Paul White looks at practical monitoring alternatives for gigging bands.

Pop music relies on a mix of normally incompatible elements. For example, in an all-acoustic world, the vocalist and acoustic guitarist would be completely overwhelmed by the drum kit. It's only since the advent of amplification that all these disparate elements have been brought together with no need to take account of their natural, relative levels. In the studio, we have few problems, because we can exercise absolute control over relative sound levels, but on stage, there are still a few niggling difficulties to resolve. The electric guitar, bass, and keyboard, for example, can all be amplified to any practical level to balance the drums, but there is a limit to how much amplification can be applied to vocals before feedback becomes a problem. And, because miked drums sound quite different to the unamplified kit, drummers also tend to go through the PA system for all but the smallest gigs.

To avoid vocal feedback under these kinds of conditions, it is necessary to design and operate the PA system so that as little sound as possible finds its way back to the vocal mic — and that usually involves keeping the main speakers well forward of the performers. This presents the vocalist with something of a problem as he's no longer able to hear a thing he's singing. Hundreds of watts of backline amplification only feet away from a singer with an equivalent natural output of only a few watts also means that the singer can't hear him/herself and so tends to sing out of tune. This was exactly the situation at the end of the '60s; bands were playing gigs in large stadia with no foldback monitoring. Something had to be done — the wedge floor monitor was born.

NIGGLING MONITORS

Whatever form of monitoring system is used, it is likely to be driven from the pre-fade foldback sends of the mixing console, although larger touring systems have the added sophistication of a separate monitor console, usually operated from the side of the stage. Separate monitor consoles and the systems in which they operate can be quite complicated and will be covered in a later article. Most people operating in the real world of the 'Gnome and Sprocket' lounge bar have to make do with pretty rudimentary foldback.

The general principle behind a floor monitor is that if you position it in the 'blind spot' of a cardioid vocal mic, some of the vocal mix can be directed back at the singer without increasing the risk of feedback too much. Indeed, we looked at the setting up of such monitors earlier in this series and concluded that a position behind a hypercardioid mic and to one side at an angle of around 45 degrees was about right. How well this works in practice depends on what nearby walls and other obstacles are present to reflect the sound from the monitor into the vocal mic, and also on the directivity of the monitor itself. There's little use in putting a 12-inch speaker in a box and then adding a cheap piezo-electric tweeter, because the directivity of the 12-inch driver will be reduced to a tight beam at the higher frequencies. Not only does this make it less likely to be heard from the singer's general position, it also increases the risk of a beam of high energy sound being reflected back into an open microphone.

Although it costs more money, the only way to do the job properly is to use a monitor with an integral crossover and a decent high frequency driver. Better still, use an active monitor with active crossover. A more typical budget system probably comprises a 12-inch driver complemented by a small horn-loaded, high frequency unit driven from a passive crossover and a separate power amplifier. I only mention the power amplifier, because I've heard reports of people who've bought a powered mixer, plugged monitor cabs directly into the foldback output socket — then created merry hell when they realised they needed an amplifier to go with it!

Even with a well-designed monitor, the risk of feedback is increased, because an amplified version of the vocal signal is being directed back into the general vicinity of the microphone. Feedback will always start to build up at just one frequency where the various parameters of directivity, room resonance, and system frequency response conspire to provide most gain. If you've applied any EQ boost to the vocal, then the boosted section of the audio band is especially vulnerable to feedback.

The situation can be improved by using either a graphic or a parametric equaliser in the monitor feed to apply cut in the frequency bands that are causing problems, but this relies on the expertise of the user for its success. Some graphic equalisers are now available with LEDs above the sliders, which help pinpoint troublesome feedback frequencies, making setting up a lot easier. It is important not to try too hard to notch out all the feedback frequencies using a graphic EQ, because you'll probably find that you've also notched out most of what you wanted to hear in the first place! If you keep turning the gain up to find the next feedback frequency, you'll just keep going until all faders are at maximum cut. Instead, just set the system gain so that ringing starts, then cut the worst offending bands by a few dB.

More recently, companies such as Sabine, ARX, Shure, and Roland have developed dedicated feedback suppressors, which automatically identify the frequencies that are causing trouble and apply appropriate filtering (Sabine FBX-2020 was reviewed in the January 1997 issue of Sound on Stage; ARX AFW-1 in February 1997; see also Sabine FBX-Solo review, p.86). These devices have two main advantages over simple graphic equalisers: firstly, they set themselves up automatically during the soundcheck (by turning up the gain until feedback starts), and then additional filters hunt down and take out feedback that may occur during the set. Secondly, the filters used in these devices tend to be much narrower than those used in conventional graphic equalisers, which means more cut can be applied in more bands without significantly affecting the overall PA or monitor sound.

"There is a limit to how much amplification can be applied to vocals before feedback becomes a problem."

MONITOR POSITIONING

For all this technology, perhaps the most important factor — other than the quality of the monitors — is where you put them, especially when working in small venues. From my own experience, I have found that in typical pub venues, where there may be insufficient room for floor monitors to work properly, it can be more effective to use just a pair of monitors or spare small PA cabs to cover the whole band and position these either on top of or just behind the main PA speakers, pointing backwards towards the opposite corner of the stage area. This effectively catches the whole band in the crossfire, and because the distance from the monitors is greater than usual, the sound is better dispersed before it gets reflected. This is pretty much the same principle as sidefill monitors in a large PA rig, but on a smaller scale. Figure 1 shows this setup.

In a larger PA scenario where all the band, rather than just the vocalist, have monitors, the setting up becomes a little more complex as not only do the vocal monitors have to be positioned to avoid feedback, everybody else's monitors have to be arranged so as not to direct too much sound into the vocal mic, or the overall vocal sound through the PA will be seriously compromised and the engineer will have less chance of setting up a workable balance. In such a system, it is more likely that each monitor will have its own power amplifier and be fed from a different pre-fade foldback send. This enables different performers to hear different mixes.

MINI MONITORS

Another practical approach is to use a much smaller monitor, still designed for good dispersion, and mount it on top of a mic stand very close to the person using it. These monitors are similar to miniature hi-fi speakers; something like a JBL Control 1 or equivalent would be ideal for small gigs because of its small size, high power handling and robust construction. Mic stand fittings are available for these speakers, and several other manufacturers are now designing compact speakers in a similar physical format. Figure 2 shows how a standmounted monitor might be positioned.

Although they lack the low bass response of large floor monitors, this is no disadvantage for vocals and may actually help by preventing unwanted low frequency sound being fed back onto the stage area. Again, in very small venues, this type of speaker can also be placed behind the main PA speakers and directed back towards the performers. The small physical size of the speakers makes them easy to position precisely, and I have used a similar system on several occasions with a high degree of success.

IN-EAR MONITORS

My first encounter with in-ear monitoring came many years ago when Simon Bateson designed a low power monitoring system for Shirley Gray, which comprised a low power amplifier driving in-ear phones of the type used with personal cassette players. This was all hardwired, and the phones were not custom fitted as Shirley point blank refused to allow Simon to bring his mastic gun full of silicone bathroom sealer anywhere near her ears!

Since then, in-ear monitoring has become big business, with radio links, custom-moulded earpieces, sophisticated limiters, and large invoices. The advantages are several, not the least being that almost no sound finds its way back to the microphone. Furthermore, the in-ear pieces help exclude unwanted noise from the stage, enabling the performer to monitor at a lower, and potentially less damaging, level. And in the small venue, it is equally important that the audience are not hearing more from the stage monitors than from the main PA!

Being small, these pieces are more or less invisible in use and offer the added advantage that even performers working very close to each other can have quite different monitor mixes without conflict. As you might expect, the bass response is a little limited, so they won't satisfy the drummer who insists on 2kW of sidefills, but in all other respects, the concept is a good one. For more details on in-ear monitoring, see the review of Garwood's System 3 in November 1996 and 'In-ear Monitoring Enlightenment' in February 1997 issues of Sound on Stage.

SUMMARY

Even in very small venues, some form of monitoring is desirable, but trying to use large wedges in a tiny pub can be disastrous. As stressed earlier, whatever monitor type you go for, it should be properly designed with even dispersion characteristics, otherwise it will cause far more problems than it solves. If you don't want to buy extra gear, then the simple expedient of using two wedge monitors or 1 by 12 PA cabs as sidefills is often enough to get by, and if small speakers on stands aren't too much of a visual intrusion, the stand mounted mini monitors are very useful for performers who don't need to move around too much. In-ear systems have a lot going for them, but I'm told they take some getting used to, and of course, the initial investment is quite high as it includes the radio links and limiters.

Next month, I'll be turning my attention to the various types of microphone used in live sound, along with a few hints on how to pick the right one.