Terminal Cup - A plastic cup, either round or square, that contains the terminal connectors that permits the wire from the amplifier to be connected to the speaker.

THD (Total Harmonic Distortion) - A is a measure of the how much a given audio device may distort a signal through the introduction of added harmonics or overtones. These figures are usually given as percentages. THD figures below approximately 1% are inaudible to most people. Low THD is not always an indication of a high quality amplifier. High THD can be cleaned up by using a a technique called Global Negative Feedback which excessive use of will degrade the sound quality of the amp.

Theile/Small Parameters - The work of Neville Theile and Richard Small. They discovered a method that could predict the frequency response performance, and other characteristics of a loudspeaker system, based on its physical parameters.The three Theile/Small parameters that primarily determine the frequency response of a loudspeaker are Vas (Compliance), Fs (Free-air resonance) and Qts (Response time). A number of other parameters are used to predict how different speakers react to different enclosure size and designs. These parameters are Re, Sd, BL, Mms, Cms, Rms, Re, Q, Qes, Qms and Xmax. The formulas that accomplish this are rather lengthy and complex, and are best left to a computer. There are a number of high quality computer programs on the market that automate the design process of building an enclosure. Check out our Tech Links page for some of them.

Three-Way - Generally referring to a speaker design which includes a low, mid and high frequency driver in the same enclosure working in conjunction with a crossover network to produce a full range of sound.

Timbre - The combination of harmonic frequencies in voices or instruments which give them their characteristic sound quality.

TOC (Table Of Contents) - The digital subcode information that identifies a disc title, indicates the number of tracks, the starting and ending points of these tracks and the total running time of the disc.

Toroidal Coil - An inductor or transformer whose core consists of a concentrically wound ribbon of magnetic material. Often found in the power supplies of higher quality amplifiers. Also used to filter noise on a DC supply line.

Trace - A path of conductive material, usually copper, that conveys voltage or current from one point to another on a printed circuit board.

Tracking Servo - The control circuit used to keep the pick-up over the desired track in disc reading and playback.

Transducer - Synonym for Driver or Speaker. Any electrical device that converts one type of energy into another.

Transformer - An electrical inductive device that can be used to provide circuitry isolation, signal coupling, impedance matching, or voltage step-up.

Transients - A non-repeating sound (such as percussion in music) or an abrupt change of signal voltage. How a speaker handles transients is a good indicator of its performance.

Transistor - An active three terminal solid-state device used for amplification and switching.

Tuned Port - A port opening, radiator, or tube whose size is determined by the volume (airspace) of the enclosure and woofer.

Tweeter - A driver specifically designed to reproduce only the high frequencies (treble) of the audible spectrum. The four most common designs are a cone, horn, ribbon and dome tweeters. Dome tweeters can be a hard or soft dome design.

Two-Way - Generally referring to a speaker design which includes both a low and high frequency driver in the same enclosure working in conjunction with a crossover network to produce a full range of sound.