an alliterative to hdf high density fiber board

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well i was thinking of using 2 layers of 1/2 inch mdf with a piece of 1/4 inch plate steel glued together with epoxy i have a design that allows for a ported speaker to act as if it was a much larger sealed enclosure involving polystyrene the pink foam board and polystyrene foam the yellow stuff used in furniture my issue is i am planing on housing something along the lines of 2 12 inch cerwin vegas pumping a sum min total of 500 watts in a cabinet no bigger then 7.5 cubic feet and and the main enclosure would be be between 5 and 6 cubic feet exactly how to get such a cabinet design to work is another thread but i need this speaker to be small easy 2 man carry and able to large outdoor venues the pressure wwill be very high it was boarder line for a pair of radio shack 15 inch speakers using 3/4 mdf but they held so i need to know if i can do something to stiffen mdf instead of using hdf and i am not wanting to do die-cast aluminum i want to make this in a basement shop so if i have to use hdf or double 3/4 mdf that is cool
 
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Carry and outdoor? Now you are speaking birch plywood. 18mm braced or 9mm ply-Stiff closed foam-9mm ply lamination. I do not believe in the musical qualities that Ply is supposed to have over MDF. But as far as ruggedness, high strength to weight ratio, resistance to whetness, abrasion, shock impacts and so on Ply is so much better than MDF/HDF/chipboard. The inner layer is quite protected so for cost reasons the 9mm plywood could be replaced with 6mm high density board.

A 200 liter box with 2x19mm MDF will be terrible to carry, and while doubling the thickness is improving the performance a much more weight efficient way is to use crossbraces of hardwood inside a 1x19mm box
 
if weight was not an issue i would use something called paper stone its more or less super high density fiberboard and has a stone like hardness to it but sound quality comes first on this the cabinet size i am talking about is what i will have to go with as i already have the rough plans laid out just need to fine tune them to an exact speaker driver if i have use HDF or more then 1 inch mdf this is gonna be problem to move http://www.pakwheels.com/forums/att...and-new-2-dvc-sub-woofers-sale-p4300543_2.jpg

we are expecting some weight the application are 2 fold block parties as a side job and main focus promoting local rappers at private events so we want to move the gear in plug and play and move out 2-3 hours later and cover up to 5 acres and 1000 people at some point right now block parties we need to hit it out of the park at a few block parties so we can get some rep for our independent film company witch and we do do referrals for recording contracts hoping to have our own label at some point
 
well wheels and and a ramp its doable but still not easy its for a 2 fold application block parties were we need to hit out of the park for easy publicity the other main use would be large outdoor venues to help publicize local rappers we have a small independent film company trying to get off the ground we do music videos and have recording referrals we need to get the gear in plug and play and move out 2-3 hours later i have seen a local carnaval were the sound man brings in 212 cubic speakers and 2 10 cubic footers then a dozen mics and bundle of cables about as thick as a fire hose i am not wanting to do that we need a 2 channel amp 2 speakers one mic and a 12 band EQ and a 6 channel mixer
 
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There is a reason that almost all real P.A. cabinets are made of birch ply. It's what works best for the use. It's nice to experiment, just take into consideration that a LOT of people have been down the road before you. They still use plywood. DrBoar has told use why. Just something to keep in mind while you make plans.

Please also remember, punctuation help legibility. ;)
 
Hi,

The cheapest building ply gives the best stiffness and strength
to weight ratio, used in thicker but lighter sections than birch.

rgds, sreten.

Forget 1/4" steel plate for anything portable and never use
it as the centre section of a sandwich, that is totally wrong.

Ply/Foamboard/Ply is a good option.
 
Try 3/4" marine plywood. If that's not stiff enough, coat it with epoxy, or even better laminate several thinner sheets together with epoxy.

For added strength, use interior bracing. Wood will work, but steel billet will work better. For example, cut three lengths of steel billet, one for each axis. Once they're checked for fit and location, mark the location inside the box and drill bolt holes. Tap the ends of each billet for bolts, then reinstall and bolt them in. Use Loctite to keep the bolts from coming loose. As a final step, weld the billets together where they meet in the middle. When it cools, coat liberally with a dense, sound-deadening material and maybe some batting.
 
If weight is not an issue. Build forms and pour some concrete. but if you care about weight then the BEST material is birth plywood. The key is using the best joints. The simplest good joints use a 3/4" square hardwood batten in the corners with glue and screws connecting it to the plywood. The best glue is epoxy or "gorilla glue" but the latter makes a mess.

I did an experiment once. I made up a bunch of different wood joints and then smashed them up with a sledge hammer. Maybe not a 100% scientific test but it was instructive. Finger joints turned out to be best and did not fail on the actual joint bit just adjacent to it along the besses of the fingers. Then I added a 3/4" batten glued in and also held with many 1-1/4 counter sunk screws. These were hard to destroy with the hammer.

Your results may be different but I suggest testing some of the construction techniques you can use.
 
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