Competition SPL box design - as big as possible?

[danfortner]

I was wondering how do you decide on a box's size when its for SPL only.

I am designing the box for a Kicker S12L7. This is for competition purposes only, as I already have a very good daily driver. I mean I already know how to design a box for SQ and SQL - I find this easy because you can see what the QTC will come out to every time you change the size/tuning/ect. But with an SPL box do you just go max space? I have 7.5 cuft of space to work with - would a 7.5 cuft box be better than a 6.0 cuft box for my sub? I would think there would be a limit to the size. I mean 7.5 cuft for a single 12 seems like it could **** the sub. If there was a way I could use a box design program, like I did before, and try to change the QTC to like .3 (or whatever would be good for SPL) that'd be cool.

Please help me out so I can compete this season. Thanks!

[ngsm13]

Well, for competiton purposes...i'd use all 7.5 cubes you have. This does not mean the net volume of the box should be that much. Basically, for SPL purposes you want a large ported enclosure, with lots of port area, tuned high. If this is going in ur acura you have listed, do your seat fold down? If so, when competing...fold your seats down.
The box, for 1 12" L7...i'd say around 90 sq. in of port area with a net volume of 5-6 cubes ported @ 50hz. It will peak b/w 51-54hz. So, basically you want the dimensions of the port (not length of port at all, it is not included) to have an area of 90sq. in. (for example a 30"x3" port....with what ever length needed to tune it to desired frequency.) Make sure to subtract sub displacement and port displacement when figuring final net box volume. Good luck, peace

NG

[paikiah]

Also, there will be a point of diminishing returns, which is what you were trying to ask, i think. Just because you have 40 cubes to use as a wall does not mean that the sub will be even louder. The most I would give a 12 sub would be 6 cube net, as a general rule of thumb.