Next LAs218 User Manual
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AMPLIFICATION
The LAs218 sub-woofers are designed to be used with professional power amplifiers
capable of producing 2000W to 2400W into 8 ohms (per speaker).
Care should be taken to
avoid amplifier clipping. It is important to understand that a low power amplifier
driven into clipping is more likely to damage a loudspeaker than a
higher power
amplifier used within its ratings. This is because music signals have a high peak-to-average
"crest" factor. When an amplifier is severely overdriven, its output waveform is “clipped” (its
peaks are squared off) – reducing the crest factor. In extreme cases, the waveform can
approach that of a square wave. An amplifier is normally capable of producing far more
power under these conditions than its undistorted rated power output. The use of very high
power amplifiers with outputs much greater than those recommended is discouraged.
Care should also be taken to avoid switch-on surges, which can result in momentary
power peaks in excess of specified ratings. When powering up a sound system it is important
to switch on the amplifiers last, after the mixer and control electronics have stabilised. When
powering down the system, reverse the sequence and switch off the amplifiers first.
TROUBLESHOOTING
Simple troubleshooting does not require sophisticated measurement equipment and
can be easily undertaken by users. The technique should be to segment the system in order
to identify the faulty system component: signal source, controller, amplifier, loudspeaker or
cable? Most installations are multi-channel. It is often the case that one channel works and
others do not. Trying different combinations of system elements can usually help to isolate
and locate the fault.
Some cabinet faults can be quite easily identified and corrected by the user. A simple
sweep with a sine wave generator can be very helpful though it MUST be made at a fairly
low level to prevent damage to the speakers. A sine wave sweep can help find:
Vibrations due to loose screws.
Air-leak noises: check that no screws are missing, particularly where the accessories
attach to the cabinet.
Vibrations due to a front grille badly positioned on the quick release fixings.
Foreign object that has fallen into the cabinet after repair or through the ports.
Internal connection wires or absorbing material touching the loudspeaker diaphragm:
check by removing the bass loudspeaker.
Loudspeaker not connected or phase reversed following a previous inspection, test or
repair.
