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No low frequency output from one of my studio monitors!

Discussion in 'Shock Brother's DIY Amps' started by Greg Seaman, Mar 8, 2013.

  1. Greg Seaman

    Greg Seaman Tele-Meister

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    I'm not sure if this belongs here but I suspect this is where the most knowledgeable electronics techs hang out. I did play my guitar through these monitors often (when they both worked). Fair enough?

    The problem exists with an Event active studio monitor that powers on but has no low frequency output. There is high frequency output from the tweeter. The monitor is a bi-amp affair with a separate channel for hi frequency and another for low. The woofer itself tests good with a DC resistance of about 8 ohms and no mechanical noise when the cone is moved manually.

    I assume the low frequency channel of the amplifier must be the problem. Besides a channel fuse or another obvious problem like cold solder joints, where is a good place to start troubleshooting this amp or solid state amps in general? I have a decent digital multimeter and soldering equipment but no oscilloscope, etc. Thanks in advance!
     
  2. LeroyBlues

    LeroyBlues Tele-Holic

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    I really won't be able to help you as it's over my skill level. But others will. However, a bit more info will be needed. Is "Event" a brand? I suggest you list the brand and model at min. Also do a search for any schematic for it. If you have it apart, take pictures, lots, and close up, so others can see the layout. Good luck.
     
  3. printer2

    printer2 Poster Extraordinaire

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    Other than a loose wire or fuse I would say servicing a transistor amp is pretty much above the average person's pay scale.
     
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  5. jchabalk

    jchabalk Tele-Meister

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    i had a set of JBL bi-amp monitors for a long time, something similar happened to them. There wasn't really anything i could do with them - i took them to a JBL repair guy who fixed them, i think the filtering caps had failed and needed to be replaced.

    If yours has only lost the bass and it's bi-amp it's possible that the bass amp is fried and needs to be looked at or it could be something more simple than that. sorry i can't be of more help.
     
  6. celeste

    celeste Friend of Leo's

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    To Bi-amp, you need a line level filter(actually 2 filters, one low pass, one high pass) in front of 2 amps driving 2 speaker drivers. The filter is usually active, and as such are not as rugged as passive speaker level filters (called a crossover). So you could have a failure in the low pass filter, the bass amp, the wiring connection the amp to the speaker, or the LF speaker driver itself.

    Just because a drivers voice coil measures a reasonable DC resistance does not mean the driver is good, so what have you done to check it?
     
  7. Greg Seaman

    Greg Seaman Tele-Meister

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