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Old 15th May 2008, 09:48 PM   #141
tinitus is offline tinitus  Europe
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So lets have that 15" waveguide then
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Old 15th May 2008, 10:23 PM   #142
gedlee is offline gedlee  United States
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Quote:
Originally posted by SunRa



Dr. Geddes,


could you please develop this affirmation a little? Why a 18" waveguide would have a better polar response control?

And how would the lenght of the waveguide affect the top end frequencies compared with the smaller waveguides?


Thank you!
Waveguide theory 101.

The length has no effect on the high end. The length is irrelavent actually, its the mouth size that matters. In any waveguide, there is a reflection/diffraction at the mouth from the termination, rounding helps, but you almost can't get it round enough and as the waveguide gets smaller the edge round has to get smaller. At some frequency this inevitable edge diffraction, which is all in phase on axis if the waveguide is round, leads to a hole, then a peak - cancelation followed by reinforcement. This disappears off axis.

As the waveguide gets smaller - the mouth gets smaller - this hole moves higher in frequency and deeper in effect. This can all be seen quite clearly in the three ESP models at www.ai-audio.com. I estimate that at 18" it will go away completely because it is barely present at 15".

There is also a narrowing of the polar response at the lower end of the passband. The wider the mouth the lower this goes and again at 18" it should be below the passband.

Square mouths blur this effect on axis, but the effect is there off axis where a square horn never has the degree of control of a round waveguide. There are ways that I could mitigate this effect and if I continue in this work I'll look into that.

But for now what's available is what's available.

Of course ANYTHING is available if the price is right!
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Old 15th May 2008, 10:37 PM   #143
SunRa is offline SunRa  Romania
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Thank you Dr. Geddes!

Afterall a little consumer education can't hurt. It's way maybe to increase the market share for high quality audio...
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Old 16th May 2008, 03:32 AM   #144
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Hello Dr Geddes, Any chance we will see your prefferred 12" woofer/ 15" waveguide offered as a kit anytime soon? Being overseas I would rather pay the significant shipping costs on the " best " combo that on the " compromise " 10" combo
Thanks Mike Anderson
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Old 16th May 2008, 03:41 AM   #145
gedlee is offline gedlee  United States
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Quote:
Originally posted by Michael Ando
Hello Dr Geddes, Any chance we will see your prefferred 12" woofer/ 15" waveguide offered as a kit anytime soon? Being overseas I would rather pay the significant shipping costs on the " best " combo that on the " compromise " 10" combo
Thanks Mike Anderson

Anytime soon - I would say no. It could happen down the road but there are so many other considerations that I'm not sure that it will happen.

I am supposed to get some waveguides in fiberglass in 12", but I can't promise when that will happen. Seems that my Thailand connection has dried up.

It might be better for you to get the glass ones directly from Thailand. I might be able to get that to happen. If I ever get the ones I've been promised, I'll see if I can get them to send some to you. You have to underatsnd that the ones that come out of Thailand are not complete. You have to do a lot of further work on them to make them useful.
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Old 16th May 2008, 10:14 AM   #146
EspenE is offline EspenE  Norway
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Quote:
Originally posted by Michael Ando
Hello Dr Geddes, Any chance we will see your prefferred 12" woofer/ 15" waveguide offered as a kit anytime soon? Being overseas I would rather pay the significant shipping costs on the " best " combo that on the " compromise " 10" combo
Thanks Mike Anderson
I'll second that.

Quote:
Originally posted by gedlee
It might be better for you to get the glass ones directly from Thailand. I might be able to get that to happen. If I ever get the ones I've been promised, I'll see if I can get them to send some to you. You have to underatsnd that the ones that come out of Thailand are not complete. You have to do a lot of further work on them to make them useful.
I'm interested. How can we make it happen? What kind of work?
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Old 16th May 2008, 11:08 AM   #147
tinitus is offline tinitus  Europe
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WE shouldnt be afraid of a bit of work
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Old 16th May 2008, 02:12 PM   #148
gedlee is offline gedlee  United States
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Quote:
Originally posted by EspenE


I'm interested. How can we make it happen? What kind of work?
Its all up to Thailand not me. The waveguides come as shells. The mount for the driver must be attached and the throat generally is not quite precise enough. I fix all of this with a single step by gluing on a mounting plate with epoxy that also corrects any flaws at the throat. But this requires a machined plug/fixture to align everything correctly, at the correct location. This fixture then becomes the mold for the epoxy to finish off the throat. Its doable, but its not easy.

To Europe, shipping from here makes more sense, but to Australia, shipping from Thailand makes more sense.
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Old 16th May 2008, 02:46 PM   #149
LAL is offline LAL  United States
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"Understood, but wiring the crossover is one of the most time consuming parts and my doing it would drive up the price substantially. I just don't see it as an option."

Earl,
It never occurred to me that you would personally construct the crossovers. I assumed you would have this done in Thailand or hire someone here in Michigan to do it. A high school student could be taught to do so and would work for minimum wage.

LAL
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Old 16th May 2008, 04:26 PM   #150
gedlee is offline gedlee  United States
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Quote:
Originally posted by LAL
"Understood, but wiring the crossover is one of the most time consuming parts and my doing it would drive up the price substantially. I just don't see it as an option."

Earl,
It never occurred to me that you would personally construct the crossovers. I assumed you would have this done in Thailand or hire someone here in Michigan to do it. A high school student could be taught to do so and would work for minimum wage.

LAL

This makes sense for large volumes, but the volumes are not clear at the moment. I have to assume that I will do everything, as I have been, until such time as "hiring" someone makes economic sense.

The Thailand operation is shut down. I thought that was clear. I am trying to salvage as much of the technology as possible, but everything has to be done here and by me.
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