New plate amp for JBL PB-12 subwoofer worth the effort ???

Discussion in 'Home Theater Projects' started by Dan Miller, Mar 9, 2004.

  1. Dan Miller

    Dan Miller Extra

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    I have a chance to pickup a JBL PB-12 with a fried amp. Is this unit worth the trouble of installing a fresh PE 250w plate amp? Is there another plate amp that may be more suited to a retrofit such as this?

    Is the box and speaker worthy of this expense and effort?

    If you were to rank the JBL 12" speaker used in their subs, what would your comments be? We all know the amp is toast just waiting to pop up.

    I hear stories circulating around about AM prefixes to serial numbers indicating that the JBL in question is " a good one " ???

    Any comments would be welcome.

    Dan Miller
     
  2. Geoff L

    Geoff L Screenwriter

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    The first question is what are you looking to pay for the blown JBL.??

    Next, are you sure the driver itself is fine??

    If the driver is fine and the sub is bought cheap, say $45.00 or less, then a PE or other amp that is large enough to cover the original amp cut out, may be worth it.

    The original JBL amp may have some mild boosting in it, so it a toss up on if you would want to spend the money on a after market replacement amp. If the JBL did have some boosting applied, you do not know where and or what amount. So performace regardless of the power purchased to replace the blown amp mave make/have it perform at less than it stock counterpart.

    If might be considering DIY-ing a sub at some point, then IMO it would be worth buying an amp and running the JBL until such time. In that sence, the purchase it not a waste and will be one less thing needed to purchase at that time.

    If you (do not) see yourself building a sub, or having it built for you at some later time, then scrap the idea of a after market amp ~{even if the sub can be bought dirt cheap and the driver is fine}~....

    Regards
    Geoff
     
  3. Rob Formica

    Rob Formica Stunt Coordinator

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    Geoff is right... the amp most probably has a built in bass boost at some frequency or another. Another option is you can check on how much JBL charges for a replacement amp... If the amp problem is common, the replacement price may actually be quite reasonable. It may be a couple of extra $$ BUT it’ll perform as intended and it’ll actually have a resale value to it... [​IMG]
    Rob
     
  4. Dan Miller

    Dan Miller Extra

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    My cost for the blown JBL PB-12 is about $50.00. There are one or two of these on Ebay at any given time.

    When I read comments posted at the audioreview sight, it is plain to see that JBL PB-12's pop caps and smoke other bits and pieces, on a regular basis. Opinion has it that JBL messed up on this model of sub. There are many comments posted telling of repairs that other fellows have made to these units. Makes me feel that it may be a reasonable to expect a simple repair. Schematics for this unit are everywhere. Swap out a handful of caps, upgrade their quality, move them to where the heat will not cook them and your up and running again.

    I question whether the speaker and cabinet themselves are worthy of a new plate amp. This comes from my thought that if the JBL amp is cooked beyond repair, are these components worth the cost of retrofitting a new amp? If the JBL speaker now functions with an onboard 250w amp then replacing it with a new 250w plate amp seemed to be an answer toward getting a reasonable sub up and running. The cost would run about $250 with everything shipped to my door.

    Let us forget about the blown amp on board. Would you agree that the cabinet and speaker alone are worth $80.00 delivered to your door or not? Guess that is my real question here.

    If the amp repair is easy, great! If the amp is baked out and gooney, then it is a question of do I drop $150.00 into a new plate amp or not.

    Maybe part of the question should be this ..... In your opinion, do you think the JBL speaker and cabinet are worth salvaging?

    Thanks guys,

    Dan Miller
     
  5. Wayne Ernst

    Wayne Ernst Cinematographer

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    Dan,

    Given that you could find a used 12" SVC driver for approx. $50, I'd pass on the JBL sub. Add the SVC driver to a new box with a Parts Express amp -- and you'd have a very nice sub. [​IMG]
     

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