View Full Version : Port Calc (15K)

07-04-2003, 01:34 AM
Ok, since I cant have a sub in the car, I guess Iíll have to put this sub in the house :-D Ok, I have a 15K and will soon have a Parts Express plate amp giving it 180watts. I was told by ED to go 4cuft ported tuned to 25Hz. Does everyone agree? And any pointers on these DIY sub boxes, anyone ever do one before? Thanks

Also what size (slot) port would give me 25Hz in this box (4.256cuft)? Thanks

This is what ive got so far.

07-04-2003, 01:53 AM
First, I'd almost always go with mftr specs if unsure.

Second, building the box itself would be the same as building a box for your car, I'd imagine. You just have to consider the displacement of the plate amp that will be inside the box.

Third, your box will not be 4.256cubes after port, sub and amp disaplacement. Once you figured out the length of the port, the box will be of a different internal volume.

I've calculated ported boxes by building it backwards. Set 4 cubes as your goal. THen decide on a port frequency + HEIGHT of the box. the height can determine the height of your port (-0.75" on each side for MDF) and you can get a rough estimate on your width, like 2" or something.

Then, checking winISD, you'll see the length needed. Calculate total displacement of the port, including MDF.

[port displacement + sub displacement + plate amp displacement] + 4cubic feet = total net box volume needed.

Now measure a box that will correspond to that volume. I say build slightly larger, so that you can place displacement blocks or add bracing to fill up little amounts of volume overboard.

Was that clear, or am I just rambling on again?

07-05-2003, 08:43 PM
Sub Displacement - .085
Amp Displacement - .06 (1"D x 10" H x 10"W)

But i have no idea where to go from there...