Monitoring Perfection - EMusician

Monitoring Perfection

Although I'm not prone to stage fright, I do approach every gig with a sense of anticipation. Each performance comes with its own set of potential problems.
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Although I'm not prone to stage fright, I do approach every gig with a sense of anticipation. Each performance comes with its own set of potential problems. However, few things can sabotage a performance quicker than the inability to hear one's self or fellow bandmates. An awkward stage layout, a lousy P.A., or a noisy audience all impact what you hear on stage. When musicians cannot hear themselves clearly, intonation, timing, blend, and musical interplay suffer to varying degrees.

Fortunately, there is a solution for the musician who is willing to put some time, energy, and money into solving the problem: it's called a stage-monitor system. Stage monitors are additional loudspeakers that point directly toward the musicians and away from the audience. Usually these speaker cabinets sit on the floor and are tilted upward. Because of their distinctive shape, these cabinets are often called wedges, stage wedges, or wedge monitors. Wedges make it much easier for musicians to hear themselves play, which helps ensure a successful gig.

However, you must consider some important caveats. First, a monitor system adds to the expense, weight, and setup time of your P.A. system. Second, using monitors improperly is often worse than having no monitors at all. When microphones are being used on stage, a monitor system greatly increases the chance of feedback during the performance. And a show plagued by feedback is worse than a show with out-of-tune vocals.

TO EACH HIS OWNThe mix that you'll want to achieve in your monitors isn't necessarily the same mix you would create for the audience. You may need two independent mixes instead: one for the performer and one for the audience. For instance, if I'm doing a solo guitar/vocal gig, I'd want the audience P.A. to carry both the sound of my guitar and my voice. In the monitors, I'd want to hear a lot of my vocal but perhaps a bit less guitar.

Creating an independent monitor mix requires more sophistication on your part as well as some additional items. To begin with, you'll need a dedicated power amplifier-the fact is, you can't use the same amplifier channel if you want differing mixes in the main P.A. and the monitors. In addition, you may also want to include an equalizer in the chain to combat feedback.

LET IT FLOWFigure 1 shows a block diagram of a simple sound system with a mic, mixer, amp, and speaker for the audience. In this situation, a monitor system can be added using a separate output from the mixer and a dedicated amplifier to drive a stage wedge.

Besides the extra monitor speaker and amp, you'll need to dedicate an auxiliary send on your mixer to create a monitor mix. This independent monitor mix is what makes it possible for you to hear one mix in the wedges while the audience hears a different mix in the main P.A. Even simple mixing boards these days include a couple of aux sends (also known as effects sends or monitor sends). You must dedicate at least one aux send to run your monitor system. If you have only two auxes and both are being used for effects devices, I suggest you reassess your priorities and sacrifice one effects unit in favor of a monitor mix.

A TEAM OF OXENThere are two kinds of aux sends-one works best with outboard effects, the other for creating a monitor mix. Understanding the subtle, but crucial, difference between the two requires a peek under your mixer's hood to investigate its signal flow, the path that sound takes as it travels through your mixer from input to output.

An effects send taps off part of each channel from a point in the circuit after that channel volume fader (see Fig. 2). This means that turning down the fader of a vocal mic will automatically turn down the mount of that channel's signal that is sent to an effect, such as a reverb or echo unit. This type of aux send is also called a postfader send. It's the right choice when an effects unit is connected to an aux send.

The other type of aux, a monitor send, takes its signal from a point before the channel volume fader, hence it's called a prefader send (see Fig. 3). As a rule, prefader sends are preferred for monitor applications because they provide independence between the monitors and main P.A. This allows you to adjust the house mix without causing a change in the monitor mix.

HOOK IT UPEnough theory; let's hook it up. Begin by figuring out which of your mixer's aux sends is prefader. Your mixer might include a switch that makes aux 1 pre- or postfader (or there might be such a switch on each and every channel). Find it and set it to prefader. Next, take that aux output jack and connect it to a graphic EQ, preferably one with 15 or more bands. From the output of the graphic EQ, run a cable to the input of a power amplifier channel. Finally, the output of the amplifier goes to your monitor cabinets. In most cases, three 8-ohm monitors is the maximum number of cabinets you should run from a single amplifier channel; using two 8-ohm cabinets is safer.

Now create your monitor mix. Start by turning up the monitor aux send on a channel with a vocal mic. Talk or sing into the mic. If all is well, you should hear your voice from the monitors. If the mixer has an aux-send master knob, make sure that it's turned up and that the output of the EQ and the input of the amp are also set to pass signal. Continue the process with each vocal mic until you can hear each singer in the monitors.

THAT HORRIBLE SQUEALINGFeedback is the most common (and frustrating) problem you'll encounter when doing live sound reinforcement. Feedback happens when a mic "hears" its own amplified sound coming out of a nearby speaker cabinet. As more microphones are added and the overall monitor level increases, the potential for feedback quickly increases as well.

Microphones designed for live sound usually have a tight pickup pattern, so they are more sensitive to sounds coming from the front and will reject sounds coming from the sides or rear. You can increase the mic's volume in the monitor without feedback through careful mic positioning in relation to the monitor.

To position the mics, start with the obvious: make sure the mic is pointed away from the wedge. Because cardioid mics have good rear rejection, you can tilt the mic up toward your mouth, as long as the angle of the mic is perpendicular to the wedge monitor (see Fig. 4a). Hypercardioid mics have a narrower on-axis pickup pattern and less rear rejection. Position the hypercardioid mic so that it's parallel to the stage in order to keep the wedge out of its polar pattern (see Fig. 4b).

USE AN EQAnother crucial tool in the fight against feedback is the graphic equalizer. The graphic EQ should be patched between your mixer's monitor aux out and the power amp that feeds your wedge input. As you turn up the monitor level, you'll begin to hear feedback build. Find the graphic EQ slider that corresponds to the feedback frequency and pull it down. Then turn the monitor level up until feedback begins again. Repeat the process until two or three notes begin feeding back at once. This is the practical limit beyond which feedback cannot be suppressed.

Automatic feedback suppressors can be used in combination with, or as an alternative to, graphic EQs. These devices look for concentrated signal peaks at very narrow frequencies. This allows them to identify the feedback frequency and apply a notch filter to reduce it. When shopping for automatic feedback suppressors, pick a unit with as many notch filters as you can afford. You will also need to decide whether you want filters that must be set to specific frequencies before the performance or ones that are automatically adjusted during your set (some suppressors do both).

FINDING YOUR BALANCEOnce you have feedback under control, it's time to think about fine-tuning your monitor mix. Begin with vocals and quiet acoustic instruments; set aside miked amps for the moment. Don't put drums or bass guitar in the monitors-most small monitor speakers won't be able to reproduce these low-frequency sounds adequately. In most large-scale P.A. systems, the monitor engineer counts on spillover from the main P.A. to provide the lowest of the lows for the musicians on stage. Pumping excessive low end through the monitors muddies up both the stage and audience sound, and at the same time, it reduces the headroom in your monitor chain. Furthermore, putting too many things in the monitor mix pushes the onstage sonic clutter to new heights, quickly negating the advantages of a monitoring system.

Your particular situation will dictate the number and positioning of wedges you need on stage. For example, even nonsinging drummers will need to hear the vocal, both for reference and to gauge their own dynamics relative to the singer. On a small stage, you may be able to position a front-line wedge such that the drummer can hear it as well. Of course, a separate wedge for the drummer is preferable if space and spare equipment permit it.

Multiple wedges can all carry the same monitor mix; in this case you may be able to run as many as three or four stage monitors from the same power amp, as long as the combined load of the connected wedges doesn't exceed the amp's rated specs. On the other hand, if your mixer has more than one available aux send, you could have two or more monitor mixes (for example, one for the lead vocalist and another for the backup singers). This requires an additional graphic EQ and power amp channel for each independent monitor mix.

DRIVING A WEDGEIt's fairly straightforward to get a monitor system working well enough to improve the intonation and timing of a band's musical performance. But that's only part of the story. Having the right monitor mix helps the players blend their performance with that of the rest of the band. This, in turn, will have a major effect on the total musical impact of your performance.

How does the monitor mix fit into the overall sound-reinforcement picture? Let's consider three background singers who are capable of a great vocal blend. What happens if all three of their mics are set to equal levels in the house P.A., but in the monitors one is set much louder than the other two? The singer who hears herself louder in the monitors will, naturally, pull back from her mic until she hears herself in the monitors at about the same level as the other two singers.

But what does this do to the house mix? Only two of the three vocal parts are heard clearly through the main P.A., because one singer has backed off her mic. If you have the luxury of a full-time sound person mixing your P.A., he or she would be able to compensate for this lower-level voice (assuming they were familiar enough with the material to notice that a harmony part was missing).

Unfortunately, many bands must mix their own house and monitor sound from the stage. In this case, it's really important that the relative levels of your monitor mix reflect the mix levels going to the P.A. This helps the entire band balance their own levels on stage, which is your best and only hope for good sound in the house: there is no way that you, as a performer, will be able to second-guess the house mix and make corrections to it from the stage, especially in the heat of the performance.

WEDGE ISSUEStage monitors are not just for groups playing large clubs and arenas. Any time an ensemble is in a situation that requires a P.A. system, monitors will come in handy. With a small investment and a little practice, a monitoring setup will increase your chances of having a successful gig every time you go on stage.

Rudy Trubitt is the author of Live Sound for Musicians and Mackie Compact Mixers, both published by Hal Leonard. Learn more about live sound by visiting www.trubitt.com.

Don't expect your monitor system to shoulder the entire burden. If someone on stage is having trouble hearing one of the amplified instruments, running an extension speaker cabinet off the musician's stage amp might solve the problem. For instance, most two-guitar bands set up with a guitar amp on either side of the stage. The drummer may have difficulty hearing one or both guitars.

Rather than putting the guitar signals in the stage monitors, plug a 1-by-12-inch speaker cabinet into each amp. Place the additional cabinets on the opposite side of the stage, facing in toward the band. This can help everyone hear the guitars without cluttering up the monitor mix.