Speakers Systems Overview
The last element in line between the sound source and the listener in a sound reinforcement system is the speaker system. While these are often referred to simply as speakers or cabinets it is important to realize that these are speaker systems. The part of the speaker system from which the sound emanates are the various drivers in the system but the enclosure and, if a passive system, the crossover network all must work together in the system to produce good full range sound.
The simplest form of speaker system would be one wide range driver mounted in an appropriate cabinet to which an audio signal is fed. This would work but speakers perform their best over a specific range of frequencies. In general larger speakers perform better at lower frequencies but roll off as the frequency in increased. Smaller speakers behave in the opposite manor and are subject to damage if low frequencies are applied. Speakers designed to cover the whole audio frequency spectrum generally incorporate two or more specialized drivers to cover the full range. There must be a frequency dividing network incorporated to send the appropriate signals to the drivers designed to handle those frequencies.
The enclosure or cabinet is also part of the speaker system. The enclosure is most needed for the low frequency driver. It allows the driver to work efficiently and project the sound. It also provides convenient mounting locations for the other components in the system. The enclosure must be optimized for the selected low frequency driver to provide smooth low frequency response. Other drivers in the system need to be selected to compliment the low frequency driver and extend the frequency response to provide a balanced full range sound. There is a science to the design and construction of a good speaker cabinet.
In a multi-way speaker system there must some method to divide the incoming frequencies so that the proper signals are applied to the proper driver. In a passive speaker system there is an internal passive crossover network to handle the job. Active speakers require an external active crossover network and a channel of amplification for each class of driver. In a passive crossover part of the power applied to the cabinet must be dissipated in the crossover to allow the network to work. Active systems apply the full amplifier to the selected driver.
There is an industry trend toward powered speaker systems. In a typical powered cabinet there are the drivers and a channel of amplification that supplies the required power to each driver. There is also an active crossover that divides the frequencies applied to the amplifier channels and often some signal processing to shape the sound to the requirements of the drivers. A matched column of powered speakers handles the crossover, system control and amplification for the system to provide full range sound with minimal need for external processing.
For concert and large event sound the line array speaker systems dominate the industry. A properly set up line array system can deliver a more even volume distribution over a large area. The individual enclosures are designed with wide horizontal dispersion but very narrow and controlled vertical dispersion. The speakers covering the farthest areas of the venue are played louder than the closer listening areas. Using several zones with the now familiar 'J' hang configuration allows for this even distribution.
A good quality speaker system is much more than just six pieces of wood slapped together with holes cut in one face in which to mount the drivers. For best quality sound the cabinet and all the components must be matched and designed to work together to provide smoothe rich full range sound.