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View Full Version : How to mount subwoofers on plexiglass?



Eric111e
07-11-2006, 10:08 PM
Im going to be making my subwoofer box soon and i want the front panel to be plexiglass. I will be getting 3/4inch plexiglass. Im running 2 13W7's so i dont know exactly how i would mount the subs up. Will just bolting them to the plexi glass give them enough support? Or would it eventually crack the plexi from being under so much pressure and weight after a long time?

Also im trying to think of a good way to attach the plexi to fiberglass since my whole box is fiberglass. Any ideas?

Just to give you guys a heads up on my box plans. This is going in the back of a Explorer. The box is going to be made out of fiberglass and is going to go across the whole back. Im mounting 2 13W7's with a plexiglass front. Then all the inside sides of the box im going to get mirror plexiglass so you can see 3 different reflections of the subwoofers (back, and both sides)

Then ill make a nice little amp rack infront of the subs on the floor with plexiglass covering them and i will put fans in it to cool them down.

lrgnation
07-11-2006, 10:50 PM
i probably wouldnt mount my subs to plexi glass just because i have never personally seen it done with subs of that size. but it sounds liek an awesome idea. It really depends on how strong the plexi is, i would think it would need to be reinforced.


instead you could make a wood front. cut out a lot of the area and router down some and flush mount the plexi in that. so you will still have enough support. I guess it really depends on how thick the plexi that you want to mount the subs to is.

unrated
07-11-2006, 11:20 PM
its really simple if u do it right, after u cut out the inner circleplace the sub in the proper mounting area, mark the screw holes, take out sub, drill out screw holes(do not screw into plexi it will crack), now u will half to make or get some1 to make a steel backplate, this reinforces the plexi and the screws and drill screw hols in it too, next you mount the sub on the plexi, next u take the steel circle backplate and put it on the inside of the plexi, then u get screw and nuts and washer and crank it up, now your sub and plexi are bullet proof, if you dont put a steel plate behing the plexi, and crank up the system the theres not enough reinforcement on the plexi and it will crack/shatter from the flexing

hope that helps

ravendarat
07-11-2006, 11:28 PM
its really simple if u do it right, after u cut out the inner circleplace the sub in the proper mounting area, mark the screw holes, take out sub, drill out screw holes(do not screw into plexi it will crack), now u will half to make or get some1 to make a steel backplate, this reinforces the plexi and the screws and drill screw hols in it too, next you mount the sub on the plexi, next u take the steel circle backplate and put it on the inside of the plexi, then u get screw and nuts and washer and crank it up, now your sub and plexi are bullet proof, if you dont put a steel plate behing the plexi, and crank up the system the theres not enough reinforcement on the plexi and it will crack/shatter from the flexing

hope that helps

Exactly the way I do it. I do have a question though, with what you are describing to me, why not use MDF to make the box then install your mirrored plexi on the inside. It just seems to me that what you are doing would be better suited to have ridged flat surfaces like wood as opposed to fiberglass which is going to not be flat and make it very hard to attach mirrored plexi to. If your hooked on fiberglass and want to know how to attach plexi, I would make a MDF frame at the top, mabye 2 inches thick or so. Fiberglass to the trim ring then screw the Plexi to the wood ring.

Decipha
07-11-2006, 11:28 PM
ever thought of lexan? its alot stronger and won't flex as much.

you should have a chat with bubbagumper6... I designed him a box with the same idea, a glassed front, and all mirrors in the rear and sides to reflect the subs

amartin_72
07-11-2006, 11:43 PM
I smell bs.

ravendarat
07-11-2006, 11:47 PM
I smell bs.

Why do you say that, its not that big of a job. I have done setups very similar to that, albiet with lesser subs, but still the install its self isnt that complex, except for the use of fiberglass instead of MDF which as I stated before I think is a mistake

AlpineUser
07-12-2006, 12:25 AM
do you have the w7's yet??cause if you dont and you dont know the price of them you will be wasting ur time building the box because they are rediculously expensive

Eric111e
07-12-2006, 07:28 AM
So my best bet would be to use MDF? This is definetly a box i want to do and no this isnt bs. I could get 1inch plexiglass also.

truckstoy
07-12-2006, 07:58 AM
use lexan as stated above, alot stronger than regular plexiglas.

djman37
07-12-2006, 08:03 AM
once again. here's the link to the DIY network HOW-TO.
http://www.diynetwork.com/diy/ab_parts_accessories/article/0,2021,DIY_13690_3607745,00.html

check out what gately audio does.
http://www.gatelyaudio.com/

squeak12
07-12-2006, 09:26 AM
I wouldnt worry so much about how to mount subs to plexiglass, but how to attach mirrored plexiglass to fiberglass.

helotaxi
07-12-2006, 09:54 AM
I wouldnt worry so much about how to mount subs to plexiglass, but how to attach mirrored plexiglass to fiberglass.
No kidding. If the inner surfaces are flat enough to mount mirrors to, they shouldn't be made out of fiberglass. It won't be nearly stiff enough to make a good box.

Lexan is a poor choice. Harder to work and more likely to crack. Also if you scratch it the piece is trash. Lexan is shatter resistant, but it cracks and sctarches rather easily.

Now as far as the original question goes, there are some good things in here but they neglected the most important thing when working plastic that is being used as a structural component. Any drilled holes must be perfectly smooth. All edges must be polished. Any rough spot on the edges or the drilled holes will focus stresses when it flexes (it won't flex much unless it is a very large area, but it will flex some.) and cause it to crack. If you have never worked in plastic, get someone who has to show you some of the tricks to drilling plastic and getting a smooth hole. Two of the keys are a very sharp bit and USE A DRILL PRESS. If the hole is just a little off from perpendicular to the surface, you will crack the plexi when you try to tighten the screws to hold everything together.

ramos
07-12-2006, 12:54 PM
Did I miss the part where you said how large this acrylic panel is gonna be ? 3/4 plexi over a large panel is gonna flex like a mofo unsupported. Which means your gonna have to support it, curve it, or get thicker acrylic. But too mount subs you need to get holes just like helo said . Then bolt the sub in :)

ramos
07-12-2006, 12:59 PM
No kidding. If the inner surfaces are flat enough to mount mirrors to, they shouldn't be made out of fiberglass. It won't be nearly stiff enough to make a good box.



I agree flat surfaces should be made of wood, but for the first time I disagree ( with Mr. helo anyway :p: )on why.
Fiberglass can be reinforced to be made as stiff as wood. But why go to all the trouble and expense to do it ? Wood is so much cheaper, easier , and flat to begin with. Wouldn't make sense to go to all that trouble . :)

Eric111e
07-12-2006, 01:03 PM
If 3/4inch plexiglass isnt going to be enough i could always get thicker like 1inch thick or even put 2 piece together for extra strength.

My main concern is how much the subs weight. The magnet will just be hanging in the air and i am worried that over a long period of time with all the pressure the plexiglass will start getting very tiny cracks then eventually make a noticeable crack.

Forget the fiberglass idea. I am now going to make the box out of MDF, and lets say 1inch thick plexiglass or thicker if it must be. Then plexi mirror on the inside.

Eric111e
07-12-2006, 01:13 PM
Then infront of the box i am going to make a amp rack (i guess you can call it that) out of MDF. Its going to hold my 2 amps (laying parallel) and im going to put fiberglass over the amps and put the fiberglass on hinges so you can open and close it. Then the other side of the amp rack is going to be a "door" but im going to make it so its not as noticable as the amp rack. That side is going to hold my crossovers,distro block, ground block, and all that type of stuff. Then everything is going to wrapped in black suede.

If i can pull this box off i think it would amazingly nice.

helotaxi
07-12-2006, 03:13 PM
Fiberglass can be reinforced to be made as stiff as wood. But why go to all the trouble and expense to do it ? Wood is so much cheaper, easier , and flat to begin with. Wouldn't make sense to go to all that trouble . :)
Kinda what I was getting at. By the time you built up and reinforced the fiberglass, you would have also far surpassed the weight of the wood that it should have been built of in the first place.

To the OP, as long as you don't have any sharp inside corners in the plexi, you would be amazed at how strong it is. If you are really worried about it and you have the ability to work metal, build a frame for the front section out of metal with rings for the subs to mount and inset the plexi and clamp it in. Seal around it with a gasket or silicone. The plexi won't bear any weight and won't have any stressed holes drilled in it. Done right with the W7s, there would be no fasteners showing and it would be strong and stiff as hell.

NeverEnuffBass
07-12-2006, 03:31 PM
If i can pull this box off i think it would amazingly nice.


Yes it would but if not done properly it will sound amazingly bad and expensive. 3/4- 1 inch plexi isn't cheap.

ramos
07-12-2006, 03:39 PM
indeed, that would be QUITE an expensive screw up


Ya d@mn skippy . 3/4" 1" acrylic is ridiculous price wise :)

Eric111e
07-12-2006, 09:07 PM
Do you guys think it would be a better idea to make a port in the middle of to two subs? Then a 1" piece of plexiglass would only have to support one W7.

This is kinda like what i want to make the box look like but with plexiglass as the front panel
http://images4.pictiger.com/thumbs/4f/a8ab2c15f7a58c7e382883d3258cbc4f.th.jpg

Would it be alright to make the Port out of Plexiglass instead of MDF? I dont see why not.

Cam
07-22-2006, 04:20 AM
I'm making a sealed box with a plexi front right now, with an IDMAX... and here's what I've learned/know from my research so far:

1) Plexi is stiffer than MDF by a good multiple, so don't worry about it wobbling.
2) Putting the steel ring around the back of the speaker to sandwich the plastic instead of just bolting through the plastic will be 1000% better.
3) Plexiglas can be had cheap off ebay. I got my 28x18x3/4 front panel for $28
round and flame polish all corners, especially inside corners and holes.
4) I would suggest a rear support for those phat motors to add some structural integrity to the whole assembly and reduce the stress on the glas.