input signal level of –45 dBu (minimum) activates the auto-on function. A silent period greater than five minutes activates the auto-off function. The red PWR LED on the front panel reflects the state of the amplifiers.

MAINS INPUT

Connect the power cord to this IEC socket, and plug the other end into your AC outlet.

•When the POWER MODE switch is in the ON position, and the power switch is in the ON position, applying AC power activates the muting circuit for about four seconds while the power supply and internal circuitry stabilize.

PASSIVE RADIATOR

When you mount a loudspeaker in a box, there are two things that you can do with the radiation from the rear of the cone: use it to enhance the low-frequency performance of the speaker system (bass reflex system) or soak it up (acoustic suspension system).

•A bass reflex system uses the rear radiation to extend the low-frequency response. Most systems provide holes (ports) in the front or back of the cabinet to release the rear wave. Sometimes the holes have tubes (ducts) in them. The dimensions of the holes and the volume of the cabinet work with the characteristics of the woofer to produce low-frequency extension. These systems are characterized by good low- frequency performance down to the –3 dB frequency set by the design. Below this frequency, the frequency response falls at 24 dB/octave or more.

The HR824 is a bass reflex 6th-order system. Rather than use ports, the vent takes the form of a passive radiator, a mass-loaded flat piston coupled to the air trapped within the enclo- sure. You can’t see the passive radiator because it is located at the rear of the cabinet, behind the power amplifier assembly.

•Simple ports or ducts must have sufficient surface area to prevent the velocity of the air within them from exceeding 5% of the speed of sound, which keeps the vent from becoming audible (breathing and wheezing sounds) at high signal levels.

•This requirement for sufficient surface area creates a design problem when using ports — finding enough space in the enclosure for them to fit.

The passive radiator replaces the port found on most speaker systems. It offers several advantages to simple porting:

•One primary advantage is that a passive radiator can reproduce low frequencies with lower distortion and at a higher sound pressure level (SPL) than a simple port or duct.

•Our unique passive radiator design uses a diaphragm made with a composite honey- comb material providing exceptional stiffness to the radiating surface.

•The elliptical shape of the passive radiator takes up nearly the entire surface area available on the rear of the enclosure, allowing the passive radiator to move more air than a port.

Passive Radiator

Woofer Tweeter

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