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Discussion Starter · #1 ·
Opinion needed

Building sealed enclosures (approx 6cf net) for a pair of LMS5400's. Can't decide. I'm either laminating two sheets of 1/2" birch ply together (for a 1" net) and adding an extra brace or........ using two sheets of 3/4" (for a 1.5" net). Previous enclosures were 1.5" on each side but...MDF. Either would probably work fine but obviously the 1/2" sheets will be a little less $ and lighter. Any thoughts?


Allan
 

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Properly braced a single layer of 1/2" is all you need. Very few commercial designs are properly braced, as the labor cost for installing bracing exceeds the cost of using heavier materials instead. Well braced 1/2" is as stiff as 1-1/2" poorly braced, but uses half the material and is half the weight.
 

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Quote:
Originally Posted by bill fitzmaurice /forum/post/19601714


properly braced a single layer of 1/2" is all you need. Very few commercial designs are properly braced, as the labor cost for installing bracing exceeds the cost of using heavier materials instead. Well braced 1/2" is as stiff as 1-1/2" poorly braced, but uses half the material and is half the weight.

+1
 

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I'm not sure, if this were your typical 300-500w diy build I'd say ok to 1/2".

I think 3/4" baltic birch is a good way to go, double faced as mentioned in post #2.

I don't think you'll need to fiberglass/resin the baltic stuff.
 

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Bill have you lifted a 18" LMS 5400 ?

This is not your normal light weight driver at 80 lbs...


I would suggest 3/4..... heavily braced is one thing, but double 1/2" for a mounting surface is not what I would suggest for this driver..... 3/4 minimum....


IMO I would go 3/4" all the way around and double on the front baffle + braces...
 

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Quote:
Originally Posted by Warpdrv /forum/post/19604019


Bill have you lifted a 18" LMS 5400 ?

Doubt that...

Quote:
Originally Posted by Warpdrv /forum/post/19604019


This is not your normal light weight driver at 80 lbs...

Yep, and the cones have enough inertia to cause a 160+ pound box to walk under large low frequency excursions. Bass I love you anyone?


In case you don't believe me, there is a video on Youtube with a 250+ pound box being rocked.



http://www.youtube.com/watch?v=3b-UkRvXvSc



While 1/2" is technically fine for a folded horn, where there are very small spaces between folds, in no way would it be suitable for a full range or subwoofer cabinet of decent volume, unless you had a brace every 4" on center.


An 80 pound driver hanging off a large baffle will cause the baffle to sag or 'bend' over time if it's not sufficiently strong enough.
 

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As I mentioned before I think 3/4" with a double baffle of a good solid wood ( like Baltic Birch ) , braced would be fine.. I was just trying to keep it simple by using the same size wood everywhere.. Ive sdone many low tuned car enclosures with multiple 70+ pound subs and have never had issues with 3/4 BB braced with 1/2 dowels and fiberglass/resin on all the corners..



If weight is no option and you have enough $$/wood just double it for 1 1/2" walls with a triple baffle .. IMO thats extreme overkill along with bracing tho
 

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Quote:
Originally Posted by mj79
Oh and Im sure you already know this , but dont use drywall screws.. Use T nuts / barbed inserts and Socket screws

http://www.fastener-express.com/14-2...loy-qty10.aspx
Quote:
Originally Posted by mcsoul
My worst ever diy experience involved my misuse of t-nuts. I'm going to use wood screws from now on!
BTW, 2 x 1/2" is not going to be 1" thick.....


With Baltic Birch or plywood just use the screws that come with the driver, you do not need T-Nuts.... just pre-drill with the proper drill size for the shank of the screw and thread them in....


I have mounted these drivers a dozen times and the best and easiest and least expensive solution is in my thread on how to drop in these monsters with almost zero hassle..... don't forget the super glue bit on the rubber gaskets...


Use the allens that some with the drivers, unless your using MDF.... !!
 

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Quote:
Originally Posted by mj79
Oh and Im sure you already know this , but dont use drywall screws.. Use T nuts / barbed inserts and Socket screws
I'd use the screws that come with the drive-unit, personally.


As for the cab, I would follow BF's recommendation and stick with .5" BB with a sane-but-not-stupid amount of bracing. Smaller is always better, and lighter is generally speaking better, too.


Only things I'd add to Bill's post are


1) A double-thick baffle isn't a bad idea, if only because they you can recess the driver a bit.


2) with such a heavy driver you'll probably want a small brace going from the bottom of the box for the magnet to rest upon. Well, put some Poster-tak or non-hardening modeling clay between the brace and the driver, but you get the idea.
 

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Discussion Starter · #13 ·
Thanks for the input.


The baffle was never really the issue. It will get an additional layer for flush mounting the driver regardless.


I'm not quite comfortable with .5" all the way around. Too much driver and too much power (MA-5050 per enclosure). The consensus does seem to be that .75" in Birch plywood will be fine as long as it's braced.


Any suggestions on how close to place the braces?


Allan
 

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Quote:
Originally Posted by allanf714 /forum/post/19606449


Thanks for the input.

The baffle was never really the issue. It will get an additional layer for flush mounting the driver regardless.


I'm not quite comfortable with .5" all the way around. Too much driver and too much power (MA-5050 per enclosure). The consensus does seem to be that .75" in Birch plywood will be fine as long as it's braced.


Any suggestions on how close to place the braces?


Allan

well that does nothing for the actual mounting or strength of the driver.. its cosmetic




Opinions are opinions.. I use the t nuts and bolts because IMO it looks better and cleaner, and maybe takes an extra 10 minutes.. I never said you HAVE to use tnuts, use double 3/4, OR resin/glass.. Its just what Ive used in the past and have had zero flex in builds from 1 cf sealed enclosures to 30cf walls ..


If were just giving opinions for no flex, then use 1/2" threaded rod


It all depends on the look your trying to go for
 

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I have a single LMS in a 3/4" MDF box well braced and the sub treats the box like a toy. I had a Mal-X in there prior and the box was sturdy but the LMS makes it seam like it's made of balsa wood.


I would do a minimum of 3/4" BB well braced for this monster. I even considered going dual opposed like Warp after having the LMS in my test enclosure which moves the 70 pound box.


I don't think it's a coincidence that the best commercial subs like the JL Audio's, Wilson, Seaton, SVS and the like put time and R&D to build rigid enclosures, it makes a difference.
 

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Discussion Starter · #18 ·

Quote:
Originally Posted by mj79 /forum/post/19606490


well that does nothing for the actual mounting or strength of the driver.. its cosmetic

I guess I'll add a third layer to the baffle. One for the flush.... mounting the driver onto 1.5' of plywood.


I've mounted these drivers a couple of times using the supplied allen screws. Works fine.


Any suggestions on how close to place the braces to one another? I was thinking 6" on center.


Allan
 

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Quote:
Originally Posted by allanf714 /forum/post/19606606


I guess I'll add a third layer to the baffle. One for the flush.... mounting the driver onto 1.5' of plywood.


I've mounted these drivers a couple of times using the supplied allen screws. Works fine.


Any suggestions on how close to place the braces to one another? I was thinking 6" on center.


Allan


None of the boxes I made used 1.5" for the driver mounting... they were all 3/4" and one for flush mounting, but it certainly can't hurt... On my old boxes I glued a small piece of wood behind where the screw would go for more bite....


For bracing, IMO anything less then 8" spacing is overkill... I did every 7" - 6 would be excellent as well... those boxes were 24" box cubed external.
 

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Quote:
Originally Posted by penngray
I use 1" or 1 1/2" drywall screws all the time so Im going to disagree with the "Dont use" opinion.
and Ive done a install with 4 re XXX 18s with 1 5/8" drywall screws through a double baffle as well.. I just prefer the tnuts/bolts is all I said..
 
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