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hisgoofyness

Subwoofer Enclosure - Question about Lexan

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hisgoofyness

Hi All

It's obviously been a while since my last logon as my old stereo thread seems to have went by the wayside...

I am approaching completion of my install on our new 2012 LSV 23 and hit a stumbling spot.

After conversing with a couple of indusrty professionals a couple of months back, I decided to take on the task of building my own subwoofer enclosure. I have built several sealed enclosures over the years for various cars using solely 3/4" MDF for fabrication. This time I ventured way outside of my comfort zone!

Here is where I am:

I am building the majority of my enclosure with 13 ply Balctic Birch (5 of 6 panels). The subwoofer is to be installed in the bottom panel to down fire and I then I am porting out the side. I have assembled the first five panels using Titebond III & crown staples, cut out the subwoofer hole as well as the port hole, and coated the entire thing with fiberglass resin.

Now for where I am stuck. I bought a piece of 1/2" Lexan (polycarbonate) which I intend to use as the front panel. My problem is this, how should I attach it? I do not want to use a two part epoxy which most likely amber the edges.

Could I get away with using a bead of silicone toward the inside edge and maybe a thin strip of weatherstripping around the outer edge and then screw it down?

Any advice any of you can offer would be most appreciated!

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Earmark Marine

Here is the way we do it. Mix Bondo 50/50 with the fiberglass resin (including catalysts) and apply it to the porous edge surface you will be screwing into. Sand the edge smooth being careful to not roundover the narrow surface. Use a silicon bead just to the interior and exterior of the hole pattern. Not too much on the inside. You don't want it to squeeze out and show to the interior. Work fast because silicon begins to cure right away. I'm not as comfortable with a closed cell foam gasket because of the four seams but I'm sure you can make it tight enough. Pre-drill the polycarbonate with 5/32 to 11/64" pass-thru holes so the #8 S.S. flathead phillips drive screws don't thread into the polycarbonate causing it to fracture. Add the countersink. Then pre-drill the enclosure with 1/8" pilot holes. Make your window in the facade slightly smaller than enclosure interior to hide the perimeter mounting.

David

Edited by Earmark Marine

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old skool malibu

Just picked up a piece of plexi from a local shop. I will be running a bead of silicone on the inside and using screws every 2-3 inches. The guy at the shop cautioned me not to tighten them to much or spider cracks will apprear. He also drilled the holes out slightly bigger than the screws to allow for expansion around the screws (dont worry I will still maintain a good seal with the silicone gasket and silicone in the screw holes). As the kickpannel will hide the edges of the plexi pannel I am not concerned about the appearnce. Some guys will frost or smoke the edge if you cannot hide it.

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old skool malibu

I noticed you said Lexan. When I called my local shop he suggested Plexi and Lexan is designed to bend without cracking. He was his opinion that plexi was the better material to go with.

Edited by old skool malibu

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martinarcher

Lexan is a polycarbonate and is darn near bulletproof....plexi well it's plexi and it is brittle, fragile, and as I learned the hard way growing up, a poor building material compared to lexan.

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hisgoofyness

David - I had already coated the edges which I will be screwing to with fiberglass resin. Do you think I should do another coat with the added Bondo? The fiberglass resin I used is the 3M Bondo polyester resin.

If you do not recommend the weatherstripping on the face of the enclosure, do you not recommend it on port holes or subwoofer holes either? I bought the thin weatherstripping that appears to be ribbed on one side, 1/8" thick maybe? I had intended to put it around my sub (Wet Sounds WS-12) and port (Precision Port / 3" flared on both ends). I guess I could use silicone around the port, but did not want silicone anywhere around the actual sub.

Old Skool - I have always been told Lexan was a better material for speaker enclosures, but the price normally pushes people toward plex. I would love to a side by side comparison of equal enclosures and equal subs to see if there is any noticeable difference between the two...

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Soon2BV

i would not use plexi. it is hard, brittle, will shatter and crack.

lexan / polycarbonate is bulletproof. you can drill it, glue itm nail it, pound it with a hammer. it is "nearly" impossible to make it crack or shatter.

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old skool malibu

I was going to get Lexan, it was more but not that much more. I went with the guys recommendation and he said most local stereo shops use it. Seems ok to me but time will tell.

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Earmark Marine

I like a thick mixture to fill a porous edge but if it is already smooth with the existing coating then consider it done.

Usually the thin foam gasket on the backside of the woofer or terminal cup is more than adequate to seal the woofer against a smooth surface. We only add a silicon gasket to the woofer or terminal cup when coating the enclosure with a really rough and inconsistent bedliner coating.

David

David - I had already coated the edges which I will be screwing to with fiberglass resin. Do you think I should do another coat with the added Bondo? The fiberglass resin I used is the 3M Bondo polyester resin.

If you do not recommend the weatherstripping on the face of the enclosure, do you not recommend it on port holes or subwoofer holes either? I bought the thin weatherstripping that appears to be ribbed on one side, 1/8" thick maybe? I had intended to put it around my sub (Wet Sounds WS-12) and port (Precision Port / 3" flared on both ends). I guess I could use silicone around the port, but did not want silicone anywhere around the actual sub.

Old Skool - I have always been told Lexan was a better material for speaker enclosures, but the price normally pushes people toward plex. I would love to a side by side comparison of equal enclosures and equal subs to see if there is any noticeable difference between the two...

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hollifield55

All of these ideas are inferior to the awesome factory install of my 2011 vlx's sub. As you can see the woofer is completely sealed against the already carpeted enclosure, the lack of any terminals acts as a perfect aero port, and the two screws holding the front panel on ensure an even seal.

subfront1.jpg

subrear.jpg

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