Sundown Sa18 Box Design

[jfoodstamp]

So I am trying to design a box for my 2 18 Sundown Sa18 Subs. I've got around 10.5 net after all displacements. I will be running about 1200 watts RMS each in a daily application tuned to 36hz. I've called sundown and talked to 2 people and got different responses. First person says 4 cubes ported with 15 square per while the other gentleman says 5 to 5.5 cubes and keep port at 13 per cube. If I use that formula with xmax to figure minimum ported area I come up with 205 square inches which I have room for as well. So my tentative design is right at 10 cubes net and the 205 square of port. What do you guys think Inshould do????

[Triticum Agricolam]

Well the first thing to realize is the "best" box specs for a sub really is a subjective thing. What will be best for you depends on the type of music you listen to, your vehicle, how you like your bass to sound, etc. Another thing to keep in mind is all design decisions involve some kind of trade off or compromise.

Generally speaking, the larger you make the box, the more output you will get, but only around the tuning frequency. Make the box too big and you will get peaky output, some people like that, some people don't. I feel a less peaky box is better for someone with wider musical tastes.

You want to tune the box to at, or at least near, the lowest frequency you want to play. I usually try to error on the low side, since it makes for smoother output and its harder to damage your subs, but tuning lower costs you output.

Port area only effects output if you don't have enough of it, you don't want that to happen if you can avoid it. Just how much you need depends on the size of the box, the tuning frequency, and how much power you are running.

[Joe X]

Since you are running moderate power you will get better output with 5.5 net and about 80 square inches per driver will be fine, no problem if you do more other than the larger box, here's the modeled response for that sub 5.5 net @36Hz 600W per driver :

[jfoodstamp]

I listen to a 70% rap and 30% Rock mix. Starting power will be 1200 watts total but within a month or 2 it will be 1200 watts each. I already have the amp I'm just trying to find somebody who makes a good hi output alternator for 07 Focus hatchback. This box will have to built inside the trunk and will be a woofers up port to the side configuration

[Joe X]

You will likely benefit if you tuned a little lower since low tuned music is your main thing.

[jfoodstamp]

Joe are you thinking 32-33hz range? How does that affect my curve?

[Joe X]

Yes something in the lower 30s, it's a very slight change but one in the right direction imo, yellow is 36Hz, red is @ 33Hz:

The slightly lower tuning can also reduce cone excursion a little on lower notes which makes for cleaner reproduction on them and can help protect a bit the driver from extremely loud-low notes, for additional protection you can use your amp's subsonic filter.

[jfoodstamp]

I've got an AudioControl 6xs crossover with a 33hz Subsonic filter. Will that work if I tune at 33hz????

[Joe X]

It's not too bad but I would seek a lower setting, normally within half an octave below your tuning frequency, maybe your sub amp has a more flexible subsonic filter.

[jfoodstamp]

So given that I have choices of 25 or 30hz. Which would you go with?