Sound Essentials: Understanding Indoor Environments

A significant majority of music gigs are held in indoor environments. In order to achieve the best possible results indoors, it is helpful to keep some important fundamental principles in mind. Here, in no particular order (because they're all very, very important) are some things you should always keep in mind when mixing sound indoors.

Not Everybody Can Hear the Same Thing

This isn't a recording studio. A very large proportion of your audience will hear only the speaker they're in closest proximity to, so lose the stereo panning. When you pan an instrument away from center you don't so much spread the instruments across the stereo field as attenuate them on one side or the other. In fact, a lot of pro sound techs always run in dual-mono mode for this very reason. While you're at it take a walk around the room when the band is playing and make sure you can hear all of the instruments proportionately from most of the seats in the venue.

Reflections Are the Enemy

When you surround the stage with four (or more) walls and a ceiling, usually of random length and height and built without giving acoustics more than a cursory thought, you end up with sound reflecting off all the surfaces and back into the listening field where it wreaks havoc on your mix and equalization. Bass reflecting back can cancel itself out (phase cancellation) and absorb all of your available power even as you're trying to get the bass to come across. High frequency sounds come back out of sync with the source creating audio clutter and in some particularly cringe-worthy situations can cause dreadful feedback problems. Overall your mix loses clarity and punch. Because of this you want to situate your main front-of-house speakers in such a way as to reach the most number of seats possible. You want every seat to be covered by direct sound from the mains and close enough for the direct sound to be greater than the reflected sound coming back to it. If the room is deep you may need time-delay speakers further out into the room in order to adequately cover the seats towards the back. The time delay must be carefully set to synchronize the auxiliary delay speaker with the FOH speaker or your own auxiliary speaker could become another virtual reflection!

Keep the Audience From Hearing Stage Spill

Outdoor gigs give the musicians a great deal more freedom when it comes to volume levels and stage monitors. But when the band is playing inside it is common to have the stage itself surrounded by three walls which collect all that stage volume and shoot it back at your audience with some nasty unintended changes in EQ! If the sound tech is battling with stage spillage as well as reflections it can become nearly impossible to achieve a clean, balanced mix because they can't control what the audience hears. Stage amps and monitors are at best a necessary evil (from the sound tech's standpoint), so do everything possible to remove them from the Front Of House equation. You may want to consider using a Personal Monitoring System to eliminate stage spillage altogether. The EM900 In-Ear monitor system is a good choice to consider.

Getting great results in an indoor environment takes skill and knowledge. By keeping these concepts in mind when designing your indoor sound system, you will ultimately deliver better sound at more modest levels. And when the music sounds better you tend to get more leeway on the volume levels too! What tricks and techniques do you use to address these fundamental issues? How successful have they been for you? Let us know in the comments.

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