Standardising on one good model of power amplifier (preferably the
Martin Audio
MA4.2
) and correctly set-up controller (preferably the
Martin Audio DX1
) will
provide the most dynamic system performance and protection whilst simplifying
design and reducing spares inventories. (See
Section A1.5
and
DX1 Speaker
Management System User's Guide
for further details)
Cluster balance (eg farfield-to-midfield or inner-to-outer) should be adjusted
at the
power amplifier controls
to maintain limiter tracking. See
Section A2.7.
Balancing the system using gain controls in the signal path
before
the power
amplifiers is not recommended as it will cause the higher signal level upper rows of a
big cluster to start limiting before the lower signal levels downfills resulting in tonal
changes at the mix position.
Limiter settings
The Rated Power specification in
Section A2.2
indicates the maximum long-term
power dissipation that can be tolerated before driver ageing or damage occurs through
overheating or over-excursion.
When choosing power amplifiers, do not be tempted to exceed the 800W into 8
Ω
power rating unless the amplifier's power rails are well regulated (see
Section A2.6
) -
even with properly set controllers in place. Although Martin Audio drivers are
mechanically designed to survive normal road use and the occasional operator error,
overpowered or bridged amplifiers can cause over-excursions that stress and age
drivers. The best way to get the clean, relaxed sound of an overpowered amplifier is
to choose an amplifier with plenty of current reserve - ie an amplifier with good 2
Ω
specification - and avoid running more than two cabinets in parallel.
To ensure transparent limiter operation without obvious distortion or pumping, the
DX1 limiter attack and release times are factory preset to be inversely proportional to
the subwoofer's high pass frequency as follows:
High pass filter range Attack time Release time
>31Hz 45mS 720mS
31Hz - 63Hz 16mS 256mS
These attack times allow the power amplifiers to clip momentarily but not for long
enough to be obvious to listeners or cause driver overheating. It is quite normal to see
amplifier clip indicators on the odd programme peak but continuous clipping would
indicate a cable short circuit, wrong controller settings, excessive power amplifier
gain or low mains voltage.
All material © 2007. Martin Audio Ltd. Subject to change without notice.
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