Ultrasonic - Referring to frequencies above the range of human hearing, commonly considered to be 20 kHz and up. Ultrasonic frequencies in the signal path can sometimes cause harmonic distortion in audio components that are audible and affect the quality of sound produced.

Unison - In music, when two or more tones are sounding at the same frequency or pitch, they are said to be in unison with one another.

Unity Gain - Refers to a device condition which does not change amplitude of the signal level. This setup allows a device to be plugged into a system without changing its overall levels.

Unloading - The tendency of an enclosure to produce no spring or pressure on the woofer, usually in a vented box. Unloading makes the cone acts as if it is not in a baffle, producing an uncontrollable over-excursion of the woofer cone causing it to oscillate out of control. The result is low power handling and can cause woofer damage.

VAS (a Theile Small parameter ) - (Volume Acoustic Suspension) Refers to compliance. A volume of air in an enclosure (measured in liters or cubic feet) that has the same resistance characteristics acoustically as the speaker's total suspension. It specifies the optimum internal volume of the enclosure.

Vd - Maximum linear volume of air the cone will move. Calculated by multiplying Sd times Xmax (measured in cubic meters or centimeters).

Vented Enclosure - (Ported Enclosure) Any enclosure design with ports. Ported enclosures can offer higher efficiency and increased woofer control (at the tuned frequency). For details and more enclosure types see Woofer Enclosure Designs.

Voice Coil - The voice coil is generally comprised of enamel coated copper wire wrapped around a former. It is connected to the bottom of the speaker cone. When current is applied to it, the voice coil creates a changing magnetic field. The direction of current determines whether the coils moves in or out of the magnetic field in the gap of the speaker's magnet. this moves the cone. producing sound waves (click here for Speaker parts diagram).

Voltage - The difference in electrical potential between two points in a circuit. It's the pressure or push behind current flow through a circuit. The unit of voltage is called the "volt," named after Allesandro Volta

Voltage Drop - The amount of energy consumed when a device offers resistance in its circuit. Measured in volts at the point of resistance, calculated by using Ohm's Law (E (voltage) = I (current) mulitplied by R (resistance).

Volume (sound) - The most common word used to specify the degree of relative loudness of sounds. It also pertains to the function on many electronic devices that is used to control the loudness.

Volume (speaker enclosures) - The measurement of the amount of air space enclosed behind a speaker that functions as a resonance chamber.

VOM (Volt-Ohm-Meter) - Also called a multimeter. A device that measures voltage, resistance (ohms), and amperes.

Watt (wattage) - A measurement of real power. The product of voltage and current in a resistive circuit. In speakers, wattage is a term that indicates power-handling characteristics in dealing with electrical voltage inputs from the amplifier.

Watt's Law - P = E x R where P is Power (in Watts), E is Volts and I is current. This illustrates that an increase voltage or current will produce more power.

Waveform - The waveform of a signal is a depiction of its instantaneous voltages versus time.

Wavelength - The distance between one peak or crest of a sine wave and the next corresponding peak or crest. The wavelength of any frequency may be found by dividing the speed of sound by the frequency.

White Noise - Random noise with equal energy per frequency is called white noise. Each ascending octave contains twice as many frequencies as the next lower one, causing a significant "build up" of energy in the higher octaves.

Windings - The wire that is wound around the former or a bobbin to create a coil. Generally, any coils in a voice coil, transformer, motor, instrument pickup or an inductor.

Woofer - Also called subwoofer. A speaker made to reproduce the lower range of the audio spectrum (bass), usually 200 Hz and down.

Wow - Wow is a relatively slow variation in the frequency of reproduced sound caused by slow speed variations in records, tape recorders, etc. Pitch fluctuations of one or two per second are classified as wow, while more rapid variations are called flutter.