Mackie HR626 Owner's Manual download pdf (Page 11)

11

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 ad-

vantages to simple porting:

• One primary advantage of a passive

radiator is that it 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

flat diaphragm 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.

• Flip the switch to the

ON

position and the

power amplifiers are live and operate

normally. (The front panel mute

switch

must also be OUT.)

• When it’s in the

AUTO ON

position, the

amplifiers turn on and off depending on the

presence or absence of an input signal. An

input signal level of –74 dBu (minimum)

activates the auto-on function. A silent

period greater than eight minutes activates

the auto-off function. The green power

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 mute switch

is in the OUT position), applying AC power

activates the muting circuit for about four

seconds while the power supply and

internal circuitry stabilize, then the HR626

unmutes and is ready to go.

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 HR626 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-

Tweeter

Woofer Woofer

Passive Radiator

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