Terminology
 

This should answer most of your question to abbreviations or lingo that some of you new guys dont know.




Acousta-Stuf : Acousta-Stuf is a sound absorption and dampening fiber typically used in sealed box enclosures. Acousta-Stuf is a crimped polymer fiber that was designed to offer a similar performance to long hair wool. This non-volatile synthetic fiber is superior to other materials because it is safe to handle and will not decay with age.

Acoustic Suspension: A type of loudspeaker enclosure that uses a sealed rear chamber to contain the back wave and provide damping of the cone motion. To qualify as an acoustic suspension system, the enclosure must literally be airtight.

Active Crossover: An electronic high or low-pass filter that is placed between the pre-amplifier or source and the amplifier. The benefits of an active filter include removing components from within the speaker, removing the complexities of driver impedances from the equation, and greater flexibility with regard to crossover slopes and points.

Air, Airy, Airiness: A subjective term often used to describe a speaker's ability to reproduce very high frequencies with detail and low distortion. Airiness helps provide an ambient soundfield and is very important to producing a "live" sound.

Amplifier: An electronic device responsible for increasing signal levels. A power amplifier produces the high currents necessary for driving speakers. A pre-amplifier is responsible for increasing the low voltages associated with turntables, microphones, or other low-voltage devices.

Anechoic Chamber: A room that is designed such that the walls absorb all incoming sound waves and reflect nothing back. An anechoic chamber is useful for measuring speakers without the negative influences of the typical listening room. Using an anechoic chamber can provide a superior picture of the theoretical output of a system, however real-world factors such as room gain and floor bounce cannot be measured.

Anechoic Response: The frequency response of a driver or system measured in an anechoic environment. As above, this response does not include any room effects such as room gain, floor, or wall reflections.

Attenuate (attenuation): The reduction in output of a signal. In speakers, a tweeter is oftentimes attenuated to match the level of a woofer. This attenuation can be achieved with series or parallel resistors, but often an L-pad is used to maintain a constant impedance load to the crossover.



Back plate: A steel plate that is on the back of a loudspeaker driver's magnet structure that transmits the negative magnetic pole into the pole piece. A bumped back plate has a raised central portion that helps prevent the voice coil from hitting the plate on the down stroke.

Baffle: The front panel of a speaker where the drivers are mounted. A baffle can either be the front wall of an enclosure, or a two-dimensional plane where a driver is mounted. A baffle is used to separate the radiated front and back waves of a driver.

Baffle Step: An increase in the high frequency output of a loudspeaker as the radiation pattern changes from 4-pi space to 2-pi space. At wavelengths shorter than half the width of a baffle, the waves "bounce" off the front baffle and are reinforced due to reduced acoustic impedance. At wavelengths longer than half the baffle width, the waves no longer are reinforced off of the front baffle and radiate in all directions. The result is a 6dB increase (step) in the output above the baffle step frequency.

Baffle Step Compensation: A circuit that is used in a speaker crossover to "compensate" for the increase in output at higher frequencies due to the baffle step. Typically the change in output across the baffle step is 6 dB. Baffle step compensation can be achieved by using a low-pass filter at or near the baffle step frequency to counter the natural rise. However, this will only be successful in speakers that have relatively low crossover points where excessive attenuation above the baffle step is not a problem. Baffle step compensation can also be achieved by using an inductor and resistor in parallel with a second resistor shunting to ground. Resistor values are generally on the order of the nominal impedance of the driver and the inductor is generally in the .5-1.0 mH range.

Bandpass: A combination of high-pass and low-pass filters that yield a section of flat response with a roll-off on either end. In the acoustic realm, a bandpass can be achieved by using a single driver within a front and back enclosure tuned to different frequencies. In the electronic realm, a bandpass filter is usually used on the midrange of a three-or-more-way speaker to allow only a narrow band to be reproduced.

Bandpass gain: A phenomenon that occurs in electrical and acoustic systems when the high-pass and low-pass sections of a bandpass filter interact with each other. As the passband region of the filter narrows, the amount of bandpass gain also increases.

Bass: The lowest portion of the audio frequency spectrum, generally from 20 Hz to 160 Hz.

Bessel Filter: A type of crossover filter that has a small peak in the response at the crossover frequency. The Q of the filter is slightly higher than average, and phase characteristics are average.

Bi-amp(ing): The ability of a single speaker to be driven by two separate amplifiers. Generally this is accomplished by having two sets of inputs on the back of the speaker, one going to the tweeter high-pass filter and one going to the woofer low-pass filter. It is also possible in 3 or more-way systems by combining the tweeter and midrange into one section, etc. This method can be used to allow separately adjustable levels for the treble and bass, but is not guaranteed to produce positive results.

Bi-pole: A speaker using two drivers facing opposite directions and operating in phase with each other. In home theater setups, bipolar speakers produce a somewhat diffuse sound field, but there is still some direct radiation at the listener.

Biscuit: A small spline of wood that is used to help reinforce a joint. The biscuit is placed into a slot and glued, where it absorbs moisture and swells up. The swelling action along with the increased gluing surface area yields a very secure joint.

Bi-wiring: Bi-wiring uses the same internal layout as bi-amping, but is accomplished by using one amplifier channel with two separate runs of wire to the speaker. There are many claims about the sonic improvements of this technique, but very little scientific evidence to back them up.

Binding Post: The most widely used method of accepting speaker-level connections on mid to high-end speakers. A binding post consists of a metal shoulder with a protruding threaded rod on which a nut tightens down.

Bondo®: An epoxy-based filler traditionally used in autobody repair. Makes an excellent wood filler for speaker building because of its great adhesion to MDF, fast curing time, and ease of sand-ability.

Bucking Magnet: A charged ring-type magnet that can be used to help shield a driver. The bucking magnet is secured to the rear of the motor structure with the like magnetic poles together. This will reduce the stray magnetic field, but will also affect the T/S parameters of the driver.

Bumped Back Plate: A back plate that has a protruding central portion that helps prevent the voice coil from hitting it on the down stroke.

Butt Joint or Lap Joint: In woodworking, a type of joint that connects two pieces of wood by fastening the end-grain of one piece to the face of another. The weakest type of joint, due to the lack of lateral support and the limited gluing surface area.

Butterworth Filter: A crossover filter slope that yields a maximally flat frequency response in the passband with minimal phase shift. Drawback is a shallower slope than other filter topologies.