Killing Feedback

[wildwood flower]

I'm posting here as it seems the most appropriate forum for my question.

I'm soon getting into a live play situation and I'm really ignorant about microphones. I have a shock mounted condenser mic, feeding thru a phantom power supply, into a Fishman Loudbox Mini Amp.


I realize that a lot of things can go into this, but what general info or recommendations do any of you have for reducing/eliminating feedback?

My initial tries with this rig have proven unsatisfactory. I can turn the mic gain down but this also reduces the vocals too much.

My residence is very small, and acoustically probably not the best for things like this, but I need to work this out as much as I can before I head out across 5 states to a reunion and embarrass myself.

Again, I know that many factors come into play here but any general info will be much appreciated

Thanks for reading

[pieterh]

If you are using one mic for both guitar and voice then positioning is everything. Experiment with an amp position where you get a decent volume for yourself and the space you are playing in but without the amp shooting back into the mic. It might mean you have to sacrifice a degree of on stage listening in order to prioritise the audience.

What kind of mic is it? If it has a low cut option then I would recommend that: nothing under 80hz is of any real use to you and only clutters up the sound and increases risk for low end feedback. Directionality on the mic is also essential - if it is a large diaphragm mic with different options then you really don't want an omni setting as you will be increasing its sensitivity to reflections back from the room.

Turning mic gain down is not usually the answer. The gain needs to give as strong a signal as possible before clipping (overdriving the amp input) in order to preserve the best signal to noise ratio. Turning the gain down usually means compensating later in the chain and then that can also mean turning up the noise which will increase your chances of feedback.

You may know some of this already of course, but let us know your whole setup (including what mic it is) for better advice!

[chitz]

I'd be inclined to use a good dynamic mic for live performance.

[cattzap]

For the sake of an LOL, several years ago my work sent me to Chicago and the wife went. It just so happen that someone she used to work for had moved from the same town we lived in to just down the street from where we were so we arranged a visit. Her new husband was doing a Karaoke thing that night and they invited us. Turned out it was his first one. The wife says hey you can go and help him setup. No thanks. I'm making this my vacation too. Turned out I had to set it all up for him. He had never touched a PA before. He set the participants mic directly in from of a big speaker stack. I told the wife, watch this, it'll be bad. He had the Peavey speakers that uses the auto lamps as a fuse. Those thing lit up the entire room. Never knew they would burn that bright in there. My first "help" was to walk over and move the mic, then plug it in correctly, then show him what all the knobs were for.

For real now, I really don't get feedback too often. General I see them come from monitors, but it sounds like you don't have a monitor. The next biggest culprit is someone placing or walking directly in front of a speaker. Like practically lean on it with the mic facing directly into it.

One thing you might consider. If you amp has an output, and there is a house PA, turn your amp to you and make it just loud enough that you can hear it and then let the main PA do the work. If not, getting it up off the floor seems to add more volume and punch to a smaller amp used like this. At the least, lean it back a little bit. Think if it this way. What is the height of the speaker in your amp compared to height of the listeners ears. Sending the sound down around their ankles vs sending it closer to their ear level.

I have fixed many terrible PA systems just by moving the speaker location.

[KevWind]

Originally Posted by wildwood flower

I'm posting here as it seems the most appropriate forum for my question.

I'm soon getting into a live play situation and I'm really ignorant about microphones. I have a shock mounted condenser mic, feeding thru a phantom power supply, into a Fishman Loudbox Mini Amp.


I realize that a lot of things can go into this, but what general info or recommendations do any of you have for reducing/eliminating feedback?

My initial tries with this rig have proven unsatisfactory. I can turn the mic gain down but this also reduces the vocals too much.

My residence is very small, and acoustically probably not the best for things like this, but I need to work this out as much as I can before I head out across 5 states to a reunion and embarrass myself.

Again, I know that many factors come into play here but any general info will be much appreciated

Thanks for reading

Actually the Acoustic Amplification forum is probably the most appropriate forum seeing how that is what you are talking about. Be that as it may.

First are you using the one mic for both guitar and vocal ?

If so then consider getting a picup for the guitar and do only the vocal through the mic , that will help considerably

In general for live performance what creates feedback is the mic physically picking up the sound from the PA speaker creating a feedback loop.

So rule of thumb number one get the mic out of the dispersion pattern of the speaker it will be feeding . Which in your case means get the the Loudbox out in front of mic.


If a pic up in your guitar is not an option and your going to use a condenser mic for both, then make sure it is at the very least a cardioid pattern and a super or even hyper cardioid would be even better.

[CaffeinatedOne]

We don't know if you're using the mic for vocal and guitar or just for guitar. It makes a difference. Similarly if the condenser mic has a wide polar pattern it will be pretty much uncontrollable on stage without an experienced hand.

There have been suggestions to get a dynamic mic and I think that is the least expensive / quickest result way to go here. If you need a mic for voice and for your instrument, you will very likely need two mics.

I don't know if the Loudbox has one or two channels, but let's assume it has one. I'm also assuming you have no onboard electronics for the guitar. In that case, here's what I would do.

A simple setup with two dynamic mics and stands / booms will work best. I would pick a Shure SM58 as your vocal mic and a Shure SM57 as your instrument mic.

Assuming you have only one input on the Loudbox, pick up a small (and inexpensive) live mixer, like a four channel Behringer or Peavey that you can carry in a small gym bag. These are great; you'll be using two channels. Plug each mic into one of the channels and send the mains output (if there are two, then use the left mains channel output as most mixers will summ the output signal if there's a draw only on the left side) to your Loudbox.

With the mixer you will have lots of eq, trim and gain control for each mic. Follow the classic simple signal chain approach - start with a strong signal and use subtractive techniques to massage the signal all through the chain. That means if you need more highs, don't boost the highs. Lower everything but the high end and boost the gain a touch if you need to. This subtractive approach keeps the noise floor as low as it can practically be, meaning you have less junk in the signal. With the Loudbox you'll have plenty of gain if you need it.

Other ideas - when using eq, treat it like hot sauce. Start with all controls at null - right in the center. A little adjustment goes a long, long way. When in doubt, use less eq. Always subtract signal, don't add signal, in the eq chain.

The rest is stuff like - Don't point the mic at the speakers. Don't have the Loudbox behind you or pointed at you. If there's a weird thing happening on stage, try shifting the position of the Loudbox forward or at an angle to the mics.

Once in a small, crowded bar I helped to get decent sound for a four piece band with lots of open mics by pointing their speaker cabs directly at the brick walls on the right and left side, about 6 inches from the wall. The sound bounced back like the old BOSE 901 reverse facing speakers - worked great and diffused the sound enough to drop their feedback problem.

[wildwood flower]

It's been some 3 weeks since I posted the original question, and then unfortunately I became ill. I apologize for the lack of response. My head is still a bit fuzzy, but let me take time to digest all this. I can see that i need to provide more info.

[Rudy4]

Use a feedback buster.

Watch the peak lights and lower the offending frequency. If that doesn't work you're too loud.

[CaffeinatedOne]

Originally Posted by Rudy4

Use a feedback buster.

Watch the peak lights and lower the offending frequency. If that doesn't work you're too loud.

My response here is a bit off-topic, as the OP isn't setting up the sound for the gig. But the concepts here are important to understand anyway and can be helpful for the performer.

Feedback eliminator units can be helpful, but they don't provide an adequate substitute for preparing the sound system for the room you're playing in. The technique is called "ringing in" the room, and it means that you get there early, set up, and then use an equalizer (my go to device is a graphic eq unit placed in between the main signal and its amplifier) to find resonant frequencies that will be prone to feedback. This is done by cranking up the system, having all mics and mic-equipped instruments open, and then boosting frequencies band by band until they begin to ring, or begin feedback. Although every frequency band will do this, some are very twitchy and violent about it. These are the ones that usually give you trouble. Watch for 1kHz, 4kHz and their octave equivalents. Return all the EQ settings to center (null) excepting for the twitchy ones, and those you cut a notch. When your performing signal goes out to the room, those frequency bands will be subdued. The room's resonance will make up for it.

This is what a feedback buster attempts to do on the fly, and depending on how it's adjusted, and whether it includes a good fast limiter, it might help and it might "almost" help. Ringing the room should be standard practice for any PA setup. After you've done it a few times, it becomes quick and easy.

The other butt-saving technique is to follow that by setting your outboard compressor as a limiter. You have to shut down the limiter in order to ring the room, which is one way you can tell it's effective: it will prevent feedback until your volume is in armageddon territory.

Finally, remember that an empty room is far more resonant (and therefore feedback prone) than a room full of people. People absorb and deflect sound waves. So as the room becomes more crowded, its acoustic behavior will change - a lot. The good news is that it gets less feedbacky; the bad news is you may have to increase your volume over the crowd. It's always a balancing act of sorts.

[Rudy4]

Originally Posted by CaffeinatedOne

My response here is a bit off-topic, as the OP isn't setting up the sound for the gig. But the concepts here are important to understand anyway and can be helpful for the performer.

Feedback eliminator units can be helpful, but they don't provide an adequate substitute for preparing the sound system for the room you're playing in. The technique is called "ringing in" the room, and it means that you get there early, set up, and then use an equalizer (my go to device is a graphic eq unit placed in between the main signal and its amplifier) to find resonant frequencies that will be prone to feedback. This is done by cranking up the system, having all mics and mic-equipped instruments open, and then boosting frequencies band by band until they begin to ring, or begin feedback. Although every frequency band will do this, some are very twitchy and violent about it. These are the ones that usually give you trouble. Watch for 1kHz, 4kHz and their octave equivalents. Return all the EQ settings to center (null) excepting for the twitchy ones, and those you cut a notch. When your performing signal goes out to the room, those frequency bands will be subdued. The room's resonance will make up for it.

This is what a feedback buster attempts to do on the fly, and depending on how it's adjusted, and whether it includes a good fast limiter, it might help and it might "almost" help. Ringing the room should be standard practice for any PA setup. After you've done it a few times, it becomes quick and easy.

The other butt-saving technique is to follow that by setting your outboard compressor as a limiter. You have to shut down the limiter in order to ring the room, which is one way you can tell it's effective: it will prevent feedback until your volume is in armageddon territory.

Finally, remember that an empty room is far more resonant (and therefore feedback prone) than a room full of people. People absorb and deflect sound waves. So as the room becomes more crowded, its acoustic behavior will change - a lot. The good news is that it gets less feedbacky; the bad news is you may have to increase your volume over the crowd. It's always a balancing act of sorts.

Excellent post and advice.

My only experience with seeing ringing a room done professionally came from watching my brother-in-law do it at a local club. He did sound for a world-touring blues band for 5 years before the lack of any personal life finally caused a serious change in work direction.

He used high-dollar equipment with special "lab" mics and pink noise generators and tailored the EQ for the room. It took a fair bit of time and when he was all done he stated that the process really was only slightly better than doing it on the fly after sound check and tweaking after the club was filled with people. That was due of course to the change in EQ needs after the addition of an audience.

I've done a fair amount of PA work myself but it has always been more a process of using my ears and also pulling bands down on a graphic as a result of watching the peak indicators.

[paulp1960]

You could certainly record acoustic guitar and vocal with a single condenser mic but I don't think you could successfully play live through a PA with this setup.

The mic would have to be relatively far away from both the guitar and singer's mouth to pick them both up with roughly the same levels.

This in turn will be a feedback magnet. You need either 2 mics, one for vocals and one for guitar or 1 mic for vocals and use a pickup system on the guitar.

[sdelsolray]

Originally Posted by wildwood flower

I'm posting here as it seems the most appropriate forum for my question.

I'm soon getting into a live play situation and I'm really ignorant about microphones. I have a shock mounted condenser mic, feeding thru a phantom power supply, into a Fishman Loudbox Mini Amp.


I realize that a lot of things can go into this, but what general info or recommendations do any of you have for reducing/eliminating feedback?

My initial tries with this rig have proven unsatisfactory. I can turn the mic gain down but this also reduces the vocals too much.

My residence is very small, and acoustically probably not the best for things like this, but I need to work this out as much as I can before I head out across 5 states to a reunion and embarrass myself.

Again, I know that many factors come into play here but any general info will be much appreciated

Thanks for reading

Your practice area in your residence probably has a lot to do with the volume you can obtain before feedback. Try playing outside, or take your gear to a much larger room. See what happens.