non-wired cone?

pstock
pstock Posts: 2
edited September 2009 in Vintage Speakers
Hello.

I've inherited a pair of what I imagine are rather old Polk speakers.
Because your name is so well-respected in the audio world, I thought I would try to get them working (even though I know little about audio equipment.)

I've really got just one question. One of the speakers is not functioning well. When I opened it up to see if there was some loose wiring, I was surprised to see that the bottom speaker cone seemed to have no electrical connection at all. This might be normal but I am left wondering, what function does this piece of non-electrified cone serve in the speaker?
Is it just some kind of noise-deadening baffle?

I hope you can educate me a bit.

many thanks

Peter Stock
Post edited by pstock on
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Comments

  • hearingimpared
    hearingimpared Posts: 21,136
    edited September 2009
    It's call a passive radiator. It uses the inside air from the midwoofer excursion to produce bass.
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  • pstock
    pstock Posts: 2
    edited September 2009
    well there you go.
    thank you for indulging a know-nothing neophyte.
    Peter
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  • kawizx9r
    kawizx9r Posts: 5,150
    edited September 2009
    hearingimpared wrote: »
    It's call a passive radiator. It uses the inside air from the midwoofer excursion to produce bass.

    +1
    Also you can create an even better air-tight seal by applying caulk cord in place of the stock gasket (its the ring between the driver's basket and the cabinet itself. Apply it to both the passive radiator and the active driver, which traps more air inside and utilizes it to produce tighter, forceful bass. :D

    The passive radiator acts like a port rather than another driver for those lower frequencies.
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    heiney9 wrote: »
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  • comfortablycurt
    comfortablycurt Posts: 6,745
    edited September 2009
    Welcome to Club Polk!

    Congrats on the new speakers. Those are Monitor 7A's with Peerless tweeters. Some nice speakers...I've got a pair myself.

    If you weren't getting much output from the passive radiator, it could have been due to the cabinet not being sealed properly. Since the PR runs off the back pressure of the mid-woofer, the cabinet needs to be air tight.

    Make sure that all the screws are tight, but not overly tight. Push in and hold the passive radiator and the mid-woofer will extend. It should stay out for a second or two, then start slowly moving back in over a period of 7-10 seconds or so.


    What are you planning on running the speakers with?
    The nirvana inducer-
    APC H10 Power Conditioner
    Marantz UD5005 universal player
    Parasound Halo P5 preamp
    Parasound HCA-1200II power amp
    PolkAudio LSi9's/PolkAudio SDA 2A's/PolkAudio Monitor 7A's
    Audioquest Speaker Cables and IC's
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