4th order bandpass help

[coolloco]

2- 12" kicker comp-D, kicker ix 500.1... i have 14"H x 30"L x 25"W space to work with. a guy from kicker help line emailed me this "Build a box that has 2 chambers. The first chamber will be sealed and will have both woofers sharing the sealed space. It will need to be 2.6CUFT. this will include woofer displacement. Then build a ported chamber that has 2.7CUFT. this will include port displacement. Use either two 6 round ports that are 10.25 long or a single square port that has 56 square inch opening that runs 10.25 long. This box will have a bandwidth of 39-88Hz"... i have no clue where to start... i know i rather use the square porting though. any help would be appreciated.

[RooTxBeeR]

Your best bet is to just build a regular ported enclosure, until you can actually understand what was told to you. Then try and build a 4th order. I have been in car audio for at least 5 years now and I am still skeptical about getting a successful 4th order built.

[coolloco]

My dad loves math.. he come up with some measurements but i was hoping for second opinions. using 3/4 wood he layed out a blueprint. when i did the math the cu ft seem bigger then that of what kicker emailed me. everything I've read saying 2:1 on structure. like i listed, kicker using 2.7cuft on sealed n 2.6 on ported side. I'm totally lost on measurements honestly.

[coolloco]

Ooops i was backwards 2.6 sealed 2.7 ported

[Triticum Agricolam]

I suggest you download WinISD and play around with things. You can input the specs Kicker gave you and then you will have something to compare against with design modifications.

If you don't understand the info that WinISD gives you, you probably aren't ready to be designing bandpass boxes for yourself. If that is the case we can help you learn.

[coolloco]

It's not i don't understand, its coming up with air space measurements. if i got measurements i can do the math LxWxH / 1728 gives u cu.ft. i just dunno how to do it from an already given volume

[Triticum Agricolam]

Based on the dimensions you listed in your original post, and figuring on 3/4" material you have at most 4.85 cubic feet of gross air space. So you don't have enough for 2.6 sealed and 2.7 ported. Not to mention the space the ports, sub, and any internal panels will take up. Given the space you have, you barely have enough for a regular ported box with those two 12"s.

I'm not sure what you want us to do for you.

[coolloco]

My original post included kickers email to me. it stated the sub n port displacement included. im not sure if that means space already included in airspace or what. the whole key to my post was "help" lol... im no math wiz or nothing bro. i thought using 3/4" wood was giving these measurements for the math (29.25x13.25x24.25) divided by 1728, coming out to 5.43. i can go a lil more then the space i mentioned 30W x 14H x 31L... just have to take my tool box out lol. i dunno man, i made the post in hopes of ideas.

[Triticum Agricolam]

Seriously man, if you want an idea, just build a regular ported box. You are much more likely to be happy with the performance you get out of it than you will be trying to cram a 4th order bandpass into the space you have.

[Raptorman]

If you want a 4th order bandpass you will have to get some different woofers. Those will hate a 4th. Regardless of what the rep is telling you. 39hz is a terrible roll-off point for a 4th order, and for any box.

An acceptable resonant frequency (46hz) will come into play around 2.3 cubes net sealed PER sub. And by the time you get the box that big, you will have a total lack of cone control.

TL:DR; ported box