Live Sound

Back to Basics

Every January, Mix turns the spotlight on Live Sound. In previous years, we have offered articles on such high-technology issues as in-ear monitors (IEMs) 1/01/2003 7:00 AM Eastern

Every January, Mix turns the spotlight on Live Sound. In previous years, we have offered articles on such high-technology issues as in-ear monitors (IEMs) and wireless systems. But, however important these advanced technologies may be for the future of the industry, the reality is that most working sound engineers spend their formative years grappling with wedge monitors and club sound systems. So, this year, we offer a pair of articles that address these fundamentals. Mark Frink writes about getting the most out of wedge monitors, and Buck Moore offers his tips to cope with the unexpected in a club situation.

Techniques to Get the Most Out of Floor Monitors

by Mark Frink

Mixing monitors has its rewards, but the job rarely provides the ego gratification enjoyed by FOH engineers and seldom makes up for the frustrations of having to act as a stage manager. It's no wonder that seasoned wedge wranglers sometimes take on the personalities of Snow White's seven dwarves. Here are some tips on floor monitor basics that can help you achieve inner peace and make sure that the band has a good night onstage. Though this article is intended to help the less-experienced engineer who is faced with an unfamiliar system, veterans may also find a few thought-provoking suggestions.

EQUALIZING WEDGES

After balancing the crossover, there are at least three ways to adjust floor monitors' frequency response. First is the time-honored method of repeating “check, one, two” into a vocal mic and adjusting the sliders on an outboard graphic EQ to maximize gain-before-feedback, while at the same time ensuring that the voice sounds natural; two goals that may sometimes conflict.

A second technique recognizes that, while graphic EQ filters offer a great amount of control, filters spaced at ⅓- or 1/6-octave intervals often don't line up with the exact frequencies that need correction. Parametric equalizers, which feature center-frequency sweep controls, allow you to place filters where they're needed. However, it can be frustrating to adjust a parametric equalizer by ear if you're not used to it, and neophytes often over-equalize, causing even more problems.

With a computer-based FFT measurement, such as Smaart Live, you can easily trace a speaker's response onscreen, which makes precise filter adjustment fast and easy. The computer's display typically shows that even the best speakers have a couple of response peaks that need to be smoothed out a bit; less linear speakers may have big bumps that need a lot of help.

Of course, while most monitor rigs will include graphic EQs on the outputs, not all are equipped with parametric EQs. However, some purpose-built monitor desks, like the Yamaha PM4000M, have built-in 4-band parametrics on each output, and most digital consoles allow you to assign parametrics to the outputs.

Another point in the signal chain where you can tailor EQ is in the “speaker processor.” Many digital speaker processors, which are often used primarily as crossovers, also include filters for frequency correction. Most speaker manufacturers provide preferred settings for their own or third-party processors, and it's common for sound companies to store the crossover parameters in memory for their various speaker setups. Ideally, the system engineer can quickly recall the appropriate setting for a particular speaker, which provides a good starting point that may require little or no final EQ.

ONE EQ DOES IT ALL?

No matter the amount of EQ that is used on the monitor mix bus output when each new channel is added into a mix, it may become necessary to further tweak the channel EQ. We have already seen that there can be several different equalizers active in the monitor system, so one EQ stage may be fighting another. Is this bad? Not necessarily, but there's a simpler way to go if you're not fighting for every last dB of gain-before-feedback and you've got good wedges.

The third method of monitor EQ adjustment is neither widely recognized nor often used — at least by itself. It only works with dedicated monitor boards and a matched set of monitors, because the trick is to simply employ the input channels' equalizer sections. On rudimentary systems or systems where the outboard EQ is locked, this may be the only point where an engineer can equalize, often without the benefit of fully parametric 4-band EQ. Fixed-frequency, two-knob, sweep-only equalizers and shelving filters are not going to solve most problems. But a fully featured monitor console with parametric EQ on the inputs provides the engineer with a precise and comprehensive tool that can be adjusted while standing in the sweet spot, rather than while bending over with a flashlight clamped between the teeth.

As an experiment, the next time you equalize wedges, try just using the 4-band fully parametric channel EQ first. You may find that a few dB of parametric cut — notching the right frequencies in the low mids, high mids and highs — will get you where you want to be, leaving the lowest filter to adjust for proximity effect on a per-channel basis. You can always go back to the graphics if you get in a jam.

SLICE YOUR WEDGES

Despite the name, two-way floor monitors project sound in three different ways. The woofer and the HF driver both have their own characteristics, but in the crossover region, typically between 1 and 2 kHz, both the horn driver and the woofer are contributing. In coaxial designs, the transition can be remarkably smooth; otherwise, the two acoustic centers, each with its own axis, produce interference patterns that can't easily be corrected by time delay. Also, the crossover region is where the woofer beams and distorts, and the wedge's relatively small horn loses pattern control and HF coverage balloons out. There are different ways to deal with these problems. Some engineers add filters to one slope, others use asymmetrical crossovers and others don't even try for flat summing but allow a response gap instead.

High-frequency problems occur around the mass break point of the compression driver. This is in the region where they exhibit the most distortion and where the human ear is most sensitive, which is why 2.5 and 3.15 kHz may be the most exercised sliders on graphic EQs. Wedges with this characteristic nearly always sound better with a little less bite.

When a wedge sounds boxy, it is often blamed on the preponderance of room modes in a live performance space. These standing waves certainly contribute, but the boxy sound more often comes from the response peak (300 or 400 Hz) above the half-space transition, below which the woofer stops enjoying the extra gain of baffle loading.

READY, AIM…

I often see monitor engineers struggling to get their wedges to sound good by reaching for the EQ. A better approach is simply to adjust the speaker's aim. Because the horn's coverage narrows at its highest frequencies and the woofer also “beams” in the crossover region, the floor monitor should point right at the performer's ears if he or she is to hear the wedge at its fullest fidelity. If the speaker is not aimed correctly, the performer will be missing some of the mids and super-highs that are best heard directly on-axis. And misdirected highs will probably end up going somewhere else, like into the mic's back or side. Even worse, they may bounce off of the performer's chest or guitar and back into the front of the mic. One way to visualize the on-axis coverage of the floor monitors is to hold a Mini-Mag flashlight flat against the side of the wedge next to the horn. The light should beam on the point in space that will be occupied by the performer's ears.

Every floor monitor design is based around the designer's choice of vertical angle, which determines how that wedge addresses the performer. And one angle won't work for every performer: Some folks are tall, some are short and others perform sitting down. A simple way to improve a floor monitor's performance is to adjust the vertical angle with a short length of 2×4 lumber under the front or back. Spray-painted or covered with black gaffer's tape, “audio logs” can make the difference between your wedges sounding just okay and sounding great.

LESS IS MORE

Many performers (and some engineers) believe that two ears require two wedges. If one monitor is good, says the prevailing wisdom, then two will be better. However, when two equidistant sound sources point at a single microphone, comb filtering will cancel some high frequencies. If the mic moves, then the canceled frequencies shift. If the original signal source is the vocal mic itself, then getting its level up to near the point of feedback becomes dangerous, because there's a strong chance that the mic will move around. A better solution for vocalists is often a single wedge or, if it needs to get really loud, three wedges, with the center used only for that vocal mic and the outside ones for other vocals or instruments.

But, you say, my artist insists on two wedges on the same mix because it can get just a bit louder. It will certainly look louder to the performer. Here, the solution may lie in the difference between the polar patterns of cardioid and hyper-cardioid mics. A typical cardioid mic's best rejection is at 180° off-axis, while the hypercardioid usually has its best rejection at 135°, lending itself better to double wedges and loud stages. This doesn't necessarily mean that two monitors must be angled in at 90° to match the 135° rejection pattern of the hypercardioid. Angling them out a bit or spreading them apart can improve the way they sound and increase gain-before-feedback.

Finally, remember that adjustments made for one mix can only be copied onto other equalizers if the wedges are matched and sound exactly the same. This is rarely the case, and, even if all of the wedges sound identical, adjustments made for single-wedge mixes will always require additional EQ for double-wedge setups.


Mark Frink is Mix's sound reinforcement editor and a lifelong student of pointing speakers at musicians. Send any comments, suggestions or tips to wedges@markfrink.com.

Tips to Cope with Speeches, DJs, Screenings and Cabarets

by Buck Moore

Most club sound engineers set up and operate sound equipment for bands, often several on any given night. But many clubs also host a range of events that require a different approach to sound system management and, equally important, client relations. Today's club sound engineer may be asked to handle speeches, DJ performance events, film and video screenings, slide show presentations and multi-act benefit shows that can feature a wide range of musical and non-musical acts. This article contains some helpful hints and procedures that should help the club sound engineer prepare for the unfamiliar and avoid audio pitfalls.

SPEECH, SPEECH

Setting up to project one or more voices through an existing and familiar sound system seems like child's play. However, speeches can present unusual problems for an engineer whose only previous experience is with club-level bands. First, a well-known “keynote” speaker will rarely show up for a soundcheck, so the engineer should be sure to test the mics and sound system thoroughly ahead of time. Because the mic check will likely be done in an empty room before the audience arrives and changes the acoustics, a certain amount of guesswork is involved. The important questions to consider are: Will it be loud enough? Will everybody hear and understand the speaker? Will there be feedback? By answering these questions well, you'll cut your work in half.

To make sure that you'll have enough gain-before-feedback, plug in the vocal mic and slowly bring the channel fader up until you begin to hear very mild feedback. Once you've reached that point, bring the fader down by 6 dB and smooth out the FOH response by dipping the lower mids (from about 150 Hz to 500 Hz) to get rid of any boxy vocal sounds. Ask an assistant to read a list of words for you while you walk around the venue and listen. Remember that the human speaking voice generally contains little useful energy outside the 80 Hz to 8kHz bandwidth, and an unnaturally bassy voice will be more difficult to understand than one that is higher pitched. Leave the subwoofers off, and don't be afraid to use the high- and lowpass filters on the channel EQ.

Once you are happy with the clarity and overall level, begin to add other necessary mics. If you know that the room will be particularly dead when full, set up a stage monitor to provide the speaker with some foldback. Of course, the monitor level should be only enough to reassure the speaker that he or she can be heard; set it too loud, and the speaker will probably back off of the mic.

It is essential to have a backup mic in place and ready to go. This provides you with some assurance against equipment failure and, to a lesser extent, poor microphone technique or compromised mic placement. If the guest speaker is to be introduced, you may need to have a dedicated mic set up for this purpose — just make sure that the MC doesn't hand the announce mic to the guest speaker. And mute the MC's mic whenever he or she removes or replaces it in the mic stand.

If you cannot fit a second mic on the rostrum or the speaker will be using a lavalier, a shotgun mic can serve as a backup. Figure 1a shows a shotgun mic positioned for backup should the main mic fail, though the sound quality will noticeably change. Other backup methods include attaching a lavalier mic to the main mic's underside and placing a boundary mic on the lectern. In general, it's best to use only one mic at a time; combining two mics that are equidistant from the speaker will produce cancellation and phase problems. If you decide to use two identical mics for better coverage, such as for a speaker who moves around too much for a single mic, aim them inward at an angle-coincident style (see Fig. 1b) to minimize phase problems. However, unless you have access to a pair of slim, matte-black “podium” mics, a pair of regular cardioids may appear slightly obtrusive and will obscure part of the speaker's face from some of the audience.

In a club situation, the sound person may need to light the speaker. If the speaker is using a lectern, simply put a white sheet of paper on the top surface and point a light at it from above; a clip-on light will suffice if there are no overhead spots. The reflected light will most likely flatter the speaker's appearance and make his or her face visible from a distance. Subtlety is the key, so avoid blinding the talker with bright side-wash lights or bottom lights. Because you have a blank sheet of paper already in place, why not write a note reminding the speaker to speak up and to stay close to the mic?

Once you have determined your mic technique, your levels are ideal and the talker's face is lit properly, you can concentrate on staying alert when the speakers start their presentations. If any speaker's amplified voice is too loud or too soft, adjust it immediately — there is no point in aiming for subtle level changes if the voice is inaudible or deafening. Similarly, EQ changes should be immediate and drastic if necessary. If you can get the voice sounding right by the end of the speaker's first two sentences, then no one will remember that it wasn't perfect to begin with. Bear in mind that an audience will adjust its own self-noise according to the ambient noise level: Set the sound system too loud, and the audience will become noisy and inattentive. On the other hand, if audience members have to strain to hear, they will quickly lose interest.

SETTING UP THE DJ

One may assume that a DJ can be left to his or her own devices, but a prudent venue owner will bring in a sound person to ensure that sound levels are reasonable and that the music sounds good. Most DJs now play back from a variety of sources in addition to turntables and may not have the monitoring setup (or hearing acuity) to compensate for differences among them. Leaving a DJ solely in charge of a sound system can be risky.

If the DJ sets up near the console, the DJ mixer's outputs can be patched into channel line inputs. Those outputs are typically unbalanced RCA connectors, though higher-quality mixers include balanced ¼-inch and XLR outputs. Whichever the case, chances are that the DJ doesn't have the right interconnect cables, so connecting the DJ mixer to the club sound mixer or crossover/amplifier inputs becomes the sound engineer's responsibility. A regular stereo RCA-to-RCA cable and a couple of RCA female-to-¼-inch male adapters will usually work.

Wherever the DJ sets up, he or she will commonly request one or more monitors; wedges on the floor or set at ear level on packing cases should suffice. Setting gain on the sound system mixer's inputs should be straightforward; make sure to leave enough headroom in the system so that sudden peaks from the DJ mixer's outputs won't overload the club mixer's inputs. If possible, have the DJ play a few representative tracks to determine overall levels and EQ. DJs typically drive the sub-bass and the tweeters much harder than a club band mixer, so you may have to adjust the system's overall EQ to match their expectations. Needless to say, if you have system limiters in the crossovers or across the main stereo bus, make sure that they're engaged and set at an appropriate threshold for system protection.

FILM AND VIDEO SCREENINGS

When setting up for a film or video screening, there are five things to keep in mind: equipment location, cable runs, output configurations, connections and output levels. For video playback, the projector should be relatively close to the screen, which should be between the main club system speakers, if these are to be used. With the projector between 12 and 20 feet from the screen, the image should be large enough with plenty of brightness; this is especially important for older videotapes and some film projectors.

Because AC power and signal cables will have to run under the audience's feet, take special care to route them sensibly. The simplest method is to route all cables straight to the nearest wall and then along the wall to the mixer position. This should prevent anyone from accidentally unplugging your AC in the middle of the show. Using gaffer's tape, secure cardboard strips along the length of the exposed cabling and add strips of bright masking tape in X formations to keep the cable covers visible when the lights are low (see Fig. 2). Using cardboard cable covers will keep the cables somewhat protected from equipment rollovers, as well as keep them relatively clean — plus, no tape residue to remove. Most important, well-protected and clearly marked cables will reduce the possibility of equipment failure and/or injury.

Video and film equipment's output configurations are not always straightforward. When presenting a collection of videos, you will most likely find that the producers of the different segments created their soundtracks in different formats; some soundtracks will be in mono on both channels, some will be mono on either the left or right channel, and others will be in stereo. If the VCR has a mono audio out, the soundtrack will come from this single output; hook the output to two mono ¼-inch connectors via Y cable and bring them into two channel inputs — one signal will be the main audio, the other the backup. In the case of a hi-fi VCR, feed left and right outputs to two channels. If you pick only one of the two VCR audio outputs, chances are that the audio will be on the other, leading to poor or nonexistent signal. Avoid combining the left and right into a mono Y cable unless you are sure that the soundtrack will sum to mono properly.

Once all of the cables are in place and tested, double-check all audio and AC connections and secure them as if you would expect a bored child to play with them. All RCA, phono and mini-jack plugs must be secured and not just simply plugged in. Electrical tape holds fast, stretches over contours nicely and comes off easily without leaving a lot of tape residue.

Setting levels and EQ for 1- or 2-channel audio signals from a VCR can be surprisingly tricky; in general, production values will favor the images. This is particularly true for documentary footage, which may have been shot by amateurs with only the camera's built-in mic for sound coverage. For a collage-type video, where scenes from different locations are spliced together in documentary-type style, you may need to ride gain and make frequent EQ adjustments.

I've often had to correct for “boxy”-sounding audio tracks, commonly the result of poor mic placement or a poor microphone choice. This can be easily corrected by cutting 3 to 6 dB between 250 to 500 Hz. To gain some clarity on muffled vocals, try boosting between 5 and 8 kHz, but not too much, because the EQ will also accentuate any tape hiss.

Stay alert during a screening. Murphy's law dictates that if and when you leave the console, there will be a big blast of sound as the image switches from a quiet conversation to a full-out riot. But as long as volume and audio-quality changes are within a reasonable range, the audience will be able to concentrate on what they're seeing and forget about the technology.

CABARETS AND FUNDRAISERS

Perhaps the most demanding club event is the fundraiser or cabaret show. Just about anything can happen at a cabaret: bands, solo artists, singers with backing tracks (on CD, tape or MiniDisc), video shows, ambient noise artists, poetry, comedy acts, conjurers, etc. And the craziness inherent in such a show can be further complicated if the schedule of performers is switched and the music/sound effects cues are just plain wrong. As with most technically dependent events, adequate preparation, legible documentation and easily located spares will decrease stress levels and make for a smooth-running show.

The first thing to do is ask the show coordinator/stage manager (if there is one) for the exact show requirements and running order. Check this with as many of the performers as possible and rewrite the schedule for yourself with incomplete information clearly marked. Work out a mic-input list based on the most complicated act and clearly mark mic stands and cables with unambiguous labels. A set of additional mics on boom arms marked Production #1, Production #2, etc., can help when strange or unexpected musical instruments are added at the last minute. For artists who will be using backing tracks, check the tape cues ahead of time and write the performer's name on each CD or tape, as well as the track numbers to be used.

Solo acoustic performers are common for cabarets and fundraisers, and getting them ready three to five minutes before their time slot doesn't need to be a headache, even if they have limited stage experience. If you sense that any performers are inexperienced or microphone shy, explain why the mics are positioned in a certain way and what the limitations of the miking and monitor setups are. An instrumentalist or vocalist who moves off-mic will drop 6 dB in the mix every time he or she doubles the original distance from the mic (the inverse square law), an imbalance that cannot be easily compensated for at the console without the risk of feedback.

For comedy acts and plays, which are often impossible to mike properly without rehearsals, try suspending a pair of boundary mics above the stage. Results will depend on the performers' abilities to project, but even fairly subtle reinforcement can often fill out the sound adequately. And, most “internally balanced” acts, such as small jazz and classical groups, big bands and choirs, can be reinforced very effectively with only two or three quality mics positioned downstage.


Buck Moore is a freelance sound engineer in constant pursuit of the ultimate live mix. He currently teaches Live Sound at Trebas Institute in Toronto, and is director/sound designer for BAM! Audiovisual. Moore can be reached at bacontrees@yahoo.ca.

January

2015 NAMM Show

Anaheim Convention Center, 800 West Katella Avenue , Anaheim, CA, U.S.

February

Grammy Awards

The Staples Center, Los Angeles, CA, U.S.

March