You are here

Can't get singers input gain to unity without feedback

For performing musicians and engineers: stagecraft, engineering and gear.

Can't get singers input gain to unity without feedback

Postby DavidA » Tue Jun 19, 2018 9:29 am

I'm a fairly new sound guy, learning OTJ with a lot of reading. I'm working with a 5 member band (female vocalist, guitar, bass keys & drums). I'm having trouble getting the input gain for our vocalist high enough without feedback.

I'm using a Macke DL1608 board, and with my previous singer I could always get her input gain to unity or higher, thus keeping my sliders at unity, or maybe +2db. With my current singer, I can't get the input gain much beyond -10 or -5db without feedback, thus I have trouble getting her high enough in the mix. I end up with my slider at +7db (or higher!) just to hear her. We're just at the rehearsal stage currently, having to replace a couple of other members, but when we get to playing out this will be a bad situation.

I've read a lot; she says she's not cupping the mic (we'll be testing that next rehearsal), and uses IEMs whenever possible, or points the mic correctly WRT the monitor. I've tried using the EQ to knock down in the 250Hz & 1kHz areas, with little/no luck. (Full disclaimer, I'm just learning EQ.)

I never had to work this hard to get enough signal before; any suggestions ?
User avatar
DavidA
New here
Posts: 4
Joined: Tue Jun 19, 2018 9:06 am

Re: Can't get singers input gain to unity without feedback

Postby Hugh Robjohns » Tue Jun 19, 2018 10:48 am

Feedback can only occur if the 'loop gain' around the system is positive. In others words, the overall gain in the complete loop comprising the mic, mixer, amp, monitor/PA speakers, and acoustic path back to the mic is greater than unity.

Since you obviously need a certain level of sound coming out of your PA system, the gain applied by the mic preamp and through the mixer has to be whatever it needs to be... and so the only practical way to reduce the risk of feedback is to minimise the acoustic path back to the mic.

There are lots of ways of doing that, and you will need to optimise the combination of all of them.

First, the PA speakers need to be well in front of the mic, as far away as practical, and aimed to minimise the direct sound getting back into the mic. Where possible, you might also want to minimise reflected sound getting back by hanging drapes etc on the side and back walls of the rehearsal space.

The directionality of most PA systems varies dramatically with frequency, and most are essentially omnidirectional at low mid and bass frequencies, so the effective loop gain will be much higher at the low end compared to the high end -- which is something to bear in mind and relates to the frequency response and polar pattern of the mic.

You mention mic-cupping, and that's a 'bad thing' because it can block the rear-ports of the capsule. That disables the pressure-gradient action of the capsule and converts the mic's polar pattern from a cardioid/hypercardioid etc to an omni. The inevitable result is that instead of rejecting unwanted sound from in front of the singer (primarily the monitors and PA system), it massively increases the gain with the likely result being howlrounds. So it is very important that you check whether your singer is inadvertently cupping the mic, and if they are you'll need to reprogram them!

Next, most vocal mics have an uneven response, typically intended to boost the higher mids for clarity in the mic -- but that presence peak means a higher loop-gain over that frequency region, and if it happens to coincide with peaks in the responses of the PA or monitors could also result in a greater risk of feedback. So be very careful boosting the mic's EQ in that region, and avoid setting up the PA and/or monitors with EQ peaks in that area too.

Most vocal mics are designed to be used very close, and their natural proximity effect is used to restore the low end response when held close to the mouth. The immediate benefit of this is a greatly reduced sensitivity to low frequencies from distant sources -- such as monitors and the main PA -- and that's handy because they tend to chuck out a lot or low end towards the mics! However, even so it's almost always well worth rolling some additional bass out of the vocal mics. it won't reduce the clarity of the vocals (in fact it usually helps) but it will clean up a lot of LF spill and general muddiness, and it will minimise the risk of LF howlrounds. The Mackie mixer has adjustable high-pass filters on the mic preamps, so use them set up around 150Hz or so.

Related to this proximity characteristic is the way in which the mic's sensitivity drops off radically as the source moves away from the mic. So check if your singer is holding the mic too far away from their mouth -- the closer the better in live sound. The level at which they sing will also be significant of course; it's much easier to get a decent level before feedback if the singer projects loudly, and very hard if they are a whisperer. Sometimes singers back off if they hear too much of themselves from the monitor wedge, so turning down the foldback level often encourages both a closer mic technique and more oomph from their voice!

Vocal mics are usually either cardioid or hyper-cardioid, but you need to know which because the direction of greatest rejection is radically different. A cardioid rejects sound from directly behind it (180 degrees), whereas a hyper-cardioid rejects sound from +/-110 degrees. So, if you're using a cardioid vocal mic the monitor needs to be directly behind it, where as if it's a hyper-cardioid the monitor wedge(s) need to be pulled around to the sides a bit.

You haven't said what vocal mic you're using, or the monitors or how the PA/monitors are set up, but these are all critical to maximising the system stability and minimising howlround. Only with the main PA and monitors set up sensibly can you expect good resistance to feedback.

H
User avatar
Hugh Robjohns
Moderator
Posts: 21167
Joined: Thu Jul 24, 2003 11:00 pm
Location: Worcestershire, UK
Technical Editor, Sound On Sound

Re: Can't get singers input gain to unity without feedback

Postby ef37a » Tue Jun 19, 2018 11:05 am

It is likely that your previous singer was real "belter" and probably had a good microphone technique, keeping right on it most of the time but pulling back for the big FFFs.

There is however another factor, the loudness of the rest of the band. The inescapable fact is that amplifying a vocalist is the hardest part of PA! You are always limited by feedback whereas drums are almost always naturally loud enough (some say .....!) and guitarists can be as loud as they like!

If you are happy with the singer in other respects then I fear the band might have to 'pull their collective horns' in a bit!

Dave.
ef37a
Jedi Poster
Posts: 9046
Joined: Sun May 28, 2006 11:00 pm
Location: northampton uk

Re: Can't get singers input gain to unity without feedback

Postby DanR » Tue Jun 19, 2018 11:25 am

DavidA wrote:I'm using a Macke DL1608 board, and with my previous singer I could always get her input gain to unity or higher, thus keeping my sliders at unity, or maybe +2db. With my current singer, I can't get the input gain much beyond -10 or -5db without feedback, thus I have trouble getting her high enough in the mix. I end up with my slider at +7db (or higher!) just to hear her.

Different singer is the issue if all was ok previously and nothing else has changed. Agree with the ‘belter’ point made by elf37a. Makes thing a lot easier if the source signal is strong.
DanR
Regular
Posts: 247
Joined: Sat Dec 31, 2005 12:00 am
Location: Cambridge, UK

Re: Can't get singers input gain to unity without feedback

Postby Hugh Robjohns » Tue Jun 19, 2018 11:54 am

DavidA wrote:I'm using a Macke DL1608 board, and with my previous singer I could always get her input gain to unity or higher, thus keeping my sliders at unity, or maybe +2db. With my current singer, I can't get the input gain much beyond -10 or -5db without feedback, thus I have trouble getting her high enough in the mix. I end up with my slider at +7db (or higher!) just to hear her.

Hmmm... having had this section requoted above I think it highlights a gain structure issue.

You seem to be saying you can't run the mic preamp gain as high as previously without feedback, and you are having to compensate for that by running the channel fader higher to get the voice as loud as before...

That suggests to me that the feedback is between the mic and monitors, not the PA, and that you are sending more level to the monitors via a pre-fade aux send than previously, or the monitor gain has been increased somehow, or the monitor position is no longer in the mic null or much closer?

Try turning down the pre-fade aux send to the foldback monitor on the vocal mic channel (and/or its aux master output), then readjust your channel fader and input gain as you want. Now, with a sensible gain structure established for the PA signal path, bring up the aux-send to the monitor until your singer has enough foldback level.

H
User avatar
Hugh Robjohns
Moderator
Posts: 21167
Joined: Thu Jul 24, 2003 11:00 pm
Location: Worcestershire, UK
Technical Editor, Sound On Sound

Re: Can't get singers input gain to unity without feedback

Postby CS70 » Tue Jun 19, 2018 12:04 pm

Coming from a singer perspective.. the relative level of the singer vs. the band is important: well set up mics pick up more or less that. So if the current singer is quieter than the previous one, all rest being the same, the band has to play quieter.

Obviously the band cannot go more quiet than a certain level, beyond which it's singing technique, projection and mic technique.

You usually want to have some headroom anyways but it looks what you have is not enough. I'd look at your gain structure.

Another few things to look at are:

- the singer's mic position in the room (just like with acoustic guitar, moving a step on the side and/or backwards or forwards can help, since feedback depends on the reflection pattern at the point where the mic is);
- her mouth's position with respect to the mic.. many dynamic mics are made to be "eaten", i.e. you sing with our lips touching the mic or just a millimeter near). When you step away, your level drops very quickly.
- the reverb level. Very wet signals reduce the gain before feedback in my experience. It's often a singer's preference (I like to hear myself with loads of reverb for example) but an option is to route that only to her monitor.
- of course the location - if it's a small, closed room like your typical makeshift rehearsal space, there's only so much you can do unless you treat the walls to reduce HF reflections and add bass traps to reduce the low freqs.
User avatar
CS70
Frequent Poster (Level2)
Posts: 2543
Joined: Mon Nov 26, 2012 12:00 am
Location: Oslo, Norway
Silver Spoon - Check out our latest video  and the FB page

Re: Can't get singers input gain to unity without feedback

Postby Wonks » Tue Jun 19, 2018 12:09 pm

Something must have changed significantly between the two setups. Are you using a different mic e.g if the singer has brought their own one? If so, what was the previous singer's mic and what is this one? As has been mentioned, does the new singer like more of their voice in the monitors than the old one? Is the rest of the band setting up differently?

The desk input gain positions means nothing if the mics have changed and the new one is more efficient and puts out a louder signal than the old one did. Swapping between an SM58 and a Beta 58 can give around a 3dB increase in mic signal, resulting in less desk input gain needed (which is normally a good thing) and other mics with neodymium magnets can give even hotter signals.

But if the new singer is considerably quieter than the old one, or singing a lot further away from the mic, then more overall gain will be required, which increases the likelihood of feedback. So then the only solution is that the overall band, monitor and FOH levels have to come down to compensate, or else you look round for a louder singer.
User avatar
Wonks
Jedi Poster
Posts: 5411
Joined: Wed May 28, 2003 11:00 pm
Location: Reading, UK
Now even grumpier than Ivan in his heyday.

Re: Can't get singers input gain to unity without feedback

Postby James Perrett » Tue Jun 19, 2018 1:07 pm

One other thought - keep the signal chain simple and avoid any compression until you've mastered the basics.
User avatar
James Perrett
Moderator
Posts: 7214
Joined: Sun Sep 09, 2001 11:00 pm
Location: The wilds of Hampshire
JRP Music - Audio Mastering and Restoration. JRP Music Facebook Page

Re: Can't get singers input gain to unity without feedback

Postby DavidA » Wed Jun 20, 2018 12:12 am

Another couple of data points: our current singer uses a Shure 58A mic, and in-ear monitors (IEMs from my original post). I have reached out to our previous singer to see what she used (they both provide(d) their own mic). I don't perceive a great difference in volume as compared to the previous singer, but I am awaiting opinion from other band members. The current singer insists she's not cupping the mic; I event sent a pic I found online illustrating it (much more subtle than I originally thought).

It's just a bit shocking that there's a difference of ~10 dB between the two singers. But, as I said right up front, I'm not an expert, learning on the job. That's why I'm here asking for help!
User avatar
DavidA
New here
Posts: 4
Joined: Tue Jun 19, 2018 9:06 am

Re: Can't get singers input gain to unity without feedback

Postby ef37a » Wed Jun 20, 2018 6:22 am

I suspect the IEM is the problem. Too much "her", not enough everyone else? Does she have control of her personal mix?

I had the opposite problem donkey's ago. Outside country event with a main ring and MC was in a caravan with mic. He WOULD lean in and blast the mic!

We fixed his wagon with a small speaker in the corner of the caravan that gave him just enough level to tell him to keep it sweet and even.

Dave.
ef37a
Jedi Poster
Posts: 9046
Joined: Sun May 28, 2006 11:00 pm
Location: northampton uk

Re: Can't get singers input gain to unity without feedback

Postby Wonks » Wed Jun 20, 2018 9:03 am

Not knowing the rest of the stage/rehearsal set-up, it's hard to say more. But the Beta 58A is a supercardioid mic, so has a pronounced rear-facing lobe with a pronounced null at 60° from the rear-pointing lobe.

https://www.shure.co.jp/productdocument ... eb37b8.pdf

For comparison, the Cardioid pattern of a standard SM58 doesn't have anything like the sharp null of the Beta 58A, but does reject a lot more sound directly from the rear of the mic.

http://cdn.shure.com/specification_shee ... nglish.pdf

So if you're getting the singer to point the mic's rear directly at the monitors, or any rehearsal room speakers, then you aren't getting the best noise rejection from the mic. The 58A should be capable of allowing a higher stage volume before feedback than a cardioid mic if monitors or rehearsal room speakers are placed appropriately, but you'll get less volume before feedback if not.

If the previous singer was using a cardioid mic, then it may be worth simply trying a similar mic with your current singer. They may lose the benefit of the clearer top-end that the Beta 58 gives, but that's all a bit pointless if you can't hear the vocals because you can't get them loud enough.

Putting the mic on a stand and keeping it there so it can be best positioned with regards to any monitors (I take it that the rest of the band isn't using IEMs and that there are still vocals coming through the stage monitors) is one way of getting the best from the mic, even if the singer prefers holding it in their hand.

Pointing any other stage monitors away from the singer will help.

Otherwise you may need to invest in some 31-band graphic equalisers and 'ring-out' the monitors and notch out any problem frequencies. Note that this will have to be done every time you set up in a new venue
User avatar
Wonks
Jedi Poster
Posts: 5411
Joined: Wed May 28, 2003 11:00 pm
Location: Reading, UK
Now even grumpier than Ivan in his heyday.

Re: Can't get singers input gain to unity without feedback

Postby ef37a » Wed Jun 20, 2018 9:10 am

Just a thought if it all gets serious with graphics? Put a phase flip in the mic* line, one way often gets you a dB or two before ring. If in doubt go for the ring of lowest frequency.

*Used to flip speakers or/and but not so easy these days with actives.

Dave.
ef37a
Jedi Poster
Posts: 9046
Joined: Sun May 28, 2006 11:00 pm
Location: northampton uk

Re: Can't get singers input gain to unity without feedback

Postby James Perrett » Wed Jun 20, 2018 1:28 pm

Wonks wrote:Otherwise you may need to invest in some 31-band graphic equalisers and 'ring-out' the monitors and notch out any problem frequencies. Note that this will have to be done every time you set up in a new venue

I'm not sure that I'd advise anyone inexperienced to do this - in my experience ringing out causes more harm than good.
User avatar
James Perrett
Moderator
Posts: 7214
Joined: Sun Sep 09, 2001 11:00 pm
Location: The wilds of Hampshire
JRP Music - Audio Mastering and Restoration. JRP Music Facebook Page

Re: Can't get singers input gain to unity without feedback

Postby Wonks » Wed Jun 20, 2018 1:42 pm

Hopefully the OP will find another solution, but even if it comes to ringing out, you've got to start somewhere to get the experience. There are graphics that indicate the problem frequency(ies), which can help until your ear gets trained to pick out frequencies without help. There are on-line ear training apps for doing just that sort of thing.
User avatar
Wonks
Jedi Poster
Posts: 5411
Joined: Wed May 28, 2003 11:00 pm
Location: Reading, UK
Now even grumpier than Ivan in his heyday.

Re: Can't get singers input gain to unity without feedback

Postby CS70 » Wed Jun 20, 2018 2:18 pm

As Dave says, the IEM can simply give her much of herself, therefore she doesn't sing as loud.

One more thing tough: supercardioid mics are much less forgiving when it comes to position, when singing near the mic, if you angle yourself even a little bit from the mic front you lose a lot of volume. I use one and even if it's my own, sometimes it still tricks me in rehearsal (where I need to turn my head to read lyrics for a new song).

So something to be aware of - if she has a tendency to sing on the side, that would explain a lot of the volume drop (not the more than half that you are experiencing, but a lot). A cardioid is much easier to work with.
User avatar
CS70
Frequent Poster (Level2)
Posts: 2543
Joined: Mon Nov 26, 2012 12:00 am
Location: Oslo, Norway
Silver Spoon - Check out our latest video  and the FB page

Re: Can't get singers input gain to unity without feedback

Postby DavidA » Thu Jun 21, 2018 1:50 pm

@CS70 (et. al.):

Ok, her mic is the SM58A, and the mic I use for talkback is the SM58. I'll try swapping between the two to see what sort of difference it makes. The comment about reading lyrics while singing is VERY interesting; that's exactly what's happening most of the time, as she's new and coming up to speed.

Thanks for the feedback ALL OF YOU, it's given me something(s) to work with/on. I'll report back after our practice next Monday (6/25).
User avatar
DavidA
New here
Posts: 4
Joined: Tue Jun 19, 2018 9:06 am

Re: Can't get singers input gain to unity without feedback

Postby Wonks » Thu Jun 21, 2018 5:14 pm

Don't give up, you'll get there in the end!
User avatar
Wonks
Jedi Poster
Posts: 5411
Joined: Wed May 28, 2003 11:00 pm
Location: Reading, UK
Now even grumpier than Ivan in his heyday.

Re: Can't get singers input gain to unity without feedback

Postby DavidA » Fri Jun 22, 2018 12:34 pm

She also insists on reverb in her monitor mix, and I've discovered through reading that could be a major contributor. The next rehearsal should be ... interesting! Luckily, my buddy has gotten a "pro" sound guy friend to come in and provide guidance and tips. Maybe with his backup I have a fighting chance. Hope the emphasis is not on the "fighting" part ... ;)
User avatar
DavidA
New here
Posts: 4
Joined: Tue Jun 19, 2018 9:06 am

Re: Can't get singers input gain to unity without feedback

Postby ef37a » Fri Jun 22, 2018 2:11 pm

"She also insists on reverb in her monitor mix,"

Not Shirley Bassey is she? (g'wan ask her! I dare you.)

Sounds like a reet diva!

Dave.
ef37a
Jedi Poster
Posts: 9046
Joined: Sun May 28, 2006 11:00 pm
Location: northampton uk

Re: Can't get singers input gain to unity without feedback

Postby James Perrett » Fri Jun 22, 2018 8:03 pm

ef37a wrote:"She also insists on reverb in her monitor mix,"

Not Shirley Bassey is she? (g'wan ask her! I dare you.)

Sounds like a reet diva!

Reverb in a monitor mix is standard for vocalists - just make sure that the reverb setting that you use doesn't resonate at a feedback frequency. Sometimes delay rather than reverb will work better.
User avatar
James Perrett
Moderator
Posts: 7214
Joined: Sun Sep 09, 2001 11:00 pm
Location: The wilds of Hampshire
JRP Music - Audio Mastering and Restoration. JRP Music Facebook Page

Next

Who is online

Users browsing this forum: No registered users