I also wonder.
BTW - I don't understand follow term in case of movie sound effects:
"most realistic"
this term is for me only clearly to understand in case of the reproduction of classical concerts and acoustical instruments.
Complete explanation of Rotary Sub
Here is a link that will explain, in detail, the rotary sub.Page Title
International Audio Review (Titled the ONLY SUBWOOFER) as reviewed
by Peter Moncrieff
Here is a link that will explain, in detail, the rotary sub.Page Title
International Audio Review (Titled the ONLY SUBWOOFER) as reviewed
by Peter Moncrieff
I would expect the angular rotation of the vanes to follow any electrical signal within the specified bandwidth, thus producing the frequencies within the specified bandwidth. This would include any complex mix of such frequencies.
Imagine an electrical signal on an oscilloscope. Now, let the instantaneous voltage represent the instantaneous angle of the blades. The blade angle follows the signal profile.
Imagine an electrical signal on an oscilloscope. Now, let the instantaneous voltage represent the instantaneous angle of the blades. The blade angle follows the signal profile.
Hi tiefbassuebertr,
"Most realistic" doesn't have a technical definition like a standard, so it can be used without stating anything specific.
Most ultra/infra low frequencies used in movie fx is artificial generated by down pitched samples. This technique is used widespread since it the best way to control low frequency sound. If there is usable (occasionally that happens) low frequency on a recorded track they still use this sample technique and put it on top of the original recorded sound. This way they have full control over the signal and they can make the impact of the total sound as large they want.
The sound of thunder
As one example I have a recording of a thunder clap, and the rotary
subwoofer recreates this with astonishing fidelity. The first time I
played this recording it scared my wife (her first reaction was to look
out the window for a approaching thunder storm.) My wife was in the
kitchen at the time and when I told her that this sound was coming
from my sound system, she said that it completely fooled her!
This is what I meant when I said "most realistic"
As one example I have a recording of a thunder clap, and the rotary
subwoofer recreates this with astonishing fidelity. The first time I
played this recording it scared my wife (her first reaction was to look
out the window for a approaching thunder storm.) My wife was in the
kitchen at the time and when I told her that this sound was coming
from my sound system, she said that it completely fooled her!
This is what I meant when I said "most realistic"
The fan blades vary in pitch (angle of attack) with frequency, in the case of two (or any number of tones) the low tone causes a larger pitch change, the higher tone is an oscillation (“wiggle”) in the blade during the pitch change.
As the blades pitch while rotating a pressure wave is generated, the degree (angle) of pitch determines the amplitude of the pressure wave.
The power amp modulates fan pitch and frequency, the fan rotates at a constant speed, the rotational motor does the “heavy lifting”.
Rotary subwoofers are quite expensive, require an extensive ductwork with a separate location, the TRW, for optimum performance, requires a huge box enclosure, much larger than even the largest enclosures employed by conventional subwoofers.
They don’t sound like a conventional loudspeaker, so from a monitoring standpoint would not be compelling to base your mix on a system that only a miniscule amount of listeners use.
The TRW-17 Maximum Acoustic Output: is only 115 dB , not up to the levels used in a large monitoring facility. It is recommended for use below 25 Hz.
At loud levels its fan blades go to a steeper pitch, and this creates air turbulence around the fan blade tips, which sounds “like a bird flapping its wings”.
The link araudio provided compares the rotary subwoofer to subs with a 1” peak to peak movement, at the time it was written that may have been a high Xmax sub, but now 18” drivers with 38 mm Xmax (just over 3” peak to peak) are available.
Multiples can easily surpass the TRW fan down to 15 Hz, low enough for the biggest organ pipe, and in much smaller size than the TRW.
Since music and soundtracks have little content below 15 Hz, and that range is so expensive to pursue, theaters and home systems will seldom be built to achieve that, especially using a system that has problems above 25 Hz.
There is already a thread concerning rotary subwoofer:
http://www.diyaudio.com/forums/subwoofers/98228-thigpin-trw-17-rotary-woofer.html
BTW - many sellers claim, it is a very great audible advantage, if the subwoofer goes down well below 20 Hz (e. g. 5Hz or 10 Hz cutoff)
But until this day nobody was able to demonstrate me this statement.
By various own attempts with different cuttoff frequencies at large woofer systems my conclusion is clearly, that the best choice is arround 18 and 25 Hz, independend of the individual boundary conditions like e. g. volume (number of liters) of the chamber and the listening room itself.
Cutoff frequency below 18 Hz are not helpful, even not by movie sound effects like a big earthquake or bomb explosions (IRON MAN) except, if one want to enhance resp. increase strongly the distortion components.
http://www.diyaudio.com/forums/subwoofers/98228-thigpin-trw-17-rotary-woofer.html
BTW - many sellers claim, it is a very great audible advantage, if the subwoofer goes down well below 20 Hz (e. g. 5Hz or 10 Hz cutoff)
But until this day nobody was able to demonstrate me this statement.
By various own attempts with different cuttoff frequencies at large woofer systems my conclusion is clearly, that the best choice is arround 18 and 25 Hz, independend of the individual boundary conditions like e. g. volume (number of liters) of the chamber and the listening room itself.
Cutoff frequency below 18 Hz are not helpful, even not by movie sound effects like a big earthquake or bomb explosions (IRON MAN) except, if one want to enhance resp. increase strongly the distortion components.
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My subwoofer is having 9 m long exponential horn so it is tuned to 9,5 Hz and it actually goes down to 10 Hz effortlessly. And what's best here, there are two of them.
My subwoofer is having 9 m long exponential horn so it is tuned to 9,5 Hz and it actually goes down to 10 Hz effortlessly. And what's best here, there are two of them.
Gosh, all I have is a puny Klipschorn. Any way to see, read, and/or learn about your subs?
Ben
Something like this. is the link to local forum where I (ProJet) posted some pics. Use google translate from Slovenian to English for uderstanding.
is the link to local forum where I (ProJet) posted some pics. Use google translate from Slovenian to English for uderstanding. Something like this.
FABULOUS!!! A pure horn design done beautifully. Thank you.
Wouldn't one be enough?
Ben
Thanks
Yes, but why not to gain extra +3dB ...
If you will allow a math reply:
3dB is a small difference. But two subs is almost double the cost and construction effort.... not that personal delights are linear.
Ben
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