critique my speaker box design please
 

Hello. I've never built a box before, so I am planning this carefully, and your input will be appreciated. I've got the materials covered, but it's the dimensions I am concerned about. I have a polk momo 12, the manufacture website says airspace should be 2.25 cubic feet, or 3888 cubic inches. My box design gives me 2520 cubic inches. The sub will be mounted reverse because the front in ugly, and I think it will look cool. Will these dimensions and shape result in normal operation, or is this overkill, let me know. The main area of concern is whether or no the box is too shallow, I will be going with wither 7 or 8 inches. Calculations are for 8 inches... please refer to picture for a better idea of what I'm doing.

*I took my silly picture down, lol*

will the reverse top mount give less performance than a regular mount, firing towards the rear of the car?

Hey dude, this box is all wrong. :)

First, this subwoofer requires a sealed box size of .88 cubic feet for a single 12". I think what you were looking at is the VAS which is the volume of acoustic suspension, don't worry about that spec. The proper sealed box size is .88 cubic feet and for your sub to sound best, you need to hit that number on the nose. When you originally thought the box volume was 2.25 cubic feet and your box volume was way off, you just can't do that. I try not to be off by more than a hundreths of a cubic foot.

The good news is, your box needs to be a lot smaller than it is. Don't worry about the box being shallow or too deep. There is debate as to the shape of the box affecting the sound. The shape most people agree to avoid is a perfect cube. But I've heard subs in perfect cube boxes and they sound fine.

iv built a # of my own custom boxes.
the best one was with a set of JBL GT 12 that needed 1.25 CF. i realy worked on the layout for a few month befor i cut any wood. the final layout called for 1.13 cf using 1" high density partical board, and a crap load of polly fill.
the the subs called for 350 watts RMS each, so i used a rockford 800a2 that bench tested a 1008 watts. its always best to use a slitly bigger amp and turn a gains low as to avoit heat and harmonic distotion.

anyway to make a realy long story short, i got my hands on a good DB meater and i was pounding out 138 in the front seat.

thare is so much invalved in biulding a good system.
i can't even begin to even touch on any of it.
you need to go get this book, The Car Stereo Cook Book.
im sure its still around, i read it back in 99. its full of so much helpfull info and ideas.

get the book, its worth every penny, and belive me YOU are going to need it.

You used the poly fill to make the box seem larger, right! You used it to get to your correct cf.


John


John

whew, thanks. Like I said, my first attempt, I really appreciate the kind help!

I built my box, and thanks to the advice you guys gave it really hits well. I got the airspace calculations perfect. I haven't wrapped it yet, still debating what to do, and I think I might try a different design to give more surface space in the trunk. Thanks for the help!