infinity car sub

Don't know about that one but I have had my eye on this one.
http://www.harmanaudio.com/search_br...262W-Z&status=

A speaker is a speaker and doesn't care if it's in a car or anything as long as it's in a proper box and driven properly. I remeber when my friend and I discovered that 8 inch woofers would screw into two of the mounting holes for a 6x9 in our cars, and better yet we could make custom speaker mounting boards for the rear deck in his car.
This was before all the BOOM BOOM aftermarket sub boxes and he put a set in a old Valiant and his bug. they sounded awesome and then we added good tweeters and better amps.
We later managed to make mounts for 10 inch woofers in a second gen 75 Honda civic in the rear seat area below each side window, that was like being inside a good set of headphones with great bass.
If you can make them happy and they have the sound quality your looking for think outside the box. As long as you aren't spending your rent money and can afford a gamble give it a shot.

I think if tuned low enough you should be alright. I am also thinking of something similar and would love to hear how this goes for you. Good luck

If you haven't orderd yet check sonic electronics looks like the same for only $53.

if you want to have some fun, why don't you try a ported build?

very simple, 5 cubic feet internal tuned to around 23hz with a single 4" diameter port that is 10.5" long (not ideal, but easy).

yellow is sealed 2.5 cubic feet, white is 5 cubic feet tuned to 23hz. both at 300 watts nominal power.

in your case, i suspect that you will get much more enjoyment of the larger ported configuration.

edit: yes, it will be no contest between this ported setup and an htib box toy.

no prob...i suspect that a little larger, ported, enclosure will make you most happy, as it will pound out the most bass per dollar.

a cube form factor is fine as are others. a rectangular build is just as good. within any reasonable geometry, you will be fine so long as you keep the internal volume and the port size/length the same, just don't get ridiculous and make one of the dimensions something like 2" (yeah two inches as that would start to mess up the models).

3/4" plywood is great. any bracing of the center of the panels would be good, but many commercials builds in your category don't have any bracing, so do as much as you wish. simple 1"x2" cross braces from the center of the top/bottom and left/right sides should be fine. if you want to "A-frame" the center of the back wall to the sides, that would be fine too.

for glue, use pl premium. it is a mess, but will expand to fill any air gaps if your cuts aren't perfect. you can clamp or brad nail the panels into place as the glue takes hold. once it cures, the bond will be as strong as the wood.

would you think a 18,20hz tuning would be ok. If so what cube and port size. Thanks for the help

"How do you tune the box to a specific hz? Or is that just the lowest note the sub i selected will go?"

any driver can play any frequency. the question is how efficiently it does it.

for tuning a ported enclosure, i use a freeware program called winisd.