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Don Hills
diyAudio Member

Join Date: May 2009
Location: New Zealand
Quote:
 Originally Posted by heyday So, the question becomes how do we generate a toroidal vortex sound wave so that we may concentrate the power flux of said wave?
We don't. My original post explains why such an attempt is an exercise in futility.

Quote:
 Originally Posted by heyday So, if one placed a radii of tubes at the compression area of the radiating driver, with coiled spirals of lengths corresponding likewise, as the permitted reduction above so states, (which, the added spirals would also contribute to the compression ratio of the driver) couldn't one achieve an acoustical induction and at minimum a velocity increase/power amplification of the wave?
One could not. The equations are not applicable to acoustics.

heyday
diyAudio Member

Join Date: Mar 2010
Location: Oklahoma

Quote:
 [D]oes introducing a properly designed spiral to a 130 Hz wave create SPL increasing inductance that is not mechanically possible with a 20 Hz wave?
Are you taking the position that Green's Function does not apply to acoustics?

They are discussed rather specifically within the General Solution of [sound] wave theory. Additionally I have posted material showing that Green's Function predicts concentrating the power flux of a sound wave in special circumstances.

Theory aside, it appears from published decriptions also posted by myself that these calculations have been used in designing acoustic instruments that were used to "magnify" soundwaves and thus generate an "acoustic lens," said technology being described as an advance able to reduce the size of "any" acoustical instrument.

So, excuse me if I'm not following your vague generalizations here.

Regards,
Dane

 11th April 2010, 10:11 PM #33 Don Hills   diyAudio Member   Join Date: May 2009 Location: New Zealand The solution is simple. Just answer your own question: "[D]oes introducing a properly designed spiral to a 130 Hz wave create SPL increasing inductance that is not mechanically possible with a 20 Hz wave?" Produce a "properly designed spiral" and the equations that describe its behaviour. Once you learn how to do that, you'll understand my original post.
heyday
diyAudio Member

Join Date: Mar 2010
Location: Oklahoma
Quote:
 Originally Posted by Don Hills The solution is simple. Just answer your own question: "[D]oes introducing a properly designed spiral to a 130 Hz wave create SPL increasing inductance that is not mechanically possible with a 20 Hz wave?" Produce a "properly designed spiral" and the equations that describe its behaviour. Once you learn how to do that, you'll understand my original post.
My view of being properly designed would be to design around the equations themselves, which were shown to be (at the compression level) scaled to approximately 10 centimeters to the meter.

So, where's the problem?

heyday
diyAudio Member

Join Date: Mar 2010
Location: Oklahoma
You guys are a great bunch of help. ;-)

That's ok, I have an idea...

Other than that, I have a few interesting experimental observations regarding tapped horns that may be of use to members here.

A while back I ran upon this tapped horn design at speakerplans dot com:

12" Tapped horn - Speakerplans.com Forums - Page 1

Plans are here:

MTH-30

I am in the process of building a house and happened to have some scraps of 7/16ths OSB around so I built a box out of that and coupled it with an old worn out Rockford Fosgate 8 ohm driver that made horrible noises in the sealed and vented boxes I designed for it in accordance with manufacturrrs recommendations.

I was amazed that in the TH it actually sounded half way decent, though most people thought it sounded good. I was pushing it with a Kenwood SW-30HT plate amp I cannabolized after the original driver became useless due to failures of the surrounds.(Running off the LFE output RCA connection from a Kenwood VR-606.) The amp was designed to push 4 ohms at 125 watts. I have seen posts here at diyaudio where it was explained that an 8 ohm driver will always sound better pushed from a 4 ohm amp than a 4 ohm load will, so I won't make any claims regarding the enclosure contribution to the quality of the bass output in yhis instance.

Meanwhile, a buddy gave me a 10" Sony Xploder XSL1037. Though I was able to download a pdf copy of the owners manual for that driver, not one TS parameter was provided, nor have I been able to find that information despite an intensive google search.

Then, a couple of days later my sister gave me a Pioneer SX-316S receiver. I mounted the driver onto a baffle which I screwed over the 12' cutout of the afore-mentioned sealed box and hooked it to the Pioneer out of curiosity. The Pioneer has a regular subwoofer high level speaker output rated as follows:

Quote:
 130 W (100 Hz, 10 % THD, 8 Ω)
I barely turned it up and a protection circuit within the amp shut the power down immediately, reminding me that I was using a 4 ohm driver instead of the 8 ohm Rockford I had been connecting to check out the receiever's sound in comparison to the Kenwood.

I immediately recalled reading a post in the diyaudiomobile forum about a triple driver TH design where the drivers were wired in parallel and the poster's statement that

Quote:
 Because the impedance peaks of the tapped horn are staggered, we can get away with a wiring scheme which isn't practical with a conventional horn, a sealed box, a vented box, or a bandpass. I'll measure the impedance in the next day or two, and you'll see what I mean. All the impedance "troughs" are staggered, due to pathlength differences for each woofer.
Reference: http://www.diymobileaudio.com/forum/...tml#post840026

This definately called for some experimentation!

So, accordingly, I jury-rigged the Sony into the TH enclosure after removing the 12" from the box. I predicted that the 4 ohm load would not activate the amp's protection circuit because the TH is an impedance matching device with a variable resistance that increases as the amplifier source draws power to push the driver to meet the demands created by high volume low frequency output. (I believe that I read something similar in an explanation posted here at diyaudio somewhere in the multitudes of TH threads available here.)

The result of the experiment greatly exceeded my expectation of the TH to match itself with any impedance condition imposed by the amp so that the impedance mis-match would be invisable to the protection circuit.

Not only was I able to avoid a shut down created by the the low ohm condition of the Sony, but the TH design allowed me to use the Pioneer's speaker setup function to increase the sub output + 10 DB and play music at very high volume levels for several hours without protective shutdown or any discernable heating problems within the amp.

What this all means to me is that a TH enclosure acts in such way that two driver's at the amps rated resistance load may be used within the enclosure in a parallel wiring scheme without adverse effect to the amp.

That being said, I would think that it is most likely probable that at least 3 drivers of the amps rated impedance level may be connected parallel within a TH enclosure without risk of thermal damage to the amplifying equipment.

Though there doesn't seem to be much interest here in my idea's concerning possible technological innovations to improve the Tapped Horn's performance, I plan to continue developing that concept as much as I am able to back over at the Tapped Horn Experiment Box Thread

Regards,
Dane

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