sub questions

I currently have two kicker compvr's in a sealed box, separate chambers, each about 1.8 after displacement, running in parallel getting 600watts. I would like to build a new box, but the opening of my trunk is silly small and wont accomodate a larger MDF box. I wanted to put each sub in a fiberglass box, one on each side of the trunk, but given the shape of my trunk, they would end up with strikingly different volumes, or no real imporvoment in size. My question is should I think about making one slightly oversized FB enclosure and mount the subs isobaric? Or is there another option that i am overlooking?

Isobaric loading can be a very satisfying answer to needing a small enclosure size, since the net Vas of the two woofers will be one half of  the Vas of a single woofer, which means you can build an enclosure that is half the size required for a single woofer.  The disadvantage is the performance is basically the same as one woofer in a sealed enclosure, and there is a theoretical reduction of peak Spl of up to 9db from what the same two woofers could produce mounted conventionally due to excursion limitations, although the efficiency in the operating band will be slightly increased (you can run a smaller amp for the same Spl.)  Many people love the space-saving benefits of iso loading, but that's really the only practical advantage and you have to use two woofers (twice the $$) to get the same basic performance of one. Support the12volt.com

What type of vehicle is this going into?   I would think about down sizing your box to about 1.5 cu ft per sub.   and possibly a very shallow box2009 0-1000 Trunk WR 154.0DB 2009 1001+ Trunk WR

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it's going into a 97 avalon xls...hence the SN :)    Why would I decrease box size. Isn't it almost always better, at least as far as low end response, for a bigger box in a sealed application?  Or are you suggesting 1.5 cubes for the iso setup? I don't think I understand your suggestion. btw they are fifteens.