John Curl's Blowtorch preamplifier part II - Page 2837 - diyAudio
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Old 23rd October 2012, 01:06 AM   #28361
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Quote:
Originally Posted by john curl View Post
concrete?
Yes. First of all, forms are needed. Quite robust, but assemble-able/disassemble-able. Concrete has to be made with gravel of random sizes, thickness of walls should be uneven, walls should not be flat, otherwise it will ring like a bell. Then there should be openings for speakers.
It is doable, but can you estimate market demand, so it will cover costs of such forms? I did experiment for myself, so my forms I made from epoxy, and they were quite ugly.
That's why the second experiment I did the opposite way: a first made nice looking boxes from pergo and epoxy, then molded uneven walls inside. The composite that I used was sticking better to my gloves than to the pergo surface. It was not concrete though, because adhesion of concrete to internal walls would be bad... And it shrinks...
I think if to make wooden enclosures, screw many screws in walls inside, hang iron wire between them, then mold concrete inside, it may be doable. But anyway flexibility of forms that concrete allows would be lost. So, disassemble-able forms would be the best way to go.

Costs?
All depends on your appetites. And on your budget. We can think together, what would you like to have...
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Old 23rd October 2012, 01:13 AM   #28362
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Originally Posted by Esperado View Post
Mine is much shorter, unfortunately. The next time if I decide to modify it I will definitely build something similar to your picture. And openings will be under the front wall. I re-used the hole in the floor that left from stairs that used to lead to workshop from living room: WAF, so construction is sub-optimal.
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Old 23rd October 2012, 01:15 AM   #28363
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Originally Posted by RNMarsh View Post
so we are back to the fun, easy sport of bashing the ignorant --- once again. Zzzzzz.
If you call me ignorant, with my concrete speakers, please prepare to eat your felt hat!
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Old 23rd October 2012, 02:09 AM   #28364
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Quote:
Originally Posted by morinix View Post
John just wondering if you have ever listened to JBL Project Array 1400's?
How long that 1930'th horse will be beaten to death?

Click the image to open in full size.
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Old 23rd October 2012, 03:09 AM   #28365
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Originally Posted by Wavebourn View Post
If you call me ignorant, with my concrete speakers, please prepare to eat your felt hat!
was not referring to you or about speakers.
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Old 23rd October 2012, 03:14 AM   #28366
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Has anyone heard the C.Vega folded horn speakers advertised here. I have only seen them in show room... not hooked up.... CVega has good reputation for low distortion bass.
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Old 23rd October 2012, 03:15 AM   #28367
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Quote:
Originally Posted by Wavebourn View Post
How long that 1930'th horse will be beaten to death?

Click the image to open in full size.
Greg Timbers likes horns.
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Old 23rd October 2012, 04:51 AM   #28368
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Originally Posted by Esperado View Post
Can-we imagine a foam with open cells applied over the entire membrane surface, with linear restoring forces, which would also make the compression adiabatic?
Fibreglass insulation comes very close to what you want. Use the finest stuff available. It will be white and not feel nasty at all.

I'll abstain from the other speaker/horn/carpentry discussions.
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Old 23rd October 2012, 09:40 AM   #28369
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Originally Posted by kgrlee View Post
Fibreglass insulation comes very close to what you want. Use the finest stuff available. It will be white and not feel nasty at all.
Fibers does-not break ? (with the obvious non linearity ?)
Compression/expansion movement of it does not produce noise ?
Frictional forces do not outweigh the restoring forces ?
I use to damp the back chambers of my drivers with fiberglass, but never tried-it in contact with the membrane.
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Originally Posted by kgrlee View Post
I'll abstain from the other speaker/horn/carpentry discussions.
You're right. Robert Oppenheimer and I designed an almost perfect bomb, using a certain amount of an exotic metal. In fact, two pieces of this metal, using a displacement curve i tuned with my friend Euclide de Samos, few years before.

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Old 23rd October 2012, 10:46 AM   #28370
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TIP about fiberglass or other damping materials.

Instead of gluing the foils of damping material on the walls of the enclosure, I glue them in the middle (center) of each dimension, separating the volume in 8.
It will operate where the speed displacement of the air is maximum. The standing waves will across the damping material twice. So, it will increase the damping. And you can use less damping volume material, means more freedom... More "live" sound, less dull.
While i let a whole in the center of the horizontal and vertical foils parallel to the displacement axis of the membrane, i glue the foil "waterproof" between the loudspeaker and the back of the enclosure. This foil act like a damping wall during big transients low displacements of the membrane, and you can see the foil moving with kick drums. It gives more 'Speed" and more dump to your bass sound.
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Last edited by Esperado; 23rd October 2012 at 10:52 AM.
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