Problem with QSC RMX850

Discussion in 'Home Theater Projects' started by Tom J. Davis, Sep 10, 2003.

  1. Tom J. Davis

    Tom J. Davis Second Unit

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    Just purchased the rmx850 from partsexpress and am having a little trouble. Hopefully someone has ran into this before.

    I ran the subwoofer out from my Denon 3300 into channel one of the 850 and put it in parallel input mode. Right and left speaker out to each voice coil on my 12" shiva. Problem is I have to have the gains all the way up and the subwoofer level set on 10 to reach 75db on my meter when calibrating with the internal test tones. I think the subwoofer out is clipping the amp. I know the voltage coming from the denon may not be enough to run the 850 properly and some pro amps you can change the sensitivity to match home equipment. Can this be done on the 850? If not is there anything else I can do?

    Thanks,
     
  2. Pete Mazz

    Pete Mazz Supporting Actor

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    The RMX line has fixed input sens of 1.15V. No way to change it that I know of.

    SVS sells a special made Marchand unit to fix this.

    Pete
     
  3. Kyle Richardson

    Kyle Richardson Screenwriter

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    As Pete mentioned, there's no way to adjust the sensitivity of your amp and if your receiver does not put out enough voltage the only thing you can do is to pick up a line driver to increase the voltage.
     
  4. Gregg Bishop

    Gregg Bishop Extra

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    Well, I STILL can't post URL's, but I think I found the product you're referring to on SVS' web page.

    Is there any way to tell if you'll need this? I have a RMX850 coming as well... If I can find detailed specs for my receiver what would I need to look for to know if it will work?

    Would a BFD eliminate the need for this, or is it just an equalizer?

    Gregg
     
  5. Jack Gilvey

    Jack Gilvey Producer

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    Just a note on the SVS/Marchand box. It's an excellent piece of equipment, very well made and extremely quiet! I've been using one for a few weeks and the gain and infrasonic filter options are a godsend.
    As far as receiver/amp combo which might need it...I'd bet SVS would have a pretty good-sized database at this point as to who's using it with what...send Tom an e-mail with your setup.
     
  6. Greg Yeatts

    Greg Yeatts Second Unit

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    Jack

    Does the SVS Marchand box have auto-on? TIA
     
  7. Jack Gilvey

    Jack Gilvey Producer

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    As long as it's plugged in, it's on.
     
  8. scott>sau

    scott>sau Stunt Coordinator

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    Tom, is your clipping limiter ON? Bypass your 850 crossover and implement the Bass Management feature in your prepro instead. I get an ungodly amount of power from my 850 driving dual 15s. You may want to try the Parts Express Tech Talk Forum and get a hold of Bob Lee. He is president of ASC and a engineer for QSC and writes all their manuals. Find him in the PE user board. (Yes, he writes back).
     
  9. Steve Stogel

    Steve Stogel Supporting Actor

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    Radio Shack also sells a "mini stereo amp" that you can pick up on eBay for $20-30 if you wanted a cheap fix to boosting the signal between the receiver and the amp. It's what many SVSers used before the black box came out. The black box has many more features, but I believe it's also quite a bit more expensive. As far as eBay, do a search for SA-155, and you should come up with a few of the RatShack "amps."

    Steve
     
  10. Tom J. Davis

    Tom J. Davis Second Unit

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    Thanks guys for all the suggestions.

    I bridged the amp mono and that seemed to help alot. My subwoofer out on the denon is now at -2 and the amp doesn't clip anymore. At least not yet.

    Now I just need to find a closet to hide this thing in because it is loud!

    Thanks again,
     

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