Specifications

A pair of limiter LEDs (one for LF and one for HF) are located on the rear

panel.These illuminate during engagement of the limiters in the separate low-

frequency and high-frequency sections. It is not uncommon to see these

LEDs illuminate regularly, such as on downbeats and crescendos.

If the LEDs appear to be "on" more than "off " (i.e., if they are continuously

flashing or glowing at a steady state), the loudspeaker system is being pushed

too hard for its size and power output capability.To correct this, reduce the

drive level to the speaker system, or install additional speakers to achieve the

SPL (Sound Pressure Level) required for the application.

(4) A Word About Limiters

Properly designed protective limiters can do wonders to help prevent driver

damage and extend normal driver life, but they are by no means a panacea.

Apogee limiters do not exhibit “brick-wall” characteristics because such limiters

seriously degrade sound quality. Apogee’s intelligently engineered limiter circuits

provide an excellent measure of protection, while maintaining sonic purity.

Apogee's limiter circuits are capable of effectively reducing program levels

that would otherwise damage the system’s drivers.This takes place with little

or no loss of sonic quality or dynamic range, because the circuits are designed

so that they only engage when driver non-linearity or driver damage would

otherwise occur. However, when a limiter is pushed well past its threshold of

engagement to the point where it is continually “in circuit”, by nature it

increases the duty-cycle of the program material.This happens because, as the

limiter decreases peak amplitudes,RMS values increase, causing the drivers to

heat beyond normal. Additional circuits could be employed to reduce levels

and “clamp” the output of the system, but such circuits would represent a

high level of intervention and be very audible in their action.The proper solu-

tion is for the operator to recognize that the system is being pushed past its

capabilities and either reduce the operating level or add additional speaker

systems to provide the desired Sound Pressure Level (SPL).

(5) Low-Cut Switch

The APL-220, -500, and -800 are equipped with a switchable Low-Cut filter.

The filter is of the 12 dB/octave type with a corner frequency of 100 Hz.The

Low-Cut Switch is intended to be used when the speaker system is not

required to produce full-range output, such as in downfill, front fill, and other

band-limited applications. By using the Low-Cut Switch, the speaker system

can be driven approximately 6 dB harder before LF excursion, LF peak, and

LF RMS limiters are engaged.The switch is located on the rear panel, adja-

cent to the Input XLR connector. It is recessed with only a short portion of

its handle accessible, so that it cannot easily be changed inadvertently.