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Ever think of building a Cornu Spiral horn? Now you can!
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Old 7th December 2017, 01:01 PM   #2321
xrk971 is offline xrk971  United States
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Ever think of building a Cornu Spiral horn? Now you can!
Dr Why,
OMG - That’s a monster! Truly awesome size. You must have a very understanding significant other. Good luck in the build and looking forward to seeing the most massive Cornus ever. That’s 36 square feet of baffle in case anyone is wondering. Where do you even find 1.8mx1.8mx25mm plywood?
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Old 7th December 2017, 05:21 PM   #2322
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Hi
@xrk971

It's not Plywood - the Plates are of 25mm Chipboard (in Germany we say "Mitteldichte Faser" or MDF) and is made of very fine Wood Flour. Sorry, i don't know the American Name for it...
Each Plate is 73 kg weight.

The Four Horn Contour(s) are of 10 mm bendable Plywood, glued and pressed between the 25mm MDF Plates with 8 threaded Rods 8mm and 4 threaded Rods 16mm (see pic below driver with 8 Rods 8mm).

Greetings
DW
Attached Images
File Type: jpg Gewindestangen M8 Ansicht von unten.jpg (94.4 KB, 158 views)
File Type: jpg Gewindestangen M8 Treiberseite.jpg (71.5 KB, 157 views)
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Old 7th December 2017, 06:05 PM   #2323
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Ever think of building a Cornu Spiral horn? Now you can!
MDF is medium density fiberboard and chipboard is actually chips of wood pressed together (less smooth) but stronger in my opinion from toughness standpoint. Even in MDF, 6ft x 6ft is hard to find as 5ft x 5ft or 4ft x 8ft are the standard sizes. Can't wait to see this thing built. Your 5.8m length horn should be good for 16Hz corner frequency. Organ music anyone?
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Old 7th December 2017, 06:30 PM   #2324
Doctor Why is offline Doctor Why  Germany
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Hi,

Yes, "medium density fiberboard" was the Name...

The only available Wood in this Size 6" is MDF and normal Fiberboard. The whole sheet of MDF is 2.80 x 2.05 Meter. I paid 322 Euro for all (Boards, cutting and delivering to my home).

Only for Interest:
Horn Lengh : 2x 4.8 m plus 2x 5.40m
Horn Throat Area: 300 cm² (Driver Diaphragm Area 370 cm²)
Horn Mouth Area 4x 1.80m x 0.3 m = 2,16 m² plus at least one Mirror Area (Wall) = 4.32m²

Sorry for all the metric Units...

My Goal is 32 Hz full Power (-3dB) for "normal" Music listening - no Home cinema or PA use.

Below a Pic of the drying bendable Plywood (bended wet) :
Left the short ones (4.80m) and right the longer (5.40m)

D.W.
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Old 7th December 2017, 07:02 PM   #2325
xrk971 is offline xrk971  United States
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Ever think of building a Cornu Spiral horn? Now you can!
Dr Why,
You mention that there are two drivers in push pull. So is there a driver on each face and the one on the back has front facing in. Will this be mounted on a wall or open space? If on wall, how does the back mounted one work?
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Old 7th December 2017, 07:31 PM   #2326
Doctor Why is offline Doctor Why  Germany
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Hi,

both Driveres were mounted only on the Front Plate in PP-Assembly and the Horn itself will be mouted at one Wall (very solid Brick Wall over 45 cm thick)

Below a pic of the planned final Mounting (both Driver):

D.W.
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Old 7th December 2017, 09:32 PM   #2327
xrk971 is offline xrk971  United States
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Ever think of building a Cornu Spiral horn? Now you can!
Oh, an isobaric arrangement. This is usually used to reduce the minimum chamber volume to allow a deeper bass extension in a sealed box. I’m not quite sure if you are buying anything with it in a BLH arrangement. Certainly I can simulate this in Akabak. Let me give it a shot and see what the influence of the isobaric vs a single driver is.

So for simplicity I will assume you are following a 2.5x scaled up plan of the Cornu to get 180cm x 180cm and use 30cm deep channels.
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Old 8th December 2017, 10:21 AM   #2328
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Hi,

Yes, you're 100% right - i scaled it up 2.5x and clipped it at 1.8 Meter due to Door Limitations. So the Horn contour is slightly different from the original Cornu.
Also i make the Snail in a smmoth, round Shape without edges like the original Cornu, because the bendable Plywood allows only 150 mm bending Radii (250mm when bended dry).

A Akabak Simulation with two Drivers sound interesting - for me, too. Thanks a lot.

D.W.
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Old 11th December 2017, 12:34 PM   #2329
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Just got the 8 wood Spacers (10x10x30 cm) and a new Drill 20mm x 400 mm for spearing the Spacers for the M16 threaded Bolts.

For Size comparison:
Attached Images
File Type: jpg Abstandsklotz.jpg (52.6 KB, 77 views)
File Type: jpg Bohrer 20mm Größenvergleich.jpg (52.1 KB, 32 views)
File Type: jpg Einschlagmutter M16.jpg (76.1 KB, 23 views)
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Old 11th December 2017, 01:35 PM   #2330
Doctor Why is offline Doctor Why  Germany
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Hi,

just drilled one distance Block for a short Test. Needs 30 minutes each for drilling.

Should look like this:
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File Type: jpg Distanzholz Paßtest.jpg (56.8 KB, 32 views)
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