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Old 3rd December 2012, 05:20 AM   #321
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Quote:
Originally Posted by Ed LaFontaine View Post
Create complimentary channels in the front and back to receive the strips of foam core.
Getting the spiral glued into the backpiece to fit into a groove on the front(unless it is quite wide) would be difficult at best. Front one should be left flat.

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2 Vifas and an economical tweeter? ...or 4 in a diamond mmtmm surrounding the tweeter? They are small enough that lobing shouldn't be an issue.
Need to be a very small tweeter bezel (& midbasses) to get the C-C less than a 1/4 wl at the XO.

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Old 3rd December 2012, 07:01 AM   #322
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Originally Posted by Cal Weldon View Post

Sorry Mark, I have to disagree. I too, am familiar with the Coroplast and I think once you work with the foam core you will understand.
Um... I was saying foamcore is better than coroplast. I've used sheets and sheets of foamcore, building architectural models, and I think it's a good choice and have actually made small speakers with it. Isn't that your opinion? please clarify as I'm confused...
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Old 3rd December 2012, 10:27 AM   #323
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Quote:
Originally Posted by Ed LaFontaine View Post
Seems to me that routing a template for use in a pin router would be expedient. Create complimentary channels in the front and back to receive the strips of foam core.

Also, why not go ahead and make an mtm using 2 Vifas and an economical tweeter? ...or 4 in a diamond mmtmm surrounding the tweeter? They are small enough that lobing shouldn't be an issue. There's no reason you full-rangers should have all the fun.

The use of fancy jigs, routers, and cutting channels and grooves is exactly what I was trying to deliberately avoid with this build as that is what kept so many people from trying to build the Cornu in the first place. Maybe if you want to go into production with a wooden channel version this is the way to do it ( and I believe this how the production version of the Cornu spiral is built). But what I found out in doing this using paper-faced foam core board was that you can build the spirals very easily simply by gluing sections at a time and curving it by hand to follow the trace of the spiral on the back. Literally, it takes 15 minutes per channel and 1 hour to glue all the channels. The key trick is to lightly score the CONCAVE side of the channels paper face with light cuts perpendicular to the bend - it not need be exact. These small cuts allow the inside paper to evenly compress the foam, the outside paper face goes into tension, and the whole thing is very smooth and sealed. Once glued in place, the curve looks very good. Also, a channel would necessitate thicker faced boards, adding weight. These speakers built with foam core channels and 1/4 in ply faces, or even foam core faces, in my case are extremely lightweight yet rigid. The light weight makes it easy to hang without requiring a stud in the wall or even a toggle bolt for drywall.

As far as using two Vifa TC9FD's and a tweeter, I find that the Vifa already has enough of a high end (it is very tweeter like). The diamond MMTMM would have lots of output, you can probably skip the tweeter given how high these drivers go. One nice thing with the MMMM (sans tweeter) is that we skip the X-over and it let's us wire the quad 8 ohm Vifa's as 2, 4, 8, 16, or 32 ohms. I would pick 4 ohms so that doubles the power my amps can drive. The CTC spacing of the Vifa's is 84 mm (plus they have squared off bezels to allow tight packing) - will this cause any comb interference effects? This now let's the Cornu handle up to 120 watts, with equivalent Vas of 5 liters (? simply additive?) and SPL levels that will be higher than a single, and the cost would still be less than a single 4 in Fostex (even in non tricked out form)! I think this would fit if one built a slightly larger speaker box in the center but keep the spiral lengths modest as it would be pointless trying to get the little guys to push anything below 50 Hz. I like this idea....

Last edited by xrk971; 3rd December 2012 at 10:31 AM.
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Old 3rd December 2012, 10:33 AM   #324
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Would somethink like a co-axial 2way car speaker like a 6x9 be suitable? Speaker in question is an Alpine (brand) TypeR 6x9.

In hoping someone can google the t+s specs for it to see for me as i still dont have full internet... Bloody telstra..
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Old 3rd December 2012, 10:55 AM   #325
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Originally Posted by klampykixx View Post
Would somethink like a co-axial 2way car speaker like a 6x9 be suitable? Speaker in question is an Alpine (brand) TypeR 6x9.

In hoping someone can google the t+s specs for it to see for me as i still dont have full internet... Bloody telstra..
A round 4 inch or 3.5 in coax could work, the oval just would not look very good (imo). There is a round Pioneer 3.5 (TS A 878) that is very good.

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Old 3rd December 2012, 11:56 AM   #326
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I have been looking for specs on alpine 6x9s today. (thinking about making a TL for destop speakers) Havnt been able to find anything. Im guessing its cause you usually just shove them in the parcel shelf and its job done.
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Old 3rd December 2012, 12:02 PM   #327
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I have a pair of EType alpine coaxials as well. Could t+s on those be found maybe? Theyre 4inch two way.
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Old 3rd December 2012, 12:06 PM   #328
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I would also love to know the T+S on my 70mm drivers as well. Theyre an LG
Numbers are
6400FTTC01A
F30C-D323

if anyone can help ill be greatly appreciative
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Old 3rd December 2012, 12:24 PM   #329
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looks like only the alpine type x have specs in the manual
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Old 3rd December 2012, 12:27 PM   #330
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Quote:
Originally Posted by Cal Weldon View Post
I have one bit of advice for this project:

Make sure you are happy with your choice of driver before you start.
Cal,
I think a driver used in the Cornu should have an extra peaky high end to compensate for the mondo bass, plus it will give you more 'tweeter like' abilities to anchor the imaging compared to some of the higher frequencies that may leak out the horns. I was looking at drivers that seem to have this high end peakiness and noticed that the TB W4-1337SDF may fit this bill (it's got an extra 10 dB or so from 10 kHz to 20 kHz compared to baseline SPL). It is a nice looking titanium driver too. What do you think?
Xrk971

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