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How many amplifiers do I need to drive a typical
W8L/Longbow system?
The simple rule of thumb is 3 power amplifiers for 4 W8L/Longbow cabinets...
3 x 2ch MA4.2S power amplifiers drive 4 x W8L/Longbows
6 x 2ch MA4.2S power amplifiers drive 8 x W8L/Longbows
9 x 2ch MA4.2S power amplifiers drive 12 x W8L/Longbows
12 x 2ch MA4.2S power amplifiers drive 16 x W8L/Longbows
Can I split the system into smaller racks with, say, 3 amps
per rack?
Yes. But remember that our MA4.2S amplifier weighs only 10kg so a double width
rack housing 9 MA4.2S amplifiers for a standard 12-box system may be no heavier
than a single rack system using conventional power amplifiers. A double width rack
will cater for band zoning (the progressive shelving control applied to the upper mid &
high frequency sections of line array columns to partially compensate for air
absorption) without the need for dedicated master and slave racks linked with
complicated multi-core links. See example of 3-amplifier master-slave rack system for
a 12 x W8L/Longbow system later.
Why do I need high power amplifiers for the mid & high
frequency sections?
There are several reasons for this:
1)
Although vocal and percussive signals demand fairly low continuous power,
their peak power can be much higher. Many touring systems have less than adequate
peak power at mid and high frequencies and simply clip vocal fricatives and
percussion transients producing poor mid and high frequency definition.
2)
Our mid and high frequency sections are designed to reproduce these peak
power transients faithfully without stress. We use carefully matched RC coupling
networks to compensate for high frequency driver voice coil inductance. These
coupling networks improve transient performance and present an easy load to the
power amplifier whilst maintaining a high frequency efficiency of 1 13dB/W/m.
3)
Line Arrays are designed for long throw applications. Air absorption can cause
significant high frequency attenuation at low humidity. Line array columns are usually
band zoned (ie progressive shelving control is applied to the upper mid & high
frequency sections of line array columns to partially compensate for air absorption).
This band zoning relies on the exceptional mid and high frequency performance
provided by adequately powered high-efficient mid and high frequency sections.
Please note that our standard controller limiters are set with finite attack times. This
allows all them to pass transient signals to the full output capability of the MA4.2S
All material © 2007. Martin Audio Ltd. Subject to change without notice.
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