Keep Getting Feedback

[soundo26]

Hi, from what you have written it seems that you are running the monitors from the main outputs along with the front of house speakers. I presume that you have powered monitors, if so you should run them from the Aux channels and set the aux channels to Pre fade rather than post fade, this way you will set the stage volume and it will not be affected if you turn the mains upalso in this way you will only send what you actually want to the monitors rather than the whole mix. If you have two monitors and two aux channels you can even send two different mixes to the two monitors. At sound check, set your monitor levels up first before bringing the house speakers up. It helps if you can understand the polar pattern of your mics too so that you can place the monitors towards the dead areas (usually slightly off to the side ).

 

This is a very basic guide for a simple PA setup, there is more to it but I have tried to keep it simple!

[Billy Rigby]

Your last quote worries me! I must be a real Duddits.

 

On the back of the amp, is a port for the monitor. And there are ports for the main speakers at the back, too (actually, it might help if someone here knew the amp I'm using). So, all three are connected to the back. I only use one monitor and, sorry, but I know nothing of there being any pre or post fade control on my amp.

[Jivemaster]

Hire a good sound engineer for a rehearsal and a gig. Use your mobile phone to take pictures of the controls and connectors then you can simply set the kit up again whenever you want by looking at the pictures.

 

Start SOON as the party season is everyone's busy time, and should be yours too!

[mervaka]

are you cupping the mic at all? that will create kittens with the polar pattern!

 

by the way, an SM58's dead zone should be directly behind it.

[Pyramid]

PM sent.

 

Andy

[squarewave]

I've tried to combat it by turning the main volume down and the channel volume up

 

I would suggest turning the main volume to unity (small triangle at 1 o'clock position) and having the channel volume as low as you can.

 

Most mixers have a fader at the bottom of the channel and a gain/trim/sensitivity control at the top. I find if you keep the sensitivity below unity you don't get feedback problems.

 

Your mixer doesn't have this control it just has a single volume for the channel.

If you look at the channel volume it has a small triangle in the 1 o'clock position. I expect this will indicate where unity is.

I think if you keep all the volume controls below the triangles you will have less problems.

 

If your PA is not loud enough with the volumes below unity then you need a more powerful system.

 

You will have more feedback problems with a low powered PA than you will have with a system that is more powerful than you need.

 

I hope this helps.

[Ynot]

OK.

I can't claim to be a sound expert, but here's a few simplistic answers to some of your questions.

 

I'm using a Yamaha EMX312SC integrated mixer amp

Well, the manual looks like a pretty basic starter's guide and does give a few pointers.

Anytime I turn the main volume on the amp up to at least the halfway mark, I get howling ..... I've tried to combat it by turning the main volume down and the channel volume up

The reason that won't really have any lasting effect is that turning the input (mic channel) up and the output (master) down just effectively results in the same basic signal getting through from mic to speakers.

Feedback will take the shortest route from output to input, then back to output etc, creating a 'ring' of audio which in simplistic terms just amplifies the already amplified signal til it becomes self-perpetuating.

To cure it you need to reduce the amount of speaker output getting back into the mic.

 

Look at different speaker placing - direct them (your main mix) at the punters and not back at yourself. Put as much distance between the space you sing in and those speakers as you can whilst retaining the best placing for the customers to hear you clearly.

 

Monitors - you don't always NEED to have yourself back out of the monitors, though it does help to get something. Adjust the individual channel 'monitor' knob so you get just enough of yourself on the monitors for you to work with. As they're the ones pointing AT YOU they're most likely where the feedback is originating.

 

Compression - each channel has a simple compressor built in - this should effectively ramp up the lowerquieter input signals, and squash the louder signals so the effect is to compress the signal (ie your voice) into a manageable band of audio. Again, play with this to get the best results.

The channels have dials with "high", "med" and "low" for example. But I don't have the foggiest what it is exactly that I'm doing when I turn them up or down.

Simple - Low = bass, high = treble, mid (not MED) is somewhere in between. Just a simple 3-channel tone control that affects each input seperately.

there's a graphic equaliser for the main speakers and the monitor,

That's just an overall multi-channel tone control which affects the summed outputs before it goes off to the amp.

You can try to use this to 'ring out the room' each time - ie before the gig, play with the mic levels and see what frequencies howl, and adjust the graphics channel(s) to reduce the sensitivity to feedback. Take care though, as pulling too much out of one or more frequency bands can ruin the overall sound quality!

It's no use practising with it at home, either, because I find when I get to the gig I have to tweak everything again because the size of the room will be different and, obviously, it's full of people too.

That's the way the cookie crumbles. each venue will be different and you will need to adjust some parts each time, but on the whole you'll probably find that once you get comfy with the input settings you may get away with just adjusting the main graphic EQ to suit the room size/characteristics.

[lightsource]

Snipped, but to quote bullet points...

 

I've had my kit for about eighteen months now and I keep getting the same old problem: feedback.

 

I'm using a Yamaha EMX312SC integrated mixer amp with two Peavey Pro 15 speakers and a Yamaha floor monitor (sorry, don't know the specifics of the monitor offhand). Anytime I turn the main volume on the amp up to at least the halfway mark, I get howling feedback and it's getting to be a real drag.

 

The problem is, the manual for the amp seems to rely on having a working knowledge of how an amp works...and I don't.

 

I just see all these dials and knobs and can't help but wonder what it all means.

 

The channels have dials with "high", "med" and "low" for example. But I don't have the foggiest what it is exactly

 

Similarly, there's a graphic equaliser for the main speakers and the monitor, but I'm lost as to how to use it to its fullest.

 

What I really need is an online idiot's guide to how to get the best out of my set-up. Anyone know if one exists...?

 

In a later reply you state.....

 

It's all quite embarassing, really. I mean, I started with quite a bit of dosh, enough to afford me some top-end equipment, and I haven't put in the hours to learn how to use it. That I've got so much work since I started must mean that I'm doing something half right but, ultimately, if I'm not happy and I know it can sound better, then it needs to be sorted.

 

As a professional hire company, I really would like to say a lot of things here, but somehow, I think the Moderators of the forum may take offence.

 

So I'll be pleasant.... 18 months and you still haven't a clue? It's not quite embarrasing, it's absolutley disgraceful. If you think you're doing something half right, then I'd hate to think what the rest of us are doing ;) Especially if you're getting.......

 

I've got so much work since I started must mean that I'm doing something half right.

 

 

:)

[Billy Rigby]

And that's you being pleasant is it?

 

A concurrent post has been automatically merged from this point on.

 

squarewave and Ynot, thanks for the advice. That's really hepled me out a lot insofar as I've read your posts and I actually get what you're saying! No disrespect to anyone else (although, I have to say, lightsource, that I didn't find what you said constrructive at all. I've criticised myself for this and don't really need additional criticism from you) but I think other posts here have left me a bit bamboozled.

[paulears]

Billy - I suspect that people will have read all your posts and kind of assumed you were doing things that now we find you're not. It's a lack of fundamental knowledge and you've just got into the swing (no pun intended) of just doing the shows, without understanding what is happening. Just so we don't assume - here's a potted guide to how to at least get going - and yes, you will need to do this at every venue during your soundcheck.

 

First - speaker placement. The mic 'hears' mainly in one direction, but it also hears from the rear - a bit, and normally different directions depending on the mic - but at a lower level than the end you sing into. The mic must not be able to 'see' where the sound coming out of the speakers comes from. If it can, then it picks up this sound and amplifies it again, and again and again resulting in the sudden shreaks and howls you are getting. So if your mic is in front of a line drawn between the two speakers - you will get far less volume before feedback. get the speakers as forward as is possible.

 

 

Speakers consist of low frequency drivers and high frequency drivers in the price range we're talking about here. The HF comes usually from small horn type speakers, usually right at the top. These are pretty well responsible for everything apart from the bass =a couple of feet away they blend together and do the job! These 'horns' can be two different types - one more expensive and reasonably smooth, but the other cheaper and often rather 'sharp' or 'brittle' sounding = especially when given a bit of wellie! These peizo-electric horns don't have a flat frequency response, giving certain frequencies a bit of a lift. Microphones also have the peaks and valleys in their frequency response by design - if the horn and the mic have a peak at the same frequency, then this becomes what sets the limit for maximum volume. As you increase volume, the system suddenly takes off with a howl. The idea is that you can use the graphic equaliser which has 7 separate bands to pull down the frequency that is honky - so get it to feedback - just, then find the eq fader that reduces it till it stops. Then you can try a bit more volume and maybe another note will honk out. try to find and reduce this. Each time you'll recover a bit of system volume - BUT be aware that you've now got some major 'holes' in your frequency response - this could make it sound muffled, boxy, boomy - that kind of thing. The channels all have a less sophisticated eq that allows each channel to be different - so the output graphic can help with feedback and the channel eq is best for 'tonal' adjustment. beware that you can easily boost the frequency you cut in the 7 band graphic and ruin it again - it's always a compromise!

 

 

Your amp has a row of knobs allowing each input (your mic and the track, I guess) to be sent out of a separate socket on the rear. This goes into a powered speaker, or an amp and speaker combination and lets you hear what you need - which can be different from what the audience hear - you can have very loud track and no you - or lots of you and lots of track - your choice. If you're powering your monitor from the normal speaker out, you get what they get - and gives less options. Because your monitor will be close in, it will be picked up by your mic, making it the cause of the early feedback. You could always extend the system with another equaliser in the line from mixer to amp - this would give you more feedback rejection properties. Unless the venues are big, set your mic up, increase the volume till it feeds back, trim the equaliser a little till you get more volume without too much 'muffle-ness' - a kind of workable compromise on quality v volume. If your system takes off with very low volume, then you need to spend time 'twiddling' the eq. After a bit of practice, you'll be able to identify the offending pitch and go for the right fader first time. Let me repeat - you need to do this EVERY gig, unless you have everything in the same location and made a note of every knobs position.

 

Good advice was given on 'cupping' the mic. Covering up any part of the grill alters the frequency response and the direction it's most sensitive in - so when you are working near to feedback point, covering up the head of the mic can make all hell break loose. Same thing happens when you maybe put it close in to an open mouth - the cavity in your mouth has a resonance - and if this is close to any of your problematic frequencies, off it all goes again.

 

Mic technique is also very important. Closer in and cardioid mics go very bassy, pull it away and they get 'thin' sounding - so the working distance is quite small. Do you work in very close and eq out the bass, or work further away and maybe put in some extra? Both have feedback implications. We can't predict what you want. If, as a swing singer, you want classic crooner style sound, then I'd suggest that with a 58 you never go much more away from it than two or three inches, because the warmness will vanish. Work it in close, and then eq it on the channel to sound nice - volume at close distances will also be so much better!

 

This might help a bit - if you're really stuck.

Paul

[Billy Rigby]

Thanks, Paul. You're quite right, I have glossed over the fundamentals and I make no excuses or justifications for that.

 

I'm very good at beating myself up over any shortcomings I have (lookout for my next thread where I will be asking about how to deal with pre and post gig insecurities!).

 

Thanks for taking the time out with this reply. Much obliged.

[Rob_Beech]

To follow on from what Paul says.

 

I'll start with position of your mouth and mic. No matter what style you are singing, you need to be really close to sm58, the LF and low mids roll off very quickly as you move away from them, it's no good for your style but it's not really any good for anyone elses style. Whilst it may seem silly, it is alwayts better to be closer to the mic and roll off a little LOW on the channel eq if it's required than to do it naturally by not getting as close, this will increase the amount of volume you can get before feedback quite considerably.

 

Also, frequency response is very important, there's a fair bit more to it than others have stated, but I understand they're trying to keep it simple. A speaker / microphone / desk channel has a specific frequency response. There is more to frequency response than just how low and how high it goes. If you imagine a graph of response there are peaks and troughs throughout its useable range. These peaks as Paul and others mention are where you are more likely to get your feedback problems. However, sadly it goes one step further and it's quite important to know. When we drive a loudspeaker harder (say in a big room for example) or we drive a desk channel harder, the actual frequency response changes. It's minimal on electronic components but on loudspeakers (particularly ones that aren't very expensive) it can have a significant effect. You may find certain frequencies have a tendency to feedback more in bigger rooms as you push the speakers harder. It is the frequencies that the speakers find easier to reproduce (more sensitive) that will feedback first. The same is true (though nothing like as critical) with preamps in desks. As you overdrive these and the channels peaks or clips, you'll find a small but significant change in response. It's for this reason that its important to get the levels of each part right. It's no point having a master level right at the top and the channel volume down and the gain up. This will not provide the best sound. This is called "Gain Structure" and there's lots on here to read about.

 

We can all agree that perhaps you are not going to get the best sound in the world with limited knowledge and not the biggest system in the world, but we can also agree that with the right understanding, some time and effort and maybe some help from someone local to you, you can work with your show and get the sound as good as I'm sure the performance is. It's something that needs looking at immediately especially if work is building up, however it's not something to panic about. There are all too many people such as yourself who I'm sure have very little or no knowledge, so you'll quite quickly move many steps ahead of them.

[Pyramid]

Bill

 

Don't know if you got the personal message the other day.

I was offering to come and have a look with you before your next gig and teach you how best to set up the system. We are both very local to you.

We have done training for a number of people - mostly churches and can provide exactly what you want or need: Fundamentals of sound, practical set up and operation through to troubleshooting.

 

Regards,

 

Andy

[lightsource]

Well, you have to give thanks to Paul and Rob here, because, they have given you a fundamental insight to what knowledge is needed.

 

It's up to you to decide how you want to advance, people on this forum, including myself, are here to help, but you have to bear in mind most of us have day jobs in this industry.

 

So when someone comes along and says I have a PA, and after 18 months I haven't a clue how to use it.....but, I'm getting a lot of work from it....

 

Then I think you can now understand what I said in my post. So with total ignorance, and the free advice of professionals, you're getting away with it..

 

This is NOT a rant at you. I have the greatest respect that you've laid you're cards on the table and asked for help. In some way shape or form, we all do it when we get out of our depth.

 

The problem is that this industry is very dynamic, things change on a regular basis, so keeping on top of things is a must....spending 18 months to not learn anything about sound system you own isn't going to get you anywhere in this job. You must focus more and resolve you're issues immediatley.

 

All the info that others have posted is readily available on the Internet, but you don't seem to have the self motivation to find it.

[Billy Rigby]

Bill

 

Don't know if you got the personal message the other day.

I was offering to come and have a look with you before your next gig and teach you how best to set up the system. We are both very local to you.

We have done training for a number of people - mostly churches and can provide exactly what you want or need: Fundamentals of sound, practical set up and operation through to troubleshooting.

 

Regards,

 

Andy

 

Andy, I did get your PM, thanks. I need to know your fee first, though. If you can pm that to me I can consider it further.

 

Many thanks.

 

A concurrent post has been automatically merged from this point on.

 

Well, you have to give thanks to Paul and Rob here, because, they have given you a fundamental insight to what knowledge is needed.

 

It's up to you to decide how you want to advance, people on this forum, including myself, are here to help, but you have to bear in mind most of us have day jobs in this industry.

 

So when someone comes along and says I have a PA, and after 18 months I haven't a clue how to use it.....but, I'm getting a lot of work from it....

 

Then I think you can now understand what I said in my post. So with total ignorance, and the free advice of professionals, you're getting away with it..

 

This is NOT a rant at you. I have the greatest respect that you've laid you're cards on the table and asked for help. In some way shape or form, we all do it when we get out of our depth.

 

The problem is that this industry is very dynamic, things change on a regular basis, so keeping on top of things is a must....spending 18 months to not learn anything about sound system you own isn't going to get you anywhere in this job. You must focus more and resolve you're issues immediatley.

 

All the info that others have posted is readily available on the Internet, but you don't seem to have the self motivation to find it.

 

lightsource, I'd pack in the advice now, if I were you, chief. With that last comment you've managed to undo any good will you might have intended in the rest of your post. You've already admitted to trying to restrain yourself in a previous post, lest you incur a warning from the Moderators, but you just can't seem to help yourself in getting in the little digs. I'll thank you to no longer contribute to this thread now.

 

A concurrent post has been automatically merged from this point on.

 

To follow on from what Paul says.

 

I'll start with position of your mouth and mic. No matter what style you are singing, you need to be really close to sm58, the LF and low mids roll off very quickly as you move away from them, it's no good for your style but it's not really any good for anyone elses style. Whilst it may seem silly, it is alwayts better to be closer to the mic and roll off a little LOW on the channel eq if it's required than to do it naturally by not getting as close, this will increase the amount of volume you can get before feedback quite considerably.

 

Also, frequency response is very important, there's a fair bit more to it than others have stated, but I understand they're trying to keep it simple. A speaker / microphone / desk channel has a specific frequency response. There is more to frequency response than just how low and how high it goes. If you imagine a graph of response there are peaks and troughs throughout its useable range. These peaks as Paul and others mention are where you are more likely to get your feedback problems. However, sadly it goes one step further and it's quite important to know. When we drive a loudspeaker harder (say in a big room for example) or we drive a desk channel harder, the actual frequency response changes. It's minimal on electronic components but on loudspeakers (particularly ones that aren't very expensive) it can have a significant effect. You may find certain frequencies have a tendency to feedback more in bigger rooms as you push the speakers harder. It is the frequencies that the speakers find easier to reproduce (more sensitive) that will feedback first. The same is true (though nothing like as critical) with preamps in desks. As you overdrive these and the channels peaks or clips, you'll find a small but significant change in response. It's for this reason that its important to get the levels of each part right. It's no point having a master level right at the top and the channel volume down and the gain up. This will not provide the best sound. This is called "Gain Structure" and there's lots on here to read about.

 

We can all agree that perhaps you are not going to get the best sound in the world with limited knowledge and not the biggest system in the world, but we can also agree that with the right understanding, some time and effort and maybe some help from someone local to you, you can work with your show and get the sound as good as I'm sure the performance is. It's something that needs looking at immediately especially if work is building up, however it's not something to panic about. There are all too many people such as yourself who I'm sure have very little or no knowledge, so you'll quite quickly move many steps ahead of them.

 

I don't believe I need the biggest system; I'm quite confident in the capabilities of what I've got, but - obviously - not in my own capabilities in getting the best out of what I've got. Thanks for your advice - I genuinely thought the mic should be held far away from the mouth when hitting those big, long notes, so I'll try out your tips when I next rehearse.