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View Full Version : trying to build a big ported box, need help with ports (i have diagrams already)



derek33
10-24-2004, 11:58 AM
Good evening, if you didnt already see some of my other posts, i am really interested in building myself a ported box. I am planning on using some pvc pipe as my portings, but i am sure what diameter/length to make them.

My max dimensions are 32" wide, 27" deep, and 18" tall. I am using two mtx 15" subs. here is a quick diagram i made in mspaint.

http://img.photobucket.com/albums/v143/a5bunkerking/box1.bmp

so all im looking for is how large my ports should be. and on the inside.... can it be one big chamer? or do i have to make a few chambers inside?
as for the port tuning, im looking for more sq, but without sacrificing loudness.

thanks

mrray13
10-24-2004, 12:31 PM
which mtx subs? that'll help determine overall box volume, as right now u have 9ft^3 gross to work with. also help determine tuning, though i'd guess in the low 30's..



one chamber will work fine...u'll want to brace the box a little to keep flexing to a minimum and help with the spl a little.



figuring in a couple of braces(16.5x.75x25.5 "x'd" out) and using mtx 6000 series 15's...u'll have a net volume of about 6.4ft^3, using ur current max dimensions. u'll need two 6" pvc tubes cut to 15- 5/8" to tune to 34hz.

the displacement will change with the sub model, and that'll change the tuning some.



hope that helps a little.





wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee eeeeee :peace:

derek33
10-24-2004, 12:48 PM
thanks.

i currently have the mtx 8000 subs.

by bracings do you just mean like some rods for stability purposes?

and, is the pvc 15-5/8" long, and 6" in diameter?

thanks again

mrray13
10-24-2004, 01:00 PM
i did figure the mtx 8000's....my bad, so the above numbers i posted are correct.


the bracing keeps the box from flexing..so u can use dowl rods, i u want to use dowel rod, it'll add volume to ur box and change the tuning...u'll have to shorten the ports or ur box will be tuned lower then the 34 hz...around 31-32..which isn't a bad thing, u'll lose some spl though, but probably not enuff to notice......if u do dowels, do 4 running top to bottom and four side to side(if they will fit) and trim about an inch off the ports to maintain 34hz....use 3/4" dowels.

here's a pic of some bracing i put in a box...



http://img34.exs.cx/img34/95/kevinsinstall017.jpg



look closely at the "X" shaped piece.....


the above numbers figured two braces....each 3/4" thick...16-1/2" tall and 25-1/2"long and "X'd" out like in the above image.


and yep, the 2 ports will be 6" diameter by 15-5/8" long.







wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee eeeeeeeeeee :peace:

derek33
10-24-2004, 01:09 PM
alright, thanks for your help.

i will probably add one x shaped support longwise in between my two subs, then probaly two horizontally, maybe 3, i dont have too much space long wise because i only have 32" of space, and 30 of that is occupied by subs, but ill see what i can do.

im not too picky on the frequency, this is the first sytem ive had, so i probably couldnt tell the difference between 34hz or 32hz, etc.

what size particle board should i use for the box construction istelf? 3/4?

DBfan187
10-24-2004, 01:49 PM
what size particle board should i use for the box construction istelf? 3/4?
NONE! 3/4" MDF all the way!;)

derek33
10-24-2004, 02:32 PM
NONE! 3/4" MDF all the way!;)

ohh mdf is a type of board? i thought it was a type of particle board or something.

so if i went to home depot and said i need 3/4 mdf, the person would know what im talkin about?

IgnoreMe
10-24-2004, 03:03 PM
ohh mdf is a type of board? i thought it was a type of particle board or something.

so if i went to home depot and said i need 3/4 mdf, the person would know what im talkin about?
yes. youll see it will say 3/4" mdf in the wood section of hoe depot.

req
10-24-2004, 03:06 PM
yes.

it is basically compress sawdust and glue. its very dense, and ver smooth. it looks to be a single color, but when you get up close, it basically is a bunch of little dust particles. its very tough stuff- and it dosnt soak up water like particle board - which is comprised of compressed wood chips (pretty small pieces usally, mostly used in pre-fabricated cabinets and inexpensive TV stands and such).

particle board - somewhat brittle, and soaks up water then 'bloats' eaisly
http://store.dunnlum.com/dunn/images/images_items/PARTBD.JPG

MDF (medium density fiberboard) 3\4" or thicker for boxes (usually) - you can tell how much denser\strong this is. i had water rain onto some MDF and it didnt soak it up. i was relieved to say the least.
http://store.dunnlum.com/dunn/images/images_items/MDF.JPG

mrray13
10-24-2004, 05:05 PM
I don't know why you'd use an "X" shaped brace as it reinforces the strongest parts of the enclosure (corners) and leaves the weakest parts (centers of the boards) untouched ...



ummm.....that's not what we were talking about...lol....

look at the above posted image of a box i built....it's a brace in the center between subs. some of the material is removed to the shape of an x...hence "x'd" out. :moon:





get it? got it? good!!!! lmao :banghead:








wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee:peace:

derek33
10-24-2004, 05:53 PM
k, thanks for all your help guys, i just have a few more questions before i begin.

1. to hold the mdf together, i plan on using 1-1/2 inch screws every so often, and liquid nales all around the seams. then caulk the korners on the inside and outside, right?

2. i heard wrapping your box with ducked tape adds 10db, would you recomend i do this to my box? will that sacrifice sq?

guitar012345678
10-24-2004, 06:39 PM
"2. i heard wrapping your box with ducked tape adds 10db, would you recomend i do this to my box? will that sacrifice sq?"

ya and dont forget to paint the inside of the port black too!!! lol no man duct tape isnt gunna help u gain any db's. just take ur time, measure twice and cut once, caulk the hell out of it. good luck dude

derek33
10-24-2004, 06:47 PM
k, i guess it was just a myth. thanks tho, ill be sure to take tons of pics during my process too!

guitar012345678
10-25-2004, 12:00 AM
awsome. cant wait to see it

brandontw
12-03-2004, 12:41 AM
I don't know why you'd use an "X" shaped brace as it reinforces the strongest parts of the enclosure (corners) and leaves the weakest parts (centers of the boards) untouched ...
i thought that too :p:

*oops sorry to bring this back to life*

TimberJon
12-03-2004, 12:13 PM
Visit this link for some good box building techniques. Im sure MTX has some FAQ and maybe walkthroughs on this too.

Check out the lower half of this page.
http://www.jlaudio.com/tutorials/index.html

mrray13
12-03-2004, 10:59 PM
i thought that too :p:

*oops sorry to bring this back to life*


take a look at the pic i posted...


it doesn't run corner to corner..... :banghead:








wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee eee :peace: