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 5th April 2010, 01:33 AM #11 diyAudio Member   Join Date: Nov 2005 The usfulness of a duct at LF has to do with properties of inertia, ignoring horn ideas, which I don't think you're necessarily entertaining with your main interest. The velocity and mass don't change whether you make the tube straight, spiral, or pretzel. Maybe at very high velocity you'd get some strange effect where there developed higher frictional loss and pressure on the outside of the spiral, due to centrifugal force. Never mind that. It's not happening in your speaker. Last edited by Andrew Eckhardt; 5th April 2010 at 01:45 AM.
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Join Date: Mar 2010
Location: Oklahoma
Quote:
 Originally Posted by letsbangout Two comments, coming from someone whose background is RF:
Great! Maybe you can enlighten me as to the physical properties of a TEM?

Quote:
 1) Antennas are quite a bit different from acoustics - they're designed to operate at either a single band, or multiple bands with help from a tuned circuit (i.e. an antenna tuner or phaser). Acoustics are wide-band, they're expected to perform relatively the same over several octaves whereas antennas are not.
But then, maybe not..

I have designed antenna's myself which were calculated to operate over several bands by increasing the length as well as the diameter of the element(s) of the antenna itself without the use of any electrical circuits, as the same potential subharmonic frequencies exists in an EM wave that may be made resonant to a sound wave.

In fact, the situation can be decribed as opposite to your posted opinion.

Can I design a a 1 5/8 VLF wave folded tapped horn/transmission line speaker that will give me extended coverage of the short bands and UF frequencies with or without some type of tuning device claimed as necessary by you for a wideband antenna?

Perhaps a 1/8 wave folded horn would clear up that midbass notch without needing the tap in a TH?

Regards,
Dane

Quote:
 2) Your use of the term "inductance" with regard to acoustical waveguides is incorrect. Inductance simply means the store of energy in magnetic form and implies electromotive force. Acoustical waveguides do not exhibit inductance.
Correct. They actually exhibit a resistive capacitance.

Last edited by heyday; 5th April 2010 at 01:56 AM.

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Join Date: Mar 2010
Location: Oklahoma
Quote:
 Originally Posted by Andrew Eckhardt The usfulness of a duct at LF has to do with properties of inertia, ignoring horn ideas, which I don't think you're necessarily entertaining with your main interest. The velocity and mass don't change whether you make the tube straight, spiral, or pretzel. Maybe at very high velocity you'd get some strange effect where there developed higher frictional loss and pressure on the outside of the spiral, due to centrifugal force. Never mind that. It's not happening in your speaker.
With what I know at the present, I will not contest this proposition.

But I will say at this point that I fail to understand why a spiral waveguide hasn't been designed to lead a tuned LF wave out of the enclosure at an oblique angle into a parabolic reflecter bouncing the wave into an optimised area.

And I do not believe that multiple resonators cannot be designed that would focus and intensify the tuned wave.

Plus, research has established that directed soundwaves traveling in a circular direction are amplified 180 degrees from the source.
Not in theory, but by observed facts.

At least that is the claims made by established physics that I read recently.

Dane

 5th April 2010, 02:33 AM #14 diyAudio Member   Join Date: Nov 2005 I should confess I have never seen a straight waveguide designed to lead a tuned LF wave out of the enclosure at an oblique angle into a parabolic reflecter bouncing the wave into an optimised area. I have seen these: http://www.meyersound.com/products/i...alseries/sb-1/ If you want to make a parabolic reflector woofer you'd have to build another stadium over the stadium. Last edited by Andrew Eckhardt; 5th April 2010 at 02:38 AM.
 5th April 2010, 05:30 AM #15 diyAudio Member   Join Date: Dec 2005 Location: Georgia Sorry, I forgot the emoticons. It was more a friendly jab to the ribs than a full on attack. I wasn't trying to rile you up. The post was only half serious, but really what do infrasound, helmholtz resonators, ultrasound imaging, and "hyper" sound lenses have to do with a Spiral TL/horn calculator, or spiral horn tech (to you)? Further more, you bring up a "transverse electromagnet wave" in your post to me. What does that have to do with anything listed above, to you? You have sonar, ultrasound, a cavity resonance device, and the definition of infrasound. Can you bring this all home for us? That's all I'm getting at. Link it together for us. I understand you see a link there, but from the other end it looks random-ism as is. FWIW Last edited by soho54; 5th April 2010 at 05:50 AM.
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Quote:
 Originally Posted by Andrew Eckhardt If you want to make a parabolic reflector woofer you'd have to build another stadium over the stadium.
Wow, no kidding. The Meyer rig is 54" in diameter and is rated down to just 500Hz. Imagine the 50Hz or 20Hz version!
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Quote:
 Originally Posted by heyday I have designed antenna's myself which were calculated to operate over several bands by increasing the length as well as the diameter of the element(s) of the antenna itself without the use of any electrical circuits
You can indeed increase the usable bandwidth of an antenna by using larger sized elements, but only by an order of several Megahertz, or if you want to get technical, a fraction of an octave.

To be clear, you can indeed use antennas, which are designed by default to be usable within a certain passband, in other bands. The only question is how much of an impedance mismatch can you tolerate? If you're receiving, the signal strength is degraded (which, by the way, tuned circuits will do little to help). If you're transmitting, how much reflected power and spurrious emissions can your environment and your equipment live with?

In broadcasting, we go nuts if the gauge on our FM transmitter says 50kW forward and 100 watts reflected - it's darn near intolerable. In fact, I venture to say that 100 watts of reflected power is intolerable on any band, broadcast or otherwise. Except of course for the acoustical band

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Join Date: Mar 2010
Location: Oklahoma
Quote:
 Originally Posted by Andrew Eckhardt I should confess I have never seen a straight waveguide designed to lead a tuned LF wave out of the enclosure at an oblique angle into a parabolic reflecter bouncing the wave into an optimised area. I have seen these: SB-1 : Parabolic Long-Throw Sound Beam If you want to make a parabolic reflector woofer you'd have to build another stadium over the stadium.
First time I ever saw one of those.

I was actually thinking along the lines of the reflector designed around the open source horn project developed here. (Frugalhorn)

Seriously speaking, as it is shown that sound within a circular area, (such as the whispering gallery in rome) will amplify 180 degrees from the source, why would (2) 1/8 wave designed tapped horns constucted in a semi-circular shape (Let's make them in the shape of a 1/8 segment of a full wave diameter circle) placed in a listening area a full wave apart not only reproduce the targeted frequency efficiently, but maybe even intensify it as well?

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Join Date: Mar 2010
Location: Oklahoma
Quote:
 Originally Posted by letsbangout You can indeed increase the usable bandwidth of an antenna by using larger sized elements, but only by an order of several Megahertz, or if you want to get technical, a fraction of an octave.
From Wikipedia:
BandwidthThe bandwidth of an antenna is the range of frequencies over which it is effective, usually centered on the resonant frequency. The bandwidth of an antenna may be increased by several techniques, including using thicker wires, replacing wires with cages to simulate a thicker wire, tapering antenna components (like in a feed horn), and combining multiple antennas into a single assembly and allowing the natural impedance to select the correct antenna. Small antennas are usually preferred for convenience, but there is a fundamental limit relating bandwidth, size and efficiency.

large cut & paste removed

Last edited by Pano; 5th April 2010 at 02:23 PM. Reason: clean up

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Join Date: Mar 2010
Location: Oklahoma
Quote:
 Originally Posted by soho54 Sorry, I forgot the emoticons. It was more a friendly jab to the ribs than a full on attack. I wasn't trying to rile you up.

I wasn't riled.

Quote:
 The post was only half serious, but really what do infrasound, helmholtz resonators, ultrasound imaging, and "hyper" sound lenses have to do with a Spiral TL/horn calculator, or spiral horn tech (to you)?
Infrasound

I threw in the definition of infrasound to establish that ultrasonics includes those frequencies generally considered to be necessay for subwoofer reproduction in audio/HT venues.

Ultrasound imaging

The point being conveyed is that the technology exists today whereby "any acoustical device" can be made considerably smaller.

Thus, a tapped horn might be made with equilivant SPL levels of the current designs in a considerably reduced enclosure.

helmholtz resonators

A single spiral introduced into a helmholts resonator greatly increases the SPL of the tuned frequency of that resonator.

If you still don't understand why I brought that point up, it could be that you missed my earlier discussion relevant thereto:

Spiral Tapped Horn Invention Box and questions

ultrasound imaging, and "hyper"

Quote:
 Further more, you bring up a "transverse electromagnet wave" in your post to me. What does that have to do with anything listed above, to you?
I explained earlier that I would be starting a new thread in a different forum here at diyAudio to discuss those issues:

The Catt Question- Is science being suppressed

Be patient

Quote:
 You have sonar, ultrasound, a cavity resonance device, and the definition of infrasound. Can you bring this all home for us? That's all I'm getting at. Link it together for us. I understand you see a link there, but from the other end it looks random-ism as is. FWIW
Go back and review my earlier thread, and if you still want me to "bring it all together" I will be happy to oblige.

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