How to Select Speakers
By Buck Waller

When you stop to consider the most important aspect of a worship service, it becomes amazingly apparent that nothing is more important than the sound you hear. Even the best sermon would be lost without sound that is full, clean, and clear.  

Here are some of the major decisions that need to be considered when looking at this all-too-important decision to improve your sound system.

The speakers are the most important aspect of your live sound system. If budget is driving the decision on a new sound system (and there are very few cases where this is not the driving factor), don’t overlook this point. If you do a comparison between a system with excellent signal processing including the mixer and other electronics coupled with mediocre speakers vs. a system with excellent speakers and mediocre signal processing, the system with excellent speakers wins for sonic performance every time.  

More Bands Are Better
The typical speaker system divides the sound spectrum into multiple bands. Some speakers are two-way, others are three way, and few are four-way designs. The reason for dividing the spectrum into multiple bands is that a single speaker simply cannot cover the entire audio spectrum from 20Hz to 20,000Hz.

Most professional speakers are two-way, meaning the audio spectrum is divided typically at 1 to 1.5KHz, which is about the midpoint of the audio spectrum. With a two-way design, you have a woofer that covers the sound for the lows and a tweeter or compression driver that covers the high portion of the spectrum.

Higher-performance systems will include a separate speaker to cover the critical mid frequency portion of the spectrum, thus allowing better clarity in the critical mid-band part of the spectrum. What few realize is that a woofer cannot simultaneously reproduce, with any efficiency, the pounding lows and the critical mid-band portion of the spectrum.

In reality, when a paper cone speaker is reproducing deep bass frequencies, it cannot simultaneously reproduce the mid-band frequencies, and the result is that the mid frequencies will be modulated by the low frequencies. This side effect is called intermodulation distortion, and the result is a huge loss of mid frequency clarity.

It is important to understand that the mid-band portion of the spectrum is where all of the clarity and intelligibility of the spoken word comes from. If you compromise the mid range performance of a system, you lose more than you may think.

A few systems available are designed with four bands, giving each band a smaller portion of the spectrum to cover and thereby further improving the definition and clarity of the system. It goes without saying that the more bands a speaker system has the more expensive and difficult to design the system is. This is why most manufacturers only offer two-way and three-way designs. 

Active or Passive
In recent years, numerous companies have started to offer active or powered speaker systems. This is the wave of the future and where the cutting-edge speakers are focused. 

The advantage of the active speaker is that the system is matched in terms of having the exact amount of power required to power each band of the speaker cabinet. A second advantage is that most of the passive speaker cabinets include internal passive crossovers.   A passive crossover used in the passive cabinet is typically a second order design providing only a 12db per octave slope at the crossover point.

By contrast, an active design uses an active crossover with higher order crossover slopes of 18 to 24db per octave. This translates into better rejection of the high frequencies in the low band output and better rejection of the low frequencies in the high band. This further reduces the intermodulation distortion of the system improving its clarity.

Yet another advantage of the active powered speaker is that micro equalization can be easily incorporated into the internal electronics to improve and flatten the frequency response of the cabinet. The active powered speaker will cost far less than the passive cabinet by the time all of the external power amplifiers and signal processing are purchased for the passive cabinet. This provides a definite cost vs. performance advantage for the powered speakers. They are also more easily installed with less runs of wires to external amplifier racks.

Headroom Is Critical
Once you select the speakers that are right for the room, be sure to determine how loud the system needs to play to meet the needs of its intended use. Never select speakers that will be driven to their limits in normal use. By designing the system with adequate headroom, the system should provide years of trouble-free use.

I cannot stress this point enough, but you should nearly double the power output of what would be required. At some point the system may be driven to its limits, but for typical use, the system will not be running at the maximum output, which will also improve the clarity and fidelity of the system.  

The performance of the system chosen will ultimately be determined by a combination of the above factors. The fidelity of the system will be better with speakers that deliver extremely flat frequency response and low intermodulation distortion. Add to this good headroom, and your system will deliver in all areas of clarity, fidelity, impact, and long-term reliability.

Buck Waller is chief executive officer of ISP Technologies, LLC, www.isptechnologies.com.