Jump to content


xti4000 clipping before zero


  • Please log in to reply
9 replies to this topic

#1 fantom

fantom

    Power User

  • Members
  • PipPipPipPipPip
  • 21 posts

Posted 15 May 2011 - 09:37 AM

Hello. Last night I was having an issue with all my xti4000s clipping before zero. There was one green light left off before the red clip light would turn on. So I connected to band manager. The inputs were no were near peaking. They were reaching about halfway. The outputs were also only reaching about half way but the clip indicator was turning on simultaneously with the light on the face of the amps. Mostly during big hits in the music or when all vocals were singing. But the output meter never even got close to zero.  

Also I've heard other JBL728 like mine and they seem to bump like crazy. Does anyone have any suggestions on how to get the most out of one xti4000 for every srx725 and 728 in bridge mono mode.

#2 Kevin Heber

Kevin Heber

    Power User

  • Crown Staff
  • 883 posts

Posted 16 May 2011 - 08:24 AM

You are probably getting current limiting.  The I/O meters are based on voltage, but running the SRX's bridged-mono, which have a minimum impedance of around 3.2 ohms, will cause the XTi4k to run out of current before they clip.

Frankly the XTi4k is the absolute smallest amp to match up to the SRX's.  To help them survive, use a highpass filter at 40Hz or so (on all speakers) and experiment with broad, low-Q cut filters in the 60-120Hz range.  The idea of the filters is to unburden the amp load in the regions where the impedance is at a minimum -- just below and just above resonance.   It would help if you had the impedance plots for the cabinets, but JBL does not publish these.

#3 fantom

fantom

    Power User

  • Members
  • PipPipPipPipPip
  • 21 posts

Posted 16 May 2011 - 10:21 AM

Thank you. Now if I use cut filters between 60hz and 120 and a low pass at 40 and I'm already using low pass at around 91 the I would pretty much not be using the subs.?? Also on tops I have a highpass at somewhere between 90 and 100 and I am experiencing the same problem.  Another thing I might add is that the electrical cable was on a long throw(about 100 ft on 12awg 120v )

#4 Kevin Heber

Kevin Heber

    Power User

  • Crown Staff
  • 883 posts

Posted 16 May 2011 - 11:34 AM

No question you should be using 10AWG wire.

Also I'm saying to do a highpass at 40Hz (not lowpass) and to experiment with cut filtering...even a mild -3dB would help, but you need to find the sweet spot to put it to get the most benefit.

#5 fantom

fantom

    Power User

  • Members
  • PipPipPipPipPip
  • 21 posts

Posted 16 May 2011 - 02:17 PM

Ok thanks. I thought you meant to cut the whole thing with a really wide Q between 60hz to 120hz. But I'll play around with it and try RTAing the system.

Also I have four xti4000 in a rack. These amps are selfsensing voltage if I remember correctly. So that being said what would be the most ideal method to power the rack electrically.

#6 Kevin Heber

Kevin Heber

    Power User

  • Crown Staff
  • 883 posts

Posted 17 May 2011 - 08:15 AM

As far as performance, you would do better with 220V in your case because of the sheer amount of current you need to give the SRX's.

#7 fantom

fantom

    Power User

  • Members
  • PipPipPipPipPip
  • 21 posts

Posted 17 May 2011 - 09:18 AM

Thanks so much. One more question though? What kind og plug could I use for the amps. The one that goes from the receptical to the amp. And I'm assuming I'm gonna run (2) hot 120 legs but should the amps be connected to the 240V or are u talking about powering the rack with 240V then splitting two legs and connecting the amp to 120V recepticals


#8 Kevin Heber

Kevin Heber

    Power User

  • Crown Staff
  • 883 posts

Posted 17 May 2011 - 09:33 AM

The standard 15-amp AC plug will work.  The amp will perform best in your case with two hot 120V legs.

#9 slimbear2010

slimbear2010
  • Members
  • 1 posts

Posted 25 July 2011 - 03:41 PM

Hello Kevin and Hello Famtom i also have been having the same issue I dont know if its cause of the current or cause of the amp already going bad i had one amp clip on me im running 2 xti4000 and running them bridged mono with 2 srx725 on each and i changed amps and that amp still clips seperate current and also works fine but when its suppose to perform it clips on me afraid i might blow a speaker. also Kevin you mentioned the xti4000 is the minimum that those speakers can run at what do you recommend for them?? i am getting 4 srx715 to do a fill in as my church is expanding and considering to swap the amps and use the xti4000 for the srx715 what are your suggestions? i figure if the eq would be an issue i would be having problems with the other side i use a yamaha m7cl board and running 2 31band eq 1 per side both eq at the same freq each and both have the same outs and system panned out correctly suggestions please!!! i also have ultra tech 4040 3 of them 2 xti4000 and also have qsc plx3602 and plx3102 for monitors running eaw's thanks for helping out. I recently down loaded the band manager and was gonna try trouble shooting if i could but seen this made me think twice same problems i am having

#10 Kevin Heber

Kevin Heber

    Power User

  • Crown Staff
  • 883 posts

Posted 26 July 2011 - 10:15 AM

The XTi can't drive two 725's in bridge-mono; 4-ohms is the minimum.  I would say that one XTi4000 (bridge-mono) per SRX725 is OK, but the SRX series really runs best with the MAi or iTech amps.  The XTi4k is really borderline with the 728's.

Ideally you'd want a MA5000i on a pair of 725's, and a MA9000i on a pair of 728's, each running stereo.

For the SRX715's, you can use a single XTi2k or 4k (or XLS2500) running bridge-mono into each speaker.

Check out the meters in Band Manager to see if you are getting input and/or output clipping.