Finally, the amplified electrical signal is fed into one or more loudspeakers. The loudspeaker acts as a sort of microphone in reverse. A cone or a diaphragm is set to vibrating by the amplified electrical current. Electrical energy is thereby converted into mechanical energy, setting up vibrations in the adjacent air once again with sound waves that are audible to our hearing.

Loudspeakers serve as our final link in reproducing the spoken word. There are many types of reproducers available. We may select column-type loudspeakers for small auditoriums, placing one unit on each side of the stage. These are especially practical for temporary installations. For permanent installations, a distributed system using ceiling-mounted speakers is usually very satisfactory. If the ceiling is relatively low, this system is especially recommended, for it allows all in the audience to sit at approximately the same distance from a loudspeaker. Ceiling speakers should be spaced in staggered rows, their distance apart being approximately one and a half times that of the measurement from the floor to the ceiling. Those loudspeakers closest to the speaker’s stand could be wired for lower power, permitting greater volume for the whole system before acoustical feedback occurs.

When wiring the loudspeakers to the amplifier, they should be electrically matched to the amplifier. This is accomplished by selecting the appropriate impedance tap on the back of the amplifier that most closely matches the impedance of the loudspeaker. Most modern amplifiers provide for what is called a “constant voltage” system for matching multiple loudspeakers. Frequently, the 25-volt or 70-volt output on the back of the amplifier is used. In some countries a 100-volt system is popular. At the lowest voltage it is unnecessary to enclose the speaker wires in conduit. The constant-voltage system requires that a small transformer be installed in line with each speaker to match the speaker to the system. You are now ready to operate your sound system.