Live PA Trauma...Not fun with no extra set of hands to help.

keithb7

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Local pub last night. Good turnout. Lots of dancing and crowd interaction.

Second set, some gawd-awful loud crack and pop punched through the PA system. We were between songs. Very loud and it was like "Holy Crap what the F was that"? A little nerve racking, but the show must go on. I was distracted and a bit shaken up. I definitely lost my groove through the next song. We held it together ok though. We got through the song all seemed seemed to be ok with no more crraack from the PA system. Then BAM!, it was back with another loud pop. WTH? We had to take a minute during the set to try and quickly find out what was going on. We determined the Cajone player's mic was dead. Was it the mic or the XLR cord? We quickly changed out the cord and mic. Seemed better. We started another song....Crack and BOOM again. What the actual heck?.... The cajone player took a sip of his water. Put his drink down. Boom crack again! We are thinking this is pretty grave now. The cajone player tapped the Crossover. The haunting crack & Boom was there. 2-3X he tapped it. It was indeed the crossover that we use to separate his single cajone mic. We quickly took a break and grabbed our spare crossover out in the car. Swapped it out. The problem was gone. Never occurred again the rest of the night. 2 more sets and no problem.

We have not looked at the system yet to follow up. We'll do that next practice. I'll consider testing all XLR cables and opening up the crossover also.
I might get lucky and find a bad solder joint or degrading component or wire.

Live on stage, putting on a show to a packed pub, it's not a fun place to be when gear issues appear. We had no sound man to assist, compensate or adjust. We were lucky that we quickly found and eliminated the problem. It could have been one of many things in the PA system. There was a point where I thought we may have to shut down the PA for the night. There are 4 guys in the band. One has a very good grasp of the entire PA system. Another guy is about 70% there and getting better each gig. 2 other guys have very limited understanding. When we are on our instruments performing and singing, it's challenging to do much about it while it's happening.

Once it was determined that the problem was addressed, indeed I was thinking about a couple straight shots to settle my nerves. Lol. I thought better of it and went with 1 beer instead. 😁 Tips and pay combined we did alright. We can easily get another crossover.
 

loudboy

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As "The Guy Who Owns The PA" I concur wholeheartedly.

You don't get paid to provide it, you really earn the $ when something goes wrong and you have to fix it, under fire.

To the OP - where in the chain is the x-over, and what are you using it for?
 

chris m.

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I'm usually the PA guy for our band, and thankfully we haven't had glitches this severe. Ironically, we hired a sound guy for two gigs ago. I was so happy to not have to worry about it. So sure enough the lead vocalist had her mike cutting in and out...affecting a number of songs until the sound guy moved her over to another channel. I think he had some dirty contacts in his analog Mackie mixer and that was creating an intermittent disconnection. He was blaming it on the microphone, which I provided from our usual gear, but it was definitely the mixer he brought since the mic worked just fine in our last gig, no issues. Plus the fact that everything worked fine once he moved the mic over to another channel made it clear that the mike itself wasn't the problem.
 

keithb7

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To the OP - where in the chain is the x-over, and what are you using it for?

We are using 1 mic placed inside a cajone. Xlr cable from cajone mic to crossover input. Then we split the highs and lows from crossover out to 2 separate channels into the powered mixer. This allows us separate eq’ing, boosting some frequencies, setting separate gains, also volume controls from the high snare and bass of the cajone. It works very well. We can tweak the low notes to thud nicely sounding like a kick drum. The highs set to snap like a snare. Board has compression dials too. Sounds good. Its worked fine at multiple rehearsals. This was our first time live. We do set the PFL gain to appropriate levels for each signal from the crossover to the main powered mixer board.

Are we using the crossover incorrectly here? Thanks.
 

loudboy

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We are using 1 mic placed inside a cajone. Xlr cable from cajone mic to crossover input. Then we split the highs and lows from crossover out to 2 separate channels into the powered mixer. This allows us separate eq’ing, boosting some frequencies, setting separate gains, also volume controls from the high snare and bass of the cajone. It works very well. We can tweak the low notes to thud nicely sounding like a kick drum. The highs set to snap like a snare. Board has compression dials too. Sounds good. Its worked fine at multiple rehearsals. This was our first time live. We do set the PFL gain to appropriate levels for each signal from the crossover to the main powered mixer board.

Are we using the crossover incorrectly here? Thanks.
I'm surprised that a mic would put out enough level to drive the line level input on the x-over? Also, the impedance mismatch is probably affecting the frequency response of the mic itself.

Are you running subs? And what mixer are you using?
 

dougstrum

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Ahh, the travails of being in the band and running sound😵‍💫 It's hectic enough without any gremlins creeping into the wires.
Sounds like you isolated the problem and made it through in good form👍
 

keithb7

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@loudboy you triggered some thoughts an I think I may know what we have done wrong.

We had the PA set up mono. 1 sub on left channel. 1 main on right channel. Low frequencies panned hard left to sub (8 ohm load). Bass guitar and lows after crossover from cajone panned to hard left. Guitars and mics panned hard right to the main speaker (8 ohm load). Sort of a single mini line-array system. The main speaker elevated right above the sub. The board is a Yamaha EMX5016CF.

Photo of our single line array setup seen here in photo below.

When the speakers cracked, I thought initially of a mismatched load on the two amps that are built into the powered mixer. Yet I thought, no shouldn't be that as I have 2- 8 ohm speaker loads on the 2 main power amps in the mixer board.

The problem is likely attributed to the fact that I had a single mic from the cajone going into a crossover. Then out of the crossover into 2 separate input channels on the mixer board. 1 input panned hard left for the sub frequencies. The other input panned hard right for highs to the main. This split the highs and the lows from the cajone. Sure sounded great as we could tweak the highs and lows individually.

I suspect what we did was; the impedance load from the single cajone mic was split it into the two separate channels into the board. The 2 cajone mic signals were boosted or cut by the crossover. The lows panned hard left as mentioned, into to the board. The highs panned hard right. This somehow put uneven impedance loads on the signal going into the board's 2 built in power amps? Somehow flashback voltage spikes were occurring in the crossover. This was happening pre-the power amps. The power amps amplified the voltage spikes and the CRACK/BOOM was sent out to the main and sub speakers. Lucky we did not blow a power amp or speaker.

Am I on the right path here? I am unsure what the impedance signal from a single mic is. I do know we split 1 mic signal to two channels. Then mixed those two channels with other single mic channels into the pre-amp buss.
Guessing the problem never showed up at practice with this same set up as we never had it turned up very loud. The louder requirements at the gig made for a perfect storm of destruction.

What is a better set up option? Two mics in the cajone I'll guess. One going to each side of the stereo crossover. Then each mic signal from the crossover going into a channel each of the mixer. I could still pan them hard left and right for separation. I could still run the PA in mono mode if wanted. Or I could runt the PA in stereo mode with 2 subs and 2 mains. As long as I am not splitting 1 cajone mic into two inputs of the board. Correct?
 

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loudboy

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@loudboy you triggered some thoughts an I think I may know what we have done wrong.

We had the PA set up mono. 1 sub on left channel. 1 main on right channel. Low frequencies panned hard left to sub (8 ohm load). Bass guitar and lows after crossover from cajone panned to hard left. Guitars and mics panned hard right to the main speaker (8 ohm load). Sort of a single mini line-array system. The main speaker elevated right above the sub. The board is a Yamaha EMX5016CF.

Photo of our single line array setup seen here in photo below.

When the speakers cracked, I thought initially of a mismatched load on the two amps that are built into the powered mixer. Yet I thought, no shouldn't be that as I have 2- 8 ohm speaker loads on the 2 main power amps in the mixer board.

The problem is likely attributed to the fact that I had a single mic from the cajone going into a crossover. Then out of the crossover into 2 separate input channels on the mixer board. 1 input panned hard left for the sub frequencies. The other input panned hard right for highs to the main. This split the highs and the lows from the cajone. Sure sounded great as we could tweak the highs and lows individually.

I suspect what we did was; the impedance load from the single cajone mic was split it into the two separate channels into the board. The 2 cajone mic signals were boosted or cut by the crossover. The lows panned hard left as mentioned, into to the board. The highs panned hard right. This somehow put uneven impedance loads on the signal going into the board's 2 built in power amps? Somehow flashback voltage spikes were occurring in the crossover. This was happening pre-the power amps. The power amps amplified the voltage spikes and the CRACK/BOOM was sent out to the main and sub speakers. Lucky we did not blow a power amp or speaker.

Am I on the right path here? I am unsure what the impedance signal from a single mic is. I do know we split 1 mic signal to two channels. Then mixed those two channels with other single mic channels into the pre-amp buss.
Guessing the problem never showed up at practice with this same set up as we never had it turned up very loud. The louder requirements at the gig made for a perfect storm of destruction.

What is a better set up option? Two mics in the cajone I'll guess. One going to each side of the stereo crossover. Then each mic signal from the crossover going into a channel each of the mixer. I could still pan them hard left and right for separation. I could still run the PA in mono mode if wanted. Or I could runt the PA in stereo mode with 2 subs and 2 mains. As long as I am not splitting 1 cajone mic into two inputs of the board. Correct?
I wouldn't plug a mic (which is running at mic level, -40 to -60dB, and 100-200 ohms) directly into a crossover which is designed to see line level of -10 and a much higher impedance.

The correct way to do this would be to:

Plug the cajon mic into a channel on the Yamaha.

Using a 1/4" TRS insert cable, come out of the Insert Jack on that channel, and into the crossover input.

Connect the Return of the TRS insert cable to the HF output of the crossover. This will send the HF back into the channel that the mic is plugged into.

Using a standard 1/4" cable, come out of the LF output of the crossover into an adjacent channel Line Input on the Yamaha.

Using panning controls, that will give you the same control over your cajon mix, while keeping all your gozintas/gozoutas correctly matched up.

Not sure what's causing the pops, but try this first and see if it helps.
 

schmee

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Fortunately my last PA failure was at rehearsal! The Yamaha Cl D powered mixer failed.
I'm avaoiding CL D stuff entirely as much as possible. Failure prone. meanwhile my old Mackie 1000 watt and 5 pounds just keeps working.
I once had to use my spare guitar amp (Crate Powerblock) for PA. It worked fine! Limited inputs though.
 

teletimetx

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Yeah. No fun. Last two gigs at Brewpub, had to bring our own PA, Bose column deal plus powered mixer (I happened to have) - for a 4-piece, no drums. Small venue, wouldn’t need to mic the drums anyway and bass player is just playing out of his amp.

I’m running 3 acoustic instruments into the Bose and 3 mics into the mixer, then to the Bose. We did a practice run, I kinda got things sorted.

But in our last gig, the other guys have a simple set up, and ready to go, waiting on me to work balances. I’m not a sound engineer - just happened to be able to get this stuff to work. Maybe that was my 1st mistake. (Really JK, this is a good band and I’m happy with it).

Got my electric guitar set up, tuned, running through small amp (like bass) then get acoustic ready. I’ve no sooner got the flattop just plugged in and other guitar launches into first song. Had just made sure acoustic has signal feed all the way through.

But guess what, hadn’t tested level on my acoustic and it’s too loud. Mr. Early Bird is giving me the hairy eyeball. All fun? Nope.

But that’s why we have knobs and sliders - just don’t like having to do it on the fly.
 

keithb7

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Using a 1/4" TRS insert cable, come out of the Insert Jack on that channel, and into the crossover input.

Connect the Return of the TRS insert cable to the HF output of the crossover. This will send the HF back into the channel that the mic is plugged into.

Using a standard 1/4" cable, come out of the LF output of the crossover into an adjacent channel Line Input on the Yamaha

@loudboy Band rehearsal is this today. I gather some adaptors. To make this work I also built my own custom insert cable with XLR on one side, the other 1/4 RTS. I spent some time this morning setting up the PA with the crossover as you suggested. It seems to be working nicely so far. I've been testing with canned ipod music inserted in the cajone channels.

I do have one question regarding the bold text above. My crossover only has XLR input and output connections. I have adapted so the LF out of the crossover goes from XLR to ¼ RTS, and then into the 1/4 RTS line input of the adjacent cajone channel. Is this necessary? Or could I go from Crossover LF XLR out, XLR cable into XLR input on adjacent mixer channel?
Keeping in mind the HF return to the board is through the ½ insert connection.

I assume maybe XLR/mic inputs run at mic level -40 db, and Line input is at 0 db? So I should not do this? I'd likely have two different signal strengths coming into the 2 adjacent cajone inputs? Thx.
 

loudboy

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@loudboy Band rehearsal is this today. I gather some adaptors. To make this work I also built my own custom insert cable with XLR on one side, the other 1/4 RTS. I spent some time this morning setting up the PA with the crossover as you suggested. It seems to be working nicely so far. I've been testing with canned ipod music inserted in the cajone channels.

I do have one question regarding the bold text above. My crossover only has XLR input and output connections. I have adapted so the LF out of the crossover goes from XLR to ¼ RTS, and then into the 1/4 RTS line input of the adjacent cajone channel. Is this necessary? Or could I go from Crossover LF XLR out, XLR cable into XLR input on adjacent mixer channel?
Keeping in mind the HF return to the board is through the ½ insert connection.

I assume maybe XLR/mic inputs run at mic level -40 db, and Line input is at 0 db? So I should not do this? I'd likely have two different signal strengths coming into the 2 adjacent cajone inputs? Thx.
Correct, I would go into the 1/4" line input on the mixer.
 




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