dynamic and complex load. Most modern touring power amplifiers claim 2 ohm
capabilities but make sure your amplifier is also capable of driving reactive (ie
inductive or capacitive) loads without prematurely clipping or developing output
stage crossover distortion.
Power reserve
Most power amplifier specifications are based on bench measurements made using
stable, high current mains supplies and well defined loads. Amplifiers sound best
when they have plenty of current in reserve for percussive peaks and sustained bass
notes.
1) Try to ensure that the mains supply stays within the amplifier manufacturer’s
specified range from no load to maximum load.
An electrical technician should check the mains supply vs demand using an
accurate rms voltage meter.
2) If unfamiliar generators are being used the electrical technician should check
the mains waveform (using a portable ’scope-meter) to make sure that it is
sinusoidal and not crawling with spikes or interference.
3) Avoid driving too many W8S drivers in parallel. I would suggest no more
than 2 x 15" or 2 x 18" per amplifier channel so that the power amplifier’s 2
ohm spec is kept in reserve for musical peaks.
4) Avoid using power amplifiers in bridged mode. Most commercial power
amplifiers are optimised for 2-channel operation. It is usually better to use the
appropriate amplifier in 2-channel mode than to use an inadequate amplifier in
bridged mode.
Note that W8S 15" and 18" drivers may be driven in parallel - i.e. in passive mode
(DX1 programmes 22 or 23) to save amplifier channels on smaller systems … but
with reduced punch and slam.
W8S' should always be driven actively (DX1 programme 24) when power amplifier
budgets allow.
Power amplifier gain or level settings reminder
Gain switches
If you are lucky enough to have amplifiers with user gain switches, set them all to
identical positions. A voltage gain in the range 23-33dB will provide a good balance
of system headroom and noise (assuming professional audio equipment is in use
FOH).
All material © 2007. Martin Audio Ltd. Subject to change without notice.
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