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  1. #1

    Member Sales Rating: (0)

    Join Date
    Sep 2013

    Default Help with blown subwoofers

    About 14 months ago, I installed a new Polk MM840 in my car on the rear deck, basically an infinite baffle application. It's powered by a Pioneer GM-D7500M amp through my stock head unit connected by a PAC SOEM-T line output converter. It worked great for about a year, until one day the MM840 developed a terrible popping noise.

    I replaced the damaged MM840 with another brand new MM840. The day after the new driver was installed, it developed the identical popping sound, making it unusable.

    So, my question...what can I do to stop ruining these speakers? I do not believe they were driven too hard. The max volume I would use is about 12/35 max on my head unit. I do not listen to hip hop or bass intensive music. I thought that perhaps my line-out converter had gone bad, but I have checked it and it appears to be fine. Any suggestions would be much appreciated because I want to get another MM840, but I don't want to damage the next one. I'm not looking for warranty service, just advice.


  2. #2
    Member Sales Rating: (0)

    Join Date
    Jul 2001
    Polk Audio


    Hi MBJ,
    Welcome to Polk's forum, I'm sorry you've had a problem. I believe the cause of the damage is that the MM840 is intended to be used in a small (0.35 cu ft) sealed enclosure not an infinite baffle design. The proper sealed enclosure provides the correct woofer loading characteristics, giving best bass performance, but also prevents overextending the woofer's suspension. You should use a woofer intended for this non-enclosure design instead of the Polk.
    If you contact Polk's CS guys they can help get your's replaced under warranty (assuming it meets the necessary criteria for warranty).
    Regards, Ken

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