Members derivicus Posted July 15, 2003 Members Share Posted July 15, 2003 Hey guys. I hang over in guitars, but I run our system and I'm having a strange problem. First, I'll describe our setup. 2) Peavey SP4X 2X12 and horn(8 OHM) 2) Peavey SP118X 1X18 subs(4 OHM) 2) Peavey 1X15 and horn floor monitors QSC RMX850 for monitors QSC RMX1450 for mains Peavey CS800X for subs Behringer 16 channel mixer w/effects and compressors in the inserts. Mixer outs into dual 15 band EQ into Peavey crossover set up for stereo 2 way operation, crossed over at 90hz. Monitors are thru aux send, thru single 31 band eq, into monitor amp. Now, with that out of the way, here's my problem: This setup[ has proven to sound very good. We've used this rig like this for almost 2 years. All of a sudden the other night at the gig, one of the subs is very weak. We replaced all cables in the path and same thing. Later, the other sub is sounding weak. I think it might be the amp, so I hook them up to our spare (a BGW 1750L, I think. Old 4 rackspace workhorse) amp and no change. I'm pissed at that point, so I say {censored} it. On with the show. Well, back at the jam space we set up the PA tonight. The whole system is freaking out. I compensate for the weak subs by cranking the gain on the crossover and turning the amp volume up, and as the bass beats, the amp is clipping like hell, and the room lights are going dim. The volt meter on the power strip is dipping to below 80 volts. Siince I saw the amp clip indicators going nuts, I think it's time for our speaker's sakes to just turn the thing off. When I take the board mains right to the sub amp, my volume is loud and proud. I think it may be the crossover. Can anyone help?!!! Link to comment Share on other sites More sharing options...
Members agedhorse Posted July 15, 2003 Members Share Posted July 15, 2003 I assume you are running the subs mono from the crossover to the amp, and that you are NOT bridging the sub amp. 1. Do both clip indicators on the sub amp "freak out"? When a clip light turns on very early, it is an indiaction that there is a problem with the load (shorted load usually) causing the error detector that drives the clip circuit to detect a fault. The fact that you seem to have problems with the BGW indicates that this MAY be a problem. 2. When you remove the speaker cables from the sub amp, do the clip lights stop flashing? Yes, then again the load is suspect. It is possible that there is a problem with the crossover, I would also suspect that if you are taking a sub out from left and right outputs from crossover, and then the amp is in bridge mode combining the two input signals plus the inverted drive signal from the in phase channel, unusual things can also result... and may also alter the function of the clip lights depending on how the clip detector works. I don't remember Peaveys, other than I know it's based on an input/output comparator that also drives the DDT circuit. To troubleshoot, be sure that you are in stereo mode, and go from crossover to amp input, then from amp output to speakers. Do this for each channel one at a time. Also, depending on the model/version of CS-800, they may not be true balanced inputs even though they are XLR, also, some require an octal bypass plug in each socket. Hope this helps! Link to comment Share on other sites More sharing options...
Members derivicus Posted July 15, 2003 Author Members Share Posted July 15, 2003 Originally posted by agedhorse I assume you are running the subs mono from the crossover to the amp, and that you are NOT bridging the sub amp. I am not using the summed mono output from the crossover. I am using the low outs fron=m the 2 way cut off at 90 hz. I have chosen not to bi-amp the SP4X's, the run from 90hz up. Okay I lied. The indicators on the Peavey are not clip indicators really, but "DDT" compression circuit indicators, indicating the internal compressors are keepin the amp from "clipping". I did not unplug the speaker cables to see if the DDT lights continued to flash. I am using the CS800X in true stereo configuration. The subs are 4 ohms, and the Peavey has proven to push them well in stereo, but now it won't. I've verified it's in stereo mode. Does this info help? Link to comment Share on other sites More sharing options...
Members agedhorse Posted July 15, 2003 Members Share Posted July 15, 2003 The LEDS are clip indicators with the DDT disabled and limiter indicators with the DDT enabled. They work that way due to the type of detector Peavey uses. Try things one output at a time to verify. It's also possible that theer is some oscillation between the output of the crossover (maybe due to the crossover itself) or due to the type of input that the Peavey presents. If the crossover is a servo balanced type, they can oscillate under some conditions where you convert balanced to unbalanced. You are using the XLR connectors right? How old is the Peavey amp? What is the crossover model? Link to comment Share on other sites More sharing options...
Members tlbonehead Posted July 15, 2003 Members Share Posted July 15, 2003 Originally posted by agedhorse The LEDS are clip indicators with the DDT disabled and limiter indicators with the DDT enabled. They work that way due to the type of detector Peavey uses.Try things one output at a time to verify.It's also possible that theer is some oscillation between the output of the crossover (maybe due to the crossover itself) or due to the type of input that the Peavey presents. If the crossover is a servo balanced type, they can oscillate under some conditions where you convert balanced to unbalanced.You are using the XLR connectors right?How old is the Peavey amp?What is the crossover model? But would this problem surface all of the sudden after working correctly for a long period of time? Link to comment Share on other sites More sharing options...
Members derivicus Posted July 15, 2003 Author Members Share Posted July 15, 2003 Its a new Cs800X. All of the crossover outputs are 1/4". The inputs from the board to the crossover are XLR. The crossover is this one: http://www.schoolmusicstore.com/prod_disp.asp?itemnum=XD234 Link to comment Share on other sites More sharing options...
Members picker13 Posted July 15, 2003 Members Share Posted July 15, 2003 This sounds very odd, either a cable has gone bad or something in the crossover/amp has gone out and "dominoe'd" the whole system. I agree with what someone said above: check your system out one component at a time. Start with your speakers. Borrow someone's (another band, friend, music store) simple mixer and power amp. Then, with one source (bass for subs, voice for tops) check out your sub and top cabinets one at a time. Might be a good idea to use new cables. Then go up chain one component at a time, including you cables, to see if you can find where the problem is. By the way, if you can sum your sub output on the crossover, I would. I know this is a pain in the ass, but it may be the only way to figure out this wierd problem. Good Luck. Link to comment Share on other sites More sharing options...
Members agedhorse Posted July 15, 2003 Members Share Posted July 15, 2003 I suspect that there is something incorrect in the wiring between the crossover and the amp, since you are using 1/4". The reason is the awe are seeing more of these issues, as manufacturers are shifting from 1/4" TS to TRS, and the handling of the balanced to unbalanced translation can be incorrectly done in the process. My first suggestion is to eliminate the 1/4" wiring and use XLR everywhere... I'll bet 2:1 that the problem disappears. It could be something else, but I'm a pretty good gambler with these things! Link to comment Share on other sites More sharing options...
Members derivicus Posted July 15, 2003 Author Members Share Posted July 15, 2003 Originally posted by agedhorse I suspect that there is something incorrect in the wiring between the crossover and the amp, since you are using 1/4". The reason is the awe are seeing more of these issues, as manufacturers are shifting from 1/4" TS to TRS, and the handling of the balanced to unbalanced translation can be incorrectly done in the process. My first suggestion is to eliminate the 1/4" wiring and use XLR everywhere... I'll bet 2:1 that the problem disappears. It could be something else, but I'm a pretty good gambler with these things! I'm running XLR cables between the mixer and the crossover, but the crossover only has 1/4" outs, so I have no choice on that matter. My amps have XLR ins, but I cannot exploit them. I've obtained another identical crossover from the music store and I'm going to the jam space now to check it out. I'll let you know what I find. Link to comment Share on other sites More sharing options...
Members agedhorse Posted July 15, 2003 Members Share Posted July 15, 2003 Originally posted by derivicus I'm running XLR cables between the mixer and the crossover, but the crossover only has 1/4" outs, so I have no choice on that matter. My amps have XLR ins, but I cannot exploit them. I've obtained another identical crossover from the music store and I'm going to the jam space now to check it out. I'll let you know what I find. Unless I read the specs wrong, there are both 1/4 and XLR outs on the xover??? Link to comment Share on other sites More sharing options...
Members derivicus Posted July 15, 2003 Author Members Share Posted July 15, 2003 Originally posted by agedhorse Unless I read the specs wrong, there are both 1/4 and XLR outs on the xover??? Sorry. Only 1/4" outs. Link to comment Share on other sites More sharing options...
Members agedhorse Posted July 16, 2003 Members Share Posted July 16, 2003 I mis-read the specs... it's a balanced 1/4" TRS output, so it wopuld be a good idea to use a 1/4"TRS to XLR male cable to connect to your amps. This way the ring doesn't get dropped, though in theory it should work correctly, manufacturers sometimes do strange things to TRS ouputs in their attempts to utilize them as unbalanced too. Servo circuits are notoriously problematic! Link to comment Share on other sites More sharing options...
Members derivicus Posted July 16, 2003 Author Members Share Posted July 16, 2003 I'm gonna buy 4 short 1/4" trs to XLR males and use those to run from the Xover to the amps. I'll let you knpow how they work. Link to comment Share on other sites More sharing options...
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