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Ever think of building a Cornu Spiral horn? Now you can!
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Old 23rd September 2018, 11:40 PM   #2541
Karl71 is offline Karl71  United States
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ANY help from the community is VERY much appreciated. However I don’t want to put you out. We Lowther owners of the 5” drivers are in a real bind when it comes to enclosures.

What kind of driver does well in the Cornu? Each “throat” of each Cornu enclosure is short. Does it go relatively “loud” because of four mouths but not very deep because the throats are short?

Last edited by Karl71; 23rd September 2018 at 11:43 PM.
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Old 23rd September 2018, 11:59 PM   #2542
xrk971 is offline xrk971  United States
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Ever think of building a Cornu Spiral horn? Now you can!
The Cornu has perhaps more bass gain than any other speaker because of the mouth:throat expansion ratio. It actually tends to need some attenuation via stuffing to reduce the bass to match the mids and treble rather than a BSC to attenuate the mids and treble.
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Old 24th September 2018, 03:38 AM   #2543
Karl71 is offline Karl71  United States
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According to the site seb:diy:audio, the developer of the Cornu specifies appropriate drivers as having an Fs of 36Hz & a Qts of .25. My DX55 units are right around there.

I know a guy who has a slicing table for foam core (picture framing shop). He’s a jerk (I was a terrible empoyee), but I think he’d cut the “sound guides” & front & back for nothing.

Xrk971 - Thanks very much for the link to that site. Maybe increasing the depth by a centimeter or so would be sufficient for the DX55. Your work with foam core is inspirational. I could stiffen the inner surface of the front panel portion of the driver chamber with, say, 3 or 4MM plywood & some very thin adhesive sound deadening material, both of which would stiffen that area to accommodate t-nuts & better support the Lowther. It’s a heavy driver.

Last edited by Karl71; 24th September 2018 at 03:48 AM. Reason: Corrections & elaborations
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Old 24th September 2018, 04:00 AM   #2544
planet10 is offline planet10  Canada
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Ever think of building a Cornu Spiral horn? Now you can!
Quote:
Cornu specifies appropriate drivers as having an Fs of 36Hz & a Qts of .25. My DX55 units are right around there.
That would mean a horn length the same, but the total volume would need to change by the ratio of the Vas (as a 1st approximation)

dave
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Old 24th September 2018, 02:29 PM   #2545
Karl71 is offline Karl71  United States
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Dave -

Do you mean the total volume of the driver chamber?
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Old 24th September 2018, 07:17 PM   #2546
planet10 is offline planet10  Canada
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The total volume of the box.

dave
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Old 24th September 2018, 07:27 PM   #2547
Karl71 is offline Karl71  United States
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Thanks for the explanation.
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Old 24th September 2018, 08:01 PM   #2548
Doctor Why is offline Doctor Why  Germany
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And my 10 "Cornu Variation drives the Tears of Joy in my Face.

At some Point I have to remove the broad Grin surgically ...

Greetings
D.W.
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Old 26th September 2018, 03:12 PM   #2549
Lingwendil is offline Lingwendil  United States
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Well, I finally got around to printing up and taping together the plans for a 20" cornu. Got out some black foamcore, and chopped up four 20" squares for the front and back. I get the plans laid out on the panels, only to find that my scaling was off a bit, and somehow ended up closer to 18"

I thought that I had even double checked and everything.

I said "screw it!" and taped the plans to the squares (centered, of course) and started laying out the spirals anyways. I'll just extend the outer channels out a bit, and bring them all the way to the edge, and space the inner channels out a smidge too, so that they work more or less as the correct scaling would.

Since the cornu is such a forgiving design, this should work fine right? I'm going for a 3" channel depth, and using the TC9FD. Just to make sure before I start cutting and gluing
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Old 26th September 2018, 05:01 PM   #2550
xrk971 is offline xrk971  United States
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Quote:
Since the cornu is such a forgiving design, this should work fine right? I'm going for a 3" channel depth, and using the TC9FD. Just to make sure before I start cutting and gluing
Make sure the driver chamber is still big enough to fit the magnet and basket. Otherwise, go for it.
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