Air Gap. A narrow cylindrical space in a loudspeaker magnet assembly where the magnetic field is concentrated. The air gap is formed by the pole piece and a circular opening in one of the steel disks of the magnet assembly. The voice coil assembly moves backward and forward inside the magnet through the air gap.

Bobbin. A cylinder of thin, lightweight aluminum, typically one inch in length and diameter, upon which a voice coil is wound.

Capacitor.  An electronic filter that protects the voice coil assembly of a tweeter from damage by high power low frequency signals.

Centering Device. A flexible fabric disc that supports and centers the voice coil assembly within the air gap of a magnet.  The centering device permits the voice coil assembly to move back and forth in the air gap without rubbing against any part of the magnet assembly.

Cone. A concave paper or plastic disc that converts the movements of the voice coil assembly into sound.

Crossover Network.  An electrical circuit that divides an amplifier signal into high and low frequencies for a tweeter and a woofer. The dividing or crossover frequency is usually around 3 kHz. This frequency is not too low to damage a tweeter, and not too high to cause excessive modulation distortion from a small woofer.

Damping. The measure of a loudspeaker’s magnetic and mechanical control over the motion of the cone at low frequencies.  Damping reduces sound distortion and is provided by the intensity or strength of the magnetic field (electromotive damping) and the mechanical stiffness of the suspension and centering device (mechanical damping).

Displacement. The forward or backward distance that a cone or dome travels.

Dome. The sound radiating surface of a tweeter that is equivalent to a cone in a woofer.

Frame. A round concave metal shell that provides a rigid support for all parts of the loudspeaker.

Inductor. An electronic filter consisting of a wire coil (typically 18 gauge wire) that blocks the passage of high frequency signals from an amplifier to a loudspeaker.

Modulation Distortion. A type of sound distortion that occurs in a loudspeaker during the reproduction of high frequency tones, resulting in a harsh tonal quality, especially at high listening levels.

Ideal Enclosure. The smallest size of enclosure that permits the maximum available low frequency output from a loudspeaker.

Pole Piece. A cylindrical portion of the magnet assembly that provides a path for the magnetic field and forms part of the air gap. The pole piece helps to concentrate the field within the air gap to improve loudspeaker efficiency.

Port. A tube that is mounted through a hole in the enclosure.  The port allows low frequency radiation to escape from within the enclosure to reinforce the bass tones that are produced by a loudspeaker.

Suspension. A flexible rubber ring that surrounds the cone.  The suspension centers the cone inside the frame while allowing it to move backward and forward.

Tweeter. A small loudspeaker that is designed to reproduce high frequency tones without modulation distortion.

Voice Coil. A length of thin, enamel-insulated wire that is wound upon a bobbin. The voice coil and bobbin together form the voice coil assembly, which is suspended in the air gap of the magnet. The voice coil generates a varying magnetic field in the presence of an amplifier signal. The voice coil magnetic field is alternately attracted and repelled by the field from the magnet, which pushes and pulls the assembly and cone forwards and backwards.

 

Links to Other Websites

• Joe Wolfe's exhaustive (no exaggeration) Music Acoustics website explores the art and science of sound. A resource for non-technical types (like me), students and teachers.
• How Does an Aircraft Wing Work? Basic aeronautic theory explained in simple Newtonian terms. Become an aeronautical authority in just ten minutes!
• The Disgruntled Film Critic Objective (emphasis here) thirty-second film reviews to help you pick the good ones...and avoid the stinkers.

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