Tourclass Protection; User Responsibility - Crest Audio LT Series Owner's Manual

safety
6

user responsibility

Your LT / ST Series amplifier is very powerful and can be potentially dangerous to loud-
speakers and operators alike. It is your responsibility to read
see the inside-front cover ) and make sure that the amplifier is installed, wired, and
(
operated properly as instructed in this manual.
Many loudspeakers can be easily damaged or destroyed by overpowering, especially
with the high power available from a bridged amplifier. Always be aware of the speak-
er's continuous and peak power capabilities. Crest Audio is not responsible for damage
to loudspeakers for any reason.
speaker protection
see—
speaker protection
All loudspeakers have electrical, thermal and physical limits which must be observed to pre-
vent damage or failure.Cone or compression drivers can be damaged (sometimes to the point
of failure) from excessive power, low frequencies applied to high frequency drivers, severely
clipped wave forms,and DC voltage. All LT / ST Series amplifiers automatically protect speak-
ers from DC voltages and subsonic signals.
see—TourClass protection
Mid- and high-frequency transducers—compression drivers in particular—are highly suscep-
tible to damage from overpowering, clipped wave forms, or frequencies below their rated pass
band.When using an electronic crossover, make absolutely certain that the low and mid bands
are connected to the correct amplifiers and drivers—and not accidentally connected to those
for a higher or lower frequency band.
The amplifier's clipping point is its maximum peak output power. At maximum peak output
power,Crest Audio LT / ST Series amplifiers will deliver more power than many speakers can
safely handle. Be sure the peak power capability of the amplifier is not excessive for your
speaker system.To ensure that the speakers never receive excessive power, and to prevent
amplifier clipping,use a properly adjusted external limiter (or a compressor with a ratio of 10:1
or higher) to control power output. Use one compressor/limiter for each frequency band in
systems with active electronic crossovers.
The ACL clip limiting circuit will automatically limit the duration of squared-off, continuous
wave forms applied to the speakers.The amplifier will, however, allow normal musical transient
bursts to pass. Of course, when the amplifier does clip, it is operating at its maximum output
power.Note that some speaker systems are packaged with proprietary "processors" that have
power limiting circuits and therefore should not require additional limiting. Do not drive any
low-frequency speaker enclosure with frequencies lower than its own tuned frequency; the
reduced acoustical damping could cause a ported speaker to bottom out even at moderate
power.Consult the speaker system specifications to determine its frequency limits,and employ
a roll-off filter if necessary.
recommended speaker cabling
The wire gauge charts will assist you in determining the optimum copper wire gauge for your
speaker cables.Remember that the speaker cable resistance robs amplifier power in two ways:
through power lost directly to resistance (often referred to as I
total load resistance, which decreases the amount of power available from the amplifier.
Appendix C gives cable length figures in feet/AWG wire gauges and in metric values.
see—wire gauge
p. 22
important precautions
2
R loss), and through increased
LT / ST owner's manual