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Audio Mixing “Live” Performing Band’s

A Review by: Alphonso Soosay

A Sound mix engineers and “Live” mixing achievement involves a huge amount of responsibility, in door acoustics, outdoor wind, and getting enough speakers in the right spot so the audience can hear something intelligible and the sound mix engineer is also expected to deal with understanding of room acoustics, complete knowledge of concert sound reinforcement equipments, choice of correct microphone applications, understanding of miking the various musical instruments for outdoor and indoor situation and also working closely with Musicians sound which is so important and the list goes on.

On one hand the challenge of capturing the “Live” performance is so rewarding when it is done correctly, as it seems to express positive satisfaction of my set-up ideas. Never misjudge the value of trying a new model microphone placement; “just to hear how it sounds” it could be the sound that you have been looking for.  

There are scores of sound reinforcement system configurations as there are live venues out there. Each venue has its own sonic irregularity. Among other factors, the type of sound reinforcement used will affect the overall acoustics of a space. This makes every live situation unique. A way of mixing for one live band may require an entirely different approach at another venue with a different room size. There are many factors to consider, for example, is the in-house system and stage monitoring satisfactory? What variety of microphones is available and in what condition are they? This list can go on and on. A good live engineer’s role involves dealing with everything, from creating an optimum acoustic environment and is expected to produce an excellent mix on that night. Here are simple step approaches as to what you should do.

Important Acoustic space:

The aim of live acoustics is to project the sound of the stage performance to the whole audience simultaneously, with the same frequency characteristics and intensity. This idea can be difficult to achieve. In a live band situation we are listening to a number of musical instruments and vocal sources at the same time, reaching the listener in different ways. Along with direct stage sound, music will reach the listener by reflecting off surfaces such as ceilings, walls and floors. Reflections around the stage area will also effect the overall sound, for example a brick wall behind the stage will cause unwanted reflections, using a back cotton cloth draped over it will reduce these problems.

One side effect of hard boundary surfaces is the formation of standing waves. In short, a standing wave will be formed if a half wavelength of the sound fits the distance between the walls. Where wave’s crests (point of maximum pressure) coincide, they combine and reinforce one another. Their position in space depends on the frequency of the sound. To combat standing waves a well designed venue has non-symmetrical walls, sloping ceilings, absorbent rear walls, and convex surfaces throughout. Unfortunately though, most music performance venues have not been designed with acoustics in mind. Most venues are acoustically “live”, with parallel walls and resonant characteristics. With this situation in mind, a sound engineer is required to make essential decisions based upon the acoustics of a room in which the band will be performing and how its sound reinforcement equipments will be set up.

Dealing with Feedback

Feedback is one of the common problems associated with performing “live”, the source of which usually originates from stage monitors. Microphones are placed closer to stage monitors than the front of the audience sound system (sound reinforcement system addressing the audience), so stage monitor placement and the choice of vocal microphone is vital for controlling feedback.

With feedback problems the option here is to use a cardioid polar response is the best choice because the stage monitor will be placed at the “Null” point of the microphone, the spot where the cardioid pattern rejects sound. Very often two stage monitor are used as extra volume for lead singers. Again there are options to use a hyper or super cardioid microphone which can be best suited to stage monitor placement because its pickup pattern rejects sound more efficiently from the sides where the stage monitors are placed facing the singer’s ears.

If your club or your band can afford removing all floor stage monitor and start using the “In-Ear” monitors then you will get rid of all feedback problems that you had been living in the past.

Use of Equalisation:

What equalisation does is that it shapes the overall sound of a live performances and it is used to eliminate any anomalies in within the Front House system and stage sound. The most valuable tool that any sound engineer would like to use is the “Graphic Equaliser” that controls frequencies at 1/3 octave intervals. One Third octave equalisation corresponds well with the critical bandwidth of the ear. One Third octave equalisers are usually found in the guise of 19-inch rack mounting units and are the most widely used means of correcting sound and controlling feedback.

In order to have such control, a 1/3 octave equaliser should be placed between the Left and Right master output of your mixing desk and the amplifiers for the sound reinforcement system. So you will require a stereo 1/3 octave equaliser for optimum tone control. This will allow Equalisation changes to be made on each side of the listener’s live audio system.

Examples are if a venue fitted with glass doors down one side for the length of the room will need corrective Equalisation, particularly on the speakers facing the glass side. Glass tend to reflect high frequencies, so by systematically boosting the higher frequencies on the audience listening system’s Equaliser, the offending frequencies will become clearly audible and can be isolated and cut to suit the off balanced audio situation. Comparison of Left and Right audience listening system Equalisation should then produce a balanced sounding room.

Using the same technique a 1/3 octave Equaliser can be utilised for each and every of the stage monitors and drum fills too. A widely used method of reducing feedback is equalising the stage monitors to attenuate the frequencies where feedback occurs or is likely to occur. The audio engineer will have to ring out each stage monitor and remove its offending frequencies. This is done by carefully raising the vocal microphone’s gain feeding that stage monitor, so that the stage mix monitor engineer can hear the offending frequencies slowly creeping up. Then its time to drop the microphone gain to avoid feedback howl and isolate that nasty frequency on the corresponding equaliser and attenuate that frequency band, thus reducing the possibility  of feedback. Constantly speaking into the microphone between equalisation adjustments will optimise gain before feedback and ensure that each adjustment is improving the stage monitor sound. Remember to give yourself extra headroom with stage monitor levels, chances are you will need it as soon as the band starts performing. Choosing microphones (SM58 or EV 957) that have high gain before feedback will help achieve a louder signal without increasing the risk of feedback occurring. Ringing out the system is best done at least two hours before the band and their fans reach their venue. This not only gives the mix engineer “Ears” a rest but also reduces the possibility of ear fatigue. Having a good reinforcement system ready to go also will give you more time to organise the band and concentrate on a good sound check.

Another method of room equalisation is by using a Real Time Analyser known as RTA. This can be more sophisticated and expensive piece of equipment in any sound engineer’s tool. RTA’s are used to obtain an instantaneous display of a sound system’s frequency response. By placing the RTA’s measurement microphone at the critical listening distance, about 2 meters away from the speaker, reverberation does not become a factor and a more accurate measurement take place. Applying a pink noise source to the main reinforcement system (before any EQ) then bring up the audio systems volume to a comfortable measuring level allows you to the systems equaliser to make adjustments for a flat frequency response. Ultimately, play some full range recordings that you are used to with and fine tune the system equalisation to your required taste.

Phase Check

Phase check is an important element in Live Sound and can impact on your overall sound in a number of different ways. Phase essentially describes the relationship between two or more waves and how they affect one another. One crucial element in any sound system is making sure the physical alignment of the speaker is okay. The positioning of the reinforcement system itself is crucial to attaining good live sound; a few inches out can make all the difference, especially in an outdoor concert. Positioning the speakers so they provide coverage of the audience rather than the walls and ceiling will help control the sound spread into a room. Poor positioning of speakers will result in dead spots where phase cancellation occurs between the conflicting output of two or more speakers cabinets and will cause uneven dispersion. Phase also refers to proper electrical wiring to your electronic equipments. Non standard wiring with your equipments can cause phase cancellation problems. Make sure you start checking all your amplifiers, equalisers and outboards effects are wired according to required specs. Keeping a multi-meter handy will help check correct wiring. Also is good to carry Phase reversal leads as they can provide an easy way of correcting phase without rewiring it. Remember, out of phase signals end up sounding thin and weak.

Tweaking the Reinforcement System

On your audio mixing desk make sure the EQ is flat or bypassed, then use the lead singers dynamic microphone to test (check one two), panning left and right to make sure each side is working well and balanced in level. At this stage try adjusting the crossover, you should be able to get a good balance of highs, mids and lows. This forms the basis for equalising the audio system. While riding the channel fader, with sub groups and master fader set at zero dB.

At this stage bring up the microphone preamp gain to where it is required. Using the mixing desk dB metering ensures that the vocal channel is not being overloaded. This method reduces the risk of distortion and gives you a more open sound. Using a high pass filter on vocals usually around 100Hz on the microphone input filters will clear unwanted low frequencies rumble. If you know the sound of the singer’s voice well enough, you should be able to attenuate frequencies that are problematic in the room. Example is: if the room is emphasising too much around 125 Hz, then use your 1/3 graphic equaliser to cut back the 125 Hz to keep the overall sound under control. When the 1/3 graphic is tuned to optimise vocals, you can then use your mixing desk EQ to sweeten the sound on individual musical instruments. Playing back your favourite music CD is another good method of checking that your audio reinforcement system is sounding as it should be.

Insight of Monitors

When working in small Pub’s and Club’s with audio mixing, chances are the stage monitors will be mixed from the main front – house mixing console. You will be sending the stage monitor mixes through the auxiliary sends. Whichever output sends you select for the monitor use, 1, 2 or 3 will go to a separate power amplifier, which is attached to their monitor speaker. The purpose of these is of course, for the performers on stage to hear themselves better.

The understanding here is that the individual musicians on stage will want to hear what instruments of the stage they can’t hear clearly, especially in a big club with rock bands,
Most drummers have a tendency to want everything in their mix, with an emphasis on kick drum, bass guitar, and any guitars onstage. Guitarists tend to want any other guitarists onstage in their mix, along with plenty of kick drum and vocals. Bass players tend to want lots of kick drum and some guitar. As for Vocalists they love to hear themselves and lots of it. Of course, it’s always a good thinking to ask the performer what they prefer in their mix, and then work from there. It’s important to make them comfortable.

In charge of Stage Volume

With smaller clubs, you will always be fighting stage volume. Getting a clear mix in the house can be difficult if you are having blaring guitar amps and loud wedges, with everything exponentially getting louder to try to compensate for everything else in volume.

Making sure that lead guitarists keep their stage volume down is of huge importance, because their amplifiers tend to get the loudest. I always tell guitarists to start off playing as soft as they can and still aim for their preferred tone, then see if they can compromise on something less. Sometimes they will, sometimes they will find it difficult. While it may seem heartless, I then remind them that it’s their show and ultimately it’s their sound  and if they want to ruin it, they are more than welcome.

Ringing Out the EQ

The first thing you’ll want to do before any performers get there is ring out the monitors. Ringing out the monitors is a simple way to reduce feedback. Feedback occurs when a loop forms between the signal source (in this case, a microphone) and an output source (in this case, the monitor wedge), and it’s, simply, a pain to deal with.

We will assume that you have graphic EQ inserted on the output of each monitor mix. If you don’t, then these adjustments will be tricky. You can accomplish something similar by cutting frequencies on the master channel, but be aware that those adjustments will affect the house mix, too.

Start by turning up one microphone a dynamic microphone, similar to what you will be using throughout the stage in one of the monitors until it begins to feed back, which sounds like a high or low pitched vibration. Once it begins to feed back, reduce that frequency in the graphic EQ until it’s no longer feeding back. Keep up that process until you can apply a great amount of gain to the microphone in the wedge without feedback. But make sure not to take too much out, or else you will kill the dynamics of the monitor output.

Let’s Start Mixing

Normally I would like to start with the drummer first. Start off by asking him to play his kick drum. Ask across the stage if anybody needs more kick drum and most likely, the other musicians will. Turn up the kick drum in each individual mix until everyone’s happy. Most times, they won’t want anything else of the drummer in their mix; if they do, they will ask you. Then, go to the bass. Most drummers as well as the bassist themselves will want plenty of bass guitar in their mix. Here’s a good advice: I usually run a DI box between the actual bass guitar and the player’s amp, and use that signal in both the front of house and monitors. Miking a bass amp is a good way to get the overall tone, but if you are in a small club, tone is the least of your worries you want to hear the definition, and have control over it in both the monitors and the house.

The next stage is to look at the vocalists. Avoid using compression in the monitors, because this actually encourages really bad mike technique for most vocalists. Compressing vocals in an in-ear monitor mix is crucial, but it’s not necessary in wedges. Acoustic guitar is the next thing to go in, if it’s onstage. Vocals and acoustic generally compete for the most gain, and therefore tend to cause feedback. Electric guitar won’t need much, if any, in the monitors, although it’s not a bad idea to ask the musicians and singers. Sometimes, a softer-playing soloist will need their signal across the stage.
Remember, every location is different, and practice makes perfect.

Drums

Drums can be difficult instruments to mix live. In order to deliver the best-sounding mix, you need to deal in what you can hear in the room naturally, without amplification. Most drum kits, in a small room, won’t need any amplification except for the kick drum.

In a good small room, I prefer to mike the kick drum, as well as the snare. Toms generally don’t need any amplification, as they are generally not played enough to warrant dedicated channels. If you are in a club that holds, say, between 250 and 500 people, you may need to mike them. If you are short on microphones, you can put one microphone for every two toms, placing them in between. Depending on the quality of the kit, you will need to compress.

Overheads and cymbal microphones are of low priority. Even some small clubs that hold less than 1,000 people may not need amplification on the overheads. Sometimes, I will mike the high-hat in a small room if the drummer plays it softly or with brushes, but generally, it’s not necessary.

I prefer to compress the kick drum separately, and EQ with a boost in the mid frequencies for that thud sound. I also, as usual with most channels, cut out everything below 80Hz.

Here’s another advice: if you have got a loud snare, but still want to add reverb to it, you can switch the reverb send on that channel to pre-fader instead of post-fader. That way you can still send the snare signal to the reverb unit while not actually putting any in the main house system.

Bass & Guitars

Quite simply, in most small rooms, you won’t need to mikes the guitar amps and bass cabinets. In fact, I am almost always finding myself having to ask the players to turn them down because they are too loud in the house. Sometimes you will find you need more definition in the bass guitar, or your drummer will want more in their monitors. In this case, I will put a DI box between the guitar itself and the amplifier. That way, you are in total control of the tone, and the amplifier on stage can still do its job as the player wishes.

Acoustic guitars are a different matter. Sometimes, you will find players with an acoustic amp, but those generally don’t cut through the mix well. Putting a DI box out for the acoustic is the best way to get the best sound; you will need to carefully EQ it to avoid feedback. I always keep a Feedback Buster a specially-designed round disk of rubber sold in most music stores to lend to guitarists who don’t have one. These block the majority of the frequencies from entering the guitar’s sound-hole, which prevents the major feedback problems you usually get.

In Concluding

Mixing live sound is not easy, but once you get the hang of it, you will be doing fine. It’s really a lot more than just riding faders and setting gain, though; don’t be afraid to really dig into the more technical concepts like compression and EQ. You will be a much better engineer if you experiment with it. Of course, mixing in a large club is completely a different deal you have much more flexibility and you are fighting less with the loudness of the instruments in the room. But for most situations, following these guidelines will give you the optimum sound possible

Alphonso Soosay

Audio Recording Engineer

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