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Bass Dropout XTI4000


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#1 eclispe1

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Posted 03 October 2011 - 01:18 PM

Hello,
I have 3 XTI amps. My high end is on an XTI2000 is working great but both of my XTI4000 are going in and out of producing bass. Both are bridged in mono and crossed over at 100hz and receive their signal from a DBX driverack. Sometimes they will play all night with no problems but most of the time it almost sounds like I'm only getting about half of what I should be and then it will cycle back in and out about every 30 seconds or so. I have bypassed the DBX and fed the amps directly from the source and the same problem exists. The source is stereo reciever and I have also bypassed this and hooked up the amps directly to a Peavey mixing board as I thought maybe I was not getting enough input gain but I still get the same problem. All limiters and compressors are turned off on the amps and the Driverack. This is driving me crazy if someone could help me, I greatly appreciate it. One amp is mfg in 2009 and the other in 2011.

#2 Kevin Heber

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Posted 03 October 2011 - 03:18 PM

Could be that the amps are overheating or the voltage line (i.e. from the wall) is sagging.  What speakers are you driving?

#3 eclispe1

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Posted 03 October 2011 - 03:48 PM

QUOTE(Kevin Heber @ Oct 3 2011, 04:18 PM) View Post
Could be that the amps are overheating or the voltage line (i.e. from the wall) is sagging.  What speakers are you driving?

The amps seem to cool to the touch, they are only used in my home and maybe have only seen about a quarter of what they can actually do the output gain is not above half on the subs or the top cabs. My furman voltage gauge stays between 121 and 125 as does my Panamax that handels the video circuts. I do have a 20amp dedicated circut just for the amp rack and nothing else is on it.
The subs are Warfedale double 18 bins at 4ohms on the speakon plug with one on each amp running in bridged mono. This will happen at any volume anywhere from quiet to window breaking volume.



#4 Kevin Heber

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Posted 04 October 2011 - 11:04 AM

What visibly happens with the amps when you hear this cut-out?  i.e., how do you know it is the amps?

#5 eclispe1

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Posted 04 October 2011 - 05:51 PM

QUOTE(Kevin Heber @ Oct 4 2011, 12:04 PM) View Post
What visibly happens with the amps when you hear this cut-out?  i.e., how do you know it is the amps?

I have tried several different sources all the way from my computer library to a cd player and my Iphone directly hooked up to the amps and using its volume control for the output level. I have tried going from my receiver directly to the amps and also all sources were tried with a brand new Peavey mixing board as well. I don't see any output drop in band manager and the amps appear to be normal and cool to the touch. I have also tried turning off the DSP and using the driverack for the dsp functions such as crossover etc... and it still cuts out. I seems as if every bit of the sub output is kinda hollow and tinty and then it will kick in with nice and strong chest pounding bass and then kick out and there seems to be no pattern to it. Nothing is even close to clipping as this is in a small home so I can't even come close to what these should be able to do. I also tried switching the bass bins out with my extra set and the same problem still exisits. My high end amp XTI2000 is running exactly as it should and it never drops its output at all. I checked the firmware and all amps are current. I would love any suggestions that may help me as I really love these amps but I can't go out on a dj gig with them acting up so much.



#6 Kevin Heber

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Posted 06 October 2011 - 11:01 AM

Sounds like a job for service.  Make sure the problem is easily repeatable first.

#7 eclispe1

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Posted 08 October 2011 - 08:59 AM

[quote name='Kevin Heber' date='Oct 6 2011, 12:01 PM' post='15267']
Sounds like a job for service.  Make sure the problem is easily repeatable first.

I have done a ton of trouble shooting and found out that if I only run one xti4000 at a time the output will stay normal, it is when I switch on the second xti4000 that the sound starts acting up. I have all three amps on 20amp seperate branch circuts drawing no more than 4amps before the crown is switched on. If I unplug the input from the "working" amp and plug it into the other amp the sound will stay normal. I can switch the input back and forth between the powered up amps and maintain awesome sound it is only when I connect the other amp via the outputs provided on the back panel that I strt to get the bass thinning problem. It is almost like the inputs are being drained by the other amp, I have tried switching the input amp around as well and it makes no difference. It will do this if the signal is fed straight into the amps or from the driverack. I have played wiith the inputs on the amps and 1+2 yeilds the best sound straight in or from the driverack. The only other thing I can figure is my input is from a stereo receiver and it is a high ohm source going the low ohm input on the amps so do you think maybe some kinda direct ohm matching box would help. It seems like the sub amps are working against each other but the high amps remain with a stable output.


#8 jgriggs

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Posted 13 October 2011 - 12:08 PM

Is it possible that there is a phase reversal in the wiring somewhere?
This would cause the sub drivers to fight each other acoustically.
This might be an explaination why it sounds this way only when both amplifiers are running.

#9 eclispe1

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Posted 13 October 2011 - 05:20 PM

QUOTE(jgriggs @ Oct 13 2011, 01:08 PM) View Post
Is it possible that there is a phase reversal in the wiring somewhere?
This would cause the sub drivers to fight each other acoustically.
This might be an explaination why it sounds this way only when both amplifiers are running.


I have double checked the wiring all along the the signal path and double checked the speakons as well. Everything checks out fine.
I bought a direct box today thinking that would help but it still is cutting in and out randomly and with the direct box it is not as clean of a sound as I get straight off of the receiver. I'm about ready to give this whole thing up and go back to my old Velodyne sub and my tower speakers. I just wanted plenty of bass which I only get now when my system decides it will allow to hear it. I just dont understand why it will work sometimes all day correctly and other times it will just cut in and out at random. I also checked the voltage at each circut with the amps loaded and the voltage only varies by around a half of volt if even that and the lowest it read was 124.3 but mostly stayed at 125.
Thank you guys for the help so far, hopefully we can get this working at its peak soon.....