Some loudspeaker systems have no internal crossover network. They are driven by dedicated electrical processors that perform the necessary signal processing before the signal is applied to the power amplifiers — an active loudspeaker system.

While this should reduce the cost of the loudspeaker system itself (less parts), loudspeakers of this type ultimately cost more to implement due to the required external processor and possibly extra amplifi er channels. Active designs can yield higher fidelity and higher sound pressure level (SPL) than passive loudspeakers.

Even so, a good passive design can provide excellent performance at a lower overall cost, plus it is usually easier to implement than an active loudspeaker system.

The Cabinet
The cabinet and its construction are a major factor regarding the price of a loudspeaker. Cabinets must be strong and stiff. If the cabinet vibrates it becomes a transducer itself, which will interact with the other transducers and degrade the overall system performance. A stiff cabinet requires a lot of mass, a lot of bracing, or both. The trade-off is the weight of the box.

Concrete is an excellent cabinet material, but is impractical for all but custom subwoofer systems. Medium density fiberboard (MDF) is also a good material. It is very dense and low cast, but it is also very heavy and is subject to warping if it gets wet.

Particle board cabinets are cheap, but should be avoided. Plywood is lighter and stronger than MDF, but it can have voids between the layers. Baltic birch plywood is best (11+ layers and free of voids), but it is also the most expensive wood for loudspeaker building.

Composite materials can be very strong and very light, but are also very expensive. Fiberglass is strong and weather-resistant, yet it is difficult to fabricate and therefore much more expensive than wood or plastic.

Molded-plastic loudspeaker cabinets have become common in recent years. They are lightweight and can be made weather-resistant. The initial high tooling costs incurred by the manufacturer are recovered through mass production over many years. This type of cabinet construction is practical for small-dimensioned enclosures, but more rigid materials are required for large boxes.

Loudspeakers that will be flown over an audience must have special rigging hardware (fly-points). They must also be pulltested to ensure cabinet and hardware integrity.

Fly-able loudspeakers don’t look a lot different than ground-stack or pole-mount loudspeakers, but will generally cost a good deal more due to the required cabinet construction, integral fly-points, and testing.

Self-Powered Loudspeakers
I have shown that the loudspeaker is a system of inter-dependent parts. This can be expanded to include the power ampli- fier. Amplifier selection can be complicated, and the ramifications for choosing the wrong one can be disastrous.

This has prompted some manufacturers to incorporate the amplifier and signal processing right into the loudspeaker. These are commonly called self-powered loudspeakers. This was not a practical approach with older amplifier topologies, but modern Class-D amplifiers are relatively small and lightweight, and they are also very efficient. They can be incorporated into the loudspeaker cabinet without undue increases in size or weight.

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