Crest Audio CPX 3800 - Manual (Page 28)

p. 2
CPX
TM
owner’s manual
safety
6
speaker protection
All loudspeakers have electrical, thermal and physical limits that must be observed to prevent
damage or failure. Too much power, low frequencies applied to high frequency drivers, severely
clipped waveforms and DC voltage can all be fatal to cone and compression drivers. The
Crest Performance CPX Series amplifiers automatically protect speakers from DC voltages
and subsonic signals. For more information, see the section on Protection Features. Mid- and
high-frequency speakers, especially compression drivers, are highly susceptible to damage from
overpowering, clipped waveforms or frequencies below their rated pass band. Be extremely
careful that the low and mid bands of an electronic crossover are connected to the correct
amplifiers and drivers and not accidentally connected to those for a higher frequency band.
The amplifier’s clipping point is its maximum peak output power and can 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 that the amplifier never clips,
use a properly adjusted external limiter (or a compressor with a ratio of 10:1 or higher) to
control power output. In systems with active electronic crossovers, use one for each frequen-
cy band. The clip limiter will automatically limit the duration of continuous square waveforms
applied to the speakers. The amplifier will, however, allow normal musical transient bursts to
pass. Some speaker systems are packaged with processors that have power limiting circuits
and should not require additional external limiting.
Fuses may also be used to limit power to speaker drivers, although as current-limiting (rather
than voltage-limiting) devices they are an imperfect solution. As the weakest links, fuses only
limit once before needing replacement. Some poor-quality fuses have a significant series
resistance that could degrade the amplifier’s damping of the speaker’s motion and may even
deteriorate the system’s sound quality. If you elect to use fuses, check with the speaker manu-
facturer to determine the proper current rating and time lag required.
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.
amplifier maintenance and user responsibility
A CPX Series amplifier requires no routine maintenance and should never need any
internal adjustment during its lifetime. Your CPX Series amplifier is very powerful and can
be potentially dangerous to loudspeakers and humans alike. It is your responsibility to
read the Important Precautions section in the front of this manual and to make sure that
the amplifier is installed, wired and operated properly. Many loudspeakers can be easily
damaged or destroyed by overpowering, especially with the high power available from a
bridged amplifier. Read the Speaker Protection section and always be aware of the speaker’s
continuous and peak power capabilities.