Absorption (Surfaces)
Absorbs energy because sound can enter its porous surface to be dissipated by being reflected off the material's fibers. In this mechanism, sound energy is converted into a minute amount of heat within the absorbing material.
Acoustic Power Level (PWL)
The total sound energy radiated by a source per unit time. The unit of measure is the acoustic watt. Also known as sound power.
Amplitude Modulation
The amplitude of the carrier voltage is caused to vary directly with the modulating voltage.
Amplitude-Frequency Response (Magnitude Response)
The variation of gain, loss, amplification, or attenuation a function of frequency.
Bottoming
At extreme volumes, when the voice coil smacks into the back of the pole plate it creates a very unpleasant sound -- similar to the sound of snow crunching under foot only much, much louder.
Capacitor
An electric circuit element composed of two metallic plates separated by a dielectric, used to store energy. Note: Capacitance also reacts to AC. While an inductor becomes more reactive at high frequencies, the capacitor becomes more reactive at low frequencies.
Class A
By definition, Class A operation provides collector (output) current during the complete signal cycle (over a 360-degree interval). Because the device is always turned on, the theoretical maximum efficiency is only 50%.
Class AB
In between class A and class B operation is class AB. The collector current occurs for more than 180 degrees of the signal cycle but less than 360 degrees. The theoretical efficiency falls in between class A and class B (50 -78.5%).
Class B
In Class B operation, the bias point is set at cutoff, the output current varying for only about 180 degrees of the cycle. The device is biased with no collector current and therefore no power dissipated by the transistor. Only when a signal is applied does the transistor handle an average current, which increases for larger input signals. Theoretical efficiency is about 78.5%.
Clipping
The occurrence of short term overload in an amplifier. (Geek version: The deformation of the oscilloscope waveform characterizing the output of an amplifier.
Comb Filtering
Comb filtering is the constructive and destructive interference between two similar sounds, but one being delayed relative to the other.
Crossover
The crossover is a circuit that divides, shapes and allocates the high and low frequencies to different drivers. A crossover is used when a speaker system has more than one driver. It keeps the drivers operating in their most accurate frequency range.