ProSoundWeb Community
Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => The Basement => Topic started by: Jonathan Johnson on March 17, 2017, 01:51:01 PM
-
What are some of the most interesting problems that you've solved in the audio world? I'm especially interested in problems that may have plagued systems for years, unique situations that required unique solutions (safe solutions, of course), or problems that were particularly difficult to resolve.
----------
As for myself, one of the churches in my denomination had a feed from the sanctuary system to the fellowship hall. They complained for years that the feed was distorted, and supposedly had several "experts" (possibly just music store salesmen) look at it without resolution. Since it's across the country from where I live, it wasn't something that I could just pop over and take a look at.
Back in 2000, that congregation hosted the national convention of our denomination and I attended. When I first walked into the fellowship hall during a service, my first impression was that it sounded like clipping -- most likely from an overdriven input. After the service, I took a look at how things were set up, and found that the feed was connected to a microphone input on the fellowship hall system, from a 1/4" speaker level output off the amplifier in the sanctuary.
It was a simple matter to move the feed from the speaker output to an available 1/4" line level output, and the problem was solved.
The moral of the story? Not all 1/4" outputs are the same. Apparently some "experts" haven't realized this.
-
What are some of the most interesting problems that you've solved in the audio world? I'm especially interested in problems that may have plagued systems for years, unique situations that required unique solutions (safe solutions, of course), or problems that were particularly difficult to resolve.
----------
As for myself, one of the churches in my denomination had a feed from the sanctuary system to the fellowship hall. They complained for years that the feed was distorted, and supposedly had several "experts" (possibly just music store salesmen) look at it without resolution. Since it's across the country from where I live, it wasn't something that I could just pop over and take a look at.
Back in 2000, that congregation hosted the national convention of our denomination and I attended. When I first walked into the fellowship hall during a service, my first impression was that it sounded like clipping -- most likely from an overdriven input. After the service, I took a look at how things were set up, and found that the feed was connected to a microphone input on the fellowship hall system, from a 1/4" speaker level output off the amplifier in the sanctuary.
It was a simple matter to move the feed from the speaker output to an available 1/4" line level output, and the problem was solved.
The moral of the story? Not all 1/4" outputs are the same. Apparently some "experts" haven't realized this.
With students when I talk about connector vs. signal types, etc. I use the phrase "just because it fits doesn't mean that you should stick it in there". :-)
Lee
-
Back in the analog 90s, I had been asked to run a local bands system for an upcoming show
went to their practice room to see what they had . after enduring about 9 seconds of the "monitor system" they had set up I stopped and asked if I could have a look at their rack.
Fun stuff , eq out to speaker outs to the next amps daisy chained 1/4 inch one to the other. I asked who hooked this up, the guitar proudly claimed the patching master piece.
he says he just kept hooking up cords till sound came out ..............uh ,,,,ok
-
Wow, most interesting? I get a lot of repair calls for offices, churches, museums, run into all sorts of crazy problems. Not sure I could even cut the list to a top ten.
Yesterday I was in a really nice museum in the city, their music room had the usual 9' Steinway piano but the sound system was a mess.
The rack had a nice enough Qu-16, but all the mic inputs (from floor pockets) were super noisy. I found some idiot had disconnected as many grounds as possible before giving up, but in the process of resoldering the shields on all the mic lines coming into the mixer I discovered that the XLR's had been wired wrong to begin with - pin 1 and pin 2 swapped, every one of the dozen channels.
-
What are some of the most interesting problems that you've solved in the audio world? I'm especially interested in problems that may have plagued systems for years, unique situations that required unique solutions (safe solutions, of course), or problems that were particularly difficult to resolve.
----------
As for myself, one of the churches in my denomination had a feed from the sanctuary system to the fellowship hall. They complained for years that the feed was distorted, and supposedly had several "experts" (possibly just music store salesmen) look at it without resolution. Since it's across the country from where I live, it wasn't something that I could just pop over and take a look at.
Back in 2000, that congregation hosted the national convention of our denomination and I attended. When I first walked into the fellowship hall during a service, my first impression was that it sounded like clipping -- most likely from an overdriven input. After the service, I took a look at how things were set up, and found that the feed was connected to a microphone input on the fellowship hall system, from a 1/4" speaker level output off the amplifier in the sanctuary.
It was a simple matter to move the feed from the speaker output to an available 1/4" line level output, and the problem was solved.
The moral of the story? Not all 1/4" outputs are the same. Apparently some "experts" haven't realized this.
Weirdest one to date:
There was a church in town that had installed their own PA (surprisingly well) and had been using it without problems for a few years. Out of nowhere, the PA would suddenly produce 3 REALLY LOUD bursts of buzz/hum out of pretty much every speaker. It would do this every 37 seconds without fail whenever the system was powered on. They tried to figure it out for a few weeks, then called me. I proceeded to perform all the standard troubleshooting stuff (lifting grounds, unplugging cables between components, etc) with no luck. As luck would have it, I left my meter back at the shop...otherwise I may have figured things out quicker.
I knew it had to be power related so I'm walking around the building (not huge...auditorium was only about 200 seats) trying to spot anything that looks like its been messed with recently. Building was small enough I could hear the hum through the subs no matter where I was.
After a couple of hours, I ended up in the basement (old building, by the way) and kept opening up doors and exploring. I wound up in a little storage closet under the FOH booth (only door I hadn't opened yet) and was about to walk out when I somehow noticed a DeWalt charger sitting on a shelf...and in turn noticed that when the lights flashed three times on top of the charger (indicating charge complete), the system hummed three times...every 37 seconds. Noticed the cobbled mess of romex going from the receptacle up to an old surface-mounted porcelain fixture. I unplugged the charger, no more humming. Plugged a lamp into the outlet: HUMMMMMMMMMMMMMMMMMMMMM!!!!!! until I turned it off.
I told them to get an electrician in there. They ended up calling someone I knew. He told me the recept was wired with the black wire where it should be, the bare wire on the neutral screws, and the white wire cut off. That circuit was somehow tied into/feeding the circuits that fed the FOH booth and he found lots of other stuff (reversed hot/neutral, missing ground, etc). It had always been wrong, but somehow never displayed a problem until someone plugged something into that recept in the storage closet (probably the first time in decades). I almost didn't go into that room...never would have found it.
-
My most interesting one was back in the VHF wireless days in the 90's.
The Pastors mic would cut out when he went to stage left.
After a bit of not getting it to cut out, I wondered about the B3 organ on that side.
I took the back off and the oil tubes were still full. It had never been oiled.
So I turned it on and the mic would cut out.
I oiled it and let it run a little while.
Then the mic didn't cut out anymore.
It was "squeeking" and causing RF spikes which were interfering with the RF.
It's not often you need a little oil to fix a wireless problem
-
I've posted this on AC Power & Grounding, but it's a good brain teaser for here:
Some 40 years ago I had seemingly random pop/buzz noise bursts on my PA in a bar that seemed to be more frequent after each dance song and when we took a break. That is, during a song we wouldn't hear it, but right after a song there would be a flurry of these pops and buzzes, sometimes every 10 seconds or so. The management had installed new electrical outlets across the back of the stage, so they assured me it couldn't be a power problem. However, I kept watching the bar for anything happening that corresponded with the noise burst. And it happened every time they rung up a sale on the cash register.
After much troubleshooting I found that all the outlet grounds on the stage were tied together along with the electrical outlet for the cash register. However, none of outlet EGC grounds were bonded to the service panel neutral. So they were all floating together without a place for the current to go. Any voltage put on the ground of one of the outlets would appear on the ground of ALL of the outlets since there was no bonding connection to act as a current sink.
When my band was done playing a song, and the patrons were done with a fast dance they all ran to the bar for a drink, and every time the cash register made a sale the old-school solenoid on the drawer put a voltage spike in the EGC outlet ground. That voltage spike went right in my PA system ground and produced a big pop and buzz noise. It appeared to be random, but the noise burst was tied to another non-random event.
My point is that documenting the period of a failure and observing seemingly non-related events can give you a clue as to its source. There are very few truly random events. Most of them are caused by something we haven't observed directly which confuses us. Consider that before Nicolaus Copernicus stated “We revolve around the Sun like any other planet.” there were a lot of crazy calculations required to explain why the planets seemed to move in strange ways, sometimes appearing to go backwards. Early astronomers didn't understand the concept of the sun being the center of the solar system, with all the planets orbiting about it.
Troubleshooting problems is getting to be a lost art since it takes time and logic we often don't have. But it's time and brainpower well spent.
-
I have one 'audio' related thing happening to many years ago that really baffeled me...
I bought a car alarm for my car and did the install by myself plus some friends 'helping'.
After the installation was finnished I started to test it and noticed after a while that one of the piezo horns were always sounding. If was quite faint, like a speaking level tone coming from it. I was first going to ignore it but it became annoying quite quickly.
Since the piezo cable was pulled behind and hidden under the chassis I cursed as I belived that the insulation on its wire had been scratched somewhere when feeding the cable inside the chassis and was causing a slight shortcut of the power.
I decided to cut the red wire as it was starting to get late and fix it the day after. After cutting the wire the piezo was still sounding and I thought that I must somehow mixed up the black and red wire and decided to cut the black wire as well.
The piezo was still sounding with both its wires cut! No electrical connection whatsoever...
After one or two hours later I decided to give up and hope that no one else became annoyed by the sound during the night. When I was about to take the keys I noticed that for some reason I had inadvertently turned down the panel lights so I turned them back up again and the piezo pitchshifted! I realized that when the panel lights was fully lit the piezo was not sounding but as soon as I started to dim the lights the piezo started to sound.
I then realized that my car was not using a reostat for the panel lights but a pwm operated dimmer. For some reason the rfi leakage from that dimmer was enough to operate the piezo from a distance.
This has been one of my weirdest 'audio' related issue ever.
-
Just ran into an interesting situation on Friday, while providing a very basic PA and extremely small light rig for a small corporate party. About 100 people mingling in a training room on the 4th floor of a newish building. Only one circuit for the front of the training room, which is where they wanted the PA gear and lights.
Got everything set-up, tested the wireless mics, and got ourselves situated in an out of the way location. iPad in hand, all set to go, when all of a sudden there's the loudest 60Hz ground loop hum I've heard in quite some time. Runs for about 10 seconds, then stops.
I run up to the front, and check on the connections. While I'm checking, the noise starts again. I have my X32R on a UPS, so I unplugged the UPS from the wall - noise is still there. The powered speakers are also plugged into the same circuit (duh).
So, I put ground lift plugs in place, and there's no noise. Until about 3-4 minutes later when that same 10-second hum appears again. I'm starting to sweat because the event starts in 10 minutes. I'm trying to find a solution when the organizer/host comes up to me with a cup of coffee in hand, asking if we are ready to go.
I explain the phantom noise, and as I'm doing so, the noise appears again. In comes another person with a cup of coffee. It dawns on me... so I ask, "Do you guys have a coffee vending machine here?"
The guy says, "Yep - you need a coffee? It's right outside."
I walk outside, and there's a small coffee/latte/espresso vending machine on a counter. I order up a coffee and press "start" - and there's my buzzing noise.
We unplugged the coffee machine and put a "temporarily out of order" sign on it. The event went perfectly, and when we were done, the machine was reinstated.
-
Not audio related:
Many years ago, my father was a central heating system designer (back in the days when every piece of equipment, pipe, fitting etc. was put on a drawing).
A system was fitted in a house and a few days later, the owner complained about a noise. A fitter was sent out several times but could find no fault.
After another call, my father sent someone out instructed sit in the kitchen drinking tea until he heard the noise.
After a while, sure enough, there was the offending noise. The house owner said "that's it - did you hear it?". To which the reply was "yes madam - that's your fridge!".
Steve.
-
Also not Audio related...
Back in the late 70's, my first job out of high school was for a security company.
A year goes by, and I am transferred to night duty.
Install division puts in a fancy (new) microwave setup in this warehouse.
We had never seen something like this before.
1 transmitter, 1 receiver over 1,000 feet apart.
Stretched across the loading/shipping docks.
Idea was, it made a 15 foot round "cylinder" protecting the docks.
Living or not, ANYTHING bigger than a mouse would set it off.
Worked great that summer and fall. Then winter came.
That fukin system was going off at any time, no real pattern.
One night I responded. and while nothing was happening inside, the snow was freshly cleared from the outside.
Hmmm. mouse inside, Dozer outside. Why not?
I filed a report that said "NTF, send a watchman at next snowfall"
They did.
He called in to report snow removal had arrived at the same time CO got an alarm.
I went up and "deflated" the sensitivity a bit. All good.
Your eyes, ears and brains are the most powerful tools you have.
Don't fuck them up.
Chris.
-
I setup a system in a school auditorium for a singer/songwriter guy. He sounded great in the house, but kept complaining about feedback. After repeated "There it is!" moments I turned the system off, walked on stage where he was sitting, and started having a conversation with him. There was the feedback sound - with the system completely off. This room has a funny acoustic resonance right at front dead center of the stage that sounds just like 1K feedback. Apparently Wenger has been out to look at the room, and they can't figure it out.
I've been back there several times, and I always point the noise out to the artist before I get blamed for it.
-
I used to do shows at a university student union theater. It had a thrust stage, a trapezoid with a semicircle at the end. The center point of the semicircle was also the center point for the hard plaster walls at the back of the house. Whenever they had someone come in to give a speech they ALWAYS wanted to stand at that center point, till they tried to talk. They got a slapback echo which made speech very difficult.
-
Troubleshooting problems is getting to be a lost art since it takes time and logic we often don't have. But it's time and brainpower well spent.
Mike,
I remember one troubleshooting event I had to solve quickly, and did.
After a very long day that began in Minneapolis and ended in Fargo, I fell asleep at FOH after the local opening band engineer had began to mix.
Something in the sound had changed, which woke me up. The band engineer was pointing at the Soundcraft console in the universal "it no worky" way, my first thought was "no lights, dead power supply, must plug in back up", my second, when I found the PSU push on/push off switch in the off position was "how did my shoe happen to hit the worst possible point in space just moments after I fell asleep?".
STS policy then became all console power supplies must be protected from any possible "foot traffic" ;^).
At another event, Billy Squire started his encore, the sound was a bit different, his sound man turned to me- "I've got no bloody mains!".
A quick look for obvious problems revealed some punter had pulled the euro cord from the back of the main EQ while we waited for the band to return to stage!
This led to a redesign of all FOH racks to include a closing back cover.
Richard Neesom (I think that was Billie's FOH) after that show told of the most nefarious "figure it out" problem- several snake channels had come up connected to each other- channel 10 connected to 17, a mid signal bleeding in to a low send, etc.
A look at the multi-connectors revealed no problems with them.
They ran a second smaller snake, and "patched around" the problem channels.
During load out, a stagehand yelled out after he pricked a finger while rolling up the multi-core. It turned out that some evil person had pushed a sewing pin in to the snake, then cut the push head off with a diagonal cutter. The push pin had effectively connected any of the conductors in it's path.
Ouch.
Art
-
I setup a system in a school auditorium for a singer/songwriter guy. He sounded great in the house, but kept complaining about feedback. After repeated "There it is!" moments I turned the system off, walked on stage where he was sitting, and started having a conversation with him. There was the feedback sound - with the system completely off. This room has a funny acoustic resonance right at front dead center of the stage that sounds just like 1K feedback. Apparently Wenger has been out to look at the room, and they can't figure it out.
I've been back there several times, and I always point the noise out to the artist before I get blamed for it.
TJ,
An interesting acoustical problem!
There are certain venues with reflective seats, stairways or cement seating. Sound reflected off those will take on a "period" dependent on the distance between the surfaces, the "period" can sound remarkably like a certain note, or pitch, regardless of the nature of the sound that is reflected.
In a "fan" shaped venue, with seating set in arcs, often the worst (or best) place to hear the effect is down stage center, the exact spot one tends to place the main artist.
Clackity-Clack, it talks back...
Art
-
I'm consulting on a system redesign right now for a hotel. Their ballroom has speakers in the ceiling. I mean, actually IN the ceiling, as in they are above the sheet rock/plaster ceiling and not ported to the actual room. Their prefunction reception space just outside the ballroom has a similar install with the speakers actually inside the columns in the room. :o
In talking to them, they don't want to do any construction on the room or the columns, so those old speakers will stay there, walled up like a bad Edger Allen Poe story. And we'll install new surface mounted speakers somewhere that is as unobtrusive as possible.
-
I remember one troubleshooting event I had to solve quickly, and did.
After a very long day that began in Minneapolis and ended in Fargo, I fell asleep at FOH after the local opening band engineer had began to mix.
Something in the sound had changed, which woke me up. The band engineer was pointing at the Soundcraft console in the universal "it no worky" way, my first thought was "no lights, dead power supply, must plug in back up", my second, when I found the PSU push on/push off switch in the off position was "how did my shoe happen to hit the worst possible point in space just moments after I fell asleep?".
STS policy then became all console power supplies must be protected from any possible "foot traffic" ;^).
Not audio: a local radiology clinic had an MRI machine for which the main power switch was about 6" off the floor. This switch was on the front of the controller, which happened to face a busy hallway (I think you can see where this is going).
If the power to this MRI was lost (even momentarily), it took at least 24 hours for the temperatures in the magnetic core to stabilize. If the power was down for an extended period, then it could take as long as three days. They could not use the MRI until the temperatures had stabilized.
Well, after a few instances of "unscheduled downtime" due to the switch being accidentally flipped (even though it was recessed), they taped a piece of stiff, clear plastic over the power switch. That resolved the problem for several years until they upgraded the MRI.
---
Audio related: one time I was helping a band in a church during their rehearsal. The power switches for wireless mics happened to be at knee level. Took me a bit to find out why one of the mics went dead. After that I was more careful about where I put my knees.
-
Mike,
I remember one troubleshooting event I had to solve quickly, and did.
After a very long day that began in Minneapolis and ended in Fargo, I fell asleep at FOH after the local opening band engineer had began to mix.
Something in the sound had changed, which woke me up. The band engineer was pointing at the Soundcraft console in the universal "it no worky" way, my first thought was "no lights, dead power supply, must plug in back up", my second, when I found the PSU push on/push off switch in the off position was "how did my shoe happen to hit the worst possible point in space just moments after I fell asleep?".
STS policy then became all console power supplies must be protected from any possible "foot traffic" ;^).
Ouch.
Art
That happens more frequently than you might expect as people like to mount rackmount PS under large consoles with the front panel lights visible facing forward. Making the power switch inaccessible creates a PIA for normal operation. No easy answer without some inconvenient compromise, but operators usually learn to not make that same mistake repeatedly.
Less of a problem with modern SMPS technology making it easier to place PS internal to consoles.
JR
-
What are some of the most interesting problems that you've solved in the audio world? I'm especially interested in problems that may have plagued systems for years, unique situations that required unique solutions (safe solutions, of course), or problems that were particularly difficult to resolve.
A high school called me, reporting that Football Stadium was getting a series of loud pops during every game. I attended a game in the press box, but heard no pops. (Audio was piped in through the rooms in the Box.) Game ends, I'm about to leave, when the Athletic Director finds me and says the problem always happens shortly AFTER the game, so I stuck around.
As people are leaving the Press Box, a security guard comes through the box to tell people to leave. He comes into the announcer's booth where I and a couple other people are, then he keys his walkie-talkie to report how many people are still in the Box. "POP POP POP POP..." I see the lights on the Sennheiser EW300 wireless receiver going NUTS. I turn down the volume on that channel, asked him to report again. The wireless receiver lights go nuts again, but no pops. (The wireless fin antennas are just outside the announcer's booth.)
My recommendation to them: EITHER (1) Turn down the wireless volume immediately after the game, or (2) Tell the security guard to go somewhere else, away from the antennas, to make his report.
-
What are some of the most interesting problems that you've solved in the audio world? I'm especially interested in problems that may have plagued systems for years, unique situations that required unique solutions (safe solutions, of course), or problems that were particularly difficult to resolve.
Then there was the time in the 90s I was working FOH for a theater. The play was "Always, Patsy Cline".
The play opened with a dark stage. I would play a short voice-over on cassette with a southern-voiced announcer saying something like, "Please welcome to our stage at the Grand Ole Opry, Miss Patsy Cline!", then lights would come up on the star.
One night, the cassette would not play. Realized the lights were out on cassette deck. Can't troubleshoot in the dark, and no time. But I knew the line, so I just shouted out (in southern accent), "Please welcome to our stage..." and the play went on.
When lights came on, I realized I had kicked the power plug for the tape deck loose from its receptacle.
-
Thanksgiving at the in-laws and I hear a peeping noise from the kitchen. My mother-in-law says, "Oh, we have a rabbit nesting under the deck upp by the foundation. It makes that little squeaky noise."
I look under the kitchen sink and find a smoke alarm which had been taken down and tossed in there. Low battery alarm...peep, peep, peep.
-
With students when I talk about connector vs. signal types, etc. I use the phrase "just because it fits doesn't mean that you should stick it in there". :-)
Lee
In the 1970s, long before the invention of the speakon, the usual thing for Australasian PA systems was to use
XLR3F->XLR3F cables for speakers (thus amps and speaker cabs used XLR3M chassis connectors) so speaker
cables couldn't be confused with mic cables.
In the "just because it fits" department, you'd be surprised how much sound you can get out of an SM58....
M
-
Again back in the 90s, I was standing in as a BE for a local band. They warned me that the lead vocals had to really be pushed in the monitors, but only during the performance.
During sound check there were no problems with the monitors. Once the show started the lead dropped out of the monitors. I had to push it 10-12dB hotter!
The second set started and I noticed that the lights on the system compressor weren't acting like I expected. They weren't more or less in sync as you would expect for a stereo set up. I grabbed a flashlight and looked at the back of the rack. Nope! Not stereo. It was mono with a "Y" adaptor into the compressor. The lead vocal was patched into the other side of the compressor then back into the monitor matrix. It was an old dbx stereo only compressor.
So during sound check the compressor was acting only on the vocal. Once the whole band started playing it was acting on the overall signal and squashing the vocal in the monitor. I pulled the patch for the vocal out of the compressor, patched the stereo back in properly and the show and monitors sounded much better.
I recommended they buy additional compressors for vocals.
-
The sound system that hummed when powered OFF. A speaker speaker zones cable had gotten stepped on and the insulation cut through on the positive line making contact with the buildings steel frame. If the negative line had gotten cut through it probably would have gone un-noticed. There was a couple volt difference between the building frame and the power ground for that zones amp. The positive lead coming in contact with the building frame made for a complete circuit.
This one could start a separate topic "customer education"
A school was complaining that no one could understand or really even hear announcements during basketball games.
It worked out to stop by a game one evening on the way home from another job, I know that this gym has a decent system.
Get to the school, meet my contact, go and sit down a few rows behind the announcer at the scorer's table. No more than a minute later he makes an announcement reading some player stats holding the mic about a foot and a half off to his side while looking down at the stat sheets.
-
The sound system that hummed when powered OFF. A speaker speaker zones cable had gotten stepped on and the insulation cut through on the positive line making contact with the buildings steel frame. If the negative line had gotten cut through it probably would have gone un-noticed. There was a couple volt difference between the building frame and the power ground for that zones amp. The positive lead coming in contact with the building frame made for a complete circuit.
This is one reason the install business prefers transformer isolated 70v speaker feeds.You can ground either lead and it still works, only when you short both does it suffer.
JR
This one could start a separate topic "customer education"
A school was complaining that no one could understand or really even hear announcements during basketball games.
It worked out to stop by a game one evening on the way home from another job, I know that this gym has a decent system.
Get to the school, meet my contact, go and sit down a few rows behind the announcer at the scorer's table. No more than a minute later he makes an announcement reading some player stats holding the mic about a foot and a half off to his side while looking down at the stat sheets.
-
At a club I worked at, the power would sometimes cut out when it had rained earlier. I don't mean the PA or FOh cut out, the ground fault switch for the entire panel tripped. After a couple years of this, it stopped at the same an installed light for some lounge seating element failed to come back on after the previous panel reset. When the light was investigated it was found that the power cable outer jacket had been stripped off in installation and patrons movement on the seating element had pinched the cable conductors to a steel frame which was part of the building, which happened to leak the ever slightest bit of water from the roof during heavy storms and like the water of the tao, find the place it wants to.
At a hotel I sometimes freelanced at, one of the wireless mics would randomly pop. Not often enough for the customers to notice, but drove me fucking crazy. I only worked there every few months and nobody else was bothered enough to try and track it down. As we were doing out setup once for a conference, it popped again while we had plenty of time to investigate. Eventually found it was the xlr output on a patch panel. Since the AV company was a bit lazyand the receiver lived in the rack, nothing ever happened to the panel and a short mic cable became the new patch.