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Any way to tone down JBL PRX hiss for acoustic performance?

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  • Any way to tone down JBL PRX hiss for acoustic performance?

    I've noticed the hiss in the past, but prior use for these was as monitors in a rock/blues band.  It wasn't an issue.  I was trying to get an acoustic duo thing that went under and I've decided to try and strike out on my own.  For the first time in a few months I fired up the PRX through my mixer and there is a huge hiss.  It seems to mostly be driven by the acoustic guitar. 

    My experience with doing sound and operating this stuff is extremely limited.  I have not done it in a band, although I've always tried to pay attention once the gear is setup.  Usually most bands I've played with used powered mixers into non-powered speakers.  While it might not be possible to eliminate the hiss, is there any way to tone it down?  I don't really want to go out and buy another set of powered speakers at this point.  When I strum chords it is not noticeable, but when I finger pick and or am not playing it is pretty bad.

     

    Here is the gear in question....

    Speakers:  JBL PRX 512 (2)

    Mixer:  Carvin C1644P

    Guitar:  Guild acoustic with Fishman Presys Plus

    Mic:  SM 58

    Types of music:  typical acoustic rock, pop, blues type stuff like Wagon Wheel, Wonderwall, She Will Be Loved, etc, etc

    The speakers are going into the balanced (XLR) of the mixer. 

    http://www.reverbnation.com/thedubiouscapture<br>

  • #2
    Does the hiss mostly (or completely) go away if you mute the acoustic channel? If so, the issue is with the acoustic guitar signal chain. If it's present with nothing plugged in, then it's the PRX. Use a methodical approach, starting with only the PRX adding one device at a time to determine the source of the hiss.

    Comment


    • #3

      Yer Blues wrote:

      I've noticed the hiss in the past, but prior use for these was as monitors in a rock/blues band.  It wasn't an issue.  I was trying to get an acoustic duo thing that went under and I've decided to try and strike out on my own.  For the first time in a few months I fired up the PRX through my mixer and there is a huge hiss.  It seems to mostly be driven by the acoustic guitar. 

      My experience with doing sound and operating this stuff is extremely limited.  I have not done it in a band, although I've always tried to pay attention once the gear is setup.  Usually most bands I've played with used powered mixers into non-powered speakers.  While it might not be possible to eliminate the hiss, is there any way to tone it down?  I don't really want to go out and buy another set of powered speakers at this point.  When I strum chords it is not noticeable, but when I finger pick and or am not playing it is pretty bad.

       

      Here is the gear in question....

      Speakers:  JBL PRX 512 (2)

      Mixer:  Carvin C1644P

      Guitar:  Guild acoustic with Fishman Presys Plus

      Mic:  SM 58

      Types of music:  typical acoustic rock, pop, blues type stuff like Wagon Wheel, Wonderwall, She Will Be Loved, etc, etc

      The speakers are going into the balanced (XLR) of the mixer. 


      I have never had any hiss from the PRX612m's that I used.  Even when turned way up in sensitivity, they were quiet as could be.

      Give this a try....

      1. Start with the speakers disconnected from any input.  Power them on and turn the sensitivity knob all the way up.  Any hiss?  I am guessing very little, or none at all.
      2. Turn your speaker off.  Plug in the outputs from your mixer into your speakers, but don't have anything plugged into the mixer.  I would have the speakers at about the middle of sensitivity.  Keep all faders all the way down on the channels.  Turn up just the main faders all the way up.  Any hiss?
      3. Still with nothing plugged into any channel in the mixer, proceed to turn up each channel fader.  Any hiss?
      4. Turn off your speakers.  Turn off your mixer, and turn down the main faders.  Plug in just your vocal mics.  Turn the mixer on, then your speakers.  Turn the main faders all the way up.  Turn up each mic (watch out for feedback).  Any hiss?
      5. Finally, redo (4) with your acoustic guitar.

      I don't think the hiss is from your speakers, but then again, anything is possible.

      If you find the hiss is from a specific mic or instrument, it still may be the mixer.  If possible, borrow a mixer (or rent one) like an A&H Zed 10Fx.  I have this mixer myself and can tell you that there is very very little noise from this mixer.  If your inputs make noise on a ZED, then it is the input item, not the mixer.

      Good luck!

      With Greater Knowledge Comes Greater Understanding

      Comment


      • agedhorse
        agedhorse commented
        Editing a comment

        Almost certainly noisy electronics in the acoustic's signal path.


    • #4
      Check your gain structure. Does the hiss go down when you turn the speaker's input control down? Try turning your mixer up and your speaker down by the same amount.
      Don Boomer

      Comment


      • Unalaska
        Unalaska commented
        Editing a comment
        Gain structure problem. Question: the 1644P is a powered mixer right? Are you using the 1/4 speaker outputs into the xlr inputs on the speakers?
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