Q: single 12"sealed, or 2 12" isobaric
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=62301
Printed Date: May 13, 2024 at 11:52 PM
Topic: Q: single 12"sealed, or 2 12" isobaric
Posted By: aaronk
Subject: Q: single 12"sealed, or 2 12" isobaric
Date Posted: September 06, 2005 at 7:28 PM
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??? The reason behind it is space. Right now they are both in a sealed box and it takes up 2/3 of the trunk (3cu.ft.). Thats why its either one single or two isobaric... Since we have two speakers and an amp already, I jsut figured might as well use both speakers and load down the amp to its rated 4ohms...
Suggestions?
[IMG]https://www.the12volt.com/images2/sealed.gif[/IMG]
[IMG]https://www.the12volt.com/images2/isosealed.gif[/IMG]
[IMG]https://www.the12volt.com/images2/isocompsealed.gif[/IMG]
[IMG]https://www.the12volt.com/images2/isobacksealed.gif[/IMG]
[IMG]https://www.the12volt.com/images2/isoplanarsealed.gif[/IMG]
Replies:
Posted By: DYohn
Date Posted: September 06, 2005 at 8:25 PM
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
Posted By: Silvrefox
Date Posted: September 06, 2005 at 9:30 PM
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?
Thanks
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BOOSH!!
Posted By: haemphyst
Date Posted: September 07, 2005 at 7:24 AM
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!
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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."
Posted By: DYohn
Date Posted: September 07, 2005 at 8:33 AM
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
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