View Full Version : SA-12(s) in a 4th order in a beemer :)

06-24-2011, 05:14 PM
Im looking to build a 4th order bandpass box for 2 sa-12s (one now and another one in the future) to put in the trunk of a e39 5 series bmw. I'm a totally unworthy noob when it comes to designing boxes but I was thinking that a 4th order would be good here because im a metal head so I want accurate bass (4th orders are good for that, right ?) and with a 4th order I can have the port firing through my ski passthrough, so i can have all the lovely magical bass airwaves of death go into my cabin instead of being wasted in my trunk.

Uh. Yeah. So I need some help.

My max dimensions are 17 inches high and 33 inches wide, and depth is limited to the length of my trunk. I would like to keep as much usable space in my trunk as possible, so Id like to have the box be as tall and wide as possible, so it wont be too deep and eat up my trunk.

Like i said I only have one now but i would like to build a box that could accommodate two in the future (so it would have a separate ported chambers for each speaker).

From what i can tell, i need a box that's around one cube sealed and 2ish ported and tuned to the high 30s?

So my questions are:
What should my seal and ported sizes be?
At what frequency should I tune my box and how do i achieve this (what should i make my square inches of port per cube be?)
Is a fourth order too much effort/ too much for this type of thing? I know that they can be rather sensitive to measurements so that's why i'm asking here to try to establish some numbers... Should i just forget about building a 4th order and make a normal ported box just for one, and build another for 2 in the future?

Also I've attached a rather ghetto rough mspaint draft of what the box would look like (without measurements) so you can see what im talking about. The box will be placed flush against the far side of my trunk so that the ports will be firing directly into the cabin via the ski passthrough.

06-24-2011, 05:16 PM
On second thought I will probably just build half of the box now for the woofer I have currently and then build an identical one when i get another and position them as shown above, just in case I decide to change my mind on my future setup

06-24-2011, 08:05 PM
38 inches of port, 1ft sealed and 1.5 or 1.75 ported, tuned to 41.5hz

F1 is around 32 hz on the low end and 52 on the high i believe.

How does that sound?

06-27-2011, 01:23 AM
For a decent response, the front chamber will be smaller. The SAs are pretty sensitive to chamber sizes, as are most.
If youre building for metal, youll want a smooth response up to 80hz to pick up the extension. Metal doesnt normally go all that low unless youre listening to screamo (which is teh ghae)
Also, youll want to model the response sloping upward to match the cabin gain. Firing forward you get the more normal slope gain as you get lower in the response (normally).