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Thread: Push-Pull benefits

  1. #21
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    you are comparing apples to oranges. to simplify, if you have your 6.5 in a box, then double that, two boxes, two 6.5's, you did not just double your BL. You just doubled SD. That's not push-pull either, in the traditional sense of the term.

  2. #22
    Senior Member cvjoint's Avatar
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    So if we model two 6.5" and a fantasy driver that has all the same specs but double SD they should model the same? All I could find about doubling BL and push-pull was on isobaric designs.

  3. #23
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    You bet. Which is precisely what push-pull means in the traditional sense.

  4. #24
    Senior Member cvjoint's Avatar
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    Well I did and they model differently. Something doesn't add up.

  5. #25
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    NOW, if you are talking about "mounting one driver in opposite direction and flipping phase" as per post #5, then you are back to doubling Sd and changing nothing else, assuming your box size doubles. As per the example I gave of one 6.5 in a box, then double that to have two 6.5's in two boxes. BL is the same. Just double Sd. And if the passband is below the threshold to interact with the motor that is now sticking out of the box (bass frequencies) then the whole thing doesn't really care if you invert mounted the driver. It's just the same as having a two-woofer system (bass example).

    I can not explain why LAT calls their design push pull if there is no isobaric chamber. Unless they simply mean having two motors acting on the same diaphragm, regardless of how complex that diaphragm may be. If that's the case, we could make all sorts of speculation as to why they used two motors. My speculation is that it allows the physical size of the mechanical frame to be reduced to provide the same rigidity and power as compared to a system that has to move multiple diaphragms and framework but all from a single end.

    But not really the traditional sense of push pull. Certainly not the idea of the multi-element system on a folded baffle, and definitely definitely not a 2 motor system where one motor is simply invert mounted and wired in reverse polarity. Not Push-Pull!

  6. #26
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    I'd imagine there is an issue with the model I really strongly suspect we are talking about two completely different things.

  7. #27
    Senior Member cvjoint's Avatar
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    WinISD is what I use.

    As for traditional push-pull I don't think there is a set design but rather a category. From what I gather isobaric is usually referred to as simply isobaric and push-pull is what this site refers to as compound push-pull:
    Audio Innovation - by Dan Marx www.danmarx.org
    Linkwitz's H-frame is also push-pull even though it's not isobaric in anyway:
    Dipole Woofer

  8. #28
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    As for the the dan marx website, he confirms my suggestion:

    "Response it essentially identical to building two smaller enclosures of exactly half the size "

    As for the linkwitz site, that's the folded baffle I suggested in post 25. If the design were to mount the cones facing each other, would you still consider it push-pull?

    From the T/S perspective, I'm pretty sure they (the drivers) don't care. from a distortion perspective, I'll let those with more experience chime in.

  9. #29
    Senior Member cvjoint's Avatar
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    My only point was that searching for the "traditional" push-pull is not clean cut. Here Linkwitz refers to his H-frame as push-pull:
    http://www.linkwitzlab.com/Orion-TSS-review.pdf

    The response will be the same but the distortion profile would not. In the compound push-pull design even order distortion will be minimized. Linkwitz or LAT type push-pulls will minimize even order and high order by virtue of reducing rattles and cabinet resonance.

  10. #30
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    Ah so now it makes sense how the LAT is configured. I always thought they were all connected and polarity was flipped.

    They are opposite of isobaric push-pull, because your BL is the same, but you have more mass due to the extra cones and mechanics involved. The only advantage of the LAT system is the orientation of the cone motion with respect to the front baffle (travels along instead of perpendicular), and opposing forces. At least that is what I see.

    I don't think (but don't know for sure) the LAT would have the even order distortion cancellation that compound push-pull, or Isobaric would have. In the LAT, the motors are moving in the same direction always, and the rest are mechanically driven passive radiators in a sense and just become part of the motor it is attached to. You would need to measure. Run one motor in a box sized for one motor, then run both in a box sized for both. Is the even order reduced?

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