Dimensions for sealed 18" sub box

20" depth seems to be reasonable. Eagerly waiting for your flatpacks & kits.

Just curious when I use the dimensions 23" x 22" x 20" (HxWxD) I get a cubic volume of 5.8, not 4.5? Also what would be an acceptable width and height for say a 18" sub? Would an inch of "meat" be adequate?

Keep in mind those are external measurements. Depending on the thickness of the panels the internal dimensions will be different. Volume is based on internal dimensions.

Sounds good Erich; excited to see this coming together!

Yes I am well aware of how volume is calculated and are these box dimension calculators not using inside dimensions? Typically when talking about a machined/manufactured part inside dimensions should be used when discussing the size. Also this gives the person, if they decide to build this on their own, the oppurtunity to use whatever thickness material they might have on hand and it would not affect the volume.

http://www.the12volt.com/caraudio/boxcalcs.asp

Go there and use that calculator, you will see with 0.00" thick panels, it gives what you found. With 3/4" panels, it comes to 4.71 internal volume which leads me to beleive Erich is using just that size box with a double front baffle, should yield right at 4.5 cuft exactly

Any measurement that will fit your application will be adequate. So design your enclosure size based on the driver specs and what will fit in your room. You can make it from anywhere as small as will allow for mounting of the driver to the size of a refrigerator. There is no one right size. Usually people will select the driver based on certain criteria like allowable enclosure size and desired performance and cost. Different drivers even though they are the same size will have different enclosure requirements.


Not even really sure what you're asking. Do you mean an inch of material extending beyond the driver frame. As in an 18" driver needing an additional 1" of front baffle so the WxD would be 20"? If so, that would again depend on your driver selection and panel thicknesses.

Now if you're referring to the baffle thickness then again, it will depend on your driver choice and mounting. If you are flush mounting an LMS which weighs in at close to 90lbs then I would not go below 1.5" thickness. 1" in fine for top mounting.

The third thing I can think of what you mean is the the overall panel thickness. If that's the case, I think 3/4" thickness will be fine provided you sufficiently brace the walls. The exception would be noted above for the front baffle.



Different calculators use different methods. As beastaudio has pointed out, you will have to look at them carefully. If they have a field for panel thickness then they are calculating external dimensions. If not, they are using internal dimensions.


Not always true. It depends who your target audience is. The consumer is not interested in internal dimensions when buying a sub for the most part. They need to know what the exterior dimensions are to determine if it will fit in their space. In this case, it is for DIYers who do need to know, but the external dimensions plus the net volume provided will give them the info the need to make an informed decision.


Eric H. is not providing info for the end user to make his own enclosure. He is asking about exterior dimensions for a flat panel he will be making and supplying to us for purchase. He is asking if those exterior dimensions would be acceptable to the majority of users here on the forum. Well, at least I'm assuming that's his motive for this post.

Like everything you hear and read, it needs to be taken in context.

Sure I get it, but my point is why worry about the material thickness? If for example you have a 24" x 18" x 16" (HxWxD) internal dimensions that gets you a 4.0 (internal) cu. ft. box. Then the only thing you should need to subtract is the bracing material and driver volume. Now if you leave the driver out of the equation, since we will be using varying products and use say 3/4" material cut to a 3" strip by 18 and/or 16" long for the bracing it comes to around 3.9 cu. ft.

duc135 you would have to ask ErichH what his intentions are, but from my standpoint he is asking for a generic sized box that will accommodate as many driver options as possible and have a re-usable panel in different sized boxes to keep manufacturing costs down. An example would be using a (depth) panel of 20" that could be used in both 3 and 4 cu. ft. boxes.

19 x 19 x 20 = 4.18
16.5 x 16.5 x 20 = 3.15

Yes I was trying to ask for the minimum material thickness needed past the driver frame, which in turn dictates minimum height and width for the box. So if we are putting a 18" sub into the 19 x 19 x 20 box would the 19" x 19" baffle be sufficient?

What bracing style is the box using??

A quick, cheap cardboard mock-up can help you to see how it looks.
Sometimes tweaking a couple of dimensions a little can make the enclosure look better. Just a thought.

Like I said, you have to take everything in context. Eric posted dimensions. You, assuming he meant internal dimensions, stated his calculations are incorrect. We let you know these were external numbers and you questioned why anyone would give external dimensions so I told you why. Material thickness has everything to do with it. Material thickness of 3/4" panels is how he derived his volume based on the external dimensions he provided.

You are thinking in absolutes that are convenient for you for your requirements. You need to take things in context. Again, Eric provided external dimension because he was asking us for our opinions and if it would work for us (in general) so that he can create the flat packs as you alluded to.



I thought you just said we don't need to worry about material thickness?

See what I mean about taking everything in context?

Anyhow, yes, material thickness has an affect on minimum baffle size. Again, this all depends on your driver measurements and the clearance of the basket. Just a rough guesstimate I would say the bare minimum based on a 3/4" panel thickness would be 1" greater than the bolt hole diameter of the driver or the exact measurement of the driver frame whichever is greater. It wouldn't look very nice, but it will work. In other words, so long as the internal dimension will accommodate the width of the basket and the exterior dimension will accommodate the bolt holes then you can go as small as you want.

another thing to consider, for leaving 1 inch on either side of the speaker. what if you decide you want the front baffle recessed from the edges instead of overlaying them? then you have only a 1/4" of material between the speaker cutout and the end of the baffle...Not optimal at all. I only say this because I made that mistake way back in the day, just rushing through a quick design/build and not thinkin at all...

Were grills going to be cut for the subwoofers?

If not, parts express sells grill kits but it needs to be less than 23x22 to make two out of one kit.
http://www.parts-express.com/pe/show...number=260-346

Agreed, there are a lot of things to consider when building a box, but Spec4 asked what is the minimum without providing any other criteria. That's why I said that the minimum would probably look ugly, but it would work.

If you are keeping a log for hole cut-outs...the Mach audio 18" cut out is 16.7 for the basket and 18.2" for the recess..and 22 wide x23 tall looks very nice with an 18" driver installed.....that is the size i cut for my ported box...with the slot port adding a few inches to the bottom.

If you are afraid of the driver showing then put some feet and down fire it

for the 'kit folks', total packages are much favored over figure-it-all-out-for-yourself builds.

the less decisions...the better.

Listen guy I'm not going to argue with you, my first post was questioning HOW he got those dimensions, no where did I state he was wrong and also the OP did not mention material thickness. All of my original questions where in the context of his OP and you assumed he meant external dimensions. My intention was to raise the question of why should we care what the external dimensions are when it's the internal dimensions that matter.

Erich, I was attempting to ask the group what is the minimum amount of baffle material surrounding a given driver, so that you could figure out the minimum size for the HxW of each box...which I see you just asked.

Erich,

The overall dimensions sound good, looking forward to getting a 15" box. Are you leaning toward the end user cutting both baffles, or just the inner? Leaving it all for the buyer may be the way to go, too many variables.....some may not want to recess the driver, or may not want it centered vertically.

My apologies. I didn't meant to appear argumentative. From your original post I thought you were actually asking those questions because you wanted to know to build a box for a particular driver. I didn't take it as a question to initiate discussion.

spec4, try keep it light so it remains fun. :-)

the seaton submersive employs baltic birch and dual opposed 15" drivers. you can see that the driver extends right to the edge of the internal cab.

"It's funny, I've been working on box designs for a couple days, and I keep wanting more and more different box sizes."

erich, lol, that is how it goes...

one possibility is to get into the shopbot network. they have a network where you can take a plan to a local guy with a shopbot and have then cut the wood locally. since most work could be done in 'down time', and there would be no shipping charge, the total cost might be quite reasonable. just a thought.

Or buy a small CNC machine to cut the holes, and also modify the master cuts that you get from your main supplier...charge an up cost for hole cut outs, and custom sizing. But just so you know i cut a 16" hole in a 3 layers BB glue up for my box on my CNC....and then cut a larger recessed outer hole. and it took well over an hour...even though i did other things while it cut...there is a limit to home many you can do in a day.

you could look into a used cnc, that would probably give you a better price performance ratio. Cutting the above mentioned hole through Baltic, or mdf, on the fadel I use at work wouldn't take more than five minutes, with a finish cut that made it look like jewelry.

Erich, could these be for those mystery 18's you where working on a while back? What's going on, on that front?

Kind of a cart before the horse moment. Most of us just need a flat pack for an 18"

DIY drivers are cheap, a sundown audio 18" will slay, the problem is paying $500 to elemental designs for a box on a driver that doesnt even cost that much.

Lets say you only have $650 for a passive sub and no woodworking tools, almost all of that goes towards the box. because a box is a box and its not like you can buy a cheaper box just because youre using a cheaper driver.