slot port question

[bombsaway]

Attached is a screen shot of some specs that I'm considering for my next box. Is 1.5" too thin for the port in this application? Would I get any benefits by altering the dimensions?

Click to read more...

 

[bombsaway]

I just realized that the attachment uploader resized the image and it's really hard to read so here's everything from that shot in plain text:

Width: 28

Height: 12

Depth: 15.5

Thickness: .75

Port width: 1.5

Port height: 10.5 (-1.5 from thickness)

Vb: 2.25 ft^3

Fb: 35hz

Port Length: 12.09

I've read that it's best not to exceed a ratio of 9:1 for the port. Does this mean the port's width in respect to the box width? The WxH of the port? I came across people talking about both and I'm confused.. WxH of the port comes to about 7:1 whereas portW x BoxW comes out ~15:1. I just want to be sure before I make another box that I'm unsatisfied with. I am open to altering what I have now, all the dimensions can give or take a couple inches with the exception of the depth, 15.5 is as deep as I can go.

 

[bombsaway]

Up....

Just need someone with the knowhow to verify for me.

 

[mklett33 10+ year member]

I just realized that the attachment uploader resized the image and it's really hard to read so here's everything from that shot in plain text:
Width: 28

Height: 12

Depth: 15.5

Thickness: .75

Port width: 1.5

Port height: 10.5 (-1.5 from thickness)

Vb: 2.25 ft^3

Fb: 35hz

Port Length: 12.09

I've read that it's best not to exceed a ratio of 9:1 for the port. Does this mean the port's width in respect to the box width? The WxH of the port? I came across people talking about both and I'm confused.. WxH of the port comes to about 7:1 whereas portW x BoxW comes out ~15:1. I just want to be sure before I make another box that I'm unsatisfied with. I am open to altering what I have now, all the dimensions can give or take a couple inches with the exception of the depth, 15.5 is as deep as I can go.

You are correct that that is in fact a 7:1 ratio. BUT, that isonly 15.75 inches squared of cross sectional area, depending on how much power, and what sub, you may encounter port noise. This is where using aprogram like WinISD pays off as you can get an idea of the port velocity. This is where some ball park numbers come from, I find that generally 12-16 square inches of port cross sectional area per cubic foot of volume are a good starting point.

 

[bombsaway]

Thanks for your help! Unfortunately I don't have windows so that program is out of the question for me.

depending on how much power, and what sub, you may encounter port noise

For about a month or two longer I will be running a Solo Classic 12 @ about 600rms (MRX-M110). Still deciding between a CVX, W6, re s-ex, TypeX, or maybe a few others. I'm now considering an L port to tune a little lower.

Here's what I have now:

Width: 28

Height: 13.5

Depth: 15.5

Thickness: .75

Port width: 2

Port height: 12

Vb: 2.24 ft^3

Fb: 32hz

Port Length: 12.75

Port Length2: 7

Port Area: 24

Does this look better?

Edit: I couldn't find information on subwoofer placement in the box.. With an L port, do I want it to be closer to the port? Because the L part of the port is only 7", would this be a bad Idea and I should place the sub on the opposite end? Dead Center?

 

[bombsaway]

bump

Anyone else with input? I got a sheet of MDF and will be pulling the trigger sometime this weekend. Leaning more towards the L port.