Finding the right loudspeaker for your church can be a daunting task. Each year it seems the manufacturers come up with new designs and updated technology to add to the confusion. The best way to choose speaker cabinets is to consult a number of different sources (other churches, magazine articles, dealers, contractors, etc.) about the products available. But most importantly, listen to the speakers.
Application-specific is a term that manufacturers often use to describe speaker cabinets designed for specific situations. In a concert sound environment, you may change your speaker requirements to provide extended low end and high output. Your speaker selection would be quite different if used to reinforce a traditional choir and speech. Differences in intended application are why not all speakers sound alike even though they may appear to have similarities in design. The changes in sound are the result of different components, crossover design, and the physical size and make up of a cabinet.
While MacPherson may not be the most well-known loudspeaker manufacturer, this Chicago, Illinois-based company has been around for many years and has built a solid reputation making loudspeakers for installations and concert touring. Their PC12 loudspeaker is a two-way speaker with a 12- inch woofer and a one-inch exit compression driver that can be stand mounted or flown. It is an eight-ohm, passive (nonpowered) speaker cabinet utilizing an internal crossover network to divide frequencies between the low and high components. In a two-way active box you need an external crossover as well as two separate amplifier channels. You can use the PC12 with only one side of an amplifier, provided you have between 300 and 500 watts per channel.
I go back to the application-specific comments again because this cabinet fits a certain situation for use in churches. At first listen, this speaker may not be right for everyone. It is designed to have a relatively flat frequency response from 80 Hz to 18 kHz. But this means that you will not find the lowend boost found in many loudspeakers which makes music sound warm. That frequency boost is often designed into the crossover to accentuate the low-end when the components or physical cabinet size do not do so naturally.
MacPherson designed the PC12 cabinet with choirs and speech - specifically talking presenters using lavalier microphones - in mind. In this specific application, keeping the frequency response as flat as possible is important. Indeed, the speaker accomplishes this and provides plenty of gain before feedback–the sound engineers’ constant battle of physics?
Gain before feedback refers to the maximum sound pressure level that can be attained before the sound from the speaker enters the microphone and is amplified a second time, creating a loop that only builds on itself: feedback. Feedback can happen because of a number of factors. Reflections and reverberation are two key culprits in the amount of gain before feedback you will have.
With sanctuaries often being reverberant environments, the reflections off walls or floors can bounce back into the microphone and reduce the gain before feedback. Leaving a book open on the lectern or carpeting the top of it has also been known to reduce unwanted reflections close to the microphone.
Also, each time you double the number of open mics you lose 3 dB of acoustical gain in your system. With four microphones on, the system has a loss of 6 dB before you reach the threshold of feedback.
The design of the PC12 speaker is meant to reduce unwanted frequency boosts or cuts which can also adversely affect the acoustical gain of the PA. Specifically in the vocal range, the speaker responds smoothly, making it easier to minimize the potential for feedback.
After listening to the speaker using recorded voice, live voice using a lavalier mic and recorded music, I connected my Earthworks M30 measurement microphone and using SIA Smaart analysis, I evaluated the frequency and phase response of the cabinet.
SIA Smaart is an acoustical analysis program which evaluates the signal coming out of the console versus what the measurement mic “hears” the loudspeaker doing in the room. The corresponding results are displayed together in a transfer function graph on the computer screen showing phase shift in the sound as well. Phase shift is the timing difference in a signal, expressed in degrees through the frequency range of the speaker. This is an important function because it allows us to measure the reference signal from the console versus how the sound is propagating from the speaker cabinet. Both the frequency and phase response of the speaker can affect the gain before feedback in the system.
I found that the speaker lived up to what I heard when using the lavalier microphone– the frequency response is relatively flat from 125 Hz to 16 kHz. By relatively flat I mean within ±3 or 4dB. At 250Hz, a rise in frequency response gives the cabinet a thick sounding low-mid component which users may find to their advantage in warming up the bottom of the vocal range. Others may wish to EQ a bit of this out. In the primary vocal range between 400 Hz and 2 kHz, the response was flat as can be, with the phase response remaining rock solid as well. Debate can be made on whether you can hear phase shift from a single point source, but in this case the speaker held true to its design and the phase response of the cabinet was smooth throughout the usable frequency range.
Keeping the frequency response flat can mean that the listener is fooled when they first hear the cabinet. So often we are used to speakers that are tuned to boost the low end and make music and instruments sound good. However, those products often do not have a flat frequency response and the phase shifts are dramatic causing the system to lose gain before feedback because of the timing differences in the sound.
Sound reinforcement is a tricky business because people have different opinions on how they want the mix to sound. Some people prefer to have an exaggerated sense of amplification by hearing the mix come from the loudspeaker, as in a loud concert setting. Other engineers prefer a more transparent mix that lives up to the word–reinforcement by allowing the listener to hear exactly what is being said without distracting them with unwanted loudness, unnatural frequency boosts in the speaker, or a loss of intelligibility because of phasing differences.
The PC12 is designed for smooth vocal reproduction and is good for acoustical music where a high degree of sonic transparency is desired. In other words, it is good for amplifying lecterns, choirs, lavaliers, solo singer mics, and smaller musical ensembles but not necessarily for large, contemporary-service bands with higher sound pressure levels and extended low end.
Also, the PC12 is not designed to be arrayed horizontally with other cabinets because of the design of the horn, as well as the rectangular cabinet itself. Arraying this cabinet would create unwanted phase interactions between the horns of each box where they overlap with one another in coverage, again reducing the gain before feedback and increasing unintelligibility.
The box has a solid feel with the heavy plywood construction and metal grill screen on the front, and is manufactured in white or black. If the cabinet took a spill, I got the feeling it would not split open at the seams as cheaper speakers have a tendency to do. When I opened the front grill screen of the cabinet, I noticed the wood reinforcement of the drivers and sides of the cabinet for extra stability. I also liked the fact that the NL4 connectors were mounted at the rear at a 45- degree angle so the speaker cable looks cleaner when it is mounted on a stand.
It is a rectangular, standalone cabinet for use as a mono or stereo point-source PA. The horn coverage is 60 x 50 degrees, defined by the -6dB points at the edges of the horn pattern. The 50-degree splay in the vertical axis does lend itself to an overhead, singlecabinet hang because you don’t have to point the box as far down as you have to with other narrower horn configurations.
At a list price of $1200.00, this cabinet will not be for everyone. But if your application warrants a speaker that reproduces vocals or music accurately and transparently, then I recommend getting your hands on a pair of MacPherson PC12’s to help you make the final decision. You may find that your application benefits from the flat frequency response and the extra gain before feedback.
By keeping the frequency and phase stable through the vocal range, MacPherson designed a product specifically for the church market where critical listening is a part of everyday life in the sanctuary. If this is your application, then you will want to check out the PC12.
Pete Tidemann is principal of Linear Velocity, an audio consulting
firm based in Minneapolis, MN. He can be reached at hanzlander@earthlink.net.
