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9.4 Unpowered Loudspeakers - Limiters
CAUTION: The assumptions that must be made about how to set a limiter and what a
driver's power handling limits are cannot address all conditions of use. As such, limiters
cannot provide absolute protection nor provide any guarantee against damage or failure
from excessive inputs. At best, they can only provide some degree of protection.
9.4.1 Limiters And Limiting
Limiters can help avoid either of two things, depending on the signal frequency content and
the amplifier / driver power ratings. The choice depends on which will be exceeded first.
Exceeding a Loudspeaker's Thermal Limit:
The limiter is used to prevent the amplifier, operating within its capabilities, from
exceeding the loudspeaker's capabilities.
Exceeding the Amplifier's Output Limit (Clipping).
The limiter is used to prevent the amplifier from exceeding its capabilities, even though
the loudspeaker is operating within its capabilities.
9.4.2 MX8750 Limiter Design
EAW has done the work of determining the MX8750's limiter characteristics with real
audio signals by performing a number of tests on its behavior with real audio signals and
analyzing how this relates to both loudspeaker power handling limits and sonic
performance. Based on measurement and analysis of the above variables, EAW
Engineering was able to formulate a set of "rules" for setting MX8750 limiters. Listening
tests determined settings that maintain good sound quality while maximizing protection.
These rules are incorporated into the MX8750 Output Limiter Wizard. See Section 9.4.3.
Because limiters differ in their behaviors from manufacturer to manufacturer, EAW can
only provide limiter settings for its own MX Series of processors. These are the only ones
on which the required analysis was done to optimize settings. As such, EAW limiter
thresholds are only valid for use with an EAW MX8750 digital processor and with amplifiers
that have or are set to 32 dB gain for all passbands. This assumes that the factory gain
settings for the processor outputs are also used. For amplifiers with gain other than 32 dB
and for loudspeakers where no factory limiter settings exist, use the MX8750 Output Limiter
Wizard to determine the correct limiter threshold settings. See Section 9.4.3.
9.4.3 MX8750 Output Limiter Wizard
The MX8750 Output Limiter Wizard is an Excel-based program intended to provide
limiter settings that can help protect loudspeaker drivers from damage or failure. The
program can be downloaded from the EAW web site.
Apply the settings determined from the Wizard to the MX8750 using the MXWare control program.
NOTE: The Wizard's settings apply only to the MX8750. They should not be applied to
other limiters for the reasons stated above.
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