Mackie MR8MK2 User Manual download pdf (Page 8)

MR8mk2

Protection Circuits

Input Signal Wiring

You should use high-quality, shielded cable to connect

the signal source to the signal input jack [1] on the

MR8mk2.

• For balanced signals, foil shielded cables, such as

Belden 8451, 8761, or 9501 are commonly used for

studio wiring.

• Microphone cables work well for the XLR input.

• The better the shield, the better the immunity from

externally induced noise (like EMI and RFI). Route the

cable away from AC power cords and outlets. These are

common sources for hum in an audio signal. Wall warts

and line lumps are especially insidious hum inducers!

Quality cables may be purchased from Mackie dealers.

•

In certain home theater applications, it may be necessary

to connect the speaker outputs from a stereo receiver to

the inputs of the MR8mk2, if the receiver doesn’t have

preamp outputs or other line-level output connections.

CAUTION: Do not attempt to connect a

speaker output directly to the input of the

MR8mk2! Speaker levels are much higher

than line levels and can damage the input circuitry in

the MR8mk2.

However, it is possible to insert a speaker-level to

line-level signal attenuator between the receiver’s

speaker output and the MR8mk2’s input. The local

Mackie dealer should be able to assist, or you can build

your own.

Care and Cleaning

Mackie Reference Studio Monitors will provide many

years of reliable service if you follow these guidelines.

• Avoid exposing the monitors to moisture.

• Avoid exposure to extreme cold (below freezing

temperatures).

• Use a dry cloth to clean the cabinets. Only do this when

the power is turned off.

There are several protection mechanisms designed

into the MR8mk2 to safeguard the loudspeakers and

ampliﬁers from inadvertent damage.

CAUTION: The protection circuits are

designed to prevent damage to the

loudspeakers under reasonable and sensible

conditions. Should you choose to ignore the warning

signs (i.e., excessive distortion), you can still damage

the speakers in the MR8mk2 by overdriving them. Such

damage is beyond the scope of the warranty.

Overexcursion Protection

A 12 dB/octave high-pass ﬁlter at 40 Hz just prior to

the low-frequency ampliﬁer prevents very low

frequencies from being ampliﬁed. Excessive

low-frequency energy below 40 Hz can damage the

woofer by causing it to “bottom out,” also known as

overexcursion, which is equivalent to a mechanical form

of clipping.

Thermal Protection

All ampliﬁers produce heat. The MR8mk2 is designed

to be efﬁcient both electrically and thermally.

• If for some reason the heatsink gets too hot, a thermal

switch activates and turns off the ampliﬁer. This

protection operates independently for the

low-frequency and high-frequency ampliﬁers. Therefore,

it is possible for only the low frequency or high

frequency ampliﬁer to shut down while the other

remains on.

• When the heatsink cools down to a safe temperature,

the thermal switch resets and normal operation

resumes.

• If the heatsink temperature again gets too hot, the

shutdown process repeats. Should this happen, make

sure that airﬂow to the rear of the cabinet is not

restricted.

Integrated Magnetic Shielding

The MR8mk2 contains drivers with large magnetic

structures. The drivers’ magnets are shielded to help

prevent the magnetic ﬁeld from radiating out into the

environment and playing havoc with computer monitors

or TV screens. Unshielded speakers can cause

distortion in both the shape and color of the picture

if placed too close to a CRT (cathode ray tube). If you

have a particularly sensitive computer monitor or TV

screen, it may be necessary to move the speakers a few

inches away.

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Mackie MR8MK2 User Manual Page 8

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