Contents: • Microphones • Mixers • Digital Signal Processors • Speakers • Recorders • Cassettes

A sound system can be as simple as a bullhorn, or as complex as a computer-controlled console with sophisticated line array speakers. Yet the purpose of a sound system remains the same—deliver the intact audio signal from the sender to the receiver.

Each component of a sound system must perform at an acceptable level for the system to provide acceptable results. From the input devices (microphones) through control and routing devices (mixers and processors) to gain-staging devices (amplifiers) and on to the final converters (speakers), each step is vital to the whole.

For most churches, upgrading the entire system is only practical during capital expansions. Individual component upgrades are most common, especially just prior to a large Christmas program or Easter play when the need becomes critical. To help guide your church toward the appropriate choices, this section is divided into the major sound system components with pointers and recommendations for any type of worship environment.

Mics are the frontline of any sound system. Without microphones, voices and acoustic instruments would be lost to our ears. Microphones convert acoustical energy into electrical signals that are then altered and amplified by a sound system and finally reconverted back into acoustical energy by a loudspeaker. In essence, mics are small speakers in reverse.

The majority of live-sound mics use either the dynamic or condenser operating principles. Dynamic mics, such as the venerable Shure SM-58, place a pressure-sensitive diaphragm above a magnetic field. A coil of wire attached to the diaphragm moves in conjunction with varying air pressure to create an electromagnetic signal at the output.

In contrast, typical back-electret condenser mics use two electrically charged plates, one fixed and one floating. Changes in air pressure created by sound waves change the distance between the two plates, and a corresponding voltage change is sent from the mic to the downstream components.

It is helpful to consider the dynamic mic as the "male" and the condenser as the "female" of the species. The dynamic male is given to loud noises, is somewhat insensitive, and is simple to operate. The condenser female is focused on nuances, is sensitive to the surroundings, and more complex.

Dynamic mics are perfect for loud singers, guitar amps, and drums, while condenser mics excel at picking up details in a violin or bringing out a distant ensemble. Condensers are best on choir, grand piano, and lecterns, while dynamics are perfect for the youth, testimonials, and outdoor use.

In addition to operating principle, all microphones rely on a specific pickup pattern to convert atmospheric pressure changes to an electrical signal. Omni-directional mics are sensitive to sound from any orientation. They are used for lapel mics and congregational response pickup.

The most common pattern is the cardioid, or heart-shaped polar response, so called because the plot resembles an inverted human heart. The cardioid is most sensitive to energy in front of the mic and least sensitive to energy from the rear of the mic. Cardioids are excellent for stage use since they respond to vocal input on the front while rejecting stage monitor signals from the rear.

Super- and hyper-cardioid mics are simply extreme versions of cardioids with an exaggerated frontal sensitivity and a reduced off-axis (non-frontal) response. However, they do exhibit an anomaly termed lobing that creates some rear sensitivity in exchange for the highly directional pattern. Thus, super- and hyper-cardioids will feedback with a monitor directly behind the mic, making a rear-side monitor placement the best solution. Super- and hyper-cardioids work best in acoustically challenging environments such as gyms or converted bowling alleys.

Every sound begins and ends as an analog signal. However, every analog processing step adds noise to the signal. Digital is simply a temporary state designed to preserve sonic quality or insure repeatability.

Live mixing consoles were exclusively analog until the advent of powerful, low-cost processors made affordable digital consoles a reality. Led by the original Yamaha 01V, the spate of sub-$5000 digital mixers continues to grow.

Digital consoles, though, have two Achilles' heels. The first is reduced instant access control. A single knob strip assignable to any channel replaces the traditional rows of channel strip knobs. While this "e-strip" scheme works well in a controlled studio environment, it fails to deliver the instant reach needed when fighting feedback on Aux three in channel twenty-two.

Improvements, in the form of reduced screen menus, have helped the situation, but the issue remains a concern. Sony's high-end Oxford series and its subsequent trickle-down siblings pioneered the clustering of channel controls in a single place with "jump to" assignment when a channel fader is altered. Yamaha's flagship PM-1D added context-sensitive screen information and on-strip alphanumeric readouts for easy channel identification.

The second weakness of digital consoles has been a dearth of mic inputs. In a live environment, the use of twenty to thirty simultaneous microphones is common. Though a digital mixer advertisement may boast about dozens of inputs, the majority of those inputs are simple line level signals, incapable of handling microphones or advanced routing schemes.

Newer models, such as Mackie's TT24, possess a full array of mic inputs and elaborate routing paths, yet manage to keep the asking price below $7000. The TT24 eschews a fancy control surface in favor of operational usefulness and solid construction. As designers learn to fine-tune their offerings, the digital console will continue to improve.

Unfortunately, even with the dizzying improvements in access and inputs, all digital consoles suffer from the same malady as computers—system crashes. A digital console is simply an application-specific computer with all the benefits and shortcomings of any PC. Just as Windows XP goes down at the most critical moment, so too, a digital console will only crash during the Easter or Christmas extravaganza.

Analog consoles must suffer a catastrophic loss for the signal to go down, while digital consoles are much more vulnerable to the whims of the power company and nature. To meet the need for a robust platform, Digidesign debuted the Venue with the ability to pass signal even when the computer fails. Though its $65,000 price tag limits its appeal, in a church with a ProTools recording suite, the Venue's ability to seamlessly integrate with ProTools may be the key to a workable audio environment.

Currently, the best application for a digital console in the worship arena is as a submixer to a larger analog desk where orchestra and band presets can be recalled instantly or where service formats change several times during a Sunday. Digital is here to stay, but analog will be around for the foreseeable future.

Between the mixer and the loudspeaker the signal must be adjusted, equalized, routed, and amplified. Recently, most of the non-amplifier devices have undergone a digital makeover. Where once the "drive rack" sported rows of graphic equalizers (EQS), a crossover, several signal delays, and the occasional notch filter, now a single digital component resides there with its glowing LCD display. Digital signal processor (DSP) systems (also called loudspeaker management systems, or LMS) house multiple functions in one unit, reducing the system cost while improving performance.

Single-function pieces still exist but their purpose is highly defined. Power amplifiers have become lighter and more powerful due to switching power supplies and increased efficiency. A new trend is toward multi-channel amplifiers capable of powering main, monitor, and subwoofer speakers from a single box.

Noted acoustical consultant and respected system designer R. Bob Adams suggests the two priorities in sound systems should be the room's acoustic signature and the choice of loudspeakers. The grandest sound system falls short when confronted with either inferior speakers or improper speaker location.

Until recently, the standard approach to church speaker design revolved around the central cluster, a tight grouping of speakers above the pulpit area. The keyword was "point-source"—the goal of creating the aural illusion that all sound emanates from a central location above the minister's head. However, the rediscovery of a decades-old concept, the line array speaker, has replaced the central cluster and its cousin, the exploded cluster, in most church vocabularies.

Line arrays use tight vertical spacing of similar elements to create a more-or-less seamless coverage pattern across the vertical plane, while broadening the horizontal coverage beyond a traditional loudspeaker's ninety-degree maximum. The idea is as old as a Shure Vocal Master speaker column. The closer the devices are stacked atop one another, the narrower the vertical dispersion and the broader its horizontal.

In theory, a well-designed line array in the proper room can yield almost identical sound front-to-back and side-to-side across the entire seating area. Naturally, what works well in one room is wholly inappropriate in another, so the inclusion of a veteran loudspeaker integrator is essential to the project's success. No other product in the audio chain is as dependent on location and orientation as a loudspeaker.

The cassette is dying. Its forty-year run has come to an end. Originally designed as a dictation tool, the Philips Compact Cassette overcame its small tape area and slow head speed to reign as the ultimate recording format—until the invention of the CD burner.

As with all digital formats, CD recording eliminates hiss and noise but requires the user to set levels with care, for digital overload is surely an unpleasant experience. Live music and speech contain great variance between loud and soft passages. This extended dynamic range must be reduced if the recording is to be useful. Compressors bring down high levels while leaving low levels unaffected, making them perfect tools to use in front of a CD recorder.

DBX's 1066 and Crest's CPC-1088 are good examples of how a $300 compressor can make a Wal-Mart special CD recorder sound like an expensive studio piece. By taking an auxiliary output from the mixing console and routing it through the compressor and on to the recorder, only those signals that need to be recorded are sent to disc. The recorded levels remain consistent for playback—important for high ambient noise environments like inside an automobile.

If the direct recording still turns out to be too raw, the message can be edited in any number of computer programs, from Final Cut to Vegas. These programs can edit out coughs, awkward moments, and the occasional dropped hymnbook. Some hardware recorders include an internal hard disc drive to lay the recording into for simple editing and duplication, since a master CD does not then need to be running.

Using audio editing software is similar to using word processing software. The incoming audio signal is graphed onto a timeline and divided into sections. Moments as short as a few milliseconds can be removed or lengthened. Complete areas can be relocated within the recording and headers and footers can be added to complete the professionalism of the project. The primary restriction is the time needed to implement the changes and seamlessly integrate them into the whole. However, for any ministry serious about reaching shut-ins or reinforcing the sermon throughout the week, the effort is well worth the time invested.

About the author
Kent Morris engineers live sound for Tommy Walker, Paul Baloche, and Israel Houghton. He has taught technology classes for over a decade with Integrity and Maranatha Music. He has also pastored a church in the Atlanta area and currently is system designer with Cornerstone Media in Atlanta. He has been a member of the Audio Engineering Society for twenty years, and teaches for GMA, NAMM, NAB, NSCA, and LDI. He is a technology consultant to several equipment manufacturers and leads thirty sessions each year on the role of technology in worship.