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So I have big plans for my (on order) two 12" punch p1s, but I'm getting weird numbers. As a chemical engineering student, I don't like weird numbers. The way my box is turning out is that it has a shallower depth than it is wide and tall - fosgate says that the p1s are "optimized for small sealed enclosures" so maybe this is why my numbers are weird.


The recommend volume for a sealed box per sub is 1.25 cubic feet, and after I add on the displacement that the sub takes up and allow for 1.5" on each side of the sub (in other words the sub is 12" in diameter, so I make the front piece 15" x 15" to allow for 1.5" at the top, bottom, or either side of the sub) at the mounting locations I get these dimensions for my box:

15" High
15" Wide
9.9" Deep

The mounting depth for these p1s is 5.6", so that only leaves me about 4.3" from the back of my drivers to the back of my box - is this okay? The subs are nice but I doubt they'll be moving 4.3", heh. Maybe I am allowing too much room around where my subs will be mounted, but I figured that leaving about 1.5" around the sub was a good number.

Thanks again

 
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dont worry about the subs moving. The sub is cant move any further than the surround will allow it, and theres no way it will ever retract past the metal basket. As long as the magnets not hitting the box, you'll be fine.

 
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i think what hes asking is if thats too much room behind the subs. personally i dont think so because most sub boxes are actually deeper than that. go for it.

 
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thanks for the info guys :-) I was just worried that my box was going to have weird dimensions and there be too much/little space at the back of the subs, both very helpful comments, thanks again!

 
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there seems to be enough space behind the sub...

just make sure it's not right up against the box if the speaker has a vented pole...

 
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I'm just gonna make the box sealed, I think I'd like to make it ported but I don't know if there is a nice write up on how to do that. I know there is some way you "tune" the ports, and I wouldn't know how to do that, if any of you guys know a guide for that link me please.

 
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i have all the formulas to figure out dimensions for a ported box in my tool box at work, ill bring them home with me on wed. and ill type something up

 
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Grenloch if you did I would be forever grateful. I was originally planning on making this crazy box with a parabolic curve, and proceeded to do some cal-3 kungfu on it to get the volumes - but after some deliberation I realized it looked pretty gross. The volume worked, but it looked nasty. I'm sure I could work the formulas if you supplied them, I think you've answered all my questions I've made over the last few days - I really owe you.

Thanks,
synod

 
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hey sorry for taking so long to reply, Im sitting here in my bay waiting for the next appointment to show up so i figured nows as good of a time as ever. the design for a vented box is broken up into a few equations.

Box Volume (Vb)
Qts^2.78 * Vas * 15 = Vb

3 dB Down Point of System (F3)
Qts^negative 1.4 * .26 * Fs = F3

Port Tuning Frequency (Fb)
(Vas / Vb)^.31 * Fs = Fb

Vent Length (Lv)
14630000 * Vr^2 / (1728 * Vb * Fb^2) - (1.463 * Vr) = Lv


Suggested Port Diameters Based on Speaker Size (inches)
8: 1-2
10: 2-3
12: 3-4
15: 4-6
18: 4-6
22: 6-12
36: 6-12

If you want the formula for a slot port let me know.

 
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Those crazy Theile-Small parameters! Thanks for the great info again!

For anyone wondering - those parameters (like Qts, Vas, Fs) are usually given by the manufacturer of the sub, and you can usually find them online at the manufacturer's website, for instance all the information I need for my beautiful new 12" P1s that just came in TODAY can be found here. After that its just "plug and chug" as us chemical engineering undergrads say.

 
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gotta love graphing calculators where you make a program to do all the chugging for you