Apogee APL-220, Руководство пользователя

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Many product designers would summarily reject such a driver, because its fre-
quency response is not inherently flat, even though its response is excep-
tionally linear and its distortion extremely low.
Now the synergy of integrated design comes into play. The processor is
designed to correct the driver’s deviation from flatness with a proprietary
high-frequency filter circuit that flattens the driver’s response curve.
Simulating the effect of this particular circuit would be difficult, to say the
least, with a generic loudspeaker controller. In fact, if using a generic digital
controller, the required curve would most likely collide with the controller’s
anti-aliasing filter, making it impossible to duplicate. Does that mean this
unusual driver is not a good choice for a professional loudspeaker? Not at
all! On the contrary, when coupled with the processor’s compensation cir-
cuit, the driver exhibits a flat response and the lowest distortion of any high-
power, horn-loaded compression driver that we know of. The driver merely
required a properly designed compensation circuit to achieve its potential. It’s
that simple.
Here’s another way of looking at it. The compensation circuit is similar to the
pre-emphasis and de-emphasis circuits used for decades in analog tape
recorders. Only in the case of the HF driver, instead of reducing tape noise,
distortion is reduced. The de-emphasis side of the equation is really the
mechanical function of the driver's HF roll-off, and the pre-emphasis is the
EQ compensation circuit. The resultant reduction in distortion comes from
the highly damped nature of the diaphragm. A damped material is not prone
to resonance and, therefore, does not produce the harmonic distortion
products of a resonant material.
(3) Driver Protection
Apogee APL-Series speakers utilize a special, highly-evolved set of limiter
parameters and controls. Multiple limiters are used simultaneously with
attack, release, integration time, and slopes that have been carefully matched
to the individual speakers thermal and mechanical limits over time.
All of this occurs without compromising dynamic range or otherwise unnat-
urally compressing the program material. The protection circuits only act
when the drivers would otherwise be damaged and, therefore, are excep-
tionally transparent. They are effectively “out of circuit” when below the
threshold of engagement. The result is extremely clean sound quality, with
effective protection of potential damage to the drivers under abusive
conditions.
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