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Old 14th August 2004, 09:48 PM   #1
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Default Clear PA Enclosures

Hey all,

I am new to this forum, seems like a lot of good exchanges from my search, glad to have found it.

I am planning to build some enclosures for a friend of mine who DJs. The theme is see-through.

I was considering plexiglass, clear acrylic sheets. Any idea how thick it should be for the proper stiffness? Anyone know of this being tried and how it worked out? Does plastic stand up to the rigors of gigging?

Because the idea is to just see the driver inside the box, i am struggling with design issues of a substitution for internal bracing and the lack of damping material inside the enclosures. Any ideas?

thanks

Dan
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Old 15th August 2004, 12:00 PM   #2
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Acrylic may be too brittle, especially for PA stuff that gets knocked around. Not sure about PET or its relatives (used for fizzy-drink bottles), it could be good. Polycarbonate would probably be the best due to its immense impact strength (used in bullet-proofing applications), though it's still just a plastic and can be scratched. Of all readily available plastics polypropylene is one of the best for absorbing vibrations, but it's not transparent (it's a creamy yellow), and don't even think about it. PP is only good for melting and moulding into shapes, once you start cutting or drilling it, it'll be such a gooey mess and such lot of effort that you'll wish you were never born!

The best thing would probably be to find a plastics merchant who has his/her own proper cutting tools, and get them to cut the plastic for you.

Glueing is another question, maybe the pieces should be bolted together and silicone be used to make everything airtight.

You shouldn't need to go much above 10mm or 12mm (11/24"), and remember that what looks good are good design practices. If it needs lots of bracing, then add lots of bracing. If it needs pillow stuffing, then add that too. Someone could argue that sports cars look ugly because of their aerodynamic design. People should be able to see why the speaker sounds good, not why it sounds bad.
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Old 15th August 2004, 12:16 PM   #3
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You will need at least 12.5mm ( 1/2 inch) thick material to be strong enough, and it will need plenty of bracing. It will cost lots of money, and be very heavy.

You will also need to be very careful when moving them around, as the plastic will scratch easily and start to look tatty very quickly.

However, if this was for a permanant install, where the above factors are not important, they could look quite cool.
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Old 15th August 2004, 12:37 PM   #4
dnsey is offline dnsey  United Kingdom
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How about compromising a bit, and making the cabs out of MDF or whatever, with plasic windows in the walls? If these were inset, they'd be better protected from scratching (you could even make clip-in 'shutters' for transport), and the whole thing would be easier to make, and a lot lighter too.
You could also incorporate concealed coloured lighting in the cabs (like some people use now on computer cases), which might look quite cool!
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Old 15th August 2004, 04:00 PM   #5
Bull is offline Bull  United Kingdom
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These dj monitors by VOID ACOUSTICS are made of plexiglass i think?
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Old 15th August 2004, 04:34 PM   #6
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Bull, beat me to it.

The drivers are P.Audio BM-12CX38 and a crossover that makes them +- 2dB is available from www.proaudioparts.co.uk . Look under http://www.proaudioparts.co.uk/page19.htm . They are said to be very loud by Rog Mogale (the designer) and almost indestructible (ie survive kamikaze DJs) becasue of the 3" vc compression driver (1.5" exit). Search Ro'g forum (www.speakerplans.com)
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Old 15th August 2004, 06:43 PM   #7
Greg B is offline Greg B  United States
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Quote:
I am planning to build some enclosures for a friend of mine who DJs. The theme is see-through.
Cool.

Quote:
I was considering plexiglass, clear acrylic sheets. Any idea how thick it should be for the proper stiffness? Anyone know of this being tried and how it worked out?
It depends on the dimensions of your cabinets, but essentially, as thick as you can afford. You may want to look up some basic engineering info, and calculate it so that it's about equal to 3/4" birch ply.

Quote:
Does plastic stand up to the rigors of gigging?
I would recommend polycarbonate, since it is tougher and less resonant. I built a front horn from it once. Acrylic is more expensive, and easily cracked. OTOH, polycarbonate (lexan) is more flexible. Either could be made to work.


Quote:
Because the idea is to just see the driver inside the box, i am struggling with design issues of a substitution for internal bracing and the lack of damping material inside the enclosures. Any ideas?
First of all, if it were me, I would curve the sidewalls to maximize stiffness and minimize cost and weight. Polycarbonate will bend cold, acrylic will need heat.

Damping material? Yeah, what's the point if you have to fill it with fiberglass.... Bubble wrap would work OK. How about getting some mesh colanders to make balls, stuff them full of fiberglass or polyfill, and hang them inside the boxes? Could look kool.

GB
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Old 15th August 2004, 11:01 PM   #8
urapnes is offline urapnes  United States
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Ive used plexiglass for car stereo installs. If you are goignt o try and make some bass you need to use 1" or THICKER material.

Polycarbonate is no good as you cant polish the edges.

good luck
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Old 15th August 2004, 11:08 PM   #9
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~ $20 per square foot in 1/2", yes?
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Old 16th August 2004, 12:21 AM   #10
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Lightbulb Glass?

What about glass?

Surley there'll be some sort of glazing company who will cut glass pannels for you? Glass is hard (more scratch resistant than most/all plastics) and ridged (little bracing needed). On the other hand it is also very brittle (so may not be so great for moving about unless you are very carefull) and not a very good absorber of sound either I'd immagin.
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