I feel that I should restrict most comments on mixing to areas that are peculiar to reinforcement. This is difficult because there is a great similarity to mixing for recording.
Microphone mixing and equalization go hand in hand with microphone selection and placement. The person responsible for engineering/production should have direct communication with and control over the stage microphones and environment.
However, often the person making production decisions will not be too familiar with the requirements and peculiarities of the audio system. For that matter, he may not know reinforcement technology in general.
An understanding should therefore be reached, before the show, about who will do what, and about when and where it will be done.
The system operator will usually be responsible for program continuity, including any recorded music or announcements during the intermission and set changes (“The group will be showing up any minute now, folks!”).
The usual signal processing techniques are used, but exercising extra care in the area of compression, limiting and equalization. These all have severe effects on the amount and the nature of feedback.
On the other hand, “hard” limiting is often used to protect the speakers. The best place for this is after the crossover, as this avoids modulation effects (specifically, the higher energy, low frequencies will not modulate the gain of the highs).
When there arc problems obtaining the desired degree of intelligibility, which frequently occur on the vocal channels, it is recommended that the mixer resist the urge to raise the gain of the respective middle or high frequency equalization. Instead, try turning everything else down, and start to work from there.
To do otherwise is an invitation to get caught up in the circle of increasing high frequency threshold shift, requiring further increase in HF boost. This results in listening fatigue, poor quality sound, and ultimately severe feedback. The combined effects of the hearing loss, due to threshold shift, and of the EQ allow the feedback to get out of control before it is noticed.
For every performance setup, some responsible person should walk throughout the audience areas to determine that the distribution of sound is even in most sections of the room. Any gross inadequacies in dispersion, reverberation, reflection, or phasing can be dealt with before the sound check. The sound system can then be adjusted to taste from the position of the mixing console.
Preparations Prior To The Gig
Some of the recommendations set forth in this article are idealistic, to say the least. Compromises will be made.
Various types of equipment and differing complexities of staging, audience, and artist requirements will demand compromises not to mention money, or the lack of it. This author is of the opinion that sufficient advance notice of some unusual requirement will always help the situation.
If need be, some special equipment can be rented for a single show. Artists’ managers, their agents and soundmen should know what their performance requires in the realm of equipment and of service. They should make some effort to communicate these requirements to the sound system operator at least a week in advance so that the necessary provisions can be made.
Editor’s Note: This is a series of articles from Recording Engineer/Producer (RE/P) magazine, which began publishing in 1970 under the direction of Publisher/Editor Martin Gallay. After a great run, RE/P ceased publishing in the early 1990s, yet its content is still much revered in the professional audio community. RE/P also published the first issues of Live Sound International magazine as a quarterly supplement, beginning in the late 1980s, and LSI has grown to a monthly publication that continues to thrive to this day.
Our sincere thanks to Mark Gander of JBL Professional for his considerable support on this archive project.