# Rotary Woofer facts



## rotfan (Feb 19, 2011)

I have owned Eminent Technology's TRW-17 Rotary Woofer for over two years and this 
subwoofer is the most exciting audio product that I have ever owned. Following are
facts about this rotary subwoofer.
1. Response is from 25 hz down to 1 hz.
2. High efficiency at very low frequencies
3. No equalization needed for response to below 1 hz
4. Has enough acoustic output to move an open door .5" between 1 and 5 hz
5. Transient response is near perfect
6. Requires a very large enclosure to absorb fan noise
7. Infinite baffle enclosure to prevent front and back wave cancellation (I use my
entire basement of over 2000 sq. feet
8. The smaller the back venting the lower the efficiency (reduced output)
9. Requires a low pass xover (recommended xover frequency is between 15 and 
25 hz @ 18 db per octave (I use Marchand Electronics rotary woofer controller
which provides an adjustable xover from 15 to 25 hz, 200 watts of power for
pitching the fan blades, gain control, adjustable phase and damping. 
10. Requires a motor controller to adjust the speed of the rotating fan and also 
maintains constant speed when the fan blades are being pitched. This 
controller is used to set the speed of the rotary fan to match the volume of 
one's room. My room is 29' long x 19' wide x 11' high cathedral ceiling and
I use considerably less speed than the maximum.
11. The required opening into the room (minimum is 3' x 3') I use 4' x 4'
12. The enclosure needs to be quite large (I use an 8' long x 4' wide x 4'
high enclosure that is braced, caulked and all the surfaces are lined with 6" fibergalss
insulation. 
13. All the electronics should have excellent very low frequency response to prevent rolloff 
14. The rotary woofer matches the impedance of the air (horn enclosures do the same,
but would be enormous in size with the very low frequencies involved.
15. Requires a 120 vac circuit for fan motor and controller. One can use 240 vac
with the proper controller.


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## rotfan (Feb 19, 2011)

Picture of rotary woofer controller by Marchand Electronics


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## Warpdrv (Mar 3, 2007)

Whats the chances of an audition...?

I live on the north side of Milwaukee, I'd love to check this thing of beauty out... 
I have hosted speaker and subwoofer GTG's for the masses a few times now, it'd be nice to experience one of these in person...


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## Warpdrv (Mar 3, 2007)

What are you running for the 25hz up area ? 
Other equipment list ? 
Gotta be just down right awesome !!!


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## rotfan (Feb 19, 2011)

Warpdrv: See my pictures and list of equipment in home theater room pictures under combined audio and home theater.


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## Moonfly (Aug 1, 2008)

Lucky lucky fella rotfan. Do you have any videos of it in action, I would love to see the thing in action just to be nosey on how it looks when in operation.


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## rotfan (Feb 19, 2011)

Check out Youtube: Just type rotary woofer and you can watch videos of the sub in action


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## Zeitgeist (Apr 4, 2009)

Thread moved to Home Audio Subwoofers.


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## rotfan (Feb 19, 2011)

*Re: DIY Rotary Woofer*

If one builds the enclosure the rotary subwoofer is about 12k. I built the enclosure for 
the rotary subwoofer and the cost was about half. One of the issues that many people
would have, is one needs a very large space (volume) behind the rotary woofer for it
to operate efficiently and the large opening into the room (3' x 3' minimum opening). I
vent into my basement which is over 2000 sq. ft and the opening into my room is 
4' x 4'. Important also is time aligning the rotary woofer with the other woofers in one's
system (adjusting phase helps, but aligning the rotary with the upper bass speakers 
works much better.


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## sub_junkie (Apr 14, 2009)

*Re: DIY Rotary Woofer*

Wow, that is amazing, rot. How does it sound??


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## rotfan (Feb 19, 2011)

*Re: DIY Rotary Woofer*

Thanks, the rotary subwoofer is the most exciting and realistic sounding audio product
I have ever owned. I have been an audiophile for 50 years and this rotary subwoofer
excels in reproducing very low bass. The added excitement that one gets with this
sub is exhilarating. Listening to the Mormon Tabernacle choir with that immense pipe
organ is awesome with this rotary subwoofer. It is so solid and clean sounding with
out a hint of strain. In the past I used infinite baffle subwoofers (two 24" Hartley
subwoofers) built into the floor of my room. They worked well, but couldn't come close
to the performance of the rotary subwoofer. We are talking about frequencies down
to 16 hz with the pipe organ, and that is we are just loafing around. Going down from
there it gets better and better. There is lot of movies with content below 10 hz and
some that go much lower. I also have several cd's that have very low bass, that without
the rotary subwoofer, one would not hear and feel the tremendous power and
extension. Some of these recordings would destroy conventional subwoofers (Apollo 13
rocket taking off with bass content below 5 hz) is one example. As good as the rotary
subwoofer is with bass that is low and continuous, transients are its forte. A great
example is the very low thunder clap (Telarc CD-80447 Surround Sounds, track 9), with bass
that is frightening and sounds very realistic. I only use around half its total output and because
of this there is even lower distortion and headroom to spare!!!!!!!


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## rotfan (Feb 19, 2011)

*Re: DIY Rotary Woofer*

These are pictures of the 24" Hartley subwoofers that I used to use.


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## Mike P. (Apr 6, 2007)

*Re: DIY Rotary Woofer*

$11,000 for a manifold? That doesn't sound right.


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## rotfan (Feb 19, 2011)

*Re: DIY Rotary Woofer*

The price of the manifold varies with the type of installation. I talked to Bruce
Thigpen about the requirements of the manifold, location and size of the opening
and made a detailed drawing and sent the drawing back to Bruce for approval. After
receiving approval, I constructed the manifold and took pictures and sent the photos
back to Bruce for his comments. The manifold that I constructed was approved by
Bruce and I then ordered the rotary woofer, motor controller and rotary woofer controller.
The next step, after I received these items, was installation of the rotary subwoofer
and testing. Bruce Thigpen's assistant, Winston Wright, flew out from florida to do the
final installation of rotary woofer and motor controller. Because I constructed the manifold and did the design the cost was considerably less. If Bruce did all the design,
construction, installation and testing the cost would have been 20k. Every installation
is different depending the location of rotary subwoofer and opening into one's room.
One of his customers had a lot of reconstruction of the room to allow for the rotary to
operate properly and the cost was far more.


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## rotfan (Feb 19, 2011)

*Re: DIY Rotary Woofer*

Some pictures of another rotary install.


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## SinCron (Dec 20, 2010)

*Re: DIY Rotary Woofer*

Mmmmmm. Gear Pr0n. I hate this thread for making me really want one of these.... effortless low end down below 1hz and not having to worry about it the way you would a traditional speaker. No worries of over exerting the driver for the low frequencies and not worrying about overpowering it. My main problem with audio equipment is worry. I worry about abusing the equipment and also worry about disturbing others with it. That's why I got an 18" driver that can easily do 800 watts max and am only giving it 500 max. I would very much like to see some video of this thing in action .


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## rotfan (Feb 19, 2011)

*Re: DIY Rotary Woofer*

There are videos of the rotary woofer operating on youtube. Yes, you are correct
about overdriving conventional subwoofers. In the past I used two 24" Hartely
subs and was always concerned about exceeding the excursion limits, as well as,
overheating. The way I handled that problem was to use subsonic filtering and 
limiting protection. I used a Velodyne Digital Drive SMS-1 subwoofer management system
which had adjustable (15hz - 35hz subsonic filter (12db/octave to 48db/octave. 
Before I used this device I occasionally bottomed out the woofers and thought I destroyed
them. Now with the rotary subwoofer that is not a concern (I am not even close
to the full output. The rotary is built very well and requires no maintenance. I also
have a few close up pictures of the rotary subwoofer and this might be of some help
for trying to build one (diy). It is unfortunate that this rotary subwoofer is so
expensive, but being a custom product and the fact that not many are being sold,
its understandable. When I purchased the rotary subwoofer,only 28 of these units
had been sold. Feel free to ask any other questions about the rotary sub.


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## lsiberian (Mar 24, 2009)

Does the technology appear scalable. It would be pretty amazing to see one in the normal passband for reduced cost


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## rotfan (Feb 19, 2011)

The rotary woofer could not compete with conventional woofers when producing
frequencies above 30 hz. The fan speed would have to be much faster and the 
mechanical linkage would have problems pitching the fan blades faster, causing high
distortion. The increased fan speed would also cause way too much noise and
turbulence. This design is for very low bass only.


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