PA Speaker: Buying Guide

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Powered Speakers – So, What’s The Big Deal?

The “Big Deal” with Powered PA speakers comes down to convenience and sound quality. Before the affordable active speaker, sound engineers and gigging musicians had to haul around heavy, bulky amplifiers and accompanying cables and speakers – all of which have been replaced with the active speaker! If you’re not familiar with active PA speakers, the idea is that the power and all connections are simply built into the same cabinet as the speaker. This all-in-one design also takes the heat off of those of us who don’t really know how to marry the right power amp with the right speaker, which can lead to degraded sound quality at best and damaged gear at worst.

Bi-amplification Explained

Bi-amplification is the process of dividing a single audio signal into two frequency ranges, which are then sent to two separate amplifiers that in turn drive separate loudspeakers. An active crossover network is used to divide the audio into frequency ranges that are more suitable for the drivers that will be used to reproduce them. Bi-amping also allows the amplifier(s) to be chosen or designed specifically to match the speakers and enclosures. Bi-amping, tri-amping, and beyond have been used in sound reinforcement systems for years and have become quite common in active studio monitors as well.

 

 

Understanding Crossovers

A crossover is a device that divides an audio signal into separate frequency ranges to route to different transducers (speakers, tweeters, horns, etc.) in an audio reproduction system. This is accomplished by running the audio through a set of filters. For example, a 2-way crossover may comprise a lowpass filter that passes a signal with low frequencies to a woofer and a highpass filter to pass frequencies appropriate for the tweeter.

Crossovers can be “passive” or “active” designs. Passive crossovers are usually found inside speaker cabinets along with the speaker components, but can be purchased as outboard equipment also. These often connect to the outside world via a single jack, but sometimes each speaker component also has its own jack in case you want to bypass the passive crossover. Active crossovers are placed before the power stage and route each frequency range to its own power amp and its own transducers. This is where the terms “bi-amp” and “tri-amp” come from.

There are a number of different types of filter configurations used in crossovers and they each produce subtly different results. One of the big variables is how steep the roll-off – or the rate of attenuation – is at the cutoff frequency. Common configurations are 12, 18, or 24dB per octave. Each design has its own strengths and weaknesses, but in general steeper roll-offs are considered better in modern applications.

 

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