Tech Feature

In part one of this series on generators (FRONT of HOUSE, June 2013, page 50), we investigated some underlying details behind Ohm’s law, and that led to investigating when and why current flows in electrical circuits. We then investigated two key concepts in power distribution: bonding and grounding. We showed that bonding — not grounding — creates the primary low-impedance path for fault current in the circumstance where a ground-fault event occurs. In this second article on portable power distribution, we build on the concepts in part one and investigate generator grounding and bonding in light of the existing 2011 National Electrical Code (NEC).

Generators, and portable power distribution in general, are central to professional audio. Electricity is a powerful means of transferring energy; it is the lifeblood of all pro audio gear. While electricity is ever-present, it is rarely discussed technically in print, in part because of the liability that accompanies its underlying power.

Over the past two years of FRONT of HOUSE, we have covered substantial ground with respect to subwoofers. Whether on the specifics of setting up a basic cardioid array or on how to design your own vented box, we have presented several nuts and bolts articles on the ever-important bottom-end that keeps sound reinforcement exciting.

This installment is very much in keeping with the previous practical articles on subwoofers. I am suppressing my inner egghead tendencies towards discussing topics like “phaser summation in the far-field,” or “radiation impedance,” and instead will look at a number of subwoofer configurations as they were implemented in the field of real gigs. We will briefly overview each configuration and discuss the implementation, and the goals behind the implementation.

In the early 1980s, there were no real solutions for musicians hearing onstage. With the support of the Who’s Pete Townshend, H.E.A.R.® (Hearing Education and Awareness for Rockers), a San Francisco-based non-profit organization, was instrumental in conducting the first public information campaigns on music hearing conservation throughout North American and worldwide media with MTV, PBS, BBC, Time magazine, Rolling Stone and many others.

Virtually everything about our pro audio world acknowledges the existence of multiple channels of audio and, most commonly, stereo channels (i.e., left and right). Nearly every piece of audio gear provides both stereo inputs and outputs. At concerts, there are almost always left and right speaker arrays. Essentially almost all music playback material is in stereo. This month, let’s take a look how we localize sound, and how that relates to the traditional use of the stereo configuration. We will consider stereo’s advantages, limitations, and place in the pro sound environment. We’ll also discuss how sound technicians can shape their mix to get the best overall results for the majority of the listening audience.

Last month, we looked at conductivity and electricity, the lifeblood behind our industry. Without electricity, and conductors to direct it, there would be no professional audio. We discussed what defines electrons, electric and magnetic fields, and how electrons moving inside of conducting materials give rise to resistance and the famous Ohm’s law equation, V = IR. That article was focused on the internal effects of electrons inside the crystal lattice of a conductor. This month’s article now turns to the realm of how the electric and magnetic fields characteristic of electrons influence several other aspects of the conductors we use in professional audio.

This month, we’ll take a look at wire and conductivity, the electronic lifeblood behind our industry. In a rigorous sense, wire is metal that drawn through a sequence of ever-shrinking dies until it exists in fine, conductive form. If we relax that definition slightly to include any conducting element in electronics, like those on a circuit board or behind a touch screen, we have hit on a key piece of how virtually all audio equipment operates. Without electricity, and conductors to direct it, there would be no professional audio!

For the last four months, this column has focused on the physical behavior of horns and the drivers that are attached to them. We intentionally tried to present these subjects with enough technical meat to be interesting even to very experienced pro sound practitioners. This month, we step back and re-examine frequency response, something that’s common in pro audio, and displayed on most equipment datasheets.

One mic to hear them all… if only that were possible. Area miking is an art, but also a curse in sound reinforcement circles. A choir, an orchestra and the occasional bluegrass group who saw it on O Brother, Where Art Thou? Not a good idea. But moving to the topic at hand, here are some things to think about when miking a group.

Once upon a time, the very idea of recording the band and capturing multitrack performances from the FOH position was unheard of — a nearly impossible task. Analog recorders — while today worshipped in the studio for their thick, “phat” sound — were never really suited for life on the road, being somewhat fragile, and also limited to a 33-minute record time on a 10.5-inch (2,500-foot) reel of tape. That said, there were some pioneers, like Ron Wickersham (also co-creator of the Grateful Dead’s famous/infamous wall of sound) who modified early Ampex decks to take 14-inch reels to capture the Dead’s 1972 European tour.

Miking Unamplified Instruments Onstage

Larry Cumings is hardly a newcomer to the art of mixing and miking acoustical instruments. This Grammy Award-winning engineer spent nearly a quarter of a century on the road doing FOH with the David Grisman Quintet and has been the audio producer and FOH engineer for the acclaimed Strawberry Music Festival for 30 seasons. Held in a large campground at 4,600 feet, high in California’s Sierra Nevada Mountains just outside of Yosemite National Park, the event takes place during the Memorial Day and Labor Day weekends each year, with the three-day festival offering a non-stop lineup of bluegrass, folk and other styles of acoustic music.