22
The rejection ratio achieved is described in minus dB
. The CMRR of a system
follows the formula 20Log(V
output
/V
input
). In other words a CMRR of –
40dB
means that all garbage entering the unit will be made 100 times smaller. The
piece of equipment with poorest CMRR will effectively determine the hum and
RFI
level of the system. Effectively the weakest link in the chain. Highest
quality audio systems should quote a CM RR figure of –80dB or better.
Positioning
Ancillary
Equipment
Positioning of your source equipment (tuner, video, disc, tape, record, decks)
is
important. To avoid airborne frequency peaks, place them well away from your
loudspeakers and not in the corners of your listening area.
Loudspeaker
Placement
Loudspeaker placement is a controversial issue; suffice to say that room corners
are general
ly the worst situation. Everything which constitutes your listening
area, including the materials used in its construction, will affect the sound itself
and the sound stage created. Equally, you have to live with your system and
therefore compromises wil
l have to be made in line with your particular
priorities. The best advice we can give concerning the choice of loudspeakers is,
establish clearly in your mind your requirements; listen to many makes and
models, and if at all possible audition your prefer
red choice in your own
listening area and trust your own ears.
Matching
Amplifier and
Speaker
Ratings
When matching speakers to amplifier wattage –
ordinarily, the amplifier should
have a continuous RM S output power rating the same as or higher than the
speakers at the same impedance rating. For example, 100W
RMS
, 8Ω speakers
driven by a 100W
RMS
at 8Ω amplifier is not as ideal as 100W
RMS
, 8Ω speakers
driven by a 160W
RMS
at 8Ω amplifier.
Note:
100 Watts is twice as loud as 10 Watts, not ten times as loud.
Perreaux equipment is designed with substantial headroom built in –
that is, the
reserve necessary to reproduce musical peaks without clipping.
Final
Thoughts
High fidelity systems are an investment deserving of careful thought and
personal time. Your preferences, priorities and constraints will dictate the
parameters of your purchase; your ears will tell you what the right choice is
for
you. Our experience tells us that the bitterness of dissatisfaction lingers long
after the fragrance of cheap price is forgotten, hence our use of the term
–
investment.