Passive Rads....

Discussion in 'Speakers' started by Anthony_I, Oct 28, 2003.

  1. Anthony_I

    Anthony_I Stunt Coordinator

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    What is the point? why the differences in weight and how is the sound different from vented?

    Isnt this basically just a speaker with no magnet???
    Could one simply use a speaker instead of a rad??

    what changes if yo uhave a 12" sub with say an 18" PR as opposed to a 12" driver with a 12" PR?
    I had a computer sub that was a bandpass/PR box.... the rear of the speaker was facing the front of the cabinet (where its PR was) and there was a small port in the divider that held the speaker inside the box.
    the PR is simply like a piece of cardboard with other material on it to make it resemble a speaker.
    the actual speaker was 4" and this Pr is 8"..... why would the company do this?? (im not even sure if all that crap i just told you is relevant to the question at hand)
     
  2. LanceJ

    LanceJ Producer

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    Read about passive radiators here. (this is a really neat site)

    PR's used to be much more common in the late 70s & up to the mid 80s, but I think their cost vs. their advantages over a simple hole/plastic tube assembly just wasn't worth it for most companys. And possibly the "fake speaker" perception was a marketing problem also.

    LJ
     
  3. LanceJ

    LanceJ Producer

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    Extra trivia [​IMG] :

    The most common woofer/PR configuration I remember was the 8" woofer + 10" PR system. Most probably because an eight inch woofer can still reproduce midrange frequencies quite well but is still capable of good bass too. But the addition of a PR lowered its bass frequency cutoff and increased its output, all for the price of a woofer cone, its supporting spider and basket (magnets & its cast iron structure are the expensive parts). It made a large difference--almost like there was a 12" woofer in there. And some PR's are just a fiberboard disc, surround and supporting frame--there was (and is) no need to get fancy with them. This 8"/10"PR speaker design is one of my favorites & I'm always on the lookout for it at garage sales.

    This Genesis Model 44 was a nice example of all this. I actually got to hear its predessesor(sp?), the Genesis Model 210 at a store in San Marcos, Texas in 1985 (there's a nice little college there......"Homework? What's that?" [​IMG] ) and they sounded very good. Don't let the frumpy looks fool you!

    LJ
     
  4. Seth_L

    Seth_L Screenwriter

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    In a good PR design the PR should be able to displace 4x as much air as the driver itself. Hence why you see larger PRs with smaller drivers.
     
  5. Rory Buszka

    Rory Buszka Supporting Actor

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    PRs often are the only way to get the heavy cone and voice coil of a high-excursion woofer to work well in a small box without resorting to EQ. However, some subwoofers do quite well with a long-excursion driver in a small sealed box with Eq providing the bass extension - basically doing everything with brute force.
     
  6. Jack Keck

    Jack Keck Second Unit

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    I don't know if this will add to anybody's understanding of passive radiators. It seems that they are now used exclusivelly in subwoofers. However, I have a pair of Polk Audio Monitor 7s from the days of yore. They have a 6 1/2" mid-woofer and a 10" PR. My friend's Klipsches have the 8' woofer and 10" PR mentioned before. I always thought those speakers sounded great. I don't know why Polk and Klipsch went with PRs instead of ports at the time (My speakers were designed in ghe early '70s), but my ears say thay did the right thing.
     
  7. EdNichols

    EdNichols Second Unit

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    VMPS makes their subs today with PR's. It produces the lower octives at high volume with no port noise.
     
  8. Kevin_R_H

    Kevin_R_H Stunt Coordinator

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    Ed,

    Not only does VMPS use passive radiators in their subwoofers, but my RM40s also have passive radiators.

    Kevin
     

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