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Old 29th April 2013, 11:52 PM   #791
xrk971 is offline xrk971  United States
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Very good point Don. Have you made a Cornu? Please post pics!
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Old 30th April 2013, 12:15 AM   #792
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How much flexing would one expect when you have similar pressures on either side of the walls? This is why foam core can be used so effectively here, no? Or is that not what you mean?
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Old 30th April 2013, 01:26 AM   #793
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I think the curved walls provide a more stable support structure because the curved portion that contacts the baffle defines a plane rather than a line if it were straight. It self triangulates? The acoustic pressures are minimal but they are there and we want to reduce flex which absorbs energy and makes sound less efficient.... although that is the basis of damping which we want some amount of. So I guess it depends. But your point of why foam core works well as a speaker still holds... ramble....
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Old 30th April 2013, 02:43 AM   #794
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More ramble...

Was Don speaking of baffle flex or horn wall flex? The only thought I had is that the horn walls won't be flexing but the baffles will, hence - make them from wood.
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Old 30th April 2013, 04:24 AM   #795
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No, I haven't done a speaker with it yet. My daughters use it for school projects and I've been eyeing it, wondering about speaker enclosure use, hence my interest in these foam core threads. I do have some suitable 3 inch drivers culled from HTIB systems, waiting for me to get a round tuit for measuring their T-S parameters.

As for its suitability for Cornu spiral enclosures, it's simple physics. It flexes, so it needs bracing. A Cornu spiral horn as implemented here is well suited - the spiral walls are braced by their own curvature and their relatively shallow depth, and the front and rear are braced by the spirals - closely spaced near the throat where pressures are highest, and further apart near the mouths.
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Old 30th April 2013, 04:42 AM   #796
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In a horn, aren't the pressures actually highest at the exit or mouth? The velocity is highest at driver and lowest at mouth. The horn serves as the flow diffuser to match the impedance from the driver to ambient. I just think about it like a subsonic diffuser with the pressure and velocity described by Bernoulli equation. But then this is acoustics and it may be different, but I think it's the same physics just oscillatory flows.
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Old 30th April 2013, 07:55 PM   #797
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Steve,
I was in the North Van Dollarama this morn. They have the foam core. It is in aisle 5 at the north end of the store, top shelf. It's an unopened box near the end of the aisle. Readi Board.
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Old 30th April 2013, 08:27 PM   #798
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That's full service shopping Cal.
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Old 30th April 2013, 08:38 PM   #799
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Sounds like it doesn't it?

The actual story is way less interesting so I'll just say that I drove 50 km's out of my way for you Steve.
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Old 30th April 2013, 09:06 PM   #800
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Make sure you buy the whole box. Trust us, you will use it all up.
Oh, and don't forgot to buy about 3 bags of 100 count glue sticks (unfortunately the Dollar store doesn't carry this).
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