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Thread: Push-Pull benefits

  1. #11
    Senior Member cvjoint's Avatar
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    One trick is to test a LAT with only one motor hooked up. I did get TS parameters this way having only one side working then both. I was curious as to whether the resonance peak gets reduced a lot in push-pull. It does so only marginally. Not sure why Zaph got the 250s resonant peak so low, zmax is close to 20 ohm on mine, like any low distortion 2.5" driver.

    But... I don't have Klippel to test the LAT with only one motor working and then with both. I guess to make this work one would need two LAT 700s on a baffle. Run one motor on each so that there are still 2 drivers working but not in push-pull. Then deactivate one LAT and hook up one LAT completely so that the push-pull works. This would keep all other variables fixed. Same motors, same suspensions, same inductance properties, same number of said drivers operating between conventional and push-pull.

    Heck, I can do this in my car! I can get you guys HD plots since I have two LAT 700s mounted in the trunk. It's an in car test but conditions remain fixed which is the important bit. What do you think? The non-working drivers will probably act like some passive radiators but whatever.

  2. #12
    Senior Member cvjoint's Avatar
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    If the LAT motor is highly linear then push-pull won't do much. I mostly like them for vibration canceling but I can't do rub and buzz type tests on the Dayton Omnimic to see how much they help in that department. It would be nice to start with a driver with loads of offset but otherwise gargantuan peak to peak BL and xmech.

  3. #13
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    My understanding is the biggest benefit is double the BL without changing other T/S parameters.

  4. #14
    Senior Member cvjoint's Avatar
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    Quote Originally Posted by durwood View Post
    Correct me if I am wrong, but isn't the tymphany reversed polarity? They are mechanically connected, so if one wasn't flipped they would do nothing.

    The problem I had with the PI link is it appears to compare push pull to non-push pull, but where is his exact design measured with push pull and without? Instead it compares other brands of subs...too many variables unless I missed it. I only linked it as a possible lead on further information.
    I just checked the polarity with a battery. The LAT indeed is properly color coded so that both motors push at the same time. Any two opposing woofers in the same slot move towards eachother and squeeze air through the gap. That is why this push-pull design, unlike other push-pulls also cancels vibration. It may be a misnomer and it's more like a push-push.

    Based on the Pi links this is most effective when the slots are as close as possible to each other. Again, Tympany is unmatchable here as the carbon fiber rod system can pack speakers way more densily than separate drivers in a manifold. You no longer have to account for the size of the motor when designing a small gap slot. The next best would be a shallow woofer design in a baffle but there is likely a lot more chuffing noise produced.

    Quote Originally Posted by Whiterabbit View Post
    My understanding is the biggest benefit is double the BL without changing other T/S parameters.
    Haven't heard of this one. How would the BL double?
    Last edited by cvjoint; 06-12-2012 at 11:03 PM.

  5. #15
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    The idea is with two motors working together, you get twice the force. Thus, double the BL. And in fact, you will find that the modeling shows exactly that, with 2x BL and all other *small* params the same.

    Of course, if you are not talking about push-pull but rather multiple diaphragms working to simultaneously pressurize the same space (ie using two subwoofers instead of one), regardless of whether it is multi-driver or multiple cones in some sort of clever baffle arrangement, we are talking about something different.

    But you asked about "push-pull". Which is a well understood buzz-word with a very specific meaning.

  6. #16
    Founding Member Subwoofery's Avatar
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    wrong thread lol

  7. #17
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    to answer your question anyways, I bet 10 bucks that the russian principle would hold. With NO enclosure, would be inefficient as hell, but so overblown and overkill it would still work anyways.

    Just a guess....

  8. #18
    Senior Member cvjoint's Avatar
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    Two motors, two times the BL. Sure, I don't see why not. But that's not any different than doubling the number of drivers is there? Maybe its' your way of saying push-pull doesn't work. I don't know. You can't really model THD...

    I don't see how the lack of enclosure makes things inneficient? The smaller the enclosure the more inneficient the design. It's backwards.

    Typmpany uses push-pull to describe the LATs, if it were me I'd call it more a push-push.

  9. #19
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    Quote Originally Posted by cvjoint View Post
    Two motors, two times the BL. Sure, I don't see why not. But that's not any different than doubling the number of drivers is there?

    Maybe its' your way of saying push-pull doesn't work. I don't know.
    I'm not saying anything "between the lines". I'm also not referencing anything that has anything to do with your LAT drivers. I am merely commenting on your original question about "push-pull" configurations. Based on the generally accepted and generally understood concept of what "push-pull" is and means. *Should* be double BL.

    That is totally different than doubling drivers. Doubling drivers doubles Sd, not BL.

  10. #20
    Senior Member cvjoint's Avatar
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    I think the BL does double does it not? Some drivers have the same motor going from one size to another. My guess is that it is true for say 6.5" to 8" Peerless SLS. Using two 6" vs. one 8" will generally mean smaller box for dual motors, because we get effectively similar SD with one vs. two motors (more BL).

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