# isobaric seems to be a thing of the past, but.....



## selftc (Jan 22, 2007)

...i find myself cramped for space, also willing to try consider something different. isobaric will pretty much take enclosure specs and cut them in half. since i only have .5 cu. ft. to comfortably work with, an isobaric enclosure would open up a new selection of subs. though it will hurt the pocket book, i wonder would it even be worth the added money and complexity ? or just old hat ?


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## JayBee (Oct 6, 2006)

I've done it in the past with good results. I had a couple of Lanzar DCs in a push pull config with an ring between them in a tiny ass box and it worked great.


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## Thumper26 (Sep 23, 2005)

as long as you have the depth to put an iso box, go for it. and post pics!!!


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## Aaron'z 2.5RS/WRX (Oct 24, 2007)

There are different ways of going about it, for space, like cone to magnet, nets a little more space compared to cone to cone... 

You reminded me of a hilarious story from the beginnings of my install days... 

My installation Mentor, showed me pics (all pre-digi, so I don't have copies) of his Suzuki Samurai that he had 4-15" and 6-12" in   

The 4 15's were in cone to magnet isobaric 2 behind each seat, and the 6 12's were in sealed in a V shaped box, sitting on top of the 15's... all run from Orion 225 HCCAs and he had door panels from HELL 8/6.5/5.25/3/1" speakers in each... He said it was an "exercise" in installation...


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## 89grand (Nov 23, 2006)

Isobaric boxes seem almost unnecessary these days as so many subs are small box subs anyway.


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## kevin k. (May 5, 2005)

http://www.whitledgedesigns.com


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## rsvchad (May 28, 2007)

It isn't common anymore because almost all subwoofers are designed to operate in small boxes these days. It seems the average 10" driver is designed to work in .5 - .7 sealed cu.ft. today; compare that to drivers 15 years ago, when the typical 10" car audio driver required 1+ cu.ft. As the power got cheaper drivers started to mimic the performance charateristics of an isobaric pair more and more. More mass and more motor, resulting in less efficiency, but the ability to be used in a tiny enclosure.


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## Boostedrex (Apr 4, 2007)

Have you thought about using an aperiodic enclosure? Or just finding a sub that is designed to work in the .5 ft^3 you have available?

Zach


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## selftc (Jan 22, 2007)

Boostedrex said:


> Have you thought about using an aperiodic enclosure? Or just finding a sub that is designed to work in the .5 ft^3 you have available?
> 
> Zach



i've used a couple of .5 ft^3 drivers, ie. ed 11kv & 11ov, and tc sounds tc-1000. even tried a diamond d9. just thought about trying something new. the RSDc calls for .5 gross so that is another option if i rule out an iso enclosure. its just that putting a single sub in a single sealed box seems boring at the moment...


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## thehatedguy (May 4, 2007)

A cone to magnet will take up a lot more physical space than the cone to cone. Cone to cone would have the smallest box size, but you would still have to account for the physical size of the basket and motor of the sub outside of the enclosure.


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## selftc (Jan 22, 2007)

thehatedguy said:


> A cone to magnet will take up a lot more physical space than the cone to cone. Cone to cone would have the smallest box size, but you would still have to account for the physical size of the basket and motor of the sub outside of the enclosure.


in my case, a cone to cone would be the easiest to accomodate. depth of cone to magnet would be too deep.


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## thehatedguy (May 4, 2007)

Good little primer on isobaric styles:

http://mobile.jlaudio.com/support_pages.php?page_id=152


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## DonutHands (Jan 27, 2006)

so, why in the world did http://www.whitledgedesigns.com design a setup using an isobaric enclosure. it makes no sense to me.


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## exmaxima1 (May 31, 2007)

selftc said:


> ...i find myself cramped for space, also willing to try consider something different. isobaric will pretty much take enclosure specs and cut them in half. since i only have .5 cu. ft. to comfortably work with,


As noted by several others, there are numerous subs that will accommodate .5 Ft3 sealed enclosures. If you use a 10-inch woofer, or larger, of reasonable Xmax, it is not practical to build a smaller box. The non-linearity of compressing/rarifying a smaller air space will make the sub sound compressed and lacking dynamics. 

The rule of thumb is that you cannot compress/rarify the air more than 5% of its volume without audible distortion.

Good Luck.

Matthew


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## selftc (Jan 22, 2007)

exmaxima1 said:


> As noted by several others, there are numerous subs that will accommodate .5 Ft3 sealed enclosures.


i already know this, as i've even mentioned the .5 ft^3 drivers that i've used. just the thought of trying something different lead to me creating this thread. the idea of cramming (2) 12s (cone to cone) in a .5 ft^3 enclosure sounds cool to me.


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## 89grand (Nov 23, 2006)

selftc said:


> i already know this, as i've even mentioned the .5 ft^3 drivers that i've used. just the thought of trying something different lead to me creating this thread. the idea of cramming (2) 12s (cone to cone) in a .5 ft^3 enclosure sounds cool to me.


I'm unclear as to how you only have enough room for a .5 ft3 enclosure, yet you have enough room for an Isobaric setup?

They take up space too, in fact, even when they were popular, back in the 90's, I thought they were pretty dumb.


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## selftc (Jan 22, 2007)

89grand said:


> I'm unclear as to how you only have enough room for a .5 ft3 enclosure, yet you have enough room for an Isobaric setup?



partly due to cosmetics. i want the enclosure to set the same exact height as my amp rack. given that height and also max. length and width, puts me right at .5 ft^3. i don't mind an inverted sub sticking out of the top of the box, just want box and amp rack to match up perfectly.

here's a shot of the amp rack.


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## OldOneEye (Jun 16, 2005)

internecine said:


> so, why in the world did http://www.whitledgedesigns.com design a setup using an isobaric enclosure. it makes no sense to me.


Cone to cone cancels some of the non-linearity from what I can gather (the other upside besides smaller boxes).

Juan


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## invecs (Jul 30, 2005)

OldOneEye said:


> Cone to cone cancels some of the non-linearity from what I can gather (the other upside besides smaller boxes).
> 
> Juan


Yup. I used to run an isobaric clamshell configuration using 2 Soundstream Reference 12s. I have never heard any subsystem that has such control...I miss that setup.


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## Oliver (Jun 25, 2007)

OldOneEye said:


> Cone to cone cancels some of the non-linearity from what I can gather (the other upside besides smaller boxes).
> 
> Juan


Egg zackly  [possible gain in harmonics area ]. Pretty expensive subbass, two drivers = output of one driver, twice as much power required {additional amp channel}.


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## HondAudio (Oct 19, 2006)

I saw a home subwoofer a few years ago that was a cone-to-magnet isobaric design, except the front "woofer" was actually a passive radiator. Supposedly any distortion created by the active driver would be cancelled out within the sealed box in front of the driver but behind the passive radiator.


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## HondAudio (Oct 19, 2006)

Ok, this is what I was talking about. The James Loudspeakers EMB-1000:


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## Infinity (Jun 28, 2005)

That's just a simple 4th order (single reflex) bandpass using a PR instead of a standard port. It works well, and can get BP enclosure sizes down to a reasonable level. You do need to have plenty of displacement on the PR or you'll bottom it easily. I tried to do a 6th order that way once, but it never sounded the way it modeled up.


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## JayBee (Oct 6, 2006)

The only problem i really see is your current sub amp. You would need to find 2 fairly efficient subs for the project. Some Arc, ID or eD entry level subs would work well with the power you have. You could always try to find some nice old school drivers.


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## bigjae1976 (Jun 21, 2007)

Unless you are going to for aesthetics I don't think an isobaric setup is worth doing. You can find a lot of 10" drivers that will work in a .5 cu ft vented box...without having to buy a second driver.


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## mac855t5r (Mar 13, 2008)

I'm building an clamshell isobaric pair of NOS Macdaddy 10.4's, into what is a small Merc / Dodge van cab, powered by a Genesis S3 MonoBlock.

The birth sheet for the amp shows 410w @ 4ohm and 776w @ 2ohm.

Using the original datasheet from Diamond, I'm intending to use a guide volume of 0.3 ft^3 to build an air cylinder style, 10" dia enclosure from 1/8" wall ali (dome capped).

Am I correct in assuming that each drive will 'see' about 390w?

From your experience, should I err on the large or small side of this volume to achieve a more 'musical' sub setup?

It's to partner a passive set of Dyn 362's (powered by a MiniBlock each)

Note: I too am tight on space. The intention is to 'poke' the magnet of the outer sub thru the side wall of the passenger seat box. 
I know that cylindrical forms are not the most space efficient way of doing this, and I could prob make the required vol for a single sub, but hey!, I've got the subs anyway and I've 'just' got the space to suspend the sub cylinder in a bungee cradle, just to see how it behaves when isolated is much as poss.

Dave.


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