Perspectives and Perception

by George Petersen
in Editor's Note

Just as in real-life, everything in audio seems to revolve around perspectives. For example, you might have the perspective that a new line array, some extra subwoofers or a new console would be an important upgrade to really make a difference in the audio presentation. And you’re probably right. However, your ultimate boss — whether it’s a tour/show promoter, the board of directors at a venue or governing council at a house of worship — may have an entirely different perspective.

In fact, in each of these scenarios, there might be someone who either doesn’t appreciate your outlook or comes from the camp of “these speakers are too big” and “we really don’t need/can’t afford this, anyway.” And if not that, then it’s someone (set designer/decorator/administrator, etc.) telling you that the speaker placement you’ve selected won’t work because it disturbs the “look” or creative flow they had in mind. Here again, two differing perspectives are at odds.

Here, Where You Hear

Perspective also becomes a fine line regarding the FOH engineer. Often placed in the rear of the house (ROH), a FOH mixer must always be aware that any presentation (concert, worship service, political speech, whatever) surely sounds a lot louder in the front rows of the house than at the rear of the house, where the FOH engineer makes the ultimate decision about what SPL the show takes place at. This is not necessarily an easy choice to make, as there may — and usually are — other factors at play. For example, there’s some discussion on this topic in this month’s feature on Maroon 5, where the background 108 dB ambience of screaming fans makes it pretty difficult to mix a show at a comfortable level of 90 to 95 dB’s.

Another point comes up when you’re mixing from an under-balcony position, where you may not even be able to hear the main PA, and the zone you’re in is fed mostly by small side- or ceiling-mounted speakers. This is addressed in our feature on the new system installation at the Warner Theatre in Washington D.C., where the geometry of the line array hang was set up and intended to reach the under-balcony seats (and last-row ROH mix position) from the mains — something that was certainly appreciated by the venue’s house mixer, Ishai Ratz.

Of course, the under-balcony issue is not so pretty in many venues. This month, David Morgan begins a two-part series on choosing and using near-field studio monitors to help the FOH engineer in difficult acoustical environments. The might range from situations such as under-balcony positions or simply as a reference source for creating and storing mixes, presets and channel EQ/DSP selections during pre-production rehearsals. At least the good side here is that arenas and hockey rinks don’t typically have under-balcony seating, although they do have their own set of acoustical challenges.

Left/Right/Mono or...

Now if you’re looking for a real challenge in sound reinforcement, the issue of creating a stereo image is one that’s rarely addressed, although our resident scientist Phil Graham examines this very topic in this month's Tech Feature.

But in any discussion on this matter, the size and geometry of the venue (particularly the width-to-depth ratio) and other factors, such as seating arrangements, all come into play, as well as the design of the PA array. The latter can vary from a simple L/R pair of full-range cabinets to a complex array with hangs of multiple coincident stereo pairs covering individual zones. Again, there are no easy answers. Audience members seated at the far edges are probably not getting much of a stereo perspective in those locations, and the FOH mixer that caters a mix to the centerline may be ignoring large sections of the listeners.

Even an array of stereo pairs feeding multiple zones can fall short to people between those zones, who may be subjected to a reverse stereo image when their right ears hear the left-aimed cabinet serving people to their right and vice-versa. Once you add a few more complications into the equation — such as time-delayed reflections from the various channel/array feeds and direct sounds emanating from a loud stage (instruments and wedges), the issue becomes rather complex. And we haven’t even touched on things like incorporating a center cluster, the effect of front fills, subwoofer placements and the like — all of which can affect the stereo perspective.

For a completely different take on the stereo issue, check out the Installations feature on page 34. It details a group of researchers and engineers from Stanford University’s CCRMA, who developed a 22.4 surround rig for the new Bing Concert Hall to recreate the ambience of Hagia Sophia, a massive 1,500-year-old church in Istanbul, Turkey, for a concert of Byzantine chants by famed vocal ensemble Cappella Romana.

The Flip Side of Stereo

The stereo process really begins at the source, the mics (and/or direct feeds) and with the console panning/routing. And to bring up an entirely new can of worms, before any FOH engineer creates a mix, some time must be spent planning out the stereo routings. A stereo mic pair (X-Y, M-S, ORTF, spaced pair or any variants thereof) — whether used on a piano or on drum overheads, does create a left/right signal. Yet when hard-panned and spread over a 40 foot stage, this can create a fairly strange stereo image, where the hi-hat or bass piano keys are suddenly thrust into the far right speaker, and the ride cymbal/treble piano comes out of the left. This may not exactly jive with the placement of instruments on the stage itself, yet this stereo scheme is commonly used in venues every day. It’s not necessarily right or wrong in any particular case, but is just an example of another element to consider in your mix.

As for me, sometimes a wide, hard-panned, stereo-miked Leslie upper rotor is just plain fun, even if it’s far removed from anything resembling a natural stereo image. And real or not, we need a bit of that every once in a while.