Isobarik subs

Discussion in 'Archived Threads 2001-2004' started by Ches Campbell, Jun 17, 2002.

  1. Ches Campbell

    Ches Campbell Stunt Coordinator

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    Anyone have some pictures and info on isobarik subs? I would really appreciate any help.
    The way I understand isobarik is that the subs face each other with only the thickness of the wood separating them. You build a box around one of them. Wire one in phase and oe out of phase and that's it. This is only my guess. I have absolutely no idea if this is correct, i just made up this explanation based on what little info I have about them. All i know is it uses two speakers facing each other, and doesn't require a huge box.
    Any info is greatly appreciated.
    Thanks
     
  2. Dustin B

    Dustin B Producer

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    That's the clamshell config. They don't have to be mounted that way, although that is the easiest way. The only thing is the air between the drivers has to be trapped (ie sealed in). And the smaller that space the better. So it's more difficult and results in a larger space between the drivers, but you can mount them facing the same way or with the motors facing each other.

    This cuts the Vas if half and changes a few other things that I can't remember right now. One of the more knowledgable will get here eventually to elaborate.
     
  3. Will Pomeroy

    Will Pomeroy Stunt Coordinator

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    "In order to get more bass out of a smaller box, isobaric driver mounting was invented. An isobaric system is constructed of two (usually) identical drivers mounted in a small sealed subenclosure. Wired in phase, the drivers are mounted front-to-back with the same orientation (as shown). Wired out of phase, the drivers may be mounted with either with a front-to-front ("clamshell") or back-to-back orientation. Such opposed mounting is actually preferable since it discourages standing waves between the two drivers' cones.
    As opposed to arrays, an isobaric system may be considered a multiple driver system with its drivers acoustically in series rather than acoustically in parallel as in an array. Isobaric designs are inefficient, both acoustically and financially, yet they are a legitimate means of reducing the size of a system. Unlike arrays, isobaric systems enjoy no Vd advantage over single driver systems.. Isobaric systems may be either sealed or vented."
    (Bob Stout)
    http://www.snippets.org/ldsg/boxes.php3
     
  4. Benjamin_M

    Benjamin_M Extra

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    Is size reduction the only benifit of a iso-baric sub confiruration?
     
  5. AndersP

    AndersP Stunt Coordinator

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    No, but it is the most important benefit. You also get nulled out some unlinearities from the difference in the in vs. out action of the drivers. You loose some efficiency though.
    As long as you use 2 identical drivers, there are more ways to get this last benefit.
    Buy Dickasons Cookbook and find out more. This book explains this and many other things with lots of pictures.
     
  6. Ches Campbell

    Ches Campbell Stunt Coordinator

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    Well, I think I have decided against the isobarik sub. I don't want to lose 3 db of output. Thanks for all of the replies though. I may build one in the future.
    Later
     
  7. Scott Simonian

    Scott Simonian Screenwriter

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    Some people say that the "Isobarik" configuration yields tighter, more articulate bass.
    I myself am curious of this benefit. Does this occur?
    Cause if it is substantial, Im gonna be very poor soon. [​IMG]
     
  8. Jack Gilvey

    Jack Gilvey Producer

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  9. Scott Simonian

    Scott Simonian Screenwriter

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  10. Greg Monfort

    Greg Monfort Supporting Actor

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    >Something about the when the inner woofer moves in, the gap between them has a change in pressure. (It should drop, severly) And when this happens, the outer driver is pulled with it, effectivly dampning each other like being in a sealed enclosure.
    ====
    One's wired positive and the other negative so they move in-out ~ in unison, but because one is pressurizing the cab, the other driver tries to compress the air in between. When moving out of the cab, there's a certain amount of suction on it so the other tries to draw away from it, so in theory there's some damping, but not enough to audibly impact the cab's damping, and really, it's increased distortion.

    This can be minimized somewhat though by filling the cavity between the drivers with polyfil. Ideally, they would be mechanically coupled together.

    FWIW, while even order harmonics are cancelled if they are done this way, this isn't necessarily a good thing since we find even order harmonics 'euphonic' and odd order, 'distortion'. With no/attenuated even orders to mask the odd orders, overall sound quality in theory goes down.

    GM
     
  11. Kerry Hackney

    Kerry Hackney Stunt Coordinator

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    FWIW, Subs aren't the only app for isobaric drivers. I have read some tests of Totum (sp) and Linn monitors that also use the design in monitor applications. The resultant speaker will have possibly deeper response from the same footprint and also possibly better distortion figures. The downside is lower impedence loads for the amplifier and a slightly more complicated cabinet.
     
  12. Greg Monfort

    Greg Monfort Supporting Actor

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    Yes, if you put the drivers in tandem to get the volume between them down and stuff what's left without impeding movement you can get some gains for a given Vb WRT one driver, though they will be no different than with a single driver, so to get more LF/lower distortion it's at the expense of even more efficiency loss. [​IMG]
    GM
     

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