DIY a rotary sub.

Did anyone look at that "fan" from eminent? Its a joke if you ask me. $12,900 for a fan thats probably like 1' in diameter!

http://www.eminent-tech.com/RWbrochure.htm

And they say recordings have infrasonic material in them below 10hz...

I've also heard that below 10hz becomes audible at over 120db.... has anyone here experienced 10hz at 120db in a house? You wont hear the 10hz... you'll hear rattles upon rattles upon rattles upon rattles. Ummm your walls would have cracks, pictures will fall. The neighbors would suffer the SAME effects!

Its useless for audio applications. It adds nothing to the music except maybe psychological effects and plain scaryness. For 12grand get the parthenon and at least you'd have something cool to look at!


I hate hearing infrasonic output to DC.... There is no DC pressure... DC means DIRECT CURRENT! CURRENT is electrical, not acoustical. DP (direct pressure) would be a much more intellegent thing to say
 
Its useless for audio applications. It adds nothing to the music except maybe psychological effects and plain scaryness.

I wonder if that's really true. One thing I noted when I extended the bass of my system down that way was an increased sense of "articulation" of notes even when played on instruments that do not reach the deep bass. I've speculated that it has to do with improvements in group delay for rapidly played notes, but have no evidence, other than my subjective observation. It's interesting, though, that the same sort of observation has been made by skeptics like Audio Critic when testing the ELF, which has a response down as low as 8 Hz.
 
SY,

I did not mean it doesnt add anything in a group delay or accuracy of the audible frequencys sort of way. Adding a infrasonic "fan" to your system probably isnt going to make the group delay up higher any better anyhow.... I meant that those infrasonic notes really add nothing to what you hear. Actually they smear it IMO.

I have laced music with infrasonics before(like the national phsyics lab did at a piano concert) and found that it did slightly add to the psychological aspect of the music. The way added the infrasound was mixing it directly into the recording. This really took away from the dynamics of the bass however because the infrasonic sine needed to be of large amplitude to achieve any effect without turning the music up to ear peircing levels. I find it very hard to believe that adding infrasonic output would make things sound better. Also infrasound can make things sound like you're talking through a fan. That cant be good for sound quality
 
But if you competently extend the bass, by definition you've made the group delay better lower, to put it clumsily.

but that will only really be true if you're using one driver right? Lets say you use an adire parthenon and go from 60-10hz well thats going to be alot better than using a Tempest from 60-30 and then a servo fan from 30-1 or even using the tempest from 60-20 and the fan from 20-1 because of the added crossover and it's associated phase shifts/group delay. The Group dealy below 20hz shouldnt mean anything anyhow due to our lack of perception to fine detail at this low of a frequency. 20hz group delay below 20ms is achieveable with 10hz tuning on a Vented box and you can get 10hz extension with only a 15 inch Adire tumult ($600 now, once $500) and a fraction of the cost of a Eminent fan....

I just see the fan as pointless... it's WAY overpriced, and I highly doubt that it adds even the slightest bit of realism achieved for a fraction of the price
 
Ok, I realize that I'm digging up an ancient thread, but I just came across the fan subwoofer stuff and found it interesting. Any of you ever hear one of these in use in person? I'm kinda looking at it more as an interesting idea for home theater or for PA use with electronic music than for stereo "serious listening" to music, but I'd have to DIY it as I have no intention of spending that kind of money on sub 30 cycle output unless I hit the BIG lottery. How does it work as far as "enclosure"? Does the fan just sit in a round opening to either a large sealed box or small adjacent room?
 
The Only Subwoofer

Did anyone look at that "fan" from eminent? Its a joke if you ask me. $12,900 for a fan thats probably like 1' in diameter!

http://www.eminent-tech.com/RWbrochure.htm

And they say recordings have infrasonic material in them below 10hz...

I've also heard that below 10hz becomes audible at over 120db.... has anyone here experienced 10hz at 120db in a house? You wont hear the 10hz... you'll hear rattles upon rattles upon rattles upon rattles. Ummm your walls would have cracks, pictures will fall. The neighbors would suffer the SAME effects!

Its useless for audio applications. It adds nothing to the music except maybe psychological effects and plain scaryness. For 12grand get the parthenon and at least you'd have something cool to look at!


I hate hearing infrasonic output to DC.... There is no DC pressure... DC means DIRECT CURRENT! CURRENT is electrical, not acoustical. DP (direct pressure) would be a much more intellegent thing to say

I have had the Eminent Technology TRW-17 Rotary subwoofer for over 2 years and it is awesome. Contrary to what you say, it has benefits for well recorded classical music and pipe organ, synthesizers.
Movies have a lot of content below 20 hz and with this rotary subwoofer it adds greatly to the excitement and realism. I can easily hear 10 hz and lower with this sub without shaking the house apart. Until one experiences this rotary subwoofer, making assumptions about it is wrong. IMG_0621.JPG

IMG_0740.JPG

IMG_0795.JPG
 
I have had the Eminent Technology TRW-17 Rotary subwoofer for over 2 years and it is awesome. Contrary to what you say, it has benefits for well recorded classical music and pipe organ, synthesizers.
Movies have a lot of content below 20 hz and with this rotary subwoofer it adds greatly to the excitement and realism. I can easily hear 10 hz and lower with this sub without shaking the house apart. Until one experiences this rotary subwoofer, making assumptions about it is wrong.
Adding a sub with response below 20Hz made quite a difference in my control room and living room, I agree with all you say.

Does the the fan output go through some sort of acoustic low pass filter?
Does the fan have a "direction", moving air through the the plenum and room, or is it a positive/negative modulation without a general direction?
What is the dB level of the fan when no LF content is present ?
 
Rotary Subwoofer Facts

Adding a sub with response below 20Hz made quite a difference in my control room and living room, I agree with all you say.

Does the the fan output go through some sort of acoustic low pass filter?
Does the fan have a "direction", moving air through the the plenum and room, or is it a positive/negative modulation without a general direction?
What is the dB level of the fan when no LF content is present ?

I use Eminent Technology's rotary woofer controller
that includes a variable low pass xover (15 hz to 25 hz) which I set at 25 hz. This controller has a 200 watt amplifier which pitches the blades, variable phase
control, damping and gain controls. The power comes from the ac current, rotating the fan. The only way that air would have a direction would be with a dc signal
which would never happen (- dc signal would suck air out of the room, a + dc signal would blow air into the room. A normal ac signal would be both positive and
negative, producing low frequency sound. When there is no LF content the blades of the fan are in a neutral position, producing no low frequency sound.