What would happen if I took a 1" exit compression driver... - diyAudio
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Old 12th September 2013, 11:35 PM   #1
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Default What would happen if I took a 1" exit compression driver...

...and mounted it flush in the middle of a big disc pointing up, and then I had a matching disc in above that, 0.25"-ish away so that the cross section at the exit is the same as in the exit? I get 360 of... what?
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Old 13th September 2013, 12:27 AM   #2
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Smith horn...

I would worry the reflection back down the throat from the
sudden discontinuity at the outer edge, uniformly the same
distance all around. You might get better results to put the
driver off-center, or cut some scallops into the upper plate
like JBL Aquarius...
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Old 13th September 2013, 01:18 AM   #3
gedlee is offline gedlee  United States
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Lots of standing waves, but almost Omni radiation - with a lot of coloration from the standing waves. You could reduce the coloration with some randomness as suggested above, but then you would also get some random directivity. It would have a hugely "spacious" sound as a result.
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Old 13th September 2013, 01:21 AM   #4
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Standing waves from the edges, or from in front of the driver, or both? It's not so much that I think this is a good idea as I want to understand how bad it is. I was also wondering about doing this with a round planar, or two opposing ones. I suppose I could just try it and measure for myself, hardly the most difficult thing to build.

Last edited by dumptruck; 13th September 2013 at 01:24 AM.
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Old 13th September 2013, 01:30 AM   #5
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Default Example

Quote:
Originally Posted by dumptruck View Post
...and mounted it flush in the middle of a big disc pointing up, and then I had a matching disc in above that, 0.25"-ish away so that the cross section at the exit is the same as in the exit? I get 360 of... what?
https://www.google.com/patents/US4496021

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WHG
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Old 13th September 2013, 01:47 AM   #6
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Sure, I can imagine all kinds of things like that (and some of them are commercial products), but I'm more interested in just how bad it is to do it the easy way. The easy way definitely can't involve any kind of phase plugs not already attached to the driver, nor any kind of expansion different than that already provided by the circles. Just two flat pieces, and a half- or quarter-circle roundover at the exit.

Last edited by dumptruck; 13th September 2013 at 01:49 AM.
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Old 13th September 2013, 05:38 AM   #7
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Your standing waves are from the driver to the edge of the plates.
Simultaneously too wide and too narrow to support other internal
modes. There are also room modes to worry. But in this plan, the
horn's length (and harmonics of length) will dominate.

If you can equalize the exiting sound (the big if), corrections will
apply equally in every direction. That's constant directivity for you.
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Old 13th September 2013, 06:27 AM   #8
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Sure, I can imagine all kinds of things like that (and some of them are commercial products), but I'm more interested in just how bad it is to do it the easy way. The easy way definitely can't involve any kind of phase plugs not already attached to the driver, nor any kind of expansion different than that already provided by the circles. Just two flat pieces, and a half- or quarter-circle roundover at the exit.
If it is so easy to build, then do that and observe the results to determine which of the imagined shortcomings are important and which ones are not; otherwise, simply settle for conjecture to avoid that effort. The difference between your imagined design and the example provided are most likely what is important to make the effort a success.

WHG
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Old 13th September 2013, 12:08 PM   #9
gedlee is offline gedlee  United States
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Agreed - with things like this best is to just build one and try it.

As far as standing waves, I see two main ones. Diaphragm to top plate and diaphragm to open edge. There could also be radial standing waves in the gap. Lots of possibilities.
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Old 13th September 2013, 04:09 PM   #10
badman is offline badman  United States
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I'd expect a lot of standing waves as described- a much gentler transition from driver into the "ring" a la duvel and others would be a much better solution but also much harder to build.
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