Loudspeakers Oh what a stressful night HALP!!!!!

[Jadams639]

Hey, I need some advice on some problems that arose during the live gig I was running sound for tonight.

We have a DBX DriveRack PX, a 32 channel mackie , a crown ce2000 for main house speakers which are JBL. And Altec Lansing 600w amps for subs and highs.

here is my problem, The first half of the show was great, everything was working great, and it sounded awesome. It was a talent show, so there is a lot of acts and after this techno act went off (very bass heavy music) it all seamed to go wrong... First the whole main system went out, the only thing that was working was the stage monitors... So, giving control of the board to my assistant (who wasn't that familiar with mixing live singing and instruments), I sprinted upstairs to the amp cabinet. I reset the power conditioner first. This fixed some of the highs, but I had noo mains and subs sounded like crap... So, Stressed as all hell, I quickly went to adjusting the DBx DriveRack switching to a 2 way system, running it all through horns, and subs. After the show, I put the DBx back like it was, and I can't seem to get anything through my mains! The signal indicators on the amp show that there is signal getting to the amp, but Nothing on the speakers could the amp have blown? I know the speakers are fine, I took the output and plugged it into the backup set of JBL s and still nothing? What does it sound like to you.....

 

[chausman]

Have you checked the entire signal path? At first this sounds like something just came unplugged.

 

[Jadams639]

Have you checked the entire signal path? At first this sounds like something just came unplugged.

As much of it as I could check, wherever the problem is, it's either behind the amps of the amp itself... Is there a possibility of an amp just stop working like that?

 

[MNicolai]

As much of it as I could check, wherever the problem is, it's either behind the amps of the amp itself... Is there a possibility of an amp just stop working like that?

Equipment failure is always a possibility, but 9 times out of 10 the cause of a problem is simpler than that. A faulty solder joint in a connector, someone kicking the cable out of the wall, etc.

 

[indigo7us]

I would double check connections at the Driverack as well. Also double check you speakons. Make sure your driverack settings are actually correct as well...

 

[bishopthomas]

If you're seeing signal at the amp then it will have to be downstream of that.

 

[museav]

Can you clarify the "highs" and "mains" as you are using them? Do you mean you are running the mains bi-amped and "highs" is the horns of the mains with "mains" actually being the woofer?

You mentioned seeing signal at the Crown CE2000 but are any of the other indicators such as the Clip or Fault indicator lit? Have you tired cycling the power for the amp, maybe even unplugging it for a little bit and then plugging it back in and powering it back up?

 

[Jadams639]

The signal coming from the crown is going to the highs/ high mids, which are going to the speakers on stage that I am having trouble with, the mids go through an old speaker array in the cut (which I'd like to change) and the lows go to two subs in the cut. When I lost my highs last night everything sounded muffled, so I changed the DriveRack to a two way system, with the two sets upstairs ( which didn't sound that great at all)

 

[Jadams639]

Wait wait wait wait, I think I might have that backwards.......... I believe the mids go through the Altec Lansing amp, to the speakers I'm having trouble with...... I was seeing the protect light on it last night......... I think I just figured out the problem....... I've got a backup Altec Lansing amp that ill change out Monday to see if that fixes it.

 

[FMEng]

The amp may have gone into thermal or current limit. It may latch into that state until turned off for awhile. Kill the power to the entire system for a bit, and then recheck before jumping to any conclusions.

 

[Jadams639]

The amp may have gone into thermal or current limit. It may latch into that state until turned off for awhile. Kill the power to the entire system for a bit, and then recheck before jumping to any conclusions.

Will do, I'll be there tomorrow and let you know.

 

[bishopthomas]

You can't just change DriveRack settings without changing your speaker configuration. All you're doing is sending different frequency ranges (and other settings) to the same speakers that are already there. If there's something wrong in the system then opening up your crossovers isn't going to fix it.

 

[Jadams639]

I think it's an amp or a cable problem

 

[Jadams639]

The amp may have gone into thermal or current limit. It may latch into that state until turned off for awhile. Kill the power to the entire system for a bit, and then recheck before jumping to any conclusions.

What could cause an amp to go into thermal or current limit? The music during the performance was loud, but nothing was overloading. Could it have just gotten too hot?

 

[Jadams639]

The room that the amps are in is the upstairs lighting control room, there is no ac going to that room, so it can get hot in there.

 

[Aman121]

Whats the model on that Altec amp? Altec's pro division has been out of the buisness since the 90s, the consumer audio company that bears the name today has almost no connection to the old Altec. It seems likely that the horns have gone out in your main array, and you are having to use additional speakers for your mid/highs. Those old altec drivers usually couldnt take much power, and in a bi or tri amped system with oversized amps.... inexpierenced operators could take them out pretty quick. You also could be unaware of the specifications for the exact drivers or speakers in the cluster, and you may be trying to run the wrong frequencies through the wrong components. Could you perhaps post a picture of all the speakers you are using, and perhaps include some model numbers if you are aware of any? Those amps and the instillation are likely more than 20 years old, and they may simply not be up to the task of high output and bass heavy music. Would not be suprised if you took out a driver or two. Have you verified that every individual component of your system works correctly?

Feel free to PM me with any Altec questions, I own and use a fair amount of their old hardware as a kind of hobby and may be able to help you out. Also, control booth member JD is very knowledgeable about older Altec/JBL equipment, he may be able to help you out as well. I also know a guy who worked as an installer for the company in their eastern sales office, and I could forward some questions on to him.

 

[Jadams639]

I didn't have time to check it out today, I'll try to get to it tomorrow

 

[Jadams639]

The two lower amps are Altec Lansing 9444 600 watt amps and the high end is a crown ce2000. The high amp powers a horn array in the cut, the mids come through the JBL's on stage and the lows go to 2 18" JBL Subs in the cut. I've been wanting to replace the horns upstairs with a smaller set of JBLs that I have that are not being used.

I know that the crossover is set up correctly for these speakers, it was set up by an audio engineer from Disney. I think the problem is with the mids amp, I switched them off today to give them time to cool down, I'll be tring them tomorrow to see if the amp just went into thermal limit. If the amp is completely gone, I've got a backup one I can hook up. I know that the JBLs I'm having trouble with cant be blown, they are rated for 500 watts each, surely a 600 watt amp couldn't blow 2 of them?

 

[Aman121]

Often times older amps like your altecs had less protection circuitry than modern ones, and can clip very hard sending large amounts of dc to the speakers. Speakers are designed to run on AC only, feeding them even a little bit of DC is like hitting them with a baseball bat. If the speakers are rated for 500 watts peak and not rms, and the amps were clipping, it's possible that they were damaged. (Peak rating for speakers refers to the amount of power they can take in short bursts, RMS is the amount of power they can handle constantly)

 

[Jadams639]

I'm almost certain, they are 500 watt rms. Regardless I know they aren't the problem, I plugged the output from the amps into a pair that I know works, and I'm still not getting anything. I've narrowed the problem down to the amp. I'll try hooking up my backup amp tomorrow and seeing if that will remedy the problem.