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Ultra-low frequency Rotary Subwoofer

DanielT

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What is this? Ultra-low frequency Rotary Subwoofer

I've never heard of. Seems exciting. Anyone know anything more about it? Is it possible to get it for Hifi? Or? I have no idea.:)
So for frequencies in if the audible range above 19 Hz? But how to solve it? What would you gain from that? That engine was not completely noise-free either.

 

DonH56

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It's been around for quite a while. Yes, you can get (or build) one, though the commercial version is not cheap.


HTH - Don
 
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DanielT

DanielT

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It's been around for quite a while. Yes, you can get (or build) one, though the commercial version is not cheap.


HTH - Don
Thanks for the tip and link!

Hmm, maybe that would be something for those who want it to have a real physical experience with the home theater? Although I do not know how far down in frequency recordings go (music as well as film). So if it goes below 20 Hz, the actual recordings that is.

I checked on Youtube. There were some DIY sub. Hm. If you have access to a small (hobby) workshop with machines, it should probably be possible to DIY a rotary subwoofer. :)

It is not relevant for my own part, right now at least. Though I do not know. In any case, it's always fun to learn something new. :)

Edit:
It seems awesome, in the link you referred to:

A missing link in sound reproduction. Experience special effects like never before. If you want to hear and feel the 11hz hertz fundamental frequency from a helicopter rotor, the low frequency rumble of wind, the space of a concert hall or infrasonic information contained in an explosion, this is the only woofer technology available. Over the years the generally accepted low frequency limit of hearing has been 20Hz, some suggesting 16Hz. However nothing existed to produce significant enough output to change this belief. This development will spawn new special effects and we will begin to understand the true low frequency limit of human hearing. The TRW-17 rotary woofer is now being used in theme park attractions, concert venues, professional audio applications and research projects.

I add:
Experience the neighbors' effects of anger like never before.o_O
 
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nerdoldnerdith

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There are few movies and music with appreciable content below 20Hz, and even fewer with content below 10Hz. You can get a couple JTR Captivator 4000ULF's and be good down to about 7Hz with serious output. Indeed for those bottom few Hz you would need a rotary sub or some crazy bass reflex sub built into an adjacent room to move enough air for you to feel it, but there is so little content that you could use to appreciate this that I don't really see the point. Nearfield subs and a BOSS platform will get you close enough.
 

dwkdnvr

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Got to experience this at one of the RMAF shows. Definitely a real and rather cool effect, but ultimately probably more of a curiosity than a practical device. You have to build it into the room structure to a degree and have a fairly defined closed area to allow it to pressurize properly.

Actually bought some HT subs from a guy that had one but had never gotten around to installing it.
 

DVDdoug

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I don't have a rotary woofer but I have 15-inch subs (homemade) and a DBX 120A subharmonic synthesizer. It divides the low frequencies in half to generate bass that's one octave lower. I'm not sure how low it goes and my woofers are not designed to be subsonic. But the same thing can be done digitally (where you can down to 0Hz) and you could divide by 3 or 4, etc.

...Of course this is for fun, not for high-fidelity accuracy! ;)

...The lowest note on a standard electric bass is about 40Hz and most "professional" subwoofers used in clubs & live performance are tuned for around 40Hz. Kick drums may go lower. Pianos go lower but they don't have much energy in the lowest notes. You're mostly hearing harmonics from a piano's lower notes and you can't feel the bass in your chest like from a bass guitar. Oh... There are pipe organs that can go down to 16Hz but I'm not sure if the pipe organs I've heard go that low. But I have "felt the bass" from a pipe organ.
 
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nerdoldnerdith

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I don't have a rotary woofer but I have 15-inch subs (homemade) and a DBX 120A subharmonic synthesizer. It divides the low frequencies in half to generate bass that's one octave lower. I'm not sure how low it goes and my woofers are not designed to be subsonic. But the same thing can be done digitally (where you can down to 0Hz) and you could divide by 3 or 4, etc.

...Of course this is for fun, not for high-fidelity accuracy! ;)

...The lowest note on a standard electric bass is about 40Hz and most "professional" subwoofers used in clubs & live performance are tuned for around 40Hz. Kick drums may go lower. Pianos go lower but they don't have much energy in the lowest notes. You're mostly hearing harmonics from a piano's lower notes and you can't feel the bass in your chest like from a bass guitar. Oh... There are pipe organs that can go down to 16Hz but I'm not sure if the pipe organs I've heard go that low. But I have "felt the bass" from a pipe organ.
15 inch subs cannot play subsonic frequencies with any authority unless they are in large ported cabinets tuned very low. The amount of air that needs to be moved to play these frequencies at a level that can be appreciated requires a very large ported enclosure or a lot of cone area. In any case, the subwoofer needs to be very large.
 

Ron Party

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Do a search over at AVS Forum. You will find a thread started by a fellow named Tony, user name tzucc. About 15 years ago, Tony had a group of us over to experience his concrete bunker basement home theater in which Bruce Thigpen had installed 2 rotary subs. Mark Seaton was there and IIRC so was Keith Yates, who I believe helped in the design of Amir's room.

The rotary sub is amazing tech. Circumstances have to be just right in order to use it. The whole neighborhood will know when they are in use.:) Also, if you have a sensitive GI system, it's probably not for you.
 

DonH56

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Do a search over at AVS Forum. You will find a thread started by a fellow named Tony, user name tzucc. About 15 years ago, Tony had a group of us over to experience his concrete bunker basement home theater in which Bruce Thigpen had installed 2 rotary subs. Mark Seaton was there and IIRC so was Keith Yates, who I believe helped in the design of Amir's room.

The rotary sub is amazing tech. Circumstances have to be just right in order to use it. The whole neighborhood will know when they are in use.:) Also, if you have a sensitive GI system, it's probably not for you.
Yah, "hearing" one is quite an experience! It has been many years for me, had no idea others on ASR had heard them since they are a rare beast. Or should I say BEAST! :)
 

Vladimir Filevski

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I've never heard of. Seems exciting. Anyone know anything more about it? Is it possible to get it for Hifi? Or? I have no idea.:)
So for frequencies in if the audible range above 19 Hz? But how to solve it? What would you gain from that? That engine was not completely noise-free either.
It is intended for frequencies below 20 Hz (the lower, the better). I have heard it and felt it!
It is noise-free
, sound output come from a "muffler" box (size: big PA subwoofer enclosure), not directly from the rotary driver as in video.
 
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DanielT

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Thanks for the input and the links too.

It's not something I will (should) get, but it's fun to hear stories from you who have heard, or felt it would be more correct to say, the power of this type of sub.If I ever have the chance to experience one, I will not miss that opportunity.:)
 
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FrantzM

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Hi

Back in the days, I knew a person at AVSForum who had installed one in his HT and there was a meet to which I was invited. Could not make it then. I believe Amir was at that meet (@amirm ?)... From most of the participants it was rather unsettling: This sub operates well mostly from DC to 20~30 Hz and is capable of serious output in these regions > 120 dB at Listening positions... So below 10 Hz registered for many as a sickening feeling, similar to an earthquake!
There is also a real threat to house structures.. Also, the output of these cannot be compared to your run of the mill 15 or even 21 inches subwoofers. This is capable of above 120 dB at 1 Hz and even does DC, i-e O (yes, Zero) Hz.! A concept I have some difficulties to wrap my head around :). ,
You would still need conventional subwoofers in you HT to cover the important and most audible 20 to 100 Hz.. This subwoofer is not capable or reproducing these without extremely elevated and audible distortion levels

There are indeed some movies with below 20 Hz output but .. If one has the resources and space .. Else more of a curiosity IMHO.

Peace
 

Ron Party

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Yep. Frantz, I remember you were unable to attend. You would have had a great time.

In addition to the 2 rotaries, Tony had a Wilson XS which was about as large as a refrigerator plus 2 or 3 Wilson Watch Dogs. He was the king of bass at that time. Standing in the corners was more unsettling than any other place in the room. It was a fairly large theater with at least three tiers for seating That room was highly pressurized. He had something like 500 pound steel vault doors.

I seem to recall that while there wasn't much VLF in the way of musical content it definitely showed up with video, sometimes unintentionally so because those responsible for mixing/mastering did not have equipment which would reveal it.
 

dasdoing

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while there seam to be movies with contend below 20Hz, they don't seam to pass the threshold of audibility/masking in my experience. a small room with huge room gain helps my sealed sub to go flat to 9Hz-ish (EQ-ed). a 10Hz sine wave sounds very distinguishableto me, cause it doesn't sound like a tone, but a oscilation (just like what happens when you leave rear window open in a car on a highway). never heard this in a movie explosion.
I must add that I don't realy like action movies though...so I didn't watch many. I which there was a list of "deapest explosions in movies" or something like that.
 

FrantzM

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The thing is ... below 20 Hz is not heard.. it is felt and requires substantial SPL for that.
Often when we push our sub down there, what we actually hear could well be the distortions byproducts rather than the fundamental... for exemple the second harmonics of a 14 Hz pure tone is 28 Hz.. very audible. A subwoofer trying to push 110 dB at 14 Hz could be producing THD levels over 30% in that case would produce 28 Hz at levels above 60 dB... sometimes even more... You will definitely hear some of it in a small room plus things rattling and sympathetic vibrations, etc..
That rotary sub has no issue pushing 8 Hz at 120 dB with less than 5% THD... actually the distortion rises with the frequency to such an extent that the old version ( I don't even Know if there is a new one) was unusable above 30 Hz...
The ever inventive and visionary Tom Danley actually made (in 1987!!) a subwoofer that could cover the range from 8 Hz to 80 Hz with the usual Tom-Danleyesque performances: 120 dB easy between 14 to 100 Hz... I'd like him to chime in on that design which used a hard drive motor (HDD)...
 

dasdoing

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below 20 Hz is not heard

I hear it, but can't feeel it (tested by pluging ears). I doubt anybody saying this has ever tested it.

I tested my 10Hz, harmonics is below audible threshold (and I would know I was hearing 20Hz...sounds very difrent):

index.php
 

pozz

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The thing is ... below 20 Hz is not heard.. it is felt and requires substantial SPL for that.
Often when we push our sub down there, what we actually hear could well be the distortions byproducts rather than the fundamental... for exemple the second harmonics of a 14 Hz pure tone is 28 Hz.. very audible. A subwoofer trying to push 110 dB at 14 Hz could be producing THD levels over 30% in that case would produce 28 Hz at levels above 60 dB... sometimes even more... You will definitely hear some of it in a small room plus things rattling and sympathetic vibrations, etc..
That rotary sub has no issue pushing 8 Hz at 120 dB with less than 5% THD... actually the distortion rises with the frequency to such an extent that the old version ( I don't even Know if there is a new one) was unusable above 30 Hz...
The ever inventive and visionary Tom Danley actually made (in 1987!!) a subwoofer that could cover the range from 8 Hz to 80 Hz with the usual Tom-Danleyesque performances: 120 dB easy between 14 to 100 Hz... I'd like him to chime in on that design which used a hard drive motor (HDD)...
For context, some data I compiled on infrasound:
index.php


Edit: https://www.audiosciencereview.com/...-pathways-for-hearing-bass.22167/#post-737109
 

test1223

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I hear it, but can't feeel it (tested by pluging ears). I doubt anybody saying this has ever tested it.

I tested my 10Hz, harmonics is below audible threshold (and I would know I was hearing 20Hz...sounds very difrent):

index.php
If the floor is moving you definitely feel very deep frequencies at not so loud levels. A moving floor is important for good bass. Also body vibrations can be felt but you need higher volume for that. I think there is a difference, if the tests where conducted with headphones or with speakers. There are also differences between headphones with the same measured bass extension, due to differences in coupling the drivers to the bones.
 
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