destroying enclosure

Have any of you guys ever have an enclosure break just from the sub(s)? I'm talking about a box made out of 3/4" MDF.

SPL comp cars, maybe.

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I have seen 3/4" MDF crack around screw holes and baffle area around the driver. Have never seen a box break from the shear force of the driver. Bad design, poor construction or lack of proper support would most likely be the cause.

audiocableguy wrote:

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Bad design, poor construction or lack of proper support would most likely be the cause

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I missed a critical joint in a box I built for a JL 13w6 with a deck screw - the shelf in question was only held in with dried fiberglass and a bit of Liquid Nail - the deck screw sort of screwed through the first piece of MDF and just missed the second at this sort of awkward, splintered out angle.  I missed the mistake when I was fiberglassing the box.

So for a day - it was the best sounding box I had ever built for the sub.

Two days after I built the box the thing exploded during a rendition of Eazy-E's Real G's- and took my 13w6's voice coils' with it.

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"I'm finished!" - Daniel Plainview

Sounds like an expensive afternoon! Your box or customers?

A few ideas:

15" or larger drivers get 1" baffle. Any panel larger than 12" square gets braced. Titebond glue, fine thread drywall (1.5" for countersunk and 1.75" non-counter) and T-nuts for driver mounting. Predrill all holes and hand tighten screws. Silicon joints. Bracing is same material as box.

Sorry Sedate, I was just thinking out loud about box builing and didn't mean to imply you need any tips! "A few ideas" part was just throwing it out there! Fiberglass is a whole other ballgame.

audiocableguy wrote:

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Sorry Sedate, I was just thinking out loud about box builing and didn't mean to imply you need any tips

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Naww - I mean - it was a *real* noob mistake - and as you observe, easily among the most expensive I've ever made. 

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"I'm finished!" - Daniel Plainview

I've had an enclosure I built for a friend with two Type R's come apart at one seam.

It was only because the glue we used was heavy duty liquid nails. I told my friend liquid nails is a horrible adhesive for wood and that normal wood glue is a lot stronger. But he refused my suggestion. After we finished the box and after all the liquid crap had dried I backed out all of the screws.

Then a week later the back bottom seam broke open. I could pull apart the panels with my hands. The liquid nails just failed and didn't even take any MDF with it. All liquid nails does is just "stick" the wood together. I use Titebond Original and Titebind II. Both have never failed on me even after backing out all screws

We had an Obcon pre-fab enclosure designed for the Ford F150  with dual Planet Audio 10's blow apart on a customer.  It was the only time I've ever seen that happen.

Gorilla Glue. NEVER have I seen a single seam blow apart, and I don't even use screws to hold it during cure time. Clamps, and you're done. Of course, this construction method mandates perfect cuts, so proper measurements and careful setup and use of your TABLE SAW (i.e. NOT a Skil-Saw... FAR too inaccurate) are of utmost importance.

I have actually had to DESTROY enclosures I have built this way to remove them from the vehicle in which they were installed, and the MDF gave way LONG before the joint did. Every home enclosure I have ever built is nothing but Gorilla Glue. I hate filling and sanding screw holes.

Gorilla Glue. 'Nuff said...

:::::EDIT:::::

Now what I think about it, I remember a STONE enclosure I built for a woofer... Yes, STONE! I bought floor covering, cut the pieces to the required sizes, (I used my table saw with a dry abrasive blade) laminated pieces of it for the sides, and I built an enclosure of stone for a 10" woofer once. (I want to say it was a Titanic 10 - the first version, and the thing weighed, like, 75 pounds when I was done! WHATEVER it weighed, it was pretty damn heavy for a 12 inch cube!) As far as I know, it's still running to this day, and THAT was all Gorilla Glue, as well. Yes, that stuff is THAT bad-azz!

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

An improperly built enclosure, sure.  A properly built enclosure, I have never seen one come apart.  re; Gorilla Glue.  They have a new wood glue formula that doesn't expand like their standard glues and is much easier to use for enclosures.

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heh heamph:

What kind/brand of table saws would you recommend?  What would I expect to pay for a quality box-building piece?

Anyone know any good links for cutting perfect circle cut-outs?

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"I'm finished!" - Daniel Plainview

re: cutting circles.  All you need is a good plunge router and a Jasper Jig or two.

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Hitachi, Delta, Black and Decker, Sears/Craftsman... ALL build a decent table saw, but avoid Jet, or pretty much anything you might trip across at Harbor Freight.

I'd expect to pay around 400 to 500 dollars for a respectable one. The first thing I look to, when searching for a usable table saw is the TABLE. Thin, flimsy cast aluminum is to be avoided. Cast iron, and as thick as you can carry... In addition to being FAR more durable, all that weight on top makes the whole thing more stable. Be sure the table is big enough, OR make sure that you can get table extensions. Nothing more annoying than having to have three people's hands to cut a 4x8 sheet of MDF.

At least 3/4 HP. I upgraded my motor to a 1.5HP, I like to be able to push it... Not to mention the fact that a bound blade is about as dangerous a situation you can encounter when working on a table saw... Also check the ripfence. Is it SOLID, or does it lock effectively? Does it lock at both ends? (That's a big one for me.) Are the graduations permanent? What I mean by that is this: Make sure the graduations are not on a tape, slid into a slot... those move, and your measurements CAN'T be consistent or repeatable. If you want to save a little bit on the saw itself, compromise on the fence, but be sure you can upgrade to a NICE one after the fact. The ripfence on mine was 750 dollars by itself.

DYohn, wasn't aware of the new Gorilla Glue... I'll have to look for some when it's time to buy more again! Thanks for the tip.

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

haemphyst wrote:

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Gorilla Glue. NEVER have I seen a single seam blow apart, and I don't even use screws to hold it during cure time. Clamps, and you're done. Of course, this construction method mandates perfect cuts, so proper measurements and careful setup and use of your TABLE SAW (i.e. NOT a Skil-Saw... FAR too inaccurate) are of utmost importance.

I have actually had to DESTROY enclosures I have built this way to remove them from the vehicle in which they were installed, and the MDF gave way LONG before the joint did. Every home enclosure I have ever built is nothing but Gorilla Glue. I hate filling and sanding screw holes.

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Yeah Gorilla is great I have used it in the last 4 enclosures I have built and will never use anything else now.

haemphyst wrote:

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Also check the ripfence. Is it SOLID, or does it lock effectively? Does it lock at both ends? (That's a big one for me.) Are the graduations permanent? What I mean by that is this: Make sure the graduations are not on a tape, slid into a slot... those move, and your measurements CAN'T be consistent or repeatable. If you want to save a little bit on the saw itself, compromise on the fence, but be sure you can upgrade to a NICE one after the fact. The ripfence on mine was 750 dollars by itself.

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I think the ripfence is the most important part of the saw.  I've tried to build enclosures with cheap fences and cuts are horribly inacurate.  I've found that my pieces didn't come out perfectly square when done.  So far my favorite portable saw was a Dewalt where the fence was solid and moved uniformly on both sides.  Here's the one we use at work now: https://www.amazon.com/JET-708955K-Xacta-Commercial-30-Inch/dp/B0000C6DYI/ref=sr_1_30?ie=UTF8&s=hi&qid=1203141429&sr=8-30

Has anyone ever used 5/8MDF? I built 2 boxes using 5/8" I cut all my pieces on our table saw at work. Everything is nice and quare and fits perfectly. I then used titebond glue which we use to glue our center stringers to the back of our stairs. I also used 1 1/4 long 1/4 wide staples. I then sanded the outside of the box ONLY to get the excessive glue off at the joints.

5/8" MDF is too thin IMO. Unless you brace it well. I'd rather have a stronger enclosure with 3/4" MDF.

5/8" seems cheap

if you are getting 5/8 for free I would just double up all the sides. just take the demensions of the sides and glue them to what you have now.

audioman wrote:

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Has anyone ever used 5/8MDF? I built 2 boxes using 5/8" I cut all my pieces on our table saw at work. Everything is nice and quare and fits perfectly

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aznboi wrote:

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5/8" MDF is too thin IMO. Unless you brace it well. I'd rather have a stronger enclosure with 3/4" MDF.

5/8" seems cheap

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I dunno - I exclusively use 1/2" MDF for all my enclosures/amp racks/trunk floors/everything.  I abhor 3/4 MDF - the stuff is impossibly heavy.  Two or three coats of fiberglass after the thing is all put together produces, I believe, acoustically identical results to any equivalent 3/4" enclosure.

.... unless you miss a critical joint with a deck screw...

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"I'm finished!" - Daniel Plainview

The cost of fiberglass mat/cloth and resin out weighs the cost for a sheet of 3/4" MDF though.

I don't trust mounting my 18 inch sub to 1/2" MDF. 1/2" will flex even with fiberglass and resin if it is not braced well.

I'm not saying your enclosures are weak. But for me part of having a sturdy enclosure is weight.

Actually weight by itself means nothing.

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aznboi wrote:

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The cost of fiberglass mat/cloth and resin out weighs the cost for a sheet of 3/4" MDF though.

I don't trust mounting my 18 inch sub to 1/2" MDF. 1/2" will flex even with fiberglass and resin if it is not braced well.

I'm not saying your enclosures are weak. But for me part of having a sturdy enclosure is weight.

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Hehe - my enclosure are super-duper-strong - unless I miss a critical joint with a deck screw!

Okay - aznboi - come on an 18 is a totally irregular install situation! 

Anywho - I agree - heft is preferable - but the thing has to go into a car! Saving weight has so many beneficial impacts that I willingly spend the extra $40 or so on materials for fiberglass to cut 20 - 40 lbs from a moving vehicle!  I betcha you'd save twice that over a year in increased fuel costs. 

Anyway - for nominal install situations, 1/2 MDF and even a cursory coat of fiberglass resin is, I maintain, quite perferable to 3/4 MDF given all the trade-offs that go into the equation.

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"I'm finished!" - Daniel Plainview

DYohn] wrote:

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Actually weight by itself means nothing.

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Density correct DYohn??

I may try using 1/2" MDF for 10" and 12" enclosures. I still need to learn how to fiberglass...I've done a lot of reading up on fiberglassing but I just never have time to mess around with it...Hopefully this summer I can learn.

Actually using 1/2 inch material would help with my back not breaking trying to lift big enclosures lol.

All I know is that I copied my box off another box thats 5/8" think. That box was used for years and the box never broke except at the joints which werent even square nor joined tightly together. My box is 100% square and the joints fit very tightly together. Use titebond and staples. I think it will be ok. If a box that wasnt made very good made it several years, my box should be fine.

aznboi wrote:

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I still need to learn how to fiberglass...I've done a lot of reading up on fiberglassing but I just never have time to mess around with it...Hopefully this summer I can learn.

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I don't mean anything fancy - no glass mat or special shapes - I think that stuff looks silly anyway and I can't imagine the amount of material I'd go through trying to make somethin that looks nice - I just paint the stuff inside of all my enclosures when I'm done building them - works wonders for sealing joints and MDF absorbs the stuff really well - very pourous, MDF makes an outstanding substrate.  I'll generally use a quart of resin and two tubes of hardner for an enclosure meant for a pair of 12's.  Like I said, I can't imagine the thing is any less acoustically viable than a heavier 3/4 brethern, and at some 50% weight savings!

aznboi wrote:

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Actually using 1/2 inch material would help with my back not breaking trying to lift big enclosures lol.

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Yea that TL you built musta weighed a freakin ton!  It hurt just looking at it.

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"I'm finished!" - Daniel Plainview

Yeah...I would guess that T-line for that one 12 I weighs over 80 lbs unloaded.