EAW KF740, Руководство пользователя

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failure. The test signal has a 6 dB crest factor (peak to average ratio). A maximum continuous
voltage limit for the loudspeaker is then determined based on the test results and on the
transducer’s application in the loudspeaker. The powers listed in the table are calculated as the
square of the rms voltage limit divided by the sub-system’s nominal impedance (Z) in ohms.
5.7.2 Selecting an Appropriate Amplifier Size
The wattages listed in the above charts are intended primarily as points of comparison with the
power ratings of other loudspeakers. For this purpose, each wattage listed should be considered
as a +/-1 dB range = 0.8 to 1.25 times the wattage listed. For example, 700 W should be
considered as a range from approximately 550 W to 900 W.
In many applications, the wattages listed will NOT correspond to the best amplifier sizes for
optimizing loudspeaker reliability and performance. Proper amplifier selection requires a
considered analysis for the particular application. Amplifiers should be sized according to both the
sound levels required and the type of audio signals that will be reproduced. If you are unsure of
how to determine these parameters, consult a qualified professional or contact EAW’s Application
Support Group.
5.7.3 Selecting an Appropriate Amplifier Size Rule Of Thumb
If a KF740 Line Array is used for professionally operated concert applications, a rule of thumb can
be applied. Where the full output capabilities of the loudspeakers may be needed to achieve
appropriate acoustic output levels, EAW recommends amplifiers with power ratings up to twice
the wattages listed in the above charts. This provides a peak voltage capability of 6 dB above the
specified rms voltage limit. This assumes the audio signals will have a peak to average ratio in
excess of 6 dB, which is usually, but not always, true. Under this condition, the thermal limits are
unlikely to be exceeded. While this rule of thumb is consistent with the EAW’s testing parameters,
it does NOT guarantee trouble-free operation. That is discussed under “Operating Limits.”
WARNING: The power amplifier sizes recommended by the above rule of thumb are capable of
continuous output levels that can cause damage to or failure of the transducers. Exercise caution
in operation to avoid exceeding the specified maximum rms voltage limits.
In some cases, applying this rule of thumb to the power ratings listed in Section 5.7.1, would
indicate impractical amplifier sizes. In such cases, multiple amplifier channels each powering
fewer KF740s would be more practical.
5.7.4 Operating Limits
It is the responsibility of the audio system operator to operate the loudspeakers within their
capabilities. This is the only way to ensure that loudspeakers are not stressed beyond their limits
to the point of damage or failure.
Operation beyond their capabilities usually includes, but is not limited to, one or more of the
following conditions:
Amplifier clipping
Voltage input in excess of the specified rms voltage limit
Peak voltage input in excess of twice the specified voltage limit
Noticeable distortion
Mechanical noise (such as cones bottoming out)
A suitable means for determining these conditions is highly recommended. At a minimum, the
operator should have a meter display calibrated to indicate when the maximum rms voltage limits
will be exceeded. This assumes amplifiers are not being driven into clipping at those limits.
Page 10 of 22 KF740 OWNER’S MANUAL