Port recommendation(s)? Help!

[JG474]

So I created a .752^3in. box for a Sundown SA-8 v2. The dimensions are:

Length: 18"

Width: 10.5"

Height: 9"

Port: Width: .75"

Height: 7.5"

Length: 17.5"

Here are some pictures:

After building the box, I discovered that it creates port noise around any frequency below 44Hz (Which I guess is because I didn't keep the port's width and height to a ratio of 1:. I was wondering if anyone could possibly help me with this situation. I've looked into a round port, but the calculator said I would need at least a round port with a diameter being 4" and a length of 38", which is too long for me.. So if anyone wouldn't mind helping, I'd really appreciate the help

Thanks

[Tarball]

you need more port area. round square or whatever, larger the box = more surface area you need on the port = a longer port = a larger box.

[Joe X]

Ports get longer as the net volume gets shorter, Your gross volume is 0.7 not the net as it should be, I designed this for you, I think the easiest is repeat the box in this case:

Enclosure Specifications:

Fb = 36.055 Hz

Vb = 0.7 ft^3

External Height = 10 in

External Width = 25 in

External Depth = 10.5 in

Port Width = 1 1/4 in

Cut Sheet List:

* All Dimensions in Inches.

* Wood Thickness is 3/4 for all Parts.

External Enclosure Parts:

Front & Back = 25 x 10

Left & Right Sides = 9 x 8 1/2

Top & Bottom = 25 x 9

L Port Internal Assembly Parts:

Front to Back = 7 3/4 x 8 1/2

Extension = 17 3/4 x 8 1/2

The box assembles just like yours:

Build it or just use it as a reference.

[JG474]

Thanks. But I've looked more into it, and I think I'm going to keep the box. I've downloaded WinISD and input the SA-8 v2's parameters then messed with the port tool. This is what it gave me (with circular ports):

Which gives me a peak at ~40Hz @ 5.7dB with a 36Hz tuning, but can reach 32Hz @ 0dB. Plus the 'Vent Mach' is (from what I've read) supposed to be as close or under 5%, and .04 is 4%, so I guess I'm good there. My original port gave me a Vent Mach of .1 or 10%, which I guess is really terrible. I guess I'll take out the port and seal it, then get some 2" PVC piping and cut it to 15.5" and have about 6" of it inside the box, which should look a little something like this:

[Joe X]

Technically, probably so, you have nearly 7 square inches of port per cube (your net volume is also a bit high with this).. I wouldn't keep a box that looks like a science experiment though .Probably you have enough wood left to redo it at no cost... obviously that's only me.

Edited April 17, 2012 by Joe X