SQ box building hints/tips/primer?

[Zylo 10+ year member]

I do realize that SQ, and even SPL is 10% equipment, 90% install..

I have a 2003 F150 extended cab, and I am currently going over a few design issues.

I think I may go with a fiberglass bottom to maximize the space available.. but not to sure as of yet. (there is a ledge that I will be building over)

What are some basic things I will need to look for to build a SQ-related box? (75/25 SQ/SPL)

I have a bunch of plywood in my possesion so I can rig up some 'test' boxes to check fitment, and such.

Should I downfire the subwoofer? It will most likely be a 15" Brahma or SI 15", maybe a JL 15W3 (less mounting depth.. I think).. if the 15" doesn't fit, I will go with 2 SI Magnums, or a Brahma 12..

Downfiring sounds so good, because I am shooting for a stealthy install for security purposes (daily driver) and it keeps the sub well hidden, and free from damage incase someone does break in.

How does box alignment affect SQ? (to keep it simple, I'll use the Brahma 15)

For example:

a B15 in a .707Qtc box (2.85 ft^3)

vs.

a B15 in a .800Qtc box (1.89 ft^3)

I'd rather have a more pronounced lower-end that higher frequency response.. cutoff at 80.. 125 at most.

Also, if the role of a sealed box is to keep the backwave seperated from the front wave.. what about dynamatting the inside of the box? stupid idea??

I hope bolding the questions helped make it easier to read..

Thanks for looking, and thanks in advance for any tips/advice!! //content.invisioncic.com/y282845/emoticons/smash.gif.499e08a4a35ffaf54f4c8194fb8fe8ed.gif

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[Zylo 10+ year member]

Lower Qtc is generally a good choice, although there are exceptions. If it's possible, try a Qtc under 0.7 but be sure not to push the woofer to the point where it is exceeding its physical limits. Cut-off should probably be much lower than 80 Hz, definitely nowhere near 125 Hz ... You should have a set of mid-bass drivers capable of producing the 60+ Hz section with some authority for good staging (keeping the stage up front). The lower you set your LPF, the less the subwoofer will draw the sound stage to the back. Dynamatting the inside of your enclosure is expensive and makes only a slight difference ...

What type of sound will come from using a lower Qtc box? Obviously power handling is reduced.. but what about the sound?

50hz sound good for a cutoff? I can also do 63hz.. (using built in LPF in HU)

I will be using CDT HD 6.5" or Focal Power K2 6.5" components w/ 200W RMS, so I think I will have enough authority in the front stage.. I might go with 6.5" in kicks, and 6.5" dedicated midbasses in the doors.. either way, I should have a good front stage //content.invisioncic.com/y282845/emoticons/biggrin.gif.d71a5d36fcbab170f2364c9f2e3946cb.gif I will be running a 500W amp for the Brahma, btw.