Question about PR displacement vs driver displacement

Discussion in 'Home Theater Projects' started by Frank Carter, Jul 15, 2005.

  1. Frank Carter

    Frank Carter Screenwriter

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    I know your PR's should have ~2x the Vd of your driver(s) at a minimum. From just looking at excursion simulations, I'm not coming close to the limits of my PR.

    Would it be acceptable to use use PR's with slightly less than 2x the Vd of my driver?

    The driver I own is the Ascendant Audio Avalance 12 and the PR's I was looking at were 2 of the Dayton DVC 12" PR's. With my box dimensions I can only fit 12" PR's and these are the highest excursion PR's I could find.

    Anyone have experience with using PR's in a car environment?

    I've read a little about having high mass and a soft suspension PR's aren't as practical in a car but Boston Acoustics sells PR's for use exclusively for their car stuff.

    What kind of problems would I be likely to run into? What do you think the chances of having a problem are?



    Thanks in advance for any responses.

    Regards,

    Frank
     
  2. Marc LaPalme

    Marc LaPalme Agent

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    i can't think of any one reason why you shouldn't be able to use a passive radiator in a car other than perhaps car movement moving the cone in ways you wouldn't want.

    i'm thinking way out there that maybe the resonance of the car could induce unwanted vibrations in a cone that isn't governed by a magnet and is free to oscilate at certain frequencies that it is given.

    just a thought. i may be wrong.


    http://www.diysubwoofers.org/prd/

    this link will help you figure out the weight of your passive radiators.

    great site if you havent checked it out yet.
     
  3. stephanX

    stephanX Stunt Coordinator

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    every direction change, or movement whatsoever of the car, would change the parameters of the pr, which wouldnt be acceptable, not to mention if you hit a big bass peak below tuning while turning, the extra momentum might have enough energy to rip the PR apart. But that would be kinda cool.
     
  4. Chris Popovich

    Chris Popovich Stunt Coordinator

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    PR's can be used in cars, obviously they couldn't be down or up-firing, but short of that, sure, give it a shot -several companies have sub/pr combo's available.

    I don't think the forward/turning motion of the car would be that big of a deal, but I'd probably have the PR be side firing just to minimize the accell/braking inputs; people tend to accellerate and brake withhigher forces involved than most cornering.


    As far as the 2x Vd thing; it's not that big of a deal if you aren't running your sub to max capacity OR if you have a subsonic filter, but I'd be careful if nothing else.


    Let us know how it works,


    Chris
     
  5. Frank Carter

    Frank Carter Screenwriter

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    I think I'm going to try it. I work at Tweeter and we've had someone do a Boston Acoustics PR in their car w/no problem. If it doesn't work, I'm only out $120.

    I'll report back.
     
  6. MichaelAngelo

    MichaelAngelo Stunt Coordinator

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    Give it a whirl Frank. PR's can be used in cars- Kicker had a line of boxes ~20 yrs ago with PR's in them, a 8" woofer w a 10" PR, and a tweeter on top. Had some in a truck.
     
  7. JimPeitersen

    JimPeitersen Second Unit

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    Remember this as well, the old warnings about PR's in cars was most likely due to the construction of the old models (relatively high Fs, low excursion, loose suspensions, etc.) The newer PR's are very "sturdy" and should be able to handle the rigors of the auto environment with no problems.
    JP
     

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