Specifications

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 specialized, highly-evolved Command

Control limiting system. This system comprises five separate layers of pro-

tection triggered by an infinite variation of possible program conditions. Data

is received on three independent sensor circuits, including Apogee’s exclusive

VIProtect

™ current sensors, and is processed by an analog computer to pro-

hibit the drivers from over-excursion, excessive RMS levels, and excessive

instantaneous peak levels. By sensing voltage and current, the limiter circuits

can compensate for changes in voice coil temperature, ensuring that accurate

protection levels are always maintained.

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.