Technical information

3 way loudspeakers A loudspeaker which divides the incoming signal into three
different frequency bands (normally through an electrical circuit crossover) for
distribution to three drivers, normally, a bass, a mid range and high frequency
tweeter.
4 way loudspeakers A loudspeaker which divides the incoming signal into four
different frequency bands for distribution to drivers. It sends high frequencies to
the tweeter, upper middle frequencies to a small midrange driver, lower middle
frequencies to a larger midrange driver, and the lowest frequencies to one or
more woofers. It is possible to have as many ‘ways’ as you want, but the
crossover becomes increasingly complex.
5.1 The number of channels of audio in a modern movie. The '5' refers to full
range channels: moving clockwise, left front, centre front, right front, right
surround and left surround. In Dolby Digital, DTS and MPEG 5.1 formats, each of
these five channels is capable of a frequency response covering the full audible
range (up to 20,000 hertz) and one sub bass channel. Enhancements of the 5.1
channel surround system appear in both Dolby Digital and DTS. The Dolby Digital
version is called Dolby Digital EX 6.1 while the DTS version appears as either DTS
ES 6.1 Discrete or DTS ES 6.1 Matrix. The additional channel is intended to sit at
the rear of the room (although two speakers are recommended, even though the
same signal is provided to both). This provides a greater localization of sounds
from the centre rear. This is a very useful enhancement in cinemas where much
of the audience are sitting off-centre, but in normal rooms with a small number of
viewers, it is much less important.
6.25mm jack See Jack plug.
A
AAC Advanced Audio Coding - a lossy audio encoding scheme used, for instance,
by iTunes / iPod.
A/V Audio/Visual. Most TVs and PCs have outputs to allow high quality sound to
be produced (through additional amplifiers and loudspeakers) to enhance the
entertainment value of films, music videos and TV programmes.
AC Alternating Current. An electric current that reverses direction regularly.
More generally, AC is also used to describe voltage sources in which the polarity
of the signal reverses regularly. Power distribution networks use AC because it is
relatively easy and cheap to alter the voltage (using transformers) yielding