Where's It At

I recently sat in the audience for a live performance that had everything we've come to expect from an excellent modern concert sound system. The tone and balance of the instruments was correct; the dynamic range was supported without distortion (not even limiting); and the instruments and voices were articulate. Yet there was one aspect of the sound that was wholly missing - localization. While the performers were directly in front of me; the sound was entirely from the extreme right side of the stage.

In the more distant seating locations of venues that seat more than 5000 people, the sound from a concert loudspeaker system and the view of those tiny little performers seem to be in alignment. Unfortunately, most of those who've paid for better seats (and can see the performers without using opera glasses) must cope with the sound coming from one side of the stage. In smaller venues (soft-seaters and the like) this phenomenon is even more likely. We have reached a plateau in sound reinforcement systems. The next step, providing localization, is rarely taken. To provide an aural stage that matches the visual one requires a new level of complexity to the task of concert sound.

Only a small number of seats in any venue are equidistant between the left/right FOH loudspeaker system. These lucky listeners can enjoy the phantom centre image that can mimic the visual location of the performers. Those less fortunate, but usually 70% to 90% of the audience, will hear the sound from only one of the two channels. In all but the smallest venues, the arrival of the sound from the more distant FOH stack will too late to generate the phantom centre image. Instead, the auditory system (in the listener's head) will ignore the sound from the far side, interpreting it as a late echo. Extreme panning of specific instruments to one side will cause the balance of the mix to vary with seating location (except for those lucky few in the middle of the venue). Adding delay to individual instruments can widen the listening area where the localization "works" but has a tendency to create flamming and other detrimental effects.

Interestingly, there is one sound source which does not always appear only from the nearest loudspeaker system - reverb. The lack of correlation between the two channels of a stereo reverb will prevent the auditory system from assigning the source of the sound exclusively to the nearer side. The result is not a solution, instead, it too points to the lack of attention systems have given to creating the sound stage of a good home stereo system. For the attentive listener, the reverb will appear to decay into two distinct points that recede behind each of the left/right loudspeaker arrays. While not the type of deficiency that will cause massive refunds at the box office, it is a glaring example of just how far we need to go to create a complete and involving form of concert sound.

Even stereo sound reinforcement systems must provide coverage of the entire venue from both the left and right loudspeaker arrays. Using one array to cover only 1/2 of the audience reduces the system to a simple split-mono array. As this concept seems to be so simple and yet so commonly misunderstood, is there any hope that sound reinforcement systems will be developed that can overcome the limitations of even the best left/right array designs?

Just as home stereo was eventually incorporated into stereo sound reinforcement systems, the awareness that home theatre systems will generate in sound envelopment will need to be reflected in the concert sound system of the future. While numerous systems have experimented with adding arrays around the audience (Pink Floyd springs to mind), these were used as special effects and did not enhance the localization of the stage performance. It takes much more that another array or two to generate suitable localization for an entire audience. This has been done in some live theatres, where the budget was sufficient to allow more sophisticated loudspeaker configurations. Since the mid-70s, Delta Stereophony has addressed the issue of sound localization in a few of the live theatres in Europe. While this may not the solution to touring concert sound, the underlying principles should be considered as we look to expand the capabilities of concert sound systems.

The audience for a live concert should find the sound and the source (presumably a performer) share a common location onstage. Reverberation should surround the audience and not decay towards the stage to tiny points behind the loudspeakers. The experience of a concert should envelope the audience in the same way as the great concert halls. Audiences currently accept a two-dimensional concert sound experience, but they deserve better. We should be ready for the day they demand it.

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