Troubleshooting Mic Bleed: Vocals vs Ambient Sound

Sound design has changed in so many ways over the past several decades. PA systems are lighter, more efficient, smaller, and louder than their predecessors. The amount of rear audio rejection coming from behind these PAs is amazing. That’s good news for the performers on stage, who need that isolation from the main PA.

However, what happens when artists venture away from that “safe” zone, out among the masses of screaming fans, and in front of the PA? Engineers fight to get every last bit of gain they can use so that artists can hear themselves, and be heard, but when artists are in front of the PA, engineers often feel like they’re doing their job in an audio war zone.

Being a novice in the field of engineering, but knowing just enough to understand what engineers have to deal with, I decided to address this issue with the audio engineers who have been touring many years with Shure artist endorsers Maroon 5. Monitor Engineer Kevin Glendinning and Front-of-House Engineer Jim Ebdon shared some tips and tricks they employ to combat crowd noise on a nightly basis.

Ryan: First of all, for readers new to this issue, could you please describe the situation that causes crowd noise to bleed into a vocal mic?
Kevin: Great topic here, Ryan, a serious issue that none of us live sound mixers take lightly. With the Maroon 5 guys, we typically have at least one musician in front of the PA at all times. It's usually pretty manageable for everyone and doesn't alter or smear their ear mixes too much except for Adam [Levine, lead vocalist]. It's really a massive difference once that plane is crossed and the mic capsule goes from upstage of the PA hang to downstage and further out into the house. You go from a shrill harsh bleed, once the PA bleed occurs, to a combination of room reverberation and, as the distance increases further of course, a time smear and base delay, with waves moving in from a single point.
Ryan: During a show, how do you manage crowd noise bleeding into a vocal mic?
Kevin: The best way to combat this is to try and keep the channel send and mic pre / input trim to a minimum. However, you can get in trouble as a lot of the fans get louder once the guys get closer out there and back into the house. It's a fine balance. You back off the FX from the desk and listen to what the PA and venue is giving you and try not to completely wash away the directivity of the mix. We do use audience mics, but that is mostly for the call and response portion of their songs. Adam likes a lot of interaction, especially down front. The in-ears we use (JH Audio - Model: Roxanne) have -24dB of isolation. So, as long as they are keeping both molds in tight and secure, we introduce some of the room so they don't feel disconnected to the ticket buyers.
Jim: I suppose the first task for me with any singer who might be in front of a PA system is to find out how loud you can get that vocal before feedback. Kevin and I "ring out" the PA to find the standing frequencies in the room. I will often make him point the mic up to the sound system and ask him to deliberately try and make it feed back while he moves around the performance area. This typically tells me how much headroom I have to deal with before feedback. I will then make the necessary frequency tweaks in the PA to give us as much headroom as possible. Adam in particular has a strong singing voice, so I rarely need to do much chopping!
Jim Ebdon (Left), FOH & Kevin Glendinning (Right), Monitors

Jim Ebdon (Left), FOH & Kevin Glendinning (Right), Monitors

Ryan: Does the crowd noise bother Adam, or does he like hearing a certain amount of the crowd in his in-ear monitors?
Kevin: I'll get a look here and there if I spin up too much audience in his mix, especially at the top of show when his ears are fresh from a quiet dressing room. Recently, we did Seoul at the Olympic Arena, and the fans were so loud I kept the room mics in mute for almost all of the show. I think the fans were louder than the PA at one point even, and Jim isn't a quiet, soft mixer. His biggest “must have” request to me is that he is part of the band, so he wants to hear it all with backup vocals (vocal pitch), keys, guitars (key register) as well as bass, kick, and snare (rhythm and time).
Ryan: Adam has been out in front of the PA for years. You know that, so I imagine you have ways of mitigating the effects of this in advance of the show, during sound check. What’s your process?
Kevin: Jim and I will go through a series of ring-and-response standard operating procedures daily, pretty much me talking in my raspy low-register voice and getting the HF to ring out so he knows what the limitations will be that night. Skyboxes, scoreboards, non-draped back sections that didn't sell all come into play in this. All physics: where the sound will reflect and where it will dissipate. The band almost never comes in for sound check, so they trust Jim and me to get it all worked out before doors. If we are in a good point in an open arena without the AC on, then when we fill up the venue and get the room temp manageable in the 70s, it should all tighten up and prove to gain a dB or two before we get into ringing from the SM58s.

Jim: I am careful with my vocal EQ. I don't want to change the sound of his voice, but I want it to blend into the mix. At high volume, the sound of the lead vocal must sound clear, natural and easy to listen to.

The PA has never been a problem through the SM58® capsule: it’s the audience!! More often than not, the audience is louder than his voice, as is the snare drum. If we play on smaller stages (e.g. for corporate shows and events), the drums become louder than his voice. I can compensate by using Plexiglas for that situation, but obviously I can't compensate for 18,000 screaming audience members.

With the aid of virtual sound check, I can solo up the lead vocal channel and listen to the loudest audience spikes, which of course are inevitable and in all parts of the overall show. With EQ, I can at least make the audience sound a little more pleasing without ruining the integrity of the sound of his singing voice. So, with a singer who is moving around the stage and then out in front of the PA, the predictable SM58 capsule we use is such a stable, usable microphone. It's very hard to beat. We have tried various others but always come back to this. It suits his voice perfectly.

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Ryan Smith

Ryan Smith

Ryan is a Regional Manager of Artist Relations at the Shure office in Nashville, TN. He started at Shure in 1993 in Customer Service and joined the AR team in 1996. Ryan has over 30 years of performance experience playing drums and percussion in various groups and genres. In his spare time he enjoys woodworking, watching movies, videography, and camping with his family. His Twitter handle is @ryan_smith1969.

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