Further Considerations
These days, most powered PA loudspeakers are bi-amplified: they have one amplifier for the woofer and another for the tweeter.
Advantages of bi-amplification include:
• Distortion frequencies caused by clipping the woofer power amplifier will not reach the tweeter, so there is less likelihood of tweeter burnout if the amplifier clips. In addition, clipping distortion in the woofer amplifier is made less audible.
• Intermodulation distortion is reduced.
• Peak power output is greater than that of a single amplifier of equivalent power.
• Direct coupling of amplifiers to speakers improves transient response—especially at low frequencies.
• Bi-amping reduces the inductive and capacitive loading of the power amplifier.
• The full power of the tweeter amplifier is available regardless of the power required by the woofer amplifier.
Loudspeaker cabinets come in both wood and molded plastic.
Wood cabinets are covered with either scratch-resistant heavy-duty paint or durable fabric that’s often called, in slang, carpet.
Molded plastic cabinets have also proven durable, can feature attractive styling, and are often lighter than their wood counterparts.
For example, a quality 12-inch, 2-way model with plastic cabinet might weigh about 25 pounds, while it’s wood counterpart could be double that figure. (You can come to appreciate lower weight after several nights of muscling loudspeakers on stands.)
Some plastic cabinets, however, have a tendency to “leak” low frequencies or resonate, possibly degrading both frequency and time response.
Most cabinets include a pole cup on the bottom that accepts a 1-3/8-inch or 1-1/2-inch pole for mounting.
The pole cups are vertically aligned, with some having a second angled cup to aim the loudspeaker down toward the audience when raised.
Two models in the new QSC Audio KW Series offer a proprietary Tilt-Direct pole cup mounting system.
A turn of a dial engages a 7.5 degree downward tilt of the loudspeaker, directing more of the acoustic energy toward the audience.
Moving & Mounting
Manufacturers of portable loudspeakers typically provide stands, either included or available as an option, and of course, these work well for the vast majority of applications.
Be vigilant about stands – they should be constructed of metal (usually aluminum), offer a solid tripod base and a secure collar, and be rated to comfortably handle more than the weight of the loudspeaker.