can someone explain passive radiators to me?

Discussion in 'Archived Threads 2001-2004' started by john_focal, Sep 13, 2002.

  1. john_focal

    john_focal Agent

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    Im assuming they are for sealed enclosures.. what benefits do they offer? Drawbacks?

    Also, where can I get some beginner info on the specs you guys always toss around for cabinets and such?

    Thanks!
     
  2. Kyle Richardson

    Kyle Richardson Screenwriter

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    Passive radiator based subs act very much like ported subwoofers except thieir rolloff is steeper than a ported system below tuning. They allow different tuning of the suboofer based upon their weight and any weight that may be added.
    They are traditionally used in smaller subwoofer enclosures where ports would be too long to fit inside. Small drawbacks are that they usually cost more than ports and you have to make sure you have enough passive radiator area to compensate for the subwoofer driver movement (read: harder to design the sub if you are a novice).
    Check out diysubwoofers for a buch of information for the DIY newbie.
     
  3. Blake R

    Blake R Stunt Coordinator

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    In a more fundamental sense a passive radiator is a thin membrane structure designed to be resonant at a particular frequency or range of frequencies. The "PR" is based on the concept of "sympathetic vibration" much like the way windows will rattle when a helicopter flys low over your house. The resonant frequency would be dependendent on the thickness and diameter of the membrane. In the past speakers have been manufactured with passive radiators that even attempted resonance at higher audio frequencies, say in the audio mid band. The best application for such radiators is still at very low frequencies.
     
  4. Thy Luc

    Thy Luc Agent

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    PR = sloppy bass - LOL
    shake rattle and roll, good for games and HT.
    I don't like them for music.

    If you like them for music, two thumbs up for you.. yay!
     
  5. john_focal

    john_focal Agent

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    thanks for the links [​IMG]
    just trying to learn whats out there, hehe.
     
  6. Thy Luc

    Thy Luc Agent

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    --Wrong. That's only true of you have no idea how to design --competently. LOL.

    Nobody wins subjective arguments. Properly designed or not,
    they sound as I described above. LOL
     
  7. Will Orth

    Will Orth Stunt Coordinator

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    Well I messed with passive radiators years back and if you make a good box from the get go you are ahead of the game, I look at passive radiators as a band aid, make a great enclosure and you wont need to mess with those things, just look at the top speaker manufactures, how many do you see these days using them? I have not seen one in the last 2 years.



    Will
     
  8. RichardMA

    RichardMA Second Unit

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    More a controlled way of producing an effect similar to
    that of a port.
     
  9. Jack Gilvey

    Jack Gilvey Producer

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  10. Patrick Sun

    Patrick Sun Moderator
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    The reason you don't see many commercial subs with PRs is because ports are so much cheaper and the trade-off in price over performance is one that the subwoofer makers are happy to accept in order to meet a price point in the marketplace.
     
  11. Brian Bunge

    Brian Bunge Producer

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    The Earthquake subs use PR's. They're what I would consider a good example of a commercial sub using a PR. With that heavily textured finish they're butt ugly though! [​IMG]
    Brian
     
  12. Dustin B

    Dustin B Producer

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    VMPS, Sunfire, DefTech, Klipsch and I'm sure there are more that I just can't think of right now all use passive radiator designs.

    Oh and many people have been extremely impessed with the Stryke Powercubes.

    And Adires new Tumult pretty much has to either be used sealed (with a LT and lots of power) or with a few PRs.
     
  13. Patrick Sun

    Patrick Sun Moderator
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    And the typical price point for commercial subwoofers with PRs is? (More expensive than those with ports, I would have to assume given that ports are $4-$15 items for most makers while PRs are, estimating, a $30-$80 item).
     
  14. Thy Luc

    Thy Luc Agent

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    --I ask again, what PR's have you used in your experience?
    --What alignments? Any projects? Have you heard only
    --commercial subs?

    They all have the same sonic personality.
    I've built PR systems over 10 years ago as the poor mans
    solution to outputting more bass from small drivers.
    Most people liked it only because they were not
    audiophiles and didn't know the sonic difference
    between pr, sealed, ported.. If it rumbled, they liked
    it.
     
  15. Brian Bunge

    Brian Bunge Producer

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    Pat,

    If I had to buy a commercial sub, I'd rather have a properly designed PR based sub over a severely underported sub costing several hundred dollars less. Keep in mind that some have stated that they consider the Aerial SW12 sub underported. And it's $4500 or so!

    Thy,

    How about a super high excursion subwoofer that's almost impossible to properly port. PR's are your only alternative for a reflex design.

    Brian
     
  16. Dustin B

    Dustin B Producer

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    And people have compared the Stryke HE15 in a PR allignment vs a vented one (used a 6" flared port). They do say there was a difference, not big though. And rumble is definately not a word they used to describe the PR allignments sound.
     
  17. Patrick Sun

    Patrick Sun Moderator
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    Some people don't want to spend more than $300 (and usually less) on a commercial sub. That's pretty close to the price point which basically precludes PRs in the design.
    Sure, *WE* know they are underported, but the general public doesn't know, and don't really care. It's the ugly heads of marketing and economics that make higher price subs with PRs a tougher sale to the general public.
    And then the general public thinks you should be able to stuff any driver in an 1 ft^3 box and have good sound for $300 or less. I see this question come up time and time again ("Can I stick so-and-so car sub driver in a small box and have it sound good?"). People seem to think the laws of physics don't pertain to their purchasing decisions. [​IMG]
     
  18. Brian Bunge

    Brian Bunge Producer

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    Pat,
    I think of a PR'd sub as a higher performance and price bracket unit than what you're mentioning. If I had $2K to spend and needed a relatively small sub then the Earthquake units are what I'd look at. I wouldn't give you $.02 for a Sunfire though! [​IMG]
    Brian
     

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