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Old 30th December 2012, 04:09 PM   #211
prezden is offline prezden  Canada
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The foam core thread is a long one- It took me days to read through all that info
My plan is to build 18" units with 3" channels. I hope I got the dimensions right. I scaled the curves from Dave's drawing (thanks Dave) printed and tiled it to size. Taped the drawing to a piece of Sintra and used the pin hole transfer method mentioned earlier in this thread. Sintra is a pvc board used in the sigh industry and I happened to have some lying around so... I'll be using TB W3-881SJF drivers. Recently I used these in another small project- liked the sound but found the bass to be insufficient so I thought they might be good in the Cornu spiral.
I will post some photos as things progress.
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Old 30th December 2012, 04:17 PM   #212
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Nice to see more on board.

I have done a hand rendering of the new curve for the spiral drawing so I have something to take to the repro place. Wasn't that hard, just continued the curve to the outside of the page and it eliminated the narrowing near the mouth. Crude but usable.
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Old 30th December 2012, 06:06 PM   #213
xrk971 is online now xrk971  United States
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Quote:
Originally Posted by prezden View Post
Thanks Xrk971
The foam core thread is a long one- It took me days to read through all that info
My plan is to build 18" units with 3" channels. I hope I got the dimensions right. I scaled the curves from Dave's drawing (thanks Dave) printed and tiled it to size. Taped the drawing to a piece of Sintra and used the pin hole transfer method mentioned earlier in this thread. Sintra is a pvc board used in the sigh industry and I happened to have some lying around so... I'll be using TB W3-881SJF drivers. Recently I used these in another small project- liked the sound but found the bass to be insufficient so I thought they might be good in the Cornu spiral.
I will post some photos as things progress.
Prezden,
The PVC signage material sounds promising. The cool thing with PVC is that it can be heat bent (hold over a gas stove burner) to form channels and the whole thing could be sealed with PVC cement to form a solid PVC horn with no leaks. It would take some careful handywork to bend segments of the PVC channels to the exact shape though. Foam channels are definitely faster. The W3-881SJF looks like a nice driver for this application.
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Old 30th December 2012, 06:07 PM   #214
xrk971 is online now xrk971  United States
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Originally Posted by Cal Weldon View Post
Nice to see more on board.

I have done a hand rendering of the new curve for the spiral drawing so I have something to take to the repro place. Wasn't that hard, just continued the curve to the outside of the page and it eliminated the narrowing near the mouth. Crude but usable.
Looks very nice Cal. What driver will be used with this build?
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Old 30th December 2012, 06:39 PM   #215
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I think Dave said he has some Audax on the way, not sure the model. Dave?
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Old 30th December 2012, 07:10 PM   #216
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I also wonder about this from MA

http://www.creativesound.ca/pdf/A6P.pdf
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Old 30th December 2012, 07:43 PM   #217
xrk971 is online now xrk971  United States
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I really like the Alpairs. I think they would work really well. They have a lot if bass to start with so maybe a shallower channel depth with some compression on the throat to have more balanced output in cornu.
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Old 30th December 2012, 08:34 PM   #218
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Okay, some progress has been made. I'll admit that getting started was a bit tricky, but I got much better as things rolled along. Unfortunately the chamber and horn throats are a bit crude but there's no going back now. I haven't even checked how far off the throats are from spec (11/16" by my reckoning, for my driver).

Next is to stuff the horns and glue the backs onto the cabinets. I may or may not wait for the drivers to arrive before I do this...
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Old 30th December 2012, 08:57 PM   #219
endia is offline endia  Turkey
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Originally Posted by Cal Weldon View Post
I had a look at the PDF I downloaded and I have some concerns. The channel is wider at the red arrow than the blue.
that was my mistake! i hadn't pay attention to channel wideness while i was focusing to curving lines..
i made one more drawing just for experiment to get truly spiral paths which can be adjustable for scaling..

btw, i don't want to cause any mess about pdf files and this is the original cornu layout for who wants to build the original;
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Old 30th December 2012, 09:07 PM   #220
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I think Dave said he has some Audax on the way, not sure the model. Dave?
Aura NS3. The expensive ones.

I'm also going to be getting someof these, but you'd need to decide to spend the extra $10 each. The Madisound Speaker Store (black or silver, 4 or 8). Next step up the Fountek FR88ex (i still should have 5 at cleanance prices -- i could ship those pretty quick, just need to get a pair back from Bernie),

dave
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