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Thread: Triple Vifa NE12" vs. dual Tympany LAT 700 Showdown

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    Senior Member cvjoint's Avatar
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    Triple Vifa NE12" vs. dual Tympany LAT 700 Showdown

    3 LAT 700 were bought for the job, one as a spare.

    The used LAT 700 did not make it one piece:











    The two new LAT 700s were the last stock Madisound had. A Tympany rep said they haven't made them in 3 years now, so I yanked the second one too despite only needing two total.







    The Vifa IB setup I put together was about as good as I can get it with conventional technology:






    Light, very good sensitivity throughout the band, very low inductance, very good venting etc. The reason why I decided to try the LATs is because these 3 twelves exert enough force on the baffle to bend it, and the car with it. For the most part I'm satisfied, the music masks most of the rattles for most material at most output levels. But at the end it is all masking. Try this: turn off completely, as in mute, 200hz to 5khz in the headunit. This is easy for me because that's my midrange and the P99 has an easy mute option. No matter how good the install will get through time it will never be rattle free, or even low rattle. Even you drop cement in doors and trunk there are parts in a vehicle that have to be non concrete or have to move. Those will rattle no matter what. So I decided to try the only way I know to reduce rattles from the get go, by design. So here comes the mechanical push-pull, and the LAT 700 is the largest meanest most well built design I can use, and I will use two because I think I found a way to fit them.


    More about LAT type push-pull:

    Traditional push-pull designs are electrically out of phase, mechanically out of phase and acoustically in phase we will call this Push-pull 3.It is the least desired because it can only reduce second order distortion, and the gains are even lower with very good raw drivers.

    Take two speakers, mount one forward firing and one back firing on the same flat baffle. This is the traditional push-pull:



    1.Have the same monoblock power them. This is electrically in phase, mechanically out of phase, acustically out of phase. Acoustically out of phase is bad = no output.
    I actually tried these with a pair of subs in the past. They completely cancel eachother's output. I actually think this may be a great way to test suspension noise on subwoofers. A basic SPL readout should read only mechanical noise if mounted like this and wired off the same signal. So mechanically out of phase drivers mounted on the same board electrically in phase (mono signal, or dual signal in phase) do reduce vibrations but also cancel the acoustic output nearly completely.

    2.Next, you may want to wire one electrically out of phase so they work together.
    When you do that you lose the benefits of reduced vibration and cabinet excitation but at least they produce sound. Some distortion is reduced at low frequencies (even order) when speakers are out of phase and mounted in opposite directions, but the big one for car audio...vibration is still there. Actually I'm not sure push-pull of this milder form has any benefits for say an Illuminator. They are so symmetric from factory I doubt there is any benefit to be had.

    In conclusion, a manifold has to be built to cancel vibration while producing acoustic output. Additionally it has the standard push-pull decrease in distortion. Electrically in phase, mechanically out of phase, acoustically in phase, let's call this Push-pull 2 for being the second best. It cancels vibration, it reduces second order distortion but it doesn't make the best use of space.

    Here's a sample of what a manifold would be like:



    LAT = ideal: electrically in phase, mechanically out of phase, acoustically in phase, and most efficient, let's call this Push-pull 1 for being the best.

    The LAT then adds effciency to the best push-pull design. The secret? The LAT's make better use of space by driving multiple cones per motor. 3 7" cones are driven by each motor. Instead of having 6 motors taking up space in the cylinder Tympany built two beefy motors and used the remaining space for cones. Brilliant!


    And here is a crossection of a LAT at CES, it's a great one for seeing the inner workings:
    [/QUOTE]
    Last edited by cvjoint; 04-24-2012 at 10:23 PM.

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    Founding Member benny's Avatar
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    Interested to see how this goes. :thumbsup:

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    Senior Member cvjoint's Avatar
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    Quote Originally Posted by benny View Post
    Interested to see how this goes. :thumbsup:
    Thanks! There will be another recycled post where I'll give the Woofer Tester results and then all new stuff.

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    Tester Extraordinaire ErinH's Avatar
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    Found you!

    ;)
    Your ears: The best tools you have... and they're free, too!

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    thanks for the heads up! :thumbsup:

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    Big Daddy Chad's Avatar
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    I've always wanted to try those simply because of the mechanical cancellation. Sure am interested to hear your results.

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    Senior Member pionkej's Avatar
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    I was wondering where the second half of this testing was going to wind up. In for results.
    Do you know the difference between education and experience? Education is when you read the fine print; experience is what you get when you don't.

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    Nice!
    Can't wait to see how you get those babies mounted up!
    GL!

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    Senior Member cvjoint's Avatar
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    Lat 700 TS specs as tested with a WT2:
    Unit 1 - Used

    Unit 2 - New

    Unit 3 - New


    Comments:
    The variation across the three samples seems very low. That means a lot of good things are happening, the test methodology is reliable, Tympany did a great job with unit to unit consistency, and the longevity of the product is really good with little parameter shift over time.

    Things that peek my interest:
    * the impedance curve is smooth overall with a slight wiggle at 400hz. I take that to be some sort of resonance problem so a 200hz LP seems like a good idea.
    * the FS is nice and low at around 26.5hz like a true large sub.
    * QTS is around .56 which is ideal for pure IB. Seems to me like this LAT is not meant for a small box at all, but rather an infinitely large box. To double check my back of the envelope calculation I threw the driver in WinISD. It likes a sealed box volume of over 6 cubes for the typical .7 Q. Definitely a very large sealed box. I would compare one of these units to a single very high output 12", so it's a massive space hog compared to a typical car audio sub. Again, something about Tympany's marketing for these guys just doesn't add up.
    * lastly the inductance is quite high. Given the push-pull arrangement asymmetries don't bother me that much, but the large magnitude would make me think twice about using it up to 200hz, as a midbass. As a sub the LE performance gets a pass. Clearly the large coils while they can take loads of beating also store a lot of energy. When modeled in WinISD the high LE induces a rolloff as early as 70hz, ok for a sub, not ok for a midbass.

    This design can be easily improved by using the NE 12" motor, it would save weight, increase linear displacement, concentrate the BL in the gap better, and lower inductance. Since these LATs didn't work out for the company, skipping the higher end parts was probably a fine choice business wise but precludes the driver from being used as a midbass. A shame for some applications.

    I'm trying to get these fired up tomorrow if I can.

  10. #10
    Senior Member James Bang's Avatar
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    Good to see you active, George.

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