Meridian Audio Speaker - Manual (Page 4)

range of loads, and so on. The common
method of dealing with these possibili-
ties is to give a power amplifier four
times the current delivery capacity it
needs; and give it and its power supply
the ability to handle the strange loads
likely to be encountered in use and
abuse.
Engineering for the unknown inevitably
means over-engineering. But in a prop-
erly integrated active system, however,
each part of the system, including the
amplifiers and power supply, can be
designed specifically to provide the
power required – no more, no less –
and into a known, carefully defined
load. This can obviously improve effi-
ciency and reduce the need for over-
engineering. Thus such a design does
not have to be more expensive than a
conventional passive approach. It can
certainly be more efficient, and more
effective.
But there’s more. Imagine we are listen-
ing to a piece of music that includes a
bass part and cymbals, and that to
replay this accurately at a chosen level
on a two-way system we want to see a
not unrealistic voltage of 20v peak at
the terminals of both the tweeter and
the woofer. To do this with a passive
system, even ignoring losses in the
crossover, the driving amplifier needs to
develop 40v peak.
For a 8-ohm system, this requires an
average power of 100W (by Ohm’s Law,
the power is equal to the voltage
squared divided by the impedance). In
the equivalent active system, with a 1v
line level input, a pair of 25W amplifiers
will do the same job! (See Fig.3.)
Extend this thinking to a three-way sys-
tem, and three 25W amplifiers in an
active configuration will do the same
job as a 250W amplifier driving a pas-
sive system.
page 4 Meridian Loudspeakers: The DSP Path The Meridian Papers - 1
COMPOSITE INPUT, ˜1V PEAK
HF POWER
AMPLIFIER
LF POWER
AMPLIFIER
ELECTRONIC
CROSSOVER
COMPOSITE INPUT 40V PEAK
LF DRIVER
20V PEAK
HF DRIVER
20V PEAK
PASSIVE CROSSOVER
LF DRIVER
20V PEAK
HF DRIVER
20V PEAK
Fig. 3: Considerably less power is needed to
deliver the same voltage – and thus the same
sound level – from an active system than a pas-
sive one.
Digital Audio:
Music to the Ears
➤ ...Hence the crystal clarity of good digi-
tal sound: no detail lost, no noise added.
Paramount among audiophile truths is
that music’s electronic journey to our ears
should be as short and unadorned as pos-
sible; this preserves the fragile nuances of
live performance. This is why, for exam-
ple, audiophiles have long rejected ana-
logue tone controls, correctly seeing them
as electrical mazes where musical sub-
tleties are lost or rearranged.
Yet the typical purist hi-fi is hardly pure.
Rather, it’s a confusion of components
with varying reactive properties, tangled
together through a rat’s nest of electrical-
ly whimsical cables. Each piece lengthens
the path and damages delicate harmonic,
phase and other relationships that con-
tour music.
The amusing irony is, these boxes and
cables are generally assembled for tone
control: each piece chosen for how its
voice changes the message.
Why not simply replace the whole corrupt
chain with one transparent digital link,
particularly if the music source is digital
already?
At Meridian, that’s exactly what we did.
In essence, we decided to convert the sig-
nal from a source into digital form as
early as possible and at the highest level
of quality (if it wasn’t already), then
maintain that signal in digital form as
long as possible before converting back to
analogue (although the part of our hear-
ing system from middle ear to brain is
actually digital, analogue pressure waves
carry the sound from a loudspeaker,
through the air, to the ear). So in a com-
plete Meridian system, the signal is only
converted from digital to analogue imme-
diately before it enters the amplifier.