Four 12's in an Enclosure 20L X 36W X 14H?

Hey all, It's the neighborhood jester..........

I currently sit here, scratching my head, drinking a beer, and wondering what the hell my store manager is smoking!!!  Don't worry, it's like 10:45 p.m. so I'm not at work...

However, my store manager came to me today and wanted me to build a sub enclosure....the generic type, you know like the pre-manned ones that MTX, etc sell.... I said cool, what's it gotta hold ( figured I'd just use some general thiele-small factors and build one half a$$ good.... I thought it was gonna be for a couple 12's or something...well something was right!!! 

Now, so you can grasp my full level of confusion on this...these were my max measurements I can use....20"L X 36"W X 14"H (outside...not inside!!!)....

Here's what he wants me to design...a box to hold 4 12's!!!! 

How in the hell can I get 4 12's in an area that size!!!  I've asked some local installers around here, and they all said "What's he smoking!?!?!?!"  they than follow it up and say it can't be done.....I need to have this done by tomorrow at 6:00 p.m. CT...and I go in at 12:00 tommorrow afternoon....(tomorrow being saturday)  Oh yeah, and no fiberglass can be used....only 3/4" MDF! 

Am I the only one scratching my head on this one...I've been thinking about this since I got off at 7....I was told this morning, but thought it was a joke, plus had other installs lined up to do....so no designing went into it earlier...and when I had the time...got ticked, and busted out the beer....but still no ingenius ideas come to me....

I was thinking acoustic coupled, but he doesn't want that...so.....my mental drawing board...Ba-LANK!!!!

Any ideas, besides saying he's on crack!!  ANY!?!?!?! 

GOD I hope these speakers don't need ANY airspace....

But, Isobaric is about the only way you can go at this point.

With the parameters you specified you can still achieve this goal. 

Short of designing it for you, I cannot be much more help, but I would really look into that idea.  Mount the speakers on inner walls so their is "3 sections" the section on the left has one speaker,  middle section has 2 speakers and the third section is identical to the first.  Not sure if that gives you a good visual, but if you are still stuck on this, I may be able to draw something up in autocad and send it to you.

Craig

Thanks craig,

you just reminded me of what I left out........I can't do an isobaric......I suggested that, but he doesnt want the 3db loss...plus, no subs will be in it, he just wants a box he can throw any old 12's in!!!  He's a mother.....you can finish that statement!  I still ain't gotta clue...

hmm.

well in that case, you can go with the old, 2 12's on the top and 2 12's on the front, it will have little clearance since you height is 14 inches, but it should work, just offset the 12's on the top away from the side you put the 12's on.  Or you can put 1 12 on each side of the box, its pretty lame but you would have enough clearance (i think) I did a quick sketch on paper, and seemed to work.  But heck what do I know.......

Maybe you should instruct your boss to take some classes in wood working and accoustics, because even if you get this box to work, It will sound god awful.......

He is probably going to put Pyramid or "Super Pro Blues" in them.  

Don't bother figuring out the cubic feet, because it will just make you shake your head even more , I recommend a 12gauge shotgun to help him think :)

Craig

I agree....no I wish he was gonna put in some pyramids....but he wants it to be universal for MTX, Orion and JBL......hmmmmmmmmm...........what's wrong with that picture...high quality subs, sub quality box....oh yeah, and he figured out the Cubic feet for me....each chamber has to be 1 cubic foot (for one of the boxes..he want's two...he can blow me) and the other box each chamber is to have 1.4 cubic feet.....

Now I aint' installed for a couple years...but, ummm........that seems a lil off the wall.....and a lil big especially for the MTX and JBL...I don't know Orion.....

Nah, I'll chase him down with a 1 farad cap and make him lick the top of it........DO NOT ATTEMPT TO DO THIS!!!  REason.........what do you want on your tombstone??

Ok all, here we go...if you read my other post, you heard about the enclosure for a 4 12's.....and you read what space I had to work with....

Well guess, what, he dropped it for about a week...(think It was because of the sound off and show he had going on )....well yesterday, guess what...he asked me about it again....

Now jsut to let you know, I've tried everything to let him know it's impossible..had 4 MECP Masters tell him ( three of which help write the test and one who took it), as well as having about 16 other installers tell him it can't be done..

here's the run down. he wants an univeral enclosure to hold any four twleves he sells and can fir in the trunk of any car...which is cool and can be done...but these are the limits he gace me now ( i got him to make them a lil bigger) 36"L X 20"W X 14"H.  It can not be an isobaric, or an acoustic coupled. 

What he did was dram some lines on a piece of cardboard and placed the subs where he wanted them...and it would have worked...except, the baskets were touching and he didn't allow for the MDF (3/4") and the subs he used were the smallest 12's we sell...MTX Thunder 4000's...you knwo the ones, the ones that the only thing the magnet is good for is for a fridge! 

Now is this possible, and I'm totally missing something that is obvious or am I and everyone else who said so right when we say it's impossible?!?!?!

any words of wisdom will be considered...and yes I've already told him he's smoking something and needs to share!

The space that he gave you isn't exactly the most installer friendly. If he wants all 4 subs on the same plane that's impossible.... the most you can have is 3 on the same plane........2 on the top corners and one in the middle of the two and lower to the bottom. The last sub will have to be mounted on the top/bottom of the box in the lower middle. There will be enough space at the bottom of this sub to clear the basket of the one in the middle of the three on the opposing plane. Does this make sense ? Or does your boss not want one sub on the other plane ??

The 1.4 cu. ft is also possible with quite an extensive maze of internal braces and chambers. The box dimensions that you gave me before calculates out to be an internal volume of 10080 cu. inches. Id you have 4 subs with 1.4 cu.ft per sub then you only need 2419.2 cu. in per chamber = 9676.8 cu.in. which leaves you 403.2 cu.in. for internal chamber material. I'm not sure if this is enough or not, but I don't think the " big guy " will notice .1 or .2 cu. ft......... unless he's also psychic along with psycho .

Here's a diagram of what I think it should look like : http://www.velocitymotorsport.com/4_sub_enclosure.jpg