Help me with box volume for single 12"; sealed

I have a 4 year old MA Audio 12" sub, (MA12iL) and an older MTX 300 watt RMS amp. The sub is in a box that is around 1.3 cubic feet.

I like the way it sounds, but I have a sneaking suspicion that it could sound better (plus I hate my current box). The recommended volume for a sealed box for this sub is 1.25 - 1.75 cubic feet. They do not specify how much displacement the magnet causes, or if the volume needs to be before or after displacement.

I'm pretty sure the volume needs to be between the given figures after the sub is in the box. I've also guestimated that the sub has .2 cubic feet of displacement. (similar audiobahns list this)

Because this is in an extended cab truck, that has a weird shaped rear floorboard, max depth is about 11". I'd like to keep the height of the box less than 15", for theft reasons. Length can be up to about 36", but definitely won't need anywhere that long.

I'd like the sub to face the FRONT (aim at the back of my seat).

I've decided that 11" X 15" X 19" seems to be about right. Problem is, I need to figure in the width of the wood being used... I want the volume to be accurate. I want it to be no less than 1.5 cubic feet. Probably going with 3/4" MDF.

THANKS!!!

(Audio devices pertains to car audio too, right?)






DONE!!! SEE POST 21!!!

box size is usually always listed without the sub included.

What you could try first, is to use polyfill inside the box. Put a pound (450g approx) of polyfill in and see how it sounds. You can buy this at any Walmart, it should be less than $4 for a pound.

Try that out, let me know how you like it. I've found it makes a difference, in a good way but you may find something different. For $4, it's worth trying first.

Yeah, I did polyfill when I first got the sub, didn't change much at all. Now I just have the upgrade/DIY bug and just want a new box, that I can shape to my liking.

If volume is LxWxH, how do you factor in the width of the wood being used? (3/4")

If it's 12x12x12, would it actually be 10.5x10.5x10.5?

Measure the inside. Build the box with the internal dimensions as the external. Then you add the 3/4" when deciding on the cuts. Definitely, draw it out multiple times to make sure. If you draw it out, it will make sense. Or just use paper and put a practice one together, you'll see.

If you took the boards, all of them being 12", and put them together, it wouldn't be 10.5 x 10.5 x 10.5. At least one of the boards would be edge to edge on the inside, you would have to decide which board that is. So at least one side (2 sides) will be 12".

OUCH! You threw another kink in it.

I JUST decided on external dimensions of 26" x 10.5" x 15". That'd give me 1.72 ft^3

Not anymore though, lol. Time to do it again.

You'll get best results doing it this way:

http://forum.sounddomain.com/ubb/ultimatebb.php?ubb=get_topic;f=11;t=069744#000000

Ok, outer dimensions = 26 x 11 x 14

Now I need to figure out how to have the wood cut, which sides fit how.

I know the front and back pieces need to be 26 x 14..... OMG why is this so hard. What's the best way to place the pieces of wood? Which sides have to be cut to be made smaller?

Ok, will someone who's better at math than me and also good at building sub boxes check out these specs?

26 x 11 x 14 for the outer dimensions.
24.5 * 9.5 * 12.5 = 2909.375 = 1.6836 cu. ft. before sub displacement.

To get a box this size, I need:
2 pieces 26" x 14" (Front and back)
2 pieces 26" x 9.5" (Top and bottom)
2 pieces 12.5" x 9.5" (Left and right)

Is all this correct?!?!?!

What are the best materials to put this together? Wood glue first and then screws? How do you ensure air-tightness?

THANKS

Use 3/4" MDF for the wood, then liquid nail the boards, then use around 1.5" screws about 2-3" apart. Make sure you predrill the holes for the screws because MDF spilts very easily. Also I would use 2 pieces 26*11 for the top and bottom, 2 pieces 26*12.5 for the front and back and 12.5*9.5 for the sides. Put the front and sides together first, then the top and bottom should sit right ontop. As far as leaks, you won't really know until you install it and then check it once the sub starts pushing air. If you use liquid nail it shouldn't leak. If you want you could even put a bead of silicone around the inside seams to make sure.

harper81 said:

Also I would use 2 pieces 26*11 for the top and bottom, 2 pieces 26*12.5 for the front and back and 12.5*9.5 for the sides. Put the front and sides together first, then the top and bottom should sit right ontop.

Click to expand...

The entire diameter of my sub comes out to about 13", and will be mounted on the front of the box. Does this change your mind on wood size?

Ahhh, didn't think of that. You can do it either way. I always just found it easier to sit the top on to the box rather then trying to tuck it in.

you dont want to try ported?

ive never been a sealed box fan, dont like the sound of them, and not loud enough

Based on your calculations for size.



You will be able to build it on a 1/2 sheet of 3/4 mdf (most lumber stores sell them as 1/2's). For building it, the best thing to use is yellow wood glue. Don't use Liquid nails unless it is the one specifically for wood. Predrill the holes and use either coarse thread construction or drywall screws. Space them about 5-6" apart just to hold the wood until you get clamps on it. Find about 4 good (expensive) 36" long clamps at a big box store (Home Depot, Lowes, etc) and don't abuse them. Use them to clamp each side until it dries. When you're done with them, they should show no use and you can return them.

When finished, you should only have spent about $15. And if you ask nice, the lumber store may cut the wood for you. Simple as pie.

if you screw it, no need for clamps, if you want to get cool with it, dont use screw and just clamp it, screws dont hold the box together, glue does, once the glue dryes you could actually remove the screws and it would never come apart

i know the only place around me that carries mdf all the time is home depot, and 22$ a sheet i believe, and you pay for the whole sheet, but you can alaways use extra mdf for something, amprack, and baffles and what not
they sell 1/4 sheets for like 6 ucks io think, but you end up wasting alot
i had to use almsot 2 full sheets on my last box, 8 cuft box+port FTL

Well the wood is on lock down. (I work at lowe's) I get 10% off and I'd definitely have them cut it.

Guys on hardforum are saying my dimensions are off.

2 pieces 26" x 14" (Front and back)
2 pieces 26" x 9.5" (Top and bottom)
2 pieces 12.5" x 9.5" (Left and right)

IS THIS RIGHT?!

Bamaboy, I'd like to try a vented box (never had one), but based on my size requirements, do you think I could do one? Absolute max size is 26 x 12 x 15-17


And knacko, thank you so much for the pic. It appears the dimensions that I picked for my wood will be right. You rock!!! (what prog did you use to make that? CAD?)

I used Sketchup 5 Pro Edition. You can get a free version from Google though:

http://sketchup.google.com/

Without the sub, you're looking at about 2cu ft in a box that is 26 x 12 x 17. You "could" get away with it though, polyfill definitely recommended. I usually like 2.0 - 2.5 cu ft per 12" sub, though it does depend on the sub itself as well.

Ok, bought (almost) everything today. Picked up

2 pieces of 26x14
2 pieces of 26x9.5
2 pieces of 12.5x9.5
1 lb of 1 5/8" deck screws
Wood liquid nails
Silicone caulk

Had to buy a whole sheet of MDF though. All together cost me $31.

Got the sides and tops glued together right now, they're drying. The back is going to have the speaker terminal, so I'm leaving that off until I figure out which terminal to get and exactly where I want it. The front is having the speaker, so I need to cut the hole before I put it on.

Tomorrow I'll put screws in the tops and sides, then caulk them. Once I figure out the carpeting situation and terminals and how exactly I'm going to get the holes cut, she'll be done. I can't wait! It's gonna be the perfect size!

Pics as soon as I can borrow someone's camera

Man, my camera is BAD.



EDIT click for bigger, if you want to hurt your eyes.

If you don't want to tackle carpetting (it can be a real pain), use spray-on bed liner for trucks. You get a real nice finish for little work.