Technical information

Reactance The aspect of impedance which varies according to the frequency of
the signal it is affecting. Measured in ohms.
Receiver In the stereo world, an amplifier with a tuner built in. Often used as
short hand for home theatre receiver.
Region Code A system built into DVDs that is intended to prevent the playback of
DVDs from one part of the world in DVD players sold in another part of the world.
There are six region codes. The United States is Region 1. Europe and Japan
are Region 2.
Resistance The aspect of impedance which remains constant regardless of the
frequency of the signal it is affecting. In the case of DC voltages, the resistance is
the same as the impedance. Measured in ohms.
Resolution The amount of detail a system is capable of recording or producing.
For digital audio, it is largely determined by the bit depth.
Resonant frequency The frequency at which a system offers the lowest
impedance, allowing the highest power transfer. In the case of physical systems,
it is the frequency at which the vibration is greatest for a given input. For
loudspeaker drivers, the resonant frequencies of the drivers are very important
characteristics to take into account in the design process, avoiding placing them
in the range of operation for higher frequency drivers, and carefully designing the
enclosure to make best use of the resonant frequency of the woofer.
Reverberant sound field A speaker system in which a significant amount, perhaps
most, of the sound that you hear is coming from reflections from surfaces within
the listening space rather that directly from the loudspeakers. Reverberant sound
field speakers tend to have a larger sweet spot, and produce a more rounded
stereo image with greater depth than direct sound field speakers. Reverberant
sound field sound can be achieved by choosing speakers with a very wide
dispersion, such as bipole speakers.
RIAA Equalization Record Industry Association of America Equalization. When
converting an electrical signal to mechanical motion, there is an inconvenient fact:
the lower the frequency, the higher the excursion of the moving part for a given
signal level. This is important in several fields, particularly with LPs. The grooves
of an LP would wobble very widely if the bass frequencies were cut in direct
proportion to the signal. The playing time would, consequently, be very short and
turntables would have a great deal of difficulty in holding their styli in place within
the groove. So before LPs are cut, the signal is subjected to RIAA equalization.
This reduces the bass by an enormous amount (-17dB at 50 hertz), and
increases the treble equally hugely (+13dB at 10,000 hertz). A circuit built into