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Old 1st January 2013, 02:52 AM   #241
xrk971 is offline xrk971  United States
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Originally Posted by prezden View Post
I'm wondering how small Cornu spiral could be made with reasonably good results.

Happy New Year All
I have 14 inch x 2 inch deep Cornu's with drivers similar to Visaton FRS5 that I listen to all day. They have a lot of bass (for 2 inch drivers) even when played at low volume. A very rich and full sound from 2 in drivers running on less than a watt of amplifier power. I am very happy with them. I posted a sound clip of how they sound somewhere back in this thread. I suppose the next thing to try is a 1 inch driver - one of those aluminum concave cone deals. I actually stuck one of them into the cutout for the 2 inch driver ( before cutting it to full size) and did notice an immediate bass extension.
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Old 1st January 2013, 05:00 PM   #242
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Good news, folks: my cornus are all sealed up and ready to go. All I'm waiting for now are the drivers and terminals. I even bought some wall mounting hardware. Drivers are due to arrive on Thursday, so stay tuned.
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Old 1st January 2013, 08:12 PM   #243
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Looks great Chaz. Hopefully the drivers will arrive when expected. Can't wait to hear your thoughts.
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Old 1st January 2013, 08:17 PM   #244
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Chaz,
Those look really good. Is that quarter inch birch plywood you are using for the panels? Can you refresh my memory what size, depth and drivers you are using?
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Old 1st January 2013, 08:56 PM   #245
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Default im not sure if this has been asked in the foam core thread, but:

i would like to ask if another material instead of foamcore board is suitable for prototyping a cornu. I access to offcuts of either: 1/ Triwall corrugated board or 2/ that plastic sheet which is used for greenhouse glazing, almost corrugated in construction. Since I can get offcuts free, the idea is appealing. Can you see a good reason why i shouldnt use these other materials?
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Old 1st January 2013, 09:04 PM   #246
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It's been asked and I don't see why not other than it's more expensive and harder to work with. But if it's free, go for it. The translucent effect will be pretty cool. It will resonate more than foam.
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Old 2nd January 2013, 12:09 AM   #247
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Chaz,
Those look really good. Is that quarter inch birch plywood you are using for the panels? Can you refresh my memory what size, depth and drivers you are using?
It's 1/4" plywood but I don't recall if it's birch; it was the cheapest plywood I could get. It's 24"x3.5" depth (4" including the ply). The driver is the TB W3-926SDF. If I like these speakers, I might experiment with higher-quality drivers.
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Old 2nd January 2013, 10:04 AM   #248
xrk971 is offline xrk971  United States
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Chaz,
Your boxes with those drivers and that size looks like it's going to be a really nice combination. I'm really looking forward to hearing your listening impressions. I am wondering whether or not to try a box with 4 equal length horns without any bifurcation. That might be best to try out in all foam core but that will limit the size to 20 in square. I suppose one can use multiple pieces for the faces - not the prettiest thing but for purposes of testing sound may be the way to go in order to make an all foam core unit bigger than 20 inches. I am thinking a 24 x 4 inch size next.
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Old 2nd January 2013, 03:55 PM   #249
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Thanks xrk, I'd be lying if I said I wasn't hoping for good results myself! By the way, after the speakers are all assembled I will have them tested for frequency response and phase and report back. That may take a few weeks.

I wonder: if one wanted to try a cornu with a larger driver, is there any consequence to increasing the size of the chamber and thereby reducing the length of the horn besides raising the horn tuning frequency? That would make it possible to fit a larger, say 6.5" or even an 8" driver into a 35" cornu.
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Old 2nd January 2013, 04:11 PM   #250
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Chaz,
You can increase the driver size as you say by trimming away the internal channels and reducing the horn length. This will allow you to easily put a 4 inch driver in where a 3 inch used to be. I would not go too far with this as you will be reducing the throat area of the horn relative to the driver piston area Sd as you put larger drivers in there. This may not be a bad thing depending on how the larger driver's T/S parameters behave under a simulation. Some driver chamber compression from a restricted throat may be desirable for better performance and to reduce cone excursion for low Qts/high-BL drivers like Fostex or Lowther. It is easy enough to run a HornResp sim for a simple single horn representing the approximate single Cornu horn geometry and change the throat and length to correspond what happens when you trim the channels to widen the driver chamber. Are you going to be doing the frequency response measurements yourself?
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