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Old 28th December 2012, 01:05 AM   #951
xrk971 is offline xrk971  United States
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Quote:
Originally Posted by bcmbob View Post
I actually preferred and used a thin saber-saw blade (scrolling size) and a compass on such a small hole. Just drill a hole the size of the blade then cut inside or directly on the line (slowly) and adjust fit with sandpaper or round file.
Jigsaw is how I plan to do it with plywood - got the blades the other day. There is much less of a chance for tool to take a wild path. But then moving up from using nothing more than a razor blade to make my enclosures up to this point is a big deal.

Last edited by xrk971; 28th December 2012 at 01:08 AM.
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Old 28th December 2012, 01:09 AM   #952
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If using a jigsaw (highly recommended) the thin ply needs a down-cut blade -- an up-cut pulled apart laminations no matter how slow I tried to feed it.
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Old 28th December 2012, 01:23 AM   #953
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Cut it from the other side.
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Old 28th December 2012, 01:29 AM   #954
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Yes, but as I sealed and glued everything together before cutting, that wasn't an option.
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Old 28th December 2012, 03:13 AM   #955
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Oops.

TBH I've never heard of a reverse set blade but I would be scared of damaging the face of the wood having to press down on the saw like you would.
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Old 28th December 2012, 03:49 AM   #956
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Surface Tension,
Sounds like you were busy! I hope your friend realizes what a truly special gift this was. Thanks for the update and we are looking forward to your photos. I am thinking of moving up to wood next - the maple quarter inch 2x4 ft sheets and doing 24 inchers with a smaller 4 in driver. Does it sound different in birch vs foam?
I'm not very good at audio descriptives but regarding the birch vs foam question-

Hard to say as I did not get to compare them side by side and the drivers on the birch pair were brand new and not broken in, listening space is quite different as well. Listening to the foam pair now at a moderate level in a small room they present tremendous detail, very lively, more bass than I can believe. When pushed to louder volume it seems to break up. The birch pair seemed better balanced and controlled, especially at louder volumes in a bigger room.

And just to clarify a bit, the only wood I used was on the baffle, the spiral and back are all foam core. I really like the speed and ease of working with foam and did I say how primitive my woodworking skills are? I might try a pair with a ply back sometime although it seems unnecessary with a small driver. That 1/4" veneer ply from HD does look tempting, unfortunately was not in stock at my local store. May have to order some.

How about a short list of suitable drivers in the 4-5" range?

regards
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Old 28th December 2012, 05:39 AM   #957
xrk971 is offline xrk971  United States
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Originally Posted by surface tension View Post
I'm not very good at audio descriptives but regarding the birch vs foam question-

Hard to say as I did not get to compare them side by side and the drivers on the birch pair were brand new and not broken in, listening space is quite different as well. Listening to the foam pair now at a moderate level in a small room they present tremendous detail, very lively, more bass than I can believe. When pushed to louder volume it seems to break up. The birch pair seemed better balanced and controlled, especially at louder volumes in a bigger room.

And just to clarify a bit, the only wood I used was on the baffle, the spiral and back are all foam core. I really like the speed and ease of working with foam and did I say how primitive my woodworking skills are? I might try a pair with a ply back sometime although it seems unnecessary with a small driver. That 1/4" veneer ply from HD does look tempting, unfortunately was not in stock at my local store. May have to order some.

How about a short list of suitable drivers in the 4-5" range?

regards
Ah, a hybrid foam back, plywood face Cornu! How cool is that? That's interesting that you think The bass is more controlled and it can go louder with the wood baffle. I don't know what everyone else is trying but here is my list of drivers I would like to try in the Cornu.

TB W4-1337SDF titanium cone $47
TB W4-1329SIF bamboo paper cone $37
TB W3-315e magnesium/aluminum cone $26
TB W3-881si buyout $10
MA CHR70 $36
MA Alpair 7
Dayton RS100 (really closer to a 3.5 incher than 4 inch) $29

And of course, the list of drivers currently used with success:
Vifa TC9FD $12
Fostex FF125wk $56
Visaton FRS5 $8

There are others but I can't remember them all. Pano tried several different 3 and 3.5 inchers. Please add to this list of drivers you have used and give your subjective rating.

The thing I would look for is a driver with a rising or peaky high frequency end to balance out the heavy mid bass that the cornu makes. A lower Qts driver works better with a back loaded horn, but we have also seen higher Qts drivers work too.

My next build will be a 24 inch (61 cm) in cherry veneer face with the RS100 or Vifa. I am also designing a custom single length horn profile optimized on Hornresp and then 'rolling' it up to make a cornu with four equal lengths to see if we can smooth out the lower and mid bass response. This was Don Hill's suggestion and I am following down this path as I don't want to cut any more foam or wood until I have a better sense of the response from a model first.

Last edited by xrk971; 28th December 2012 at 06:08 AM.
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Old 29th December 2012, 05:09 PM   #958
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Good to be back home!

Giau, my brother in law has decided that the 20" is definitely the way to go so can you guys save me a little time and remind me of the right layout, channel depth and drivers so I can begin to assemble a package for him.

TIA.
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Old 29th December 2012, 05:26 PM   #959
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Hi Cal,
We have had several variations on the 20 incher. Mine had custom channels and throats so I was able to make it very thin at 2 and 3/8ths of an inch. If you use 'official' Planet10 drawing and scale that to 20 inches I think the channel depth will have to be 4.4 in deep to match Sd of Vifa. That being said, Pano had built it with 2.5 in width and Bcmbob has built a 24 inch one with 3.5 in depth. It is probably ok to have some compression in the driver chamber in the interest of keeping the profile slim, if that is what he is after. I think anywhere from 3.5 in to 4.5 in is a good depth that will work. The deeper the depth, the more the bass enhancement will be. I am surprised how good mine sound for being only 2.38 in thick (but my throats are 1.1 in wide vs 0.64 in if I were to use the scaled pdf plan). Tell your brother in law good luck. Maybe he should get online and hang out with us if he is starting this?
Good to have you back. I have been busy coming up with an ideal horn and 'rolling my own' Cornu. Let me know what you think of the two ideas so far: 24 in equal length horns, 31 in MLTL design with more even bass response. They are on the other thread.
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Old 29th December 2012, 08:58 PM   #960
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xrk971, got a link? not sure about "the other thread".
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