# INFO: Isobaric vs Box Setups ? Pros & Cons ?



## Sire One (Apr 11, 2003)

*ISOBARIC:*
The subs were mounted in an isobaric configuration (they faced each other, mounted on a baffle board). The polarity (+/-) of one of the subs was reversed so one sub would "push" while the other "pulled."









What are the pros and cons of an isobaric setup, as opposed to a conventional box setup? I would rather use my whole trunk and make that the air space.
Thanks


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## vedubau (Jan 17, 2001)

*Re: INFO: Isobaric vs Box Setups ? Pros & Cons ? (Sire One)*

Pros of Isobaric:
1. Box half the size 
2. Odd-order nonlinearities cancelled (reduced driver distortion)
Cons of Isobaric:
1. Sensitivity (loudness) of a pair will be the same as a single driver
A good reference on speaker enclosure design is the Loudspeaker Design Cookbook








http://search.barnesandnoble.c...kbook 



_Modified by cchristensen at 4:39 PM 12-30-2003_


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## vedubau (Jan 17, 2001)

*Re: INFO: Isobaric vs Box Setups ? Pros & Cons ? (Sire One)*

Also, after reading your post again, I better understand what you are asking. IMO Isobaric setups should not be used in an *infinite baffle* setup (ie. using the hole trunk as an enclosure). If you want to use the trunk as the enclosure, you want a high Q woofer (Qtc of .6 and above). Also, using just a baffle board, you will want to seal the trunk from the passenger compartment as much as possible. As I mentioned in my first post, isobaric reduces the size of the enclosure. You could still do the clamshell on a baffle board, but you will want to run high Q woofers, and I don't think you will see much advantage.



_Modified by cchristensen at 4:44 PM 12-30-2003_


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## Sire One (Apr 11, 2003)

*Re: INFO: Isobaric vs Box Setups ? Pros & Cons ? (cchristensen)*


_Quote, originally posted by *cchristensen* »_Also, after reading your post again, I better understand what you are asking. IMO Isobaric setups should not be used in an *infinite baffle* setup (ie. using the hole trunk as an enclosure). If you want to use the trunk as the enclosure, you want a high Q woofer (Qtc of .6 and above). Also, using just a baffle board, you will want to seal the trunk from the passenger compartment as much as possible. As I mentioned in my first post, isobaric reduces the size of the enclosure. You could still do the clamshell on a baffle board, but you will want to run high Q woofers, and I don't think you will see much advantage.

my trunk will be rendered useless, as i would prefer not to use it anymore. therefore i am seeking an infinite baffle setup, which will take advantage of the whole trunk. to be more specific, i am looking to cram 6+ speakers in the back of the trunk. i was looking to go isobaric, as i can readily dismantle it when needed. asthetically for me, it has minimum requirements, and can have a very clean look to it
what setups can be used for an infinite baffle setup, if isobaric is not recommended?
do you have any pics of clam shell setups?



_Modified by Sire One at 2:56 PM 12-30-2003_


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## vedubau (Jan 17, 2001)

*Re: INFO: Isobaric vs Box Setups ? Pros & Cons ? (Sire One)*


_Quote, originally posted by *Sire One* »_my trunk will be rendered useless, as i would prefer not to use it anymore. therefore i am seeking an infinite baffle setup, which will take advantage of the whole trunk.

I think you may be confusing terms. Isobarik enclosures are smaller boxes that use two speakers to work as one, and Infinite baffle are basically baffle boards, or very large enclosures such as your trunk. Why do you want to use 6 speakers? In a properly designed isobarik enclosure, those six speakers will have the same output as three of those in an enclosure twice the size. Since I'm not really sure what you are after as far as sound goes, or what products you currently have, its difficult to advise.

_Quote, originally posted by *Sire One* »_i was looking to go isobaric, as i can readily dismantle it when needed. asthetically for me, it has minimum requirements, and can have a very clean look to it

I personally don't think one can be removed easier than the other if designed properly. Installation is the key. I can remove my system and restore to factory in about 4 hours tops since I made no damaging modifications.


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## 2.ohh (Jun 21, 2002)

*Re: INFO: Isobaric vs Box Setups ? Pros & Cons ? (Sire One)*

cchristensen is giving out some good info about iso configs, but why the hell do you want 6+ subs in your trunk? if you can't do what you want to do with 4 or less, it's not really worth it







why not just get 1 or 2 really good subs, like W7, brahma, XXX, A-series, IDMAX, etc?


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## Sire One (Apr 11, 2003)

*Re: INFO: Isobaric vs Box Setups ? Pros & Cons ? (Sire One)*

first off the reason why i want to use 6+ subs, is that i already have a deal on them. this deal is way cheaper than cost, and the vendor is willing to install all of them.
i would like to use my trunk as the enclosure as there will be no box. if you can imagine the speakers suspended in an open isobaric setup, thats what i would like to accomplish.
basically there would be an upside "U" shaped box. this "U" shape would hold the speakers in place. since its a "U" shape, you can see there are open sides, thus the trunk would now be the enclosure.


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## vedubau (Jan 17, 2001)

*Re: INFO: Isobaric vs Box Setups ? Pros & Cons ? (Sire One)*

If the subs are designed for "free-air" or "infinite baffle" (generally high "Q") then it may (stress may) sound okay. But anytime you mount subs in a clamshell or any other isobarik setup, the enclosure must be half the size for the same woofer in conventional format. We would really need to know the Theile-Small parameters of the subs and more info on the baffle board. Will the trunk be completely sealed between the passenger compartment and the trunk? What size are these...8s...10s? In any speaker enclosure design one side of the speaker must be totally isolated from the other, or cancellations will occur. Ever see one of those beater specials with the 6"X9" speakers in the rear deck laying against the rear window and resting on the rear deck? They will have no bass because the rear of the speaker is producing the same as the fronts and when they come together, they cancel and all you can hear are the highs. Samething will happen with your setup, unless you completely seal or isolate the front of the baffle from the rear.


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## Sire One (Apr 11, 2003)

*Re: INFO: Isobaric vs Box Setups ? Pros & Cons ? (vedubau)*

the trunk is roughly 20" x 40" x 40" [h w d]
yes, the subs i will be selecting will be designed for free air and infinite baffle.
currently i do not have the thiele-small parameters of the subs, as i have yet to select them. right now i would really like to accomplish 8 subs in the trunk. preferably the subs would be 12", if they cannot fit, if not 10" subs will do. the total amount of speakers will be reduced if they cannot fit. for example, if 8 cannot fit, we will reduce it to 6, then to 4.
the trunk will be completely sealed from the passenger area, but i do have a question for you in regards to that. does the rear shelf need to be sealed off as well [flat area right under the rear window]? i will be sealing as much area off with plexiglass. if by some way i can seal the rear of the trunk, i will be doing that as well.
look wise, i want an open area so it looks clean. i do not like the clutter of boxes and other things like that.
now back on to the speakers, my friend has a good deal on earthquake subs.
thanks again for your input


_Modified by Sire One at 12:54 AM 1-3-2004_


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## VReihenmotor6 (Dec 12, 2001)

*Re: INFO: Isobaric vs Box Setups ? Pros & Cons ? (Sire One)*

from what I understand if one of the 2 subs mounted isobaricaly has a pinhole leak in the surround then the subs can actulay blow up as they will acutaly "pump" the area between them up with pressurised air

I can't belive this is too common, but just so ya know


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## Sire One (Apr 11, 2003)

*Re: INFO: Isobaric vs Box Setups ? Pros & Cons ? (VReihenmotor6)*


_Quote, originally posted by *VReihenmotor6* »_from what I understand if one of the 2 subs mounted isobaricaly has a pinhole leak in the surround then the subs can actulay blow up as they will acutaly "pump" the area between them up with pressurised air

I can't belive this is too common, but just so ya know

the subs will be professionally installed by a manufacturers representative. thus the speakers will be warranteed


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## vedubau (Jan 17, 2001)

*Re: INFO: Isobaric vs Box Setups ? Pros & Cons ? (Sire One)*


_Quote, originally posted by *Sire One* »_the subs will be professionally installed by a manufacturers representative. thus the speakers will be warranteed

If hese will be installed by the manufacturer or someone associated with the company, they should be able to advise you better on the install. Anytime you use the trunk as an enclosure though, you should seal everything! That means pulling out all carpeting and sealing all those nooks and crannies and the rear deck for sure...air tight.


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