August 29, 2013, by Alan Hardiman
Mixing is like driving – everybody does it, it gets you from here to there, and it seems like it’s been part of the culture forever. Driving is so pervasive that’s it’s easy to forget there are other ways of getting around.
Most of the time, though, it seems that we get behind the wheel simply out of habit. It’s only on those rare occasions when we deliberately walk to the store to pick up a loaf of bread, for example, that we remember there are other ways, perhaps better ways, of doing the simple things that need to get done.
It’s been said that when the only tool you have is a hammer, everything looks like a nail. This is particularly apt in the case of mixing for staged events. The bias toward mixing that’s pervasive in the industry is traceable in part to the large overlap in the designs of traditional recording, broadcast and live consoles, as well as to schools teaching audio (i.e., “recording schools”) that continue to focus on the art and techniques of the mixdown.
Originating in broadcast and recording sessions involving multiple microphones, and refined in multitrack recording studios producing mono or stereo masters, mixing has become so entrenched in the industry and in the minds of many who dream of working in it that it’s almost as if no other way of working with sound is even remotely conceivable.
But of course it is. Mixing live sound is a relatively recent innovation. It wasn’t so long ago that virtually all pop music acts relied on instrument amplifiers and the acoustic output of the drum kit to fill a venue, the level of the vocals being brought into balance either via a relatively primitive house sound system or a couple of loudspeaker columns at the sides of the stage. Even the Beatles toured that way. It was only during their first tour of the U.S. and Canada in 1964 that the limitations of this setup became apparent, when their then state-of-the-art 100-watt Vox amplifiers were drowned out by thousands of screaming fans.
Sound reinforcement systems evolved rapidly over the ensuing decade, spurred by the needs of bands touring large venues and the staging of outdoor festivals, such as those at Monterey, the Isle of Wight, and Woodstock, where sound system designer Bill Hanley mixed sound for the three-day festival using several Shure 4 x 1 mic mixers.
Amplifiers and drums were miked along with vocals, and consoles soon grew larger as a result, offering more and more input channels. They evolved to include EQ, dynamics processing, and eventually an output matrix section providing the ability to route a variety of inputs to any or all of a series of outputs, a capability that had proven useful on Broadway and in London’s West End theatres.
One significant difference between rock concerts and live theatre, however, is that in concerts, the sound system is employed primarily to achieve high sound pressure levels throughout the venue, whereas in live theatre, the goal is to increase intelligibility. That line is often blurred in big, dynamic rock musicals, such as those of Andrew Lloyd Webber, whose sound designers evolved separate vocal and orchestra mixes, striving simultaneously for clarity in the voices and power in the orchestra.
When the deployment of delayed loudspeakers in the audience area became a staple of sound reinforcement systems in the late 1970s and early 1980s, it became possible to permit lower volume levels at the front of a large venue than would otherwise be required to provide sufficient reinforcement at the rear. For theatres, houses of worship, and corporate events, this is critical: if voices are presented at a level that is significantly louder than their natural level, any attempt to convey an illusion of realism goes out the window. As an added benefit, remote loudspeakers can be equalized to compensate for the inevitable acoustic deficiencies that lurk under balconies and in other less-than-favorable acoustic areas of a hall.
“A matrix section on a console can help manage a complex PA system,” Craig Leerman wrote recently. “I’ll route the main console left and right outputs to the matrix and use the various matrix outputs to feed the different zones and delays. With EQ and delay available on the matrix outputs, it’s easy to tune and time align a loudspeaker zone to the rest of the PA.
“Once all of the various zones have been dialed in, any further overall level adjustments are simply handled via the left and right masters on the console. Using the matrix for this can give both stereo and mono feeds of the program, as well as a reduced stereo image feed.”
For recording or broadcast requirements with a limited channel count, a stereo or mono mix will usually fit the bill, but for the house, perhaps we can employ the matrix to go even further.
As a case in point, consider a talker at a lectern in a large meeting room. Conventional practice would dictate routing the talker’s microphone to two loudspeakers at the front of the room via the left and right masters, and then feeding the signal with appropriate delays to additional loudspeakers throughout the audience area. A mono mix with the lectern midway between the loudspeakers will allow people sitting on or near the center line of the room to localize the talker more or less correctly by creating a phantom center image, but for everyone else, the talker will be localized incorrectly toward the front-of-house loudspeaker nearest them.
In contrast to a left-right loudspeaker system, natural sound in space does not take two paths to each of our ears. Discounting early reflections, which are not perceived as discrete sound sources, direct sound naturally takes only a single path to each ear. A bird singing in a tree, a speaking voice, a car driving past – all of these sounds emanate from single sources. It is the localization of these single sources amid innumerable other individually localized sounds, each taking a single path to each of our two ears, that makes up the three-dimensional sound field in which we live. All the sounds we hear naturally, a complex series of pressure waves, are essentially “mixed” in the air acoustically with their individual localization cues intact.
Our binaural hearing mechanism employs inter-aural differences in the time-of-arrival and intensity of different sounds to localize them in three-dimensional space – left-right, front-back, up-down. This is something we’ve been doing automatically since birth, and it leaves no confusion about who is speaking or singing; the eyes easily follow the ears. By presenting us with direct sound from two points in space via two paths to each ear, however, conventional L-R sound reinforcement techniques subvert these differential inter-aural localization cues.
On this basis, we could take an alternative approach in our meeting room and feed the talker’s mic signal to a single nearby loudspeaker, perhaps one built into the front of the lectern, thus permitting pinpoint localization of the source. A number of loudspeakers with fairly narrow horizontal dispersion, hung over the audience area and in line with the direct sound so that each covers a fairly small portion of the audience, will subtly reinforce the direct sound as long as each loudspeaker is individually delayed so that its output is indistinguishable from early reflections in the target seats.
Such a system can achieve up to 8 dB of gain throughout the audience without the delay loudspeakers being perceived as discrete sources of sound, thanks to the well-known Haas or precedence effect. A talker or singer with strong vocal projection may not even need a single “anchor” loudspeaker at the front at all.
As an added benefit to achieving intelligibility at a more natural level, the audience will tend to be unaware that there is a sound system in operation, an important step in reaching the elusive system design goal of transparency – people simply hear the talker clearly and intelligibly at a more or less normal level. This approach, which has been dubbed “source-oriented reinforcement,” precludes the sound system from acting as a barrier separating the performer from the audience, because it merely replicates what happens naturally, and does not disembody the voice through the removal of localization cues.
Traditional amplitude-based panning, which, as noted above, works only for those seated in the “sweet spot” along the center axis of the venue, is replaced in this approach by time-based localization, which has been shown to work for better than 90 percent of the audience, no matter where they are seated. Free from constraints related to phasing and comb-filtering that are imposed by a requirement for mono-compatibility or potential down-mixing – and that are largely irrelevant to live sound reinforcement – operators are empowered to manipulate delays to achieve pin-point localization of each performer for virtually every seat in the house.
Source-oriented reinforcement has been used successfully by a growing number of theatre sound designers, event producers and even DJs over the past 15 years or so, and this is where a large matrix comes into its own. Happily, many of today’s live sound boards are suitably equipped, with delay and EQ on the matrix outputs.
The situation becomes more complex when there is more than one talker, a wandering preacher, or a stage full of actors, but fortunately, such cases can be readily addressed as long as correct delays are established from each source zone to each and every loudspeaker on a one-to-one basis.
This requires more than a console level matrix with just output delays, or even assigning variable input delays to individual mics, since it necessitates a true delay-matrix allowing multiple independent time-alignments between each individual source zone and the distributed loudspeaker system.
One such delay matrix that I have used successfully is the TiMax2 Soundhub, which offers control of both level and delay at each crosspoint in matrixes ranging from 16 x 16 up to 64 x 64 to define unique image definitions anywhere on the stage or field of play.
The Soundhub is easily added to a house system via analog, AES digital, and any of the various audio networks currently available, with the matrix typically being fed by input-channel direct outputs, or by a combination of console sends and/or output groups, as is the practice of the Royal Shakespeare Company, among others.
A familiar looking software interface allows for easy programming as well as real-time level control and 8-band parametric EQ on the outputs. A PanSpace graphical object-based pan programming screen allows the operator to drag input icons around a set of image definitions superimposed onto a jpg of the stage, a novel and intuitive way of localizing performers or manually panning sound effects.
For complex productions involving up to 24 performers, designers can add the TiMax Tracker, a radar-based performer-tracking system that interpolates softly between image definitions as performers move around the stage, thus affording a degree of automation that is otherwise unattainable.
Where very high sound pressure levels are not required, reinforcement of live events may best be achieved not by mixing voices and other sounds together, but by distributing them throughout the house with the location cues that maintain their separateness, which is, after all, a fundamental contributor to intelligibility, as anyone familiar with the “cocktail party” effect will attest. As veteran West End sound designer Gareth Fry says, “I’m quite sure that in the coming years, source-oriented reinforcement will be the most common way to do vocal reinforcement in drama.”
The TiMax PanSpace graphical object-based pan programming screen.
While mixing a large number of individual audio signals together into a few channels may be a very real requirement for radio, television, cinema, and other channel-restricted media such as consumer audio playback systems, this is certainly not the case for corporate events, houses of worship, theatre and similar staged entertainment.
It may sound like heresy, but just because it’s sound doesn’t mean it has to be mixed. We now have more than the proverbial hammer at our disposal. With the proliferation of matrix consoles, adequate DSP, and sound design devices such as the TiMax2 Soundhub, mixing is no longer the only way to work with live sound – let alone the best way for every occasion.
Sound designer Alan Hardiman is president of Associated Buzz Creative, providing design services and technology for exhibits, events, and installations.