Feedback problems with acoustic guitar

[Rich]

Hi Folks.

 

I'm running an acoustic night in a bar at the moment, and I've got problems getting the level of acoustic guitars up without feedback. It's fine when a guitarist is strumming away, but when it comes to the more gentle picking and solo work, I don't get enough level before feedback. I tend to DI the guitars, but some artists have faulty outputs or none at all.

 

I've tried a 57, and a 57 beta placed 3-5 inches away from the sound hole, and I've had the same problems with both.

 

Gear wise I'm using two HK Audio premium series 15" speakers, mounted on stands (all mics behind the speaker line), with a Matrix amp, and a 12ch Behringer mixer (however this will now be an A&H GL2400)

 

I've thought of trying a small diaphragm condenser, I've got a couple of low quality ones from a drum set (Red 5 Audio), and it's possible I could upgrade to C1000s in the near future, would this help?

 

Has anybody got any other suggestions?

 

Thanks for your time.

 

Rich

[misterbassman]

I have had very good results with the C1000 personally, also worth noting is that there will be a massive difference when you start using the new desk. The pre-amps in each desk are vastly different in my experience

 

Dan

[london sound]

You might consider moving the mic further up away from the sound hole, also angle the mic up a little. If the mic is pointing square on to the guitar the guitar will reflect other sounds straight back into the mic, hence feedback from monitors etc.

 

 

 

Ian

[Bobbsy]

I think you're on the right track considering a small diaphram condensor for this application but personally consider the C1000 to have a harsh, unattractive sound. As an alternative you might want to try the SE Electronics SE1A....I've been using the SE mic a lot lately and am quite impressed. It compares well to the AKG451EB which for years has been my "reference" mic for this sort of application.

 

The other thing to consider, particularly with a small condensor, is mic positioning. The null at the back is quite sharp, but sounds coming from the side will still be picked up. You can often gain several dB gain before feedback by playing with the angle of your mic.

 

Bob

[andy_s]

is it feedback from monitors? if so perhaps you could try using small nearfield monitors like the galaxy hotspots mounted on stands rather than on the stage floor - I've seen this done very successfully for musicians using acoustic instruments like guitars, bouzoukis, mandocellos etc, you can reduce the output level from the monitors and reduce the risk of feedback that way. (using the inverse square law - half the distance from ear to speaker = double the level) Its also good to have a pick-up you can DI, and there are versions which fill up the soundhole and reduce acoustic feedback, but that doesn't really help you dealing with visiting musos as you say.

 

the hotspots or perhaps something like the d&b E0 speakers are light enough to mount on a mic stand, so you don't need copious amounts of metalwork associated with them.

[Rich]

Hi there, thanks for your replies.

 

I'm not using any monitors actually, I should have said, so the feedback is through the main PA only.

 

I like the price of the SE Electronics, might look into one of those soon. How would it double up for hi hat/overhead in your experiences?

 

I shall also use your advice about mic placement the next time I'm on.

 

Thanks again.

 

Rich

[Bobbsy]

I like the price of the SE Electronics, might look into one of those soon. How would it double up for hi hat/overhead in your experiences?

 

I've been very happy with them on overheads...I've used them in that position quite a lot.

 

FYI, the SE distributors (Sonic Distribution) used to offer a free one week trial on mics...not sure if they still do but it might be worth seeing if you can do a "try before you buy".

 

Bob

[Yogi Bear]

I got superb results using 2 C1000's for guitar and singer at our local theatre, both pointing upwards and square-on to the homemade monitor. As the audience were quiet and appreciative, I got a reasonable level without feedback. I used a homemade preamp/mixer and no EQ and fed the output to the theatre mixer, amp and a couple of Ariston speakers and a parallel feed to a Matrix UKP500 and my monitors. The theatre did have some Bose 802's but they were too far back and I didn't have time to move them.

 

A local video company were impressed with the sound and decided against doubling up my mikes with theirs and took parallel feeds from the C1000's and a D95 I used on a backing singer.

 

The singer/was also impressed with the sound as he'd never heard such clear monitoring which also reproduced the low frequencies of the guitar complementing the flown Aristons which were normally used as a fill.

 

As I got fed up building more preamps, I bought a couple of medium size Behringer mixers for larger events.

 

 

Yogi Bear

[Just Some Bloke]

You could always look for something with a narrower directivity pattern.

 

I work at a theatre where we have some rifle mics which some people like to use a floats, and they work quite well with acoustic guitar, allowing you to get the level up higher than with a 57 as well as getting a nicer sound.

[Rich]

You could always look for something with a narrower directivity pattern.

 

I work at a theatre where we have some rifle mics which some people like to use a floats, and they work quite well with acoustic guitar, allowing you to get the level up higher than with a 57 as well as getting a nicer sound.

 

That's the reason I'd looked at the C1000s, because of the ability to convert it into a hypercardioid. However, for the price, it might be worth taking advantage of the try before you buy with the SE Electronics.

[dbuckley]

I'm going to get flamed to death for this, but...

 

Once you've got the mic sorted out, start trying electronics.

 

Delay the mic signal by a few milliseconds, 100% wet, no original signal, and that delay will give you a few extra dBs before "feedback". I say "feedback" 'cos its not quite the traditional howl, it's kinda weird howl, and it arrives like a steam train, so you gotta be on the fader, as you are in the "free lunch" territory, and we know there is no such thing as one of them. As long as the delay is only a few mS no-one will notice.

 

Another thing that works is to pitch shift the mic a bit, again, just a few cents, and go sharp, the ear is more sensitive to flat than sharp, but you dont want go far enough to detune the thing. Again, when it howls, it'll pin your limiters, so be careful.

 

Finally, if you have setup time, then a "feedback eliminator" (FBE) may help. But only if the feedback frequency is consistent, ie its based on the guitar's resonant frequency rather than some combination of circumstances that vary from moment to moment. Dont leave it on autohunt; bad things will happen. These are very cool because they are like parametric EQs with very narrow bandwidths and very deep cut ability, so they dont screw up the tonal qualities as much as trying to fix the howl with the swept mids. Most audio pros hate FBEs, but in reality they have limited experience of using them (like they've tried a FBE for two shows and they've got 20 years experience of running FBEless), they're a tool like any other bit of audio kit, and under the right circumstances and in the right hands they can deliver useful results. If using a FBE is too <fill in word here>, then a graphic or parametric inserted into the guitar channel will let you do a manual job in a more controlled manner than the desk eq.

 

:) A helmet smiley - how useful

[Bobbsy]

Well, I hope dbuckley doesn't count this as a flame, especially as he recently tipped me off about my current favourite web site (the American Widescreen Museum) but....

 

While all the techniques he mentions are good "last resorts" to cure feedback problems, I WOULD view them as just that...last resorts.

 

Before trying the various electronic trickery, I'd make sure I was using an appropriate mic, positioned properly and also adjusted the position of the FOH speakers etc. All these basics are better ways to cure feedback.

 

The one major item of electronics I WOULD try first (if you don't have one already) would be a 31 band graphic EQ to "ring out" your system. With practice this only takes a couple of minutes during sound check and can really help. Note that I'm not talking about using this for "hands on" control during the show--though you could--but just for establishing a basic set up in advance.

 

From the original post I'm assuming (perhaps incorrectly) that this is a pretty small rig. If that's the case, small physical changes can make a big difference to gain before feedback...and moving mics and speakers is free!

 

(And yeah, I'm one of those boring nerds who prefer to do my own EQ to stop feedback rather than trust an FBE!)

 

Bob

[paulears]

I think feedback eliminators switched to auto are the devils spawn. In my experiences, auto mode is totally useless, very unpredictable and when it does hone in and zap a real sproggie, it leave the sound thin and lacking andy definition. As Bob has said - eq is probably the savior here. I too hate C1000's - they seem to have become a condenser version of a Shure SM57, as in, use on anything and it always sounds sort of ok. I find them thin, and easy to overload, damn ugly, rather big and the hyper cardioid adaptor can never be found! Mind you, loads of people love 'em. Just not me.

Paul

[david.elsbury]

Auto feedback elim's are sh!te IMO.

I have never used, but like the look of, those graphic EQ's with the LED's that light up when they think they are identifying feedback

 

David

[mac.calder]

I have never used, but like the look of, those graphic EQ's with the LED's that light up when they think they are identifying feedback

 

Would be very interested in hearing more about these.... Anyone?