OK, just been building a big ported box for my new sub out of 18mm MDF. Everything with the construction is going fine, only problem I have is I'm a bit confused about the port sizes.

The sub is an Audiobahn Eternal Series AWES12P 12" sub. Now I'm using the instruction booklet which has recommended sizes for boxes and what size ports to use with them on a ported box.

Now for my sub, an "ultimate SPL box" has size recommended of 2.8 cubic feet and 2 ports with a diameter of 4 inches and length of 16.5 inches. The length seems too long compared to the other sizes recommended for the 10" and 15" sized versions of my sub.

For ultimate SPL, the 10" should have box size 2 cubic feet, and one port of 4 inches diameter and 11 inches length. 15" should have 4 cubic feet and two ports of 4 inch diameter and 10 inches length. What I found weird was the ports for the 12" are recommended to be bigger than the 15"... I though the 15"s would have been bigger?

I don't know alot about box tuning etc. I was just going to build it to spec, doing that I thought I couldn't go wrong and thought that possibly due to the 12" having certain frequencies and stuff that maybe it did need bigger ports to sound good.

But if you're looking at building a smaller box (listed as everyday bass performer) the ports correspond to the sub size - bigger the sub, bigger the ports. 10" has 1.1 cubic feet, and a port 3 inches diameter by 12.25 inches length. 12" has 1.95 cubic feet, and one port of 4 inches by 11.25 inches length, and 15" has box size of 2.95 cubic feet with two ports of 4 inches by 15.5 length.

Now is the size ports for the 12" with the ultimate SPL box possibly a typo or something? Can somebody with a box building program on their computer work this out? If so, let me know if you need anymore details and I'll provide them. Or if I've totally confused people with what I've written, let me know and I'll clarify. If anyone can help me out and tell me if this sounds right that would be great, before I go and put the ports in the box.

A link to an online version of the booklet - http://www.audiobahn.com/Audiobahn06/images/tech/2005/boxParams/AWES_box_specs.pdf

Get acopy of WinISD and install it. You can find it by searching google.

Run the program, input your speaker's T/S parameters

Then input your box size.

It should be able to tell you the best port diameter and length. If the post is too long, make it a wider port and it will shorten. Of course, the volume of the box also has an input of how long and what diameter your ports should be.

Basically, if you go with the manufacturer's design, you should be pretty well on the mark anyway.

I prefer a sealed box myself, and that 'Ultimate SPL' box will have a big gain spike down low, yet be a bit laggy as a result. The all round 'recommended' design will give +3dB at the tuned frequency and not be really laggy at all.

^^^ Like he said.

Keep in mind a ported box is designed for deaper bass not so much hard hitting bass.

:D

^^^ Like he said.

Keep in mind a ported box is designed for deaper bass not so much hard hitting bass.

:D

Cheers for the info. Downloaded the program... bit confusing without doing a fair bit of research into the Thiele/Small parameters, but I'm getting my head around it... slowly. SO far it's having some HUGE port lengths I have to make... but we'll see.

Yeah, 6x9's are providing some really good, hard punchy tight bass at the moment, so I'm good with that. Just need the deep bass from the sub.