High Efficiency Speaker Asylum Need speakers that can rock with just one watt? You found da place.

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Re: Leach

Posted by tomservo (M) on July 7, 2003 at 20:44:31

In Reply to: Leach posted by mikeel on July 7, 2003 at 11:57:28:

>Hi tomservo. I was wondering, how do your theories square with Leach re Webster's equation and forward and reverse wave propogation? Leach bases his math on the Webster equation, quote: 'It is assumed that the acoustic pressure p is uniform across the cross section. In this case, the pressure satisfies the Webster horn equation.'

Hi

When dealing with acoustic dimensions of less than ¼ wl, in the throat of a horn, the pressure is uniform or very close to it due to the speed of sound propagation. This method stops working just before the point that the acoustic termination reaches ¼ wl from the driver.

>With the driven point in the throat, conditions are satisfied and Leach's math describes the horn. However if the driven point is somewhere midway within the bell of the horn, the pressure is not uniform and wave propogation is not always towards the mouth. There is some swell first so how does your theory account for this?

Can I see the mathematical derivation of your theory?

No, but you can look up the patent, go to one of the patent sites, search under inventors name with mine, Thomas Danley, it should show up under Unity summation aperture, I don’t have the number handy.

What made you to draw your conclusion? Is it something you have a 'gut feel' about or is there more rigorous mathematics to support your assertions?

No, I made up my own “theory” up as I plodded along, based on lots of measured results of the real thing and then finally computer models.
Given the performance of the products vs the systems we compete against, It would be hard to argue it doesn’t also work in the real word.

> I ask because my 'gut feel' is that efficiency of the horn will fall when the the driver is placed midway in the horn. Leach's math doesn't work in this situation so I'd like to see what you have to support your theory.

Well I point out occasionally that what people think is the way things are is not always the way things really are.
Do what I did, build one or several, measure them carefully then figure out what is going on inside.
Why do you figure the efficiency would fall anyway?
There is no where for “power to flow” at the closed end, no resistive dissipation, there is some reactance (compliance of the air volume) but it is small (acoustically) but does add to the acoustic hf roll off above the ¼ wl critical length.

Cheers,

Tom

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