of hearing) is necessary.

Wow, never heard of these! Still rocking a PS Audio Superlink from the early 90s. It’s my favorite DAC of all time.

Sir you are the man!

i learn something new every day on this channel, even if it was 4 years ago.

That "raspberry' fart noise was about 20hz! Good job. 🤔🤔

Some 20 years ago, at my stereo shop, one of my product lines "Phoenix Gold" offered in pre-ordereded limited production supply, the "Typhoon", which is some what a rotary sub woofer, but was more of a reciprocal action rotor subwoofer that from the relaxed or natural or static point of the paddles or the "would be" cone, was for sure a radical thing to see, let alone, I thought it would be a good idea to have 4 of them installed in a Chevy Suburban demo display.... Ummmm, only one was actually needed, as 4 of them at full throttle, was breaking stuff on the vehicle like window glass, cash cluster, etc. How those structure of the units would not break apart themselves, I do not know. If I remember correctly, I think the maximum input power in watts, was 150 watts, with a peak of 300 watts? Running the processing active cross-overs to limit how much band width was allowed to go into them was a key factor, as if too much of too wide of a frequency spectrum they would get pretty muddy, or to say, they would get out of control and distort, but maybe a couple 5 to 10 bands worth of low frequencies for running full power, was required. At listening levels for music, you could widen the band widths from approx 5 to 300 and they would perform wonderfully, again, only at listening levels though, maybe at a yelling level, just not full wide open throttle, lol Those units had to have a compression type loading like the hatch back of an automobile, or in the corner of a room. If being run in home audio, you then needed to reduce the gain to the very lowest, as they offered a very boomy output, but, if the units were for sound quality, and to just face them towards you, in a room, as one would do with standard cone woofers, you would hear the whisping sound of the air bleeding past the paddels at lower volumes, so aiming them away from the focal point mattered, or should be indirectly mounted. Which brings up having one in my home, DON'T DO IT!!!!! ,lol... Very hard to match to the rest of the speakers output. they seem to not have the same acoustical output rise that a standard cone woofers has. Very over bearing even at lower volumes. Granted, you you are constantly rocking the house at full throttle, then yes, by all means, you are covered with one of these TYPHOONS, which were approx size to 12 inch diameter woofer, and could slide right in, if the enclosed was the correct volume for the Typoon. Now, a down side to those units, I heard stories of them being installed in the wrong sized encloseure, and they then would tear them selves apart. that never happened to me, as I didn't want to spend $800 a piece on new units, lol. they do require a large enclosure, if my memory serves me correctly. I made a coffee table that was the woofers enclosure, that didn't work, as it was just too much boom, with a massive wave length. Allow me to example, watching a movie one night, and the volume was what you would hear and feel at your typical theater, we noticed red and blue and white flashing lights through the window blinds, only to realize, our beloved police were actually standing at out front porch, banging like neck on the door, lol.... Oops!!! It was a noise complaint from my neighbors, ALL OF THEM.... and my closest neighbor lived approx a wee bit further then a half mile away or 3800 feet away. their complaint was not just the sound, but, stuff was vibrating on their shelves, lol.... I felt all bad, as I was just excited about giving the coffee table a test run, and never put any thought into the wave length that these units can achieve. I hope that none of these gets confused with the idea that these Typhoon units have a high acoustical loudness, as they are not any better or worse, rather, that the ability to control any speaker, accurately, and give the speaker clean stable power, I suppose is the idea... Please feel free to correct me... As my info is 20 years old, and have been retired from that industry for about 18 years now... Thank you for the video, I enjoyed remembering some old stories that I had forgotten about... Dru

Phoenix Gold used to build their Cyclone rotary car subwoofers. Thanks Paul

YOUR VIDEOS are so Relaxing - no Graphs, no stupid Snobs snobbing about stuff and hitting you with meters and scopes.... I could go to sleep, listening tho your Videos. Thank you!

Fart in a wind storm lol I'm dying here

I use tactile transducers in my couch. It gives a nice low frequency effect, cheap and easy.

GOOD VIDEO AS ALWAYS SIR!!

Thank you! You just explained what I experienced after 9/11 when all the planes were grounded. The silence or the lack of sub sonic sounds created by the jets, though we may not consciously hear it, we are aware when it's no longer there. I didn't fully understand what I wasn't hearing till you talked about sub sonic sounds. Again Thank you. Perhaps you could do a video on this next year about this. It was an experience I'll never forget.

Wish there were more good questions like this ...

It's crazy how ideas permeate the cyberspace. One video comes out on some other channel, and before you know it, there's a whole bunch of interest and new videos surrounding that idea. The modern age is truly something.

That is really really creative and inventive

Frequency Response: 1Hz : 30Hz ± 4dB Suggested Crossover: 20Hz @ 18dB/octave Sensitivity 94dB 1 watt 1 meter @10Hz Maximum Acoustic Output: >115dB between 1 and 20Hz.

I remember those from a Sharper Image catalog many decades ago. Still want one. Finally have a place without neighbors where it might be enjoyed.

Thank you

thanks for explaining rotary subs is, I don't have to google it.

Eminent Tech still makes really great really cool planar speakers! Absolutely still in business!

Thanks for explaining what a rotary sub is, Paul, because it was completely new to me. As you alluded to, I imagine the cost of setting up such a system would be enormous

Two companies come to mind. Intersonics and Servodrive. I heard them throughout the hall at NSCA many years ago. They were astonishing!

I thought I'd heard of every kind of speaker. Wow!

Young guy made one and posted his experience a few months ago. Pretty impressive. Channel was Daniel Fajkis. “Making the worlds most powerful subwoofer.”

Nice one Paul!

I have heard the TRW17 on a couple of occasions, and it is an awesome experience. As Paul says, one problem is finding program material which goes that low, as it really doesn’t go much above 20-25hz. The installation is complex, as you have to build it between two rooms, and run it through a labyrinth to reduce the noise before it vents into the listening room.

I think that these type of subs are good to have in some home cinema , because it can completely vibrate the room and the feeling from movie will be much better :o

Found my way here by way of a KPOP video. Glad I did. Hehe. Great stuff!

I only ever experienced one in Niagara Falls, there’s a Niagara’s Fury 4D motion theatre experience. Conventional woofers handle frequencies down to about 39 Hz, and six Eminent Technology rotary subwoofers were drilled though the floor into an electrical room below that acts as a 5,000 cubic foot box. Each motor is ⅓ horsepower, fed by custom three two-channel custom amplifiers capable of below 20 Hz content. The installation can manage 5 Hz at 125 dB, even manages 1 Hz and it is indescribable. Well, I suppose the real thing is just outside. Special microphones were used to capture the sound for the presentation.

The first time I heard a “rotary sub” used by Hammond Organ company. The bass was incredible. I believe CBS once marketed a separate speaker for sale.

Everyone who is a little interested in good sound should try to get down to 16Hz. 16Hz-16KHz is soooo satisfying 🤩

I used to have a Pheonix Gold Cyclone. Its exceptional sounding as a bass enhancement device. The benefits are high sensitivity so it doesnt need a lot of power and is super flat and very smooth yet punchy at the same time. It actually gets louder as it gets lower from say 90Hz to 20Hz. They were originally marketed for car audio and eventually went into the home theatre world and never took off. The downsides are they are pretty deep and need around 3cubic feet for a sealed enclosure. So the box is a fairly big size considering the airspace and speaker size. The only other thing i could see as a downside is that you can hear the air or flaps movement if the rest of the frequency spectrum is off or low level. But its definitely an experience to hear, i mean feel under 20Hz. We used to play Telarc and listen to harmonics of the synths at 10 and 13Hz. You wouldn't hear anything but could watch my interior of my vehicle shake cyclically.

Cool topic

Very informative video, when I saw the title i figured you meant subs in the shape of a rotary (wankel engine rotor) , I just learned something new , nice video.

I own 4 servo/drive 7's They are servo motor driven speakers set in a folded horn cabinet that uses the backs of the drivers as the forward sound source.

There was a static display at THESHOW when it was still at the Saint Tropez Las Vegas during CES (that hotel is now something else: 455 East Harmon Avenue). He was talking about putting it in the attic.

You're talking infrasonic here. You can make a conventional woofer that will go that low, but it's crazy. A friend of mine took a Piledriver 15" driver (don't remember the model, but it had a paper cone with a pleated paper surround and a HUGE magnet), and coated the piston part of the cone with several coats of epoxy. He then poured about a half inch layer of epoxy over the dust cap. This increased the mass of the cone, which lowered the FS to UNDER 20hz. (Yes we build a large box and MEASURED the T/S parameters before and after the epoxycation). The driver was mounted in a sealed box, about 20 cubic feet (size of a REFRIDGERATOR!) made of 2x4's and 3/4" plywood, and was driven by an amplifier of over well over 100W. We tested it with an HP audio oscillator (which went down to 1hz, had to test over TWO octaves). We could FEEL the output below 20hz, all the way down to 5hz! Yes this was a ludicrous design (we made TWO of them for STEREO), but my friend had a very large room and money to burn.

At 4:48 I like that expression, "like a fart in a windstorm." 😄

a very good way to get those "Infrasonic frequencies" are with a "Tactile Transducer". They are perfectly coupled to your furniture or floor or a riser and are solid down to few hertz. Very common in theaters but i also use mine for "Novelty" music listening. Much less expensive than a rotary sub and they are silent while at rest. The Clark Technic (Platinum) is the same transducer used by the military in flight simulators.

If anyone finds them on the west coast near Oregon. Evergreen Aviation museam (home of the Hughes Hercules) is using one in one of the displays. It's a pretty awesome experience, and a great museum to visit.

Very nice! A truly complicated system though, a true home theater geek's choice XD

I love you Paul!

I must be old but this is exactly what they use in theme parks like universal studios of Orlando to create that life like experience when your riding a 3-d ride.

Im in my 50's and I remember seeing those things as a kid Church organs used them for the really low notes and they were pneumatically actuated.

I believe the military used a fairly interesting subsonic speaker for testing the effects of sonic booms. Picture an air duct bent in the shape of a doughnut. At the bottom is a blower motor circulating the air around the ring. At the top is a servo controlled vane in the middle of the airflow that directs air out the front or rear facing horn. Really interesting design.

Came here to learn about rotating submarines. Novel and interesting approach to spiral through the water, I thought.

That was a great explanation of how a rotary subwoofer functions. I assume many tweaks could be done to improve the efficacy. The fan blade material could be important. I am only hyopthesising however. I also love the low bass. I want to feel it deep through my body. Not simply the surface.

seems like a subwoofer in an infinite baffle

I use a pair of Bag End double 18" inch with their ELF-1 processor. This setup will go to 8Hz (just takes power and the Krell amp makes 2000W @ 4ohms on each), but most rooms rattle and shake much below 14. Doors rattle in the frame, ceiling tiles can vibrate, anything hung on the wall dances, etc.

Very interesting. Thanks for the info. Sounds like your describing a helicopter rotor.

These have been around for more than 20 years. Phoenix Gold made one for car audio and I always wanted one but they couldn't get super loud

That explains why when I went to demonstrate how the 4×12speakers sound so much better than the one speaker I had on my guitar amplifier it didnt come across that well on the vid.It shakes the floor boards and walls in my room due to the subsonics but it only sounded a little more "hi-def" in the recording!

He said pretty much what I thought he would before I watched the video. Complicated, expensive and very large.

They work a lot like the collective pitch found on RC helicopters, in fact i see a 5 blade collective pitch head from an RC heli on that prototype picture. Ingenious idea.

Install a tactile sound transducer into your chair or couch. They are incredibly cheap, incredibly easy to drive, and don't disturb anyone because you have to have physical contact in order to feel it.

Recently saw a video where a dude put one up very cheap for 200 here on youtube. He basically used RC plane components to control the flaps. Go check it out

I've seen and heard a rotary sub back in 1995 it shook the whole entire store that it was in..

A free air infinite baffle speaker system (usually with an array 8 or more 12" and and larger woofers) will do the same but will also be capable of making very high fidelity bass from extremely low to higher up in the frequency range then the rotary woofer can manage. I used to have Celestion System 6000 dipole bass consisting of four 12" woofers mounted in a open air frame. It produced beautiful bass down to 20hz and lower but just like with the infinite baffle it needed 6db pr octave boost from 70hz and down. That is why they usually have many 12" or larger woofers in system like that to keep the cone travel at a reasonable level with so much boost at low frequency. Without the back pressure in closed enclosure the woofers do not need much power to move far so they bottom out very fast even without having a giant amp to drive them. With a an infinite baffle array of 8+ woofers you need to mount them on a manifold so they cancel out the mechanical movement or you will end up shaking your house apart while wasting a lot of energy and ruining the sound fidelity (even large concrete structures starts to vibrate when so many big woofers move 1 to 2 cm in sync). That is a mistake I see many do when they make a infinite baffle array.

Oh i have read about these Fan Like contraptions. But i've never heard one in person. Would be interesting to experience.

My next project is ultra low, high spl system built into a 50 foot steel canal narrowboat. My old pair of 20 inch jbls, driven by customised Marantz amps could make big ripples, small waves. A pair of rotaries, fitted through the roof, one at each end of boat cabin.

I remember seeing these in action in RU-vid videos back in 2009... totally forgot about these. Now that's a BLAST (HA!) from the past.. Or ceiling. Whatever.

When you need the brown note.

The person who explained them to me called them "open baffle" subs. Pretty crazy stuff

“It’s like a fart in a wind storm” - Paul McGowan

@Paul ! Hi there. I’ve been following you on youtube for a while and I thank you for all your videos. I guess I can ask my question here : I’ve been an audiophile ( At least I think i can consider myself one... ) for a while now and I’ve always wondered how different people consider an audio setup to be a good sounding one. Is there any reference method or are there any recordings that the industry uses to evaluate a system? What does PS Audio use to evaluate a prototype product ( RAC, Amp or CD Transport ) ? By the way you should come and visit Iran, It is such a beautiful place with wonderful people and many audiophiles.... Many thanks, Aram

I must have one.

I made an experimental rotary sub once, worked for literally a second. Used flexible components instead of bearings/hinges, so in theory its frequency range was more like 50-5Hz, though due to the flexibility of the blades giving them resonance, I wouldn't expect it to go DC the way Eminents can. The flexible components broke, due to g-force, so maybe when I get back to it I'll find a stronger material.

ngl this sent me down quite the rabbit hole searching about these , quite odd

My duo 18 in 3.4 cuin chambers are low enough with 500w , love bass

My friend hired a MMA fighter to punch him in the chest each time there's a bass note. And it's conveniently 100% wireless.

There's a particular segment of the US population that I believe has them installed in their cars.

Thanks for the info Paul, but the main point you made in passing is, at least for me and likely for most of us, none of the music I own and listen to has low end information below 25 Hz, where my current subs reach their limit.

I had a chance to talk to Mr. Thigpen soon after he started selling these. We chatted about the motor choice and issues like cogging and hum. The system really needs a passage to the outside to baffle the back wave, functioning like an infinite baffle. Perhaps it could be simply mounted in a "window" between two rooms. One suggestion I made to Bruce was a shaped duct surrounding the fan, to reduce turbulence and increase efficiency, vs just the edge of the baffle board. To see what I mean Google-Image search "ducted propeller" or look at vintage Vornado fans of the 1950s.

Infinite baffle subs can produce useful SPL down to around 10-12 hz which is plenty for me. As we go through our remodel I'll be looking at incorporating one for the theater. My 2 channel produces good output at 25 hz which is fine for me for music.

Why don't you see more? From their website: TRW-17 transducer $12,900.00 Motor Controller $450.00 BT-42 Amplifier and crossover $1050.00 Design and installation, typical $8,000-$12,000* Total $21,950-$25,950 *Note, design and installation fees include: 1. consulting engineering for the installation, 2. design and construction of the manifold at Eminent Technology 3. installation and setup of the TRW-17 by Eminent Technology 4. measurement and performance testing of the finished installation 5. travel for Eminent Technology employees 6. contractor fees for construction necesary for the installation