On the surface, it appears to be a simple question: Should the sound system in my church be designed to support stereophonic or monophonic sound? Ask a layperson and they will most likely tell you that stereo is better. However, ask a professional audio designer and you might get a more technical answer than you bargained for, because there are staunch proponents of each audio method for houses of worship.
In the mono camp, proponents argue that mono systems have naturally better intelligibility and cost less. Stereo devotees adamantly maintain that the stereo experience is key for modern worship and that well-engineered stereo systems present only a marginal difference in cost. With even the experts divided, knowing something about the technical aspects of audio design can help you better understand the debate and, more importantly, allow you to see where advantages might lie in choosing one method over the other for your church.
The Room
A good place to start is knowing how to interpret some of the popular design methodologies that professionals favor. According to David Ellis, president of Ellis Pro Media in Renton, Wash., visual factors are a good starting point. “It’s most important to see what the room might lend itself to,” he says. Ellis speaks from experience. As the son of a pastor, Ellis was trying his hand at fitting sound systems to rooms when he was still in high school. He was a full-time music pastor for 11 years before starting his audio business 10 years ago. Experience has shown him that some room designs present problems to the sound designer. “When I see a particularly wide room with a low ceiling height, I know immediately that sound alignment issues will present themselves,” he says.
When rooms become particularly wide, they become more difficult to cover from standard left and right speaker positions. For Ellis, software analysis generally supports his expectations from what is visible in the room. To make the decision about whether or not a system will be stereo, even before considering cost and staff ability, Ellis depends greatly upon his observations to tell him about what percentage of the room will get a good stereo image. “To take it further, you have to ask whether or not it is worth installing multiple stereo fields when they are likely to introduce many time alignment issues,” says Ellis. “We don’t force it.” Ellis believes that many church audio designers tend to think carefully about frequency response and coverage, but miss critical time alignment issues that can impair intelligibility.
To better understand Ellis’s comments about time alignment and how it can impact audio for worship, let’s look to the basic definitions of mono and stereo systems to see why some designers favor a mono system for [various] rooms.
Mono
Monophonic describes a system where all the audio signals are mixed together and routed through a single audio channel. This doesn’t mean that the system is limited to one loudspeaker source. Mono systems can have multiple loudspeakers, and even multiple widely separated loudspeakers, but the signal information for mono should not contain level and arrival time/phase information that would produce directional cues.
The most common mono systems designs include single channel center clusters, mono split cluster systems, and distributed loudspeaker systems. Devotees of mono systems can easily support their claims that a mono design can be implemented in full-bandwidth, high-quality systems and are able to reinforce both the spoken word and music, but the big advantage to a mono solution is intelligibility. Without the properties inherent in stereo signals, sounds from [a] mono source reach each seat in the room at essentially the same sound level. This uniform signal arrival improves intelligibility.
Stereo
Audio expert Chuck Walthall logged 16 years as a busy audio contractor prior to starting his design consulting firm, Walthall & Associates Inc. in Pensacola, Fla. With more than 30 years in church audio, Walthall says that for his clients the question of stereo or mono naturally evolves from his concept of “what’s desired and what’s required.” Walthall reminds us that we listen with our brains. “Sound,” he says, “is simply how the brain interprets the physical stimulus. Our ears act as transducers that receive pressure waves that, in turn, send electrical impulses to the brain. And that is what drives the design.”
"When I see a particularly wide room with a low ceiling height, I know immediately that sound alignment issues will present themselves."
David Ellis
President, Ellis Pro Media, Renton, WA.
Walthall maintains that stereo could be achieved anywhere, but it is a near impossible feat in many rooms due to the shape of the seating area. As to what’s best for worship, according to Walthall, it’s a combination of what the client desires and what the church requires. However, when the client wants stereo and the room shape doesn’t favor it, things can get complicated fast.
True stereophonic sound systems are characterized by two independent audio signal channels. But that’s only part of the sonic picture. For true stereo, the signals that are reproduced need to have a specific level and phase relationship to each other so that when played back, there will be an apparent “image” of the original sound source. For many, a true requirement for a stereo design is where there is a need to replicate the aural perspectives of a performance; for example, to localize instruments or performers to an area on stage. For this reason, stereo is a very common requirement in theaters, along with other locational techniques, like including a center channel to enhance vocal performance. These techniques can work in churches, too, but require a knowledgeable staff to mic and mix multiple channels effectively.
It is important to note that a mono signal that is panned somewhere between the two channels does not have the requisite phase information to be considered a true stereophonic signal. While artificial level differences between two channels (panning) can simulate a positional difference, this is a simulation only—not a true stereo image.
Coverage
Some audio experts maintain that good system design, mono or stereo, requires that the entire listening area must have equal coverage. For stereo, the entire listening area must have equal coverage of both the left and right channels, at essentially equal levels. This is one reason why proponents of stereo for worship contend that the price of a stereo implementation is only marginally higher than a mono system. According to Armando Fullwood, executive director of WAVE in Harrisburg, N.C., the big savings promised by mono systems don’t justify the decision to give up on stereo.
“Stereo,” Fullwood says, “is the way we like to listen to music and it’s key to the worship experience.” With both a mathematical bend as a designer and an artist’s point of view having performed as professional bassist, Fullwood can find no compelling reason to design a mono system for contemporary worship. “Mono may be easier,” he says, “but it is not the way we listen to music and, with our process, stereo isn’t any more expensive.”
The experience of the WAVE team is that a well-designed system—mono or stereo—must provide the same equal coverage. In fact, designing only stereo systems is a part of the firm’s core values. “WAVE has always stayed the course to build the best stereo systems,” Fullwood says. He asserts emphatically that the unique design features of their installations are both cost effective and provide speech intelligibility equal to that of mono installations.
The fundamental challenge of stereo is to have everyone in the room hearing the same stereo content the same way, but, as we’ve seen, that can become very complex given an awkward room design. As rooms become more restrictive, the "sweet spot" between two sounds sources at the extremes can shrink to a small number of seats in the center of the room leaving the majority of the audience to either side hearing only part of the stereo program. Additionally, for a stereo system to work properly, it must have the correct absolute phase response input to output for both channels. This means that a signal with a positive pressure waveform at input must have the same positive pressure waveform at output. A classic example is the striking of a drumhead that produces a positive pressure waveform at the microphone on stage and a similar positive pressure waveform in the room. Without proper phase, level and arrival differences (inter-aural time delay), the audience won't hear a stable stereo image. Communicating that stereo image accurately through a stereo system to an audience’s ears can become a serious challenge when a room’s architectural design and acoustical properties aren’t in your favor.
When the room gets complicated, Ellis uses his experience with speaker selection and placement to help him navigate around the structural and acoustic issues in a room. “Line array technology and software,” he says, “are very important to help handle certain situations.” Ellis aims to make the largest part of the room true stereo. Knowing what parts of the room can’t be covered practically allows him to implement a design that employs mono outfill speakers. “If we can design a room to be 80% stereo,” Ellis says, “any zones outside the stereo field would get a mono sum of the left-right mix so everyone in the room can hear everything.” As with all responsible system design, effective signal processing and tuning are key to Ellis’s many successful implementations.
Client Factors
Deciding on one system design over another isn’t just about technology. Many client factors play into the decision, including who will operate the system and how it will be used. According to Walthall, “A good designer needs to look at how people will use the system and what’s really needed.” Walthall’s experience working closely with church leaders and technology partners would indicate that the decision to go mono or stereo is generally based on more than just the budget. “How music is used for worship and the need for intelligibility of the spoken word are high on the list of most churches’ desires for their new sound systems,” he says. “For many, in fact, it’s both,” he contends. “That said, budget always remains the biggest challenge.”
Walthall has also observed that most churches approach an audio system design expecting a stereo sound. “I ask them to tell me why,” he says, “but not to talk them out of it. We can surely do it, but let’s first make sure we understand true stereo imaging.” As the discussion continues, Walthall says that you generally “see the wheels start turning” as people consider their needs and what type of system would be most advantageous to them. One question Walthall uses is, “How many out of a hundred of your congregation are going to benefit from one type of system or the other?” Then, he says, it often comes back to budget and who will be operating the system.
Other Solutions
If, in fact, the argument for stereo vs. mono audio systems for churches is really a question of music experience vs. intelligibility of the spoken word, then systems pioneered for stage performances in theaters that utilize left and right along with a center channel would seem to be a good choice for worship. Left, center, right (LCR) systems, while used for worship, present their own unique challenges. For one, the mix engineer must clearly understand, at all times, which signals must be routed to which loudspeakers, and which signal routings will create problems. It’s important to note that not all room shapes support a center channel implementation. Cost may also become a critical factor with LCR implementation since all three loudspeaker systems must each provide coverage of the entire seating area while maintaining level and directional cues.
Thinking outside the box, there are other clever ways an audio system designer can create an extended listening area for stereo coverage by using infill loudspeakers and effects. To create a stereo image, an infill speaker can be positioned to provide coverage of an area that may be inaccessible from the left or right loudspeaker mounting position. Essentially, the infill box shoots a signal over from the opposite field to create the stereo image where it would not be available otherwise. As an example, left and right infills could be implemented near the center of a wide room. Fed separately with a signal delay so that for people in the right side of the room, the signal from the left infill would arrive at the same time as the sound from the left side would have if it could have reached that location. Careful speaker selection, as well as the level and delay setting of infills, are all quite critical. If infills are too loud or timed incorrectly they will detract from the image the rest of the audience hears. DSP systems that allow a matrix of signal delays to be developed for each input are particularly handy for implementing infill systems, but, obviously, the complexity of design and operation of these unique systems are not for everyone.
The WAVE team designs stereo systems employing a unique, multiple-position platform in order to create an experience for worship that is natural and immersive. “Systems, even the most complex ones, are simply a sum of their parts,” Fullwood says, “but all those parts have to be carefully orchestrated.” Such systems imply both a high degree of technical expertise from those who will operate them, as well as a good deal of control in terms of system design. An advantage the WAVE team reports is that the company takes charge of all the touchpoints of the audio experience for its clients. They insist upon control of all finished materials, room shape, ceiling design, tuning of the system, and voicing of the room, as well as the acoustic materials used to create the right acoustical balance of sound energy absorption, diffusion and reflection. When it all comes together, the team has created what Fullwood believes an audience can perceive: a sense of space.
Which is best?
It’s likely the debate about stereo vs. mono audio systems for worship will continue into the foreseeable future. As with many questions about sound systems, there is no one right answer. A popular convention for church audio designers for some time has been that a well designed mono system will satisfy more people than a poorly designed or implemented two-channel sound system. Poorly implemented systems will always be trouble, but attitudes about stereo (both for cost and intelligibility) may be changing. For example, at larger churches where the music is part of their identity, stereo seems to be a “must have.”
“For 90% of my current business,” says Ellis, “stereo is a requirement. That’s not necessarily the case for smaller churches where other aspects of worship may be a priority, but it certainly is for larger churches where the quality of the music has stepped up.”
Whether it’s for new construction or redesigning audio systems in an existing space, a new audio system represents an opportunity to improve the worship experience. While the sound designers we spoke with for this article had varied approaches to audio design, they shared two important views: First, that the best audio design for any facility is the one that will work effectively for the programmatic, architectural, acoustical and financial constraints at that location.
Secondly, whether you determine your audio needs to be stereo or mono, the best partner to help design a sound system for your house of worship is someone who has experience designing a room that is similar yours and who is willing to take the time to understand your style of ministry.
