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Ever think of building a Cornu Spiral horn? Now you can!
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Old 8th January 2013, 09:46 AM   #351
planet10 is offline planet10  Canada
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Ever think of building a Cornu Spiral horn? Now you can!
Quote:
Originally Posted by nathanjh13 View Post
Hello. Has anybody tried this with a different enclosure shape? Aesthetically I was thinking about a circular overall shape rather than square. Good idea? Many thanks for any advice.
I posted a fibonacci pentagon concept (5 equal horns), i tcould easily become a circle. It needs detailing.

dave
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Old 8th January 2013, 09:52 AM   #352
nathanjh13 is offline nathanjh13  United Kingdom
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I'm handy with CAD and I'll have a look at this in future. Thanks
Best
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Old 8th January 2013, 10:00 AM   #353
planet10 is offline planet10  Canada
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Ever think of building a Cornu Spiral horn? Now you can!
I can send you the existing drawing if that helps

dave
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Old 8th January 2013, 10:08 AM   #354
nathanjh13 is offline nathanjh13  United Kingdom
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Duly emailed.
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Old 8th January 2013, 12:54 PM   #355
xrk971 is offline xrk971  United States
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Ever think of building a Cornu Spiral horn? Now you can!
Quote:
Originally Posted by Don Hills View Post
Nice work. Did you notice something something pretty significant? The resulting horns closely follow an exponential length/area law. You can model single-spiral (divided 4 ways) Cornu horns in Hornresp using a single exponential section, and the multi-length horns like the one in your post in AkAbak. I'll modify (simplify) my AkAbak model accordingly.
Don,
I have re-spun the cornu generator to make a reasonably sized horn than I can build: 24 in x 3.5 in deep, driver chamber cross sectional area of 148 cm^2, chamber volume of 1312 cm^2, channel lengths of 147 cm and 104 cm long, the throat cross sectional area (both) is 31.3 cm^2 - which will provide a mild level of compression for the TC9FD Sd of 36.4 cm^2. The horn mouth area is 2168 cm^2 I am still doing the bifurcation. See attached plan. I did a simplistic sim in HR for each horn independently and then combined them after the fact to see if the bumps and valleys help cancel out. I still plan to to use the TC9FD with this. I am still unclear how to specify the channel width as function of distance in Akabak for the true cornu. Thanks for trying this in Akabak.
Regards,
Xrk971
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File Type: png true-cornu-24x3p5-plan.png (34.1 KB, 656 views)
File Type: png true-cornu-tc9fd-24x3p5-HR-sim.png (14.1 KB, 640 views)
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Old 8th January 2013, 04:52 PM   #356
Jim Shearer is offline Jim Shearer  United States
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Quote:
Originally Posted by xrk971 View Post
Jim,
There are several ways to expand the throat area: custom draw the channels to have a wider throat if you want to keep external dimensions the same; increase depth of channel, or grow whole cabinet. Note that some compression is ok, if ratio of throat area to Sd is greater than 75%, it's probably ok. For low Qts, high Bl drivers with low xmax, you might want more compression to load driver and reduce excursion. It should be modeled - a simple model in HornResp with a conical horn for first section to exponential horn near mouth wirh
appropriate dimensions for driver chamber will tell you a lot about excursion of cone.

If you are using the plan from planet10's pdf diagram, I think the the throat width is 0.9 in for the 27.6 in cornu. That is 2.3 cm wide not 17 mm wide. This gives a throat area of about 57 cm^2 for a 5 in deep channel. This about a perfect match for your driver if you wanted no compression. You could probably go as thin as 4 in and be ok.

What are the T/S params for your Altec driver?

Good luck!

Xrk971
Thanks Xrk971!

All I know about the Altec 405A is what I found on the Altec site--which is nearly useless. And I haven't the tools to measure the T/S parameters. Which is why I want to try a quick, inexpensive, flexible design.

Cheers, Jim
Attached Files
File Type: pdf 405A_ceilingspkr_spec_sheet.pdf (709.1 KB, 77 views)
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Old 8th January 2013, 05:01 PM   #357
prezden is offline prezden  Canada
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Quote:
Is that the Sure TPA3110 amp you are using? How do you like it?
It is a modified TPA3110. I haven't tried it in any other configuration but I sure like it with these little guys.
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Old 8th January 2013, 10:11 PM   #358
Cal Weldon is offline Cal Weldon  Canada
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Ever think of building a Cornu Spiral horn? Now you can!
Quote:
Originally Posted by xrk971 View Post
What are the LG's?
Short of pulling them out this seems to be the only pic I have of them. They were originally used as tweeters in the 'Toolbox' as it is similar to a FAST system.

Don't let my wife see this pic or I'm in trouble. I tell her I always cover the table.
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Old 8th January 2013, 11:45 PM   #359
xrk971 is offline xrk971  United States
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Ever think of building a Cornu Spiral horn? Now you can!
Cal,
Is it those little silver ones? I didn't even know LG makes speakers. I mean I guess no reason why not they are huge like Sony. Has your BIL started yet?
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Old 9th January 2013, 01:28 AM   #360
Cal Weldon is offline Cal Weldon  Canada
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Ever think of building a Cornu Spiral horn? Now you can!
Yes they are the white coloured ones. I have been listening for the last two hours and I am still in disbelief.

BIL has not been sent anything until I am happy.

Cheers
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