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QSC RMX850 is clipping

Discussion in 'Amps and Cabs [BG]' started by GrooveMonkey, Jun 24, 2003.


  1. I've been giging with a SansAmp RBI into an RMX850 power amp for about a year now. I am also using it bridged mono (830w)into an Ampeg BSE410HLF (400w RMS) cabinet using a speakon connector. I've already rewired the speakon for bridged use and it made a big difference (Doh!). I played an outdoor show last weekend and found the amp was clipping with the SansAmp level at about 11 O' clock and both levels maxed on the QSC. I usualy never turn it up past 10 O' clock for bar gigs.

    Any suggestions? Maybe a bigger power amp?

    Mr. Lee?

    Thanks for any help.
     
  2. todd 4ta

    todd 4ta

    Apr 3, 2003
    Indiana
    Per the RMX manual, use the channel 1 input and gain control, leave the channel 2 gain control on '0' (turned all the way down). This is on pg. 11 of the manual where it says 'Bridged Mono Mode: What It Is.'

    I had the same problem with my RMX850 as you until I figured this out.

    Hopefully that will do it.

    (Mine is an Ashdown RPM-1 >> RMX850 >> Epifani 2x12 in bridged mono)
     
  3. Thanks todd 4ta! I'll give that a try tonight.
     
  4. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    What's the impedance of your speaker cabinet? It has to be 4 ohms or higher.

    Also, make sure switches 4 and 5 are set to "stereo" and not "parallel."
     
  5. Will do bob!

    The impedance is 4 ohms.

    It'll be a day before I can mess with it, I'm doing a dinner show with my B100R tomorrow and will get to play my "big" rig on Friday.

    Thanks for the help.
     
  6. OK, I tried turning the channel 2 gain knob down with no luck. The number 4 & 5 switches have been set to stereo all along.

    Could it be the cable I'm using to connect the cab to the amp? It's a 6 foot 18 Guage(I think)with a speakon connector on one end and a 1/4 inch jack on the other. I've re-wired the speakon to work in bridged mono already.

    Could it be that my cab (Ampeg BSE410HLF) is inefficient?

    I mannaged to get the level knob on my SansAmp to 12:00 at last nights show but without my compressor set to above 6:1 it'd clip.
     
  7. My bad, it's a 12 Guage cable.
     
  8. wiggleworm

    wiggleworm

    May 29, 2003
    Monkey:

    I just bought an RMX850 a couple of weeks ago... I was a little disappointed at first; I thought it would be really loud, but it's actually only pretty loud. I didn't rewire the speakon connector like you did; instead I stripped one end of the cable and used the binding posts. That made a big difference and now I have enough volume. Another couple of things that helped prevent clipping: activating the clip limiter, and using the high pass filter.

    ww
     
  9. Thanks, I just bought a binding post connector. I also followed the directions on the back of the amp that show the channel 2 limiter and filter in the off position.

    I'll keep you posted as soon as I test it out with the new connector.
     
  10. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    In bridged mono, Channel 2's clip limiter and filter don't matter.
     
  11. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    No, it wouldn't be the cable, unless it's broken or corroded.

    That might be. I don't know the sensitivity specs on that cab. Some take more power than others to produce a given sound level in the same space. It might also be that our lowest-power model just isn't enough power for what you're trying to do.
     
  12. Aram

    Aram

    Feb 2, 2003
    New York, NY
    Bob:

    Would you recommend this as a preferred way to bridge an RMX 2450? I have been using banana plugs, but they don't seem to fit too snugly into the binding post (I mean they're in, but not as tightly as I would prefer)...would the bare wire be a better bet?

    Thanks!
    Aram
     
  13. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    It might be. You can also insert the banana plugs into the side holes of the binding posts, then tighteh the barrels to hold them.
     
  14. Aram

    Aram

    Feb 2, 2003
    New York, NY
    Thanks Bob!
     
  15. GFOS

    GFOS

    Dec 27, 2002
    Athens, Alabama
    I have been using the RMX850 with an Eden 410T and an SWR 1x15 bridged for a while now. Short of arenas, I just can't see needing any more power than this.
     
  16. Thumpin4

    Thumpin4

    Nov 6, 2002

    Dumb question but I'll go ahead and ask. I'm getting ready to get a RMX1450 to power my 8X10E and I'm gonna be bridging the amp. Why do you have to rewire the speakon for bridged use???
     
  17. Bob Lee (QSC)

    Bob Lee (QSC) In case you missed it, I work for QSC Audio! Gold Supporting Member Commercial User

    Jul 3, 2001
    Costa Mesa, Calif.
    Technical Communications Developer, QSC Audio
    Because each channel has a "+" output terminal and a "-" output terminal. Bridged mono uses only the "+" output of both channels.
     
  18. Tim Cole

    Tim Cole

    Jun 12, 2002
    Findlay, Ohio
    Son of b...... I am going to be getting an RMX 1450 in the next week, and ordered two 1/4 to 1/4 cables, planning to run two 8 ohm cabs, at 4 ohms bridged. Crapola.....what cables do I need? Someone reply fast, maybe I can still change my order.
     
  19. rdkill

    rdkill

    Jan 20, 2003
    ANBassist, I wouldn't bridge into 4 ohms. The amp is almost as loud bridged into 8 ohms or (my preference) with a separate 4 ohm load on each channel - and it will run much cooler and with no risk of the dreaded "shutdown" happening. :)
     
  20. rdkill

    rdkill

    Jan 20, 2003
    GrooveMonkey, clipping isn't a "bad" thing unless you are running a tweeter. The "non-musical" part of the clipping is usually masked by them loud guitarists that you are trying to keep up with anyways. Assuming you aren't running a tweeter shut the limiter off on the amp to get significantly more volume. But in any case if you either disable the limiter or go with a bigger amp you'll cook the cab if it is only rated for 400 watts! Oh, and make sure you have the 30hz highpass filters on, they can help keep the limiter from "breathing" on subharmonics you cab can't reproduce anyways.