Q: single 12sealed, or 2 12 isobaric

My friend picked up two 12" JL W0 - 8ohm and an amp. Wants me to put them in for him. So Im building a box.

Should I go with one 12" @ 8ohms sealed, or two in an isobaric box @ 4ohm?

They say you get the same general performance, but im guessing thats running both setups at 4ohm???

Isobaric loading will cut the Vas in half (approximately, but close enough) so the net enclosure size is half what it would be for one woofer.  Clam-shell mounting is the easiest to do (woofers mounted facing each other, and wired out of phase with one another.)  Make sure you seal the two woofers together.  Efficiency will be 3db lower than a single woofer, although net output is about the same as one woofer.  If enclosure size is a consideration this can be a good way to go.Support the12volt.com

DYohn, along the same line of question, does that also work in vented boxes as well? My issue is in a S-10 single cab with 2 12" solobarics. I'd like to go ported, purely for the challenge, and the way I figure it, a single 12 in a vented enclosure is about 3 cubic foot. If what you're saying is right, I could pull it off with 1.5, but what about the vent itself? Also in half? Thanksboosh!!

fox... No, a vented enclosure is a Helmholtz resonator, and it cannot be simply halved. If you halve the box volume, your vent volume grows by approximately twice! Usually it is not space efficiency that mandates a vented isobaric loading, but the fact that many of the non-linearities in the system are removed, DUE TO the isobaric loading. Generally speaking, there are two reasons to go isobaric: 1: Enclosure volume is halved. 2: VERY high linearity. Since you asked specifically about the enclosure volume, and I have already explained that this usually is detrimental to vent volume, i.e. it gets too big to be easily implemented, this only leaves reason 2 for you. Could you go sealed? It'd make your life a whole lot easier!It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

You can build any enclosure type you choose with isobaric mounted woofers, but as haemphyst says it is not a simple halving for any enclosure alignment except sealed and ports work differently altogether.  You need to cut the Vas in half and calculate the proper enclosure specifications.  This site has a decent port length calculator once you decide what your enclosure size and tuning frequency needs to be.Support the12volt.com