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Distortion in the monitors

jefff100

Supporting Member
Jan 23, 2010
3,938
13,623
Jersey Pine Barrens
Hey all, wondering if some of you seasoned players / sound people can lend some insight here. I'm getting an unberable amount of distortion in my stage monitors, but my wife tells me the sound out in the congregation is o.k. Its a long post, but I'm trying to paint a picture of our setup.

To describe our setup:

I play in a church praise band, small to medium size church I guess. Typical Sunday morning sees about 90 to 120 in the pews. The sanctuary has a capacity for about 350 I suppose. The main portion is about 150 foot long x 80 foot wide; including the altar area. The ceiling is vaulted, probably about 25 foot in the center and perhaps 12 foot along the edges.
This is an older building, built in the 1920's, so acoustics in general & certainly not a live band were not on the horizon for construction design. Lots of stained glass, plaster & lath walls, oak pews with no cusions. No sound damping material in general other than the carpeting.

The band is set up in the front of the chuch, we are just in front of the alter, but off to the side. Our music stands & moniotrs occupy the 1st pew on that side.

Gear wise: We have 2 guitars, Keys, bass (me). Lead Guitar player and Keyboard player share lead vocals. Rythem guitar sings backing vocals. Drums on a occasional basis.
All our amps are run through the PA via line outs or mic'd.

There is a mixer in the back of the church that all vocals, instruments & the wireless mics for pastor etc. all go throuh. House Mains are driven off the mixer through a 500 watt power amp; and a pair of 1x15" cabs hang in the rafters above roughly the 3rd pew back. A line out from the mixing board is send back down on a buss circuit back the snake cable to the front pew and we have a small powered mixer head that serves as the amp for the stage monitors.

We have been noticing distortion, mostly in the highs, keys and vocals, off & on in the monitors for a month or so now.
As a test, I unplugged everything else and played music via an I-pod through the amp & monitor speakers. Played a wide variety of stuff and drove it hard, no distortion.

If we pull it back to just one instrument, or one vocal, its fine, but as we add musicans, it just builds and gets worse and worse. This morning I tried making some adjustments, initially I felt the vocals were distorted even in the mains. I cleaned them up and scooped a little midrange out, they improved. But then the stage levels were untolerable (at least in my opnion). Guitar player is constantly telling me tha the can't hear me; & OTOH I don't want to be the obnoxioulsy loud bass player in a church with a very mixed congregation. My current rig is an Ampeg SVT3 and an Epifani UL210 cab (8 ohm).

We do not have a sound tech. Its generally either me or the lead guitar have to not play, and then go up and tweak things while the others play & sing to set levels. Its a small church type thing, so none of us are paid; and we obviously cant pay a sound engineer.

I'm thinking the distortion has to be coming from the bus signal out of the mixer; just at a loss as to how to fix it.

Even if you could point me in the right direction for some good reading material, it would be great.

thanks much!
 
It amazes me that people want help but won't tell you what gear you are using. Need to know WHAT kind of speakers,mixers, power amps. We don't need to know about your bass amp since it isn't the problem. RANT OVER
 
It amazes me that people want help but won't tell you what gear you are using. Need to know WHAT kind of speakers,mixers, power amps. We don't need to know about your bass amp since it isn't the problem. RANT OVER

Yeah, that way you could tell him his speakers are a POS, based on the opinions of some posters over at Harmony Central.

Seriously, I think the problem has to do with the signal coming from the board. When I have a problem like this, I start with what is the connection from the board to the amp. If you are sending a signal to the amp from your iPod and it sounds good, then it's not the amp OR the speakers, so it doesn't MATTER what kind of amp or speakers they are.

What DOES matter is that signal. Either there is a bad cord or connection, or the problem is in the board itself.

The only way to find out is to use a different cord, to eliminate the cord. After that, I'm not sure what you can do, but I would take the board to a repair shop, to have them test it for you. It won't be very expensive.
 
That powered mixer that you are using to run monitors is a likely suspect; are you sure that the input you are using on it is a line input and not an instrument input? Try turning down the aux output of your FOH board and/or the input channel on your powered mixer and turning up the output of the powered mixer to compensate.

Something else - are you running bass or anything else with a lot of low end through the monitors? That could contribute to the problem as well; try rolling off everything under 150Hz on the monitor EQ and see if that helps.
 
O.K. Here are some detials if they mean that much - I didn't want to drivel on about things that were irrelevant to the issue. :

Monitor Amp is an 8 channel Yamaha powered mixer. XL860 or somthign like that. Speakers are a pair of old Peavey cabinets dating back to the early '80s. Picked em up used cheap a few years back, and about 2 years ago one of the cones broke up on me, so I rebuilt them using Eminence drivers & horns, crossovers rated in excess of 600 watts. They sound great. No, I'm not a speaker engineer. No; the cabinets probably werent designed for the speakers. I take this system out of the church when we set up outdoors somewhere it becomes our main PA with the speakers up on stands, and is sounds awesome. Like I said, I ran the iPod into the yamaha head, and drove it hard with stuff like RHCP, some growling vocals like Tom Waits, and some Vivaldi string orchestral music. All came through clear so I know that my cabs, and the power amp section of the Yamaha are fine. When we use this for a monitor in the church we are only using 1 channel. We use an XLR connection into the balanced input; as this is the signal out from the board. the gain on that channel is probably only around 10 o'clock on the dial, and the Yamaha master is set usually around 9 o'clock. Probably a 3 and 2 respectivly on a 1 to 10 scale.

Other equipment:
House Mains:
QSC 500 watt power amp drives a pair of Yamaha 1x15" mains with horn tweeters.
FOH mixer is a 32 channel Peavey unit. Unsure of model off the top of my head. Fairly new, as we bought this new about 4 years ago as our band started to grow.

Mics: Mostly Shure SM58's A few Senheisers. I'm not as familliar with the mics' as the guitar player bought those. He and I have more or less split the cost of all the equipment as the church has no budget for musical equipment. The monitors are mine. Guitar player plays through a Fender Blues Deluxe. I also have a Crate CA125 acoustic amp that the other guitar plays through. There is a Roland 150 watt 15" driver keyboard amp that the Yamaha Clavinova is driven through.

Setup: at this point, we've been running everything through the PA and in turn, through the Monitors as well. Perhaps this is a mistake. If I take the bass out of the PA, I have to turn it up to compensate; maybe I just need to roll of some of the low frequencies there. Keys also run through house mains as well as monitor. our keyboard player is also the church organist; but she's good about playing light on the left hand when I'm there.

This afternoon after the service I was looking at teh levels of the monitor buss output, thinking that I might need to cut that back and boost the monitor output on the power amp stage.
The line out busses have slide faders for level, and the slider for that channel was sitting at about -15 db; so that leads me to belive that it wasnt pushed that hard either.

I have been thinkng about a process of elimination / cable swapping etc. but its can be tedious and time consuming, and while the other guitar and I can play with this stuff, we only have the problem when we have the whole band playing; and when we are all set up for rehersal we dont' have the time for diagnostics. Catch 22.

More than anything we need a sound guy. Unfortunatly others are locked into the mode of "the soundboard was set up - don't touch it" I've been trying to explain that live sound is dynamic and the board needs adjustments based on how many people are in the sanctuary, what instruments are playing / change in istruments etc. I don't think they get it.
 
OK, I didn't slog through all that detail, but my money is still on the link between the FOH board and the powered mixer you are using for monitors. If the signal you are feeding it is too hot for the input, you will get clipping/distortion.

In any situation where you have a bunch of preamps in a signal chain, gain balancing is a critical issue. If any one of them is overloaded, then distortion gets into the signal, and once it's in there is no getting it out.

When you feed the output of one mixing board to the input of another, you really have to pay attention to your gain structure. It's a single point of failure. If you are feeding a hot line out (0dB or more) from your FOH board to an instrument input (-60dB or so) on your powered mixer, you can very easily push the input on the powered mixer into hard clipping = distortion. If, when you are hearing the distortion, the FOH guy turns up the feed to the monitors and the problem gets worse, that's the smoking gun.

I'll bet you five dollars that this is your problem. It's easily fixed, though. If you can't cool off the output of your FOH mixer enough or dial down the input of your powered mixer enough (and if any of your controls are down in the mud, i.e., turned down so low that the tiniest adjustment makes huge changes in volume), you can get a 1/4" line to instrument level adapter at Radio Shack for just a few bucks.
 
OK, I didn't slog through all that detail, but my money is still on the link between the FOH board and the powered mixer you are using for monitors. If the signal you are feeding it is too hot for the input, you will get clipping/distortion.

In any situation where you have a bunch of preamps in a signal chain, gain balancing is a critical issue. If any one of them is overloaded, then distortion gets into the signal, and once it's in there is no getting it out.

When you feed the output of one mixing board to the input of another, you really have to pay attention to your gain structure. It's a single point of failure. If you are feeding a hot line out (0dB or more) from your FOH board to an instrument input (-60dB or so) on your powered mixer, you can very easily push the input on the powered mixer into hard clipping = distortion. If, when you are hearing the distortion, the FOH guy turns up the feed to the monitors and the problem gets worse, that's the smoking gun.

I'll bet you five dollars that this is your problem. It's easily fixed, though. If you can't cool off the output of your FOH mixer enough or dial down the input of your powered mixer enough (and if any of your controls are down in the mud, i.e., turned down so low that the tiniest adjustment makes huge changes in volume), you can get a 1/4" line to instrument level adapter at Radio Shack for just a few bucks.

I think you make an excellent point here.
 
I think the Yamaha amp has effects in / out, we use the channel in becasue the signal is coming in via balanced cable (xlr input). would have to buy some sort of adapter to go from the balanced signal to an unbalanced line input.

Ding, ding, ding, ding.

That's your problem right there. On most mixers an XLR input is mic level only, and if you feed it a line out from something else it will distort.

You need that adapter, or use a 1/4" line out from your FOH board. You need to go into a line input on your powered mixer.

Pay me my five bucks. :p
 
I'm not sure which powered mixer you're using to run monitors but we have two cast-off (near-trashed) Peavey and Yorkville integrated PA heads which have been used for the same purpose. Both have power amp "in" jacks which will accept the input from a mixer's Aux feed whilst bypassing the the mic preamp section. It essentially becomes a slave amp and nothing else. We keep one in the trailer as an emergency back-up.

Riis
 
I think the Yamaha amp has effects in / out, we use the channel in becasue the signal is coming in via balanced cable (xlr input). would have to buy some sort of adapter to go from the balanced signal to an unbalanced line input.

Get one of these; it will fix you right up:

Invalid Link Removed

It's made for exactly what you are trying to do. Lets you plug a balanced line output into a balanced mic input.

17 bucks.
 
Thanks to all who contributed constructive advice without being too snarky. Especially to Gordon. I owe ya a beer buddy. Stop on in the next time your'e in CNJ.

PIcked up an adapter from the line level balanced XLR that is a feed from the FOH mixing board buss out, that gives me a balanced TRS 1/4" jack. The Yamaha has a 1/4" balanced input directly above the XLR input. Downloaded the manual for the mixer from the yamaha website, the sensitvity on the mic input is far greater. While we didnt have the full band at practice this morning, it was just bass, keys and vocal; the sound difference was dramatic. Next week will be a full band including a drummer, looking forward to it.

Jeff
 
Thanks to all who contributed constructive advice without being too snarky. Especially to Gordon. I owe ya a beer buddy. Stop on in the next time your'e in CNJ.

PIcked up an adapter from the line level balanced XLR that is a feed from the FOH mixing board buss out, that gives me a balanced TRS 1/4" jack. The Yamaha has a 1/4" balanced input directly above the XLR input. Downloaded the manual for the mixer from the yamaha website, the sensitvity on the mic input is far greater. While we didnt have the full band at practice this morning, it was just bass, keys and vocal; the sound difference was dramatic. Next week will be a full band including a drummer, looking forward to it.

Jeff
You are very welcome. Glad to help out.