Technical information

1080i and 1080p. 720p has a resolution of 1280 lines by 720 vertical lines and
1090i and 1080p of 1920 by 1080. 720p displays each frame in full
(progressively), while 1080i, displays each frame as one of two interlaced fields.
Most High Definition screens will scale whatever source they are fed to fit the
screen but will look their best when fed a source at their native resolution.
In parallel to the introduction of HDTV, two new High Definition DVD formats have
been introduced, HD-DVD and Blu-ray (now the dominant format). Microsoft’s
Xbox 360 gaming console is HD compatible with an optional HD DVD drive.
Sony's PlayStation 3 comes equipped with a Blu-ray drive as standard. HD
camcorders are also becoming available.
Hertz Cycles per second – a measure of frequency. Young healthy humans can
hear from around 20 hertz to around 20,000. Frequencies lower than that can
often be detected by other parts of the body.
Hi-Fi High Fidelity. This is a tricky set of four letters. 'Hi-Fi' is frequently used a
generic noun for any stereo sound system. But it should more properly be
regarded as an adjective, taking due note of the Latin roots of the word fidelity,
which means 'truth'.
Originally high fidelity described a sound reproduction system that gave a more
accurate rendition of the recording than was commonly available. The greater the
accuracy, the higher the fidelity. In absolute terms, the term changes over time -
as audio systems improve, so do those properly described as 'high fidelity'. A very
fine high fidelity system from 1970 would not qualify for the term today.
High pass filter An electrical circuit that impedes signals below a particular
frequency. In other words, it lets signals above that frequency pass through. An
example is the circuit in a home theatre receiver that stops deep bass from going
to a centre channel speaker. Compare low pass filter and band pass filter.
Home theatre receiver A multi-channel amplifier with a digital decoder and tuner
built in. The decoder always provides at least PCM and Dolby Digital decoding,
and almost always DTS as well. A few also incorporate MPEG audio decoding.
Horn loaded driver A loudspeaker driver in which a horn is placed over the front
of the driver. The primary advantage of this is to increase the efficiency of the
transfer of mechanical energy from the driver to the air. However it usually
results in reduced dispersion of sound, particularly for higher frequencies which
tend to be 'beamed' from the horn, and can colour the sound. Nevertheless,
some speaker makers have specialised in using horns, especially Klipsch, and they
are frequently used in professional sound-reinforcement installations. The
increase in efficiency can be quite marked. Klipsch loudspeakers tend to offer