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View Full Version : Can someone double check my IDMax box?



bchandler
08-23-2007, 06:11 PM
I used subwoofertools to come up with this plan. Driver displacement is 0 because I plan on mounting inverted (Will mounting inverted make a difference in SQ or SPL?) The box must be 15.25" high and 29" wide, externally. ID suggested 2.55 cubes tuned to 28hz. Plugging that data in and a few more from ID's spec sheet gave me this:

http://www.subwoofertools.com/forum/ported-box.asp?Ew=29&Eh=15.25&Dia=6&Xmax=24.9&Vd=0&NumW=1&Vb=2.55&Fb=28&Qts=&Vas=&Fs=&CE=0

Am I good to go?

bchandler
08-24-2007, 08:22 AM
bump... please? I'm having lowes cut the pieces today...

bigbang
08-24-2007, 11:53 AM
With a little research, do away with the two 180 degree bends. Do two L bends instead. It is better for air movement. I would recomend doing away with one of the teal pieces and the violet piece. Instead, make a piece 20.5" long and a piece 7" long. Have this long piece sit between the teal piece and this short piece. Do a bend at the upper left corner and a bend at the upper right corner. This design will maintain your 2.75" opening and have the same length.

Also, when you get your wood cut at lowes, have them set the blade horizontal. This way, the blade is a fixed length from the bottom vs the dude marking your wood with his ruler and having everything be a fraction of his judgment off. Strart with a couple 13.75" by 8'strips for the sides, front, back, and slot port sections. After words have them cut these strips to shorter lengths again keeping the blade horizontal. I know it sounds confusing, but hear me out and will have everything meet up without gaps. Almost every cut you need comes in multiples of two, so keep setting the saw hieght and knocking out pairs until you cut the oddball port lenghts. Trust me, I've had lowe's help me on my share of boxes, and refrain as much as possible from veritcal cuts. Yes I have alot of time on my hands, thats what happens when you break up.

bchandler
08-24-2007, 03:46 PM
So you're saying the port should wrap around the left side and then the top side (when viewing the drawing) instead of backing over itself a few times on the left?

bigbang
08-24-2007, 04:43 PM
Yes. The reason 180 bends arent too hot is because imagine a car driving down the road and trying to do a high speed 180. It will crash into the wall. Easier to just take a couple turns. Along with the analogy, putting triangular Kerfs, I think they are called in the corners also helps. Kind of like banking a road on a turn. The measurements I told you call for the slightest bit more wood because the port isn't sharing two sides of the same board, so the volume of the box will drop by an insignificant amount. Although having the woofer mounted inverted will actuall add volume to the box and more than offset this because the cone slopes inward, gaining extra airspace in front of it, also the woofer is flush mounted so the volume of the circle you cut out of the face of the box will also add to the total volume. Dont stress over going a little more then recomended volume, it will actually give you a small increase (less than a decible in this case) on the low notes.

As for SQ/SPl, not much difference. For SPl an inverted woofer cools itself better with the magnet exposed. SQ, A purist might preffer the face of the cone, even though bass is omniderictional. Also theres an extremely small chance you may hear mechanical noise or whistling wind from the back of the subwoofer, such as air venting through the voice coil so just try running the woofer a little in free air and see what kind of noise's it makes (Just dont crank it too loud, theres no air pressure to protect your woofer!).

Any way, that sub is great for SQ, and in a box tuned this low, it should sound like a million bucks.