Technical information

Destructive interference Where two signals, added together, act in opposition to
each other and reduce the signal level. For example, bass from a subwoofer may,
at certain frequencies, bounce from a nearby wall and that reflected signal may, if
arriving back out of phase, interfere with bass still coming directly from the
subwoofer to effectively reduce the output at that frequency. But it is also likely,
at other frequencies, to result in constructive interference.
Digital As opposed to analogue. It is a method of representing real-life signals
(which are generally effectively infinitely variable) by using discrete numbers, usually
binary numbers (a pattern of 1s and 0s). Holding discrete values, rather than the
infinite number of intermediate levels used by analogue, makes digital signals
relatively resistant to distortion and noise. The reason is that if any inaccuracy
creeps in, unless very severe it will not affect the signal enough to throw it off.
Consider a binary system. If all data is represented as either 0 volts or 1 volt,
then it doesn't matter if some interference causes the 1 volt level to be
sometimes 1.1 volts, sometimes 0.9 volts. The receiving module will regard any
voltage as greater than 0.5 volts as 1 volt and treat it accordingly.
Digital audio Any one of a number of systems for recording sound using a digital
representation of the sound. Some digital audio systems are straight forward
representations of the analogue signal. Examples of these are PCM, DSD and
MLP. Other systems take a simple digital signal (usually PCM) and process it
heavily to reduce its size. Examples are Dolby Digital, MPEG audio and DTS.
DIN Deutsche Institut fuer Normung. A German standards body. DIN frequently
appears in specifications to give an indication of how measurements were
conducted, and also applies to a number of connectors approved by the body.
Dipole A loudspeaker designed to offer a diffuse, non-directional sound by firing its
high frequencies in two directions, out of phase with each other, so that a listener
receives few aural clues as to their exact location. To make such speakers work
optimally, they should be placed so that the axis running through the front and
rear tweeters is at 90 degrees to a line drawn from the speaker to listener. This
will maximise the cancellation (see destructive interference) of direct radiation
from the speaker to the listener's position.
Direct sound field A speaker system in which the great majority of the sound that
you hear is coming directly from the loudspeakers, and very little from reflections
from surfaces within the listening space. Direct sound field speakers tend to
deliver a more accurate reflection of the source, and sharper stereo imaging,
than reverberant sound field speakers. Direct sound field sound can be achieved
by choosing speakers with restricted dispersion and placing them close to you.