Rep Power: 0

Hey all,
When building a box, say 1 cubic ft. do you have to take into consideration the amount of space the woofer takes up in the box and also the amount the port takes up, or just build it say 12x12x12?

Thanks!
-Frank

 
Rep Power: 310

For best performance, you should take into consideration all of the things which displace air inside your enclosure. If you don't wan't to do it mathmatically, there are software programs for the computer that calculate dimensions for you, like Boxbuilder 6.0 I think is one of them.

 
Rep Power: 328

Displacement is always a factor when you are building to specs given by a manufacturer. Their measurements are given after displacement, so you have to take that into consideration.

 
Rep Power: 0

Another box building thread? Search, several of us have made points about box building..

 
Rep Power: 337

do what I do. write a comprehensive and full tutorial, then copy and paste it into a text file and copy and paste it back into a thread 6 months later, when the exact same question is asked ;p

(havent done that here....)

so lets say you want to build a box for a 10" HCCA. You've read up it wants a 1.4 cubic foot box tuned to 42 Hz. what the heck does all that mean?

I start with my desired picture of an enclosure. my brain thinks of this:


so, after a bit of reading, you decide you are ready to build. The first thing you did, was determine the size of your baffle. to do this, you measured your trunk, and thought about it. You considered external and internal dimensions, the port size, and throught about depth (but didnt calculate that). so, In your civic coupe, you measured the trun at something like 32 inches wide and 15 inches tall. of course, this size isn't feasible, it would take up all the space, be difficult to get in there, lots of free space on the baffle (wierd aesthetic between the size of the wood panel and the speaker and the port). Furthermore, Ive decided I will go for a slot port rather than a round port. I chose slat so I dont have to buy PVC or cut more round holes than I have to. later, when I buy a table router with roundover and rabbit bits and have an expensive hole saw, I may decide pvc is more ideal. anwyays, I figure the port will be about 24 inches based on experience. I know a 4 inch port is about 12 square inches, and that my speaker is an excursive beast, so I may want maybe 20 square inches or so to make sure theres enough overkill. if I make my box about 11 inches tall internal, that translates to 13.5 inches tall external, giving a good amount of space for my 10" diameter external woofer. if its 11 inches tall internal, that will make my port maybe 1.5 inches or so for a good port. so the baffle can be a minimum of about 12 inches wide, to make space for both speaker and port. But I know ill want SOME width, so ill just throw out a number of about 20 inches wide. thisll be nice and wide, but not TOO too wide. I can adjust this later anyways. at 1.4 cubes plus speaker plus port, ill end up at around 2 cubes total, with 11x20 internal itll be about 13 inches deep. that sounds perfectly acceptable at this time. so 11x20 internal, 13.5x21.5 external it is.

now I go to the port. I figure 11x1.5 is good enough, orion spec'd out a 3" pvc port. 11x1.5 internal is over double that! I thikn I dont have anything to worry about port noise. now I jump on the JL website for the port equation, or grab winISD and do it. lets see...... 1.4 cubes.....42 Hz......11x1.5 port crossectional area.....14.58, or 14.5 inches long. that sounds more than good.

okay, I have port dimensions, baffle dimensions, now I just need a depth. I read on the orion site that the HCCA takes up .15 cubic feet of space (no idea if this is accurate). my port will share one wall with the external wall of the box, and have an internal piece of wood. furthermore, I take .75 inches fro the length since it has to poke through the .75 inch baffle. so the EXTERNAL port dimensions that are actually taking up space inside the box will be 11x2.25x13.75. thats 340 inches cubed or 340 / 1728 = .2 cubic feet. sum total box volume needs to be 1.4 + .2 + .15 = 1.75 cubic feet total, or 1.75 x 1728 = 3019 square inches. my internal baffle dimensions are 11x20, so I divide by those to get (3019 / 11) / 20 = 13.75 inches deep. if this is too deep for me, if I didnt want my box to be deeper than, say, 12 inches, I can adjust the internal dimensions. I didnt want it taller than 13.5 external, but I can make it wider. to keep 1.75 internal, and have the dimensions 11 tall, 10.5 deep (internal, 12 inches external) I would need to make it 26 inches wide. So in this case, the box would be 11x10.5x26 internal, or 12x13.5x27.5 inches external.

in either case, the only other issue before I build is what I have to do about port folding. My port only needs to be 14.5 inches long, and the box is, say, 11.25 inches deep. with only a couple inches more to go, I cant justify folding back and forth like the original picture. I'll just make it an L shape. I could just as easily fold it if it were long enough.

the total length is measured from the exact midpoint of the crossectional area as the port folds. JL has a wonderful tutorial describing this.

now we can build our box thats 1.4 cubes tuned to 42 Hz!

any questions?