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Bill Fitzmaurice Folding Geometry [message #16772]

Thu, 05 August 2004 08:42

adavis464
Messages: 64
Registered: May 2009

Viscount

You said your tuba18 is a sub?What parts of the folding geomerty causes the highend to roll off.Do the bends act as a series of filters that cause this?If so how aggressive can you get with the folding and what does it do to bandwith?You also said you did not use any particuler standard curve,did you just fudge the shape a little on design and how much can you simpifly the folding before it become a problem with bandwidth.Lots of questions I know but I value your thoughts.Thanks Tim

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Re: Bill Fitzmaurice Folding Geometry [message #16773 is a reply to message #16772]

Thu, 05 August 2004 10:59

Bill Fitzmaurice
Messages: 335
Registered: May 2009

Grand Master

The high end will roll off when you don't use rounded bends. Since this is a sub and I wanted the high end to roll off so I left the bends squared. In my DR horns, which are full range, I use rounded bends and they're good up to at least 2kHz, basically needing to be crossed over when off-axis response starts to deteriorate.

My flare for subs has a much longer pathway to cross-section that the usual. This allows a far deeper extension and efficiency from a smaller package than is possible with standard flares.

By and large you can do just about anything folding wise up to about 200Hz, but much above that you have go to round bends.

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Folding, bends, reflectors, etc. [message #16774 is a reply to message #16773]

Thu, 05 August 2004 14:49

Ralph
Messages: 75
Registered: May 2009

Viscount

I did a search and found more info. re folding, bends, reflectors, etc.

http://www.audioroundtable.com/HighEfficiencySpeakers/messages/541.html

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Re: Folding, bends, reflectors, etc. [message #16775 is a reply to message #16774]

Thu, 05 August 2004 15:31

spnman
Messages: 14
Registered: May 2009

Chancellor

Low frequencies go around corners. High frequencies don't they're line of sight. A bass horn can have dead end 180 degree turns and the bass will go right through but midrange can't. Most people don't want midrange from their bass horns so dead end turns are OK.

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Yes, but... [message #16776 is a reply to message #16775]

Fri, 06 August 2004 10:13

Bill Fitzmaurice
Messages: 335
Registered: May 2009

Grand Master

high frequencies will go around corners if the corners are properly constructed. The Huygen's theoretical concept of flat reflectors at a 45 degree angle is inherently flawed; John Sheerin's modeling with rounded bends is correct, result verified in the real world by my Snail and DR horns.

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Huygen's Principle... [message #16777 is a reply to message #16776]

Fri, 06 August 2004 11:11

spnman
Messages: 14
Registered: May 2009

Chancellor

...isn't a theoretical concept but a description of observed facts. I appreciate your many excellent contributions but wish you would get off the "every theory is wrong and my horns prove it" kick.

http://www.pas.rochester.edu/~tipton/huygens.pdf

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Re: Huygen's Principle... [message #16779 is a reply to message #16777]

Fri, 06 August 2004 12:41

Ralph
Messages: 75
Registered: May 2009

Viscount

His words may be a little strong but I've tested Bill's assertions and found them accurate. Maybe Huygen's theory isn't "flawed" but Bill applies it in a non traditional way.

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Re: Huygen's Principle... [message #16780 is a reply to message #16779]

Fri, 06 August 2004 15:09

Bill Fitzmaurice
Messages: 335
Registered: May 2009

Grand Master

Thanks, Ralph. Perhaps if Huygen's had access to a computer he would have had the same results as Sheerin. I stand by my assertion that his theories on the use of a flat reflector in a folded horn to maximize high frequency passage through the bend is flawed. High frequency sound waves simply don't work the way he postulated. If that doesn't agree with what some folks are teaching then maybe it's time they abandon the chalkboard for a while and spend some time behind a tablesaw. My claims are easy enough to either verify or refute, but with SPL meters, not abstract formulai.

And wait 'til you see what I do when it comes to flares.

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Simulation [message #16781 is a reply to message #16773]

Fri, 06 August 2004 15:12

Ralph
Messages: 75
Registered: May 2009

Viscount

Look at this simulation I found. It shows a wave being directed 90 degrees to a horn without using a curved waveguide or a reflector. Also notice the wave curving around the edge of the mouth. Interesting!

http://www.ifh.ee.ethz.ch

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Re: Huygen's Principle... [message #16782 is a reply to message #16780]

Fri, 06 August 2004 15:40

spnman
Messages: 14
Registered: May 2009

Chancellor

I'm sorry but I just don't agree. I don't want to make a big deal of this, I really don't. All I am trying to say is that round corners aren't the only answer, they're just the answer you found. I don't get it why you try to make like your horns defy the laws of physics or like you had found new properties. It is good enough that your designs work, no need to dilute the point by saying something ridiculous. Why do you insist that Huygen is wrong? Can't you see that wave travel through your horns acts just like Huygen says it does?

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