Protection Circuits

There are several protection mechanisms designed into the TH-12A to safeguard the loudspeakers and amplifiers from inadvertent damage.

CAUTION: The protection circuits are designed to protect the loudspeakers under reasonable and sensible conditions. Should you choose to ignore the warning signs

(i.e., frequent OL LED indications, excessive distortion), you can still damage the speakers in the TH-12A by overdriving them past the point of amplifier clipping. Such damage is beyond the scope of the warranty.

Overexcursion Protection

A 12 dB/octave high-pass filter at 60 Hz just prior to the low-frequency amplifier prevents very low frequencies from being amplified. Excessive low- frequency energy below 60 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 TH-12A is designed to be efficient both electrically and thermally.

The amplifier module is mounted on a large heatsink, which is cooled by convection where cool air is drawn over the rear panel, carrying the heat away. In order for this convection cooling to work efficiently, it is important to provide adequate airspace behind the loudspeaker. When you position the TH-12A, we recommend leaving at least six inches of air space behind it.

•If for some reason the internal temperature gets too hot, a built-in 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 amplifier cools down to a safe temperature, the thermal switch resets and normal operation resumes.

•If the internal 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. If the ambient air temperature is very warm, try pointing a small fan toward the rear panel to increase the airflow across the rear panel.

Driver Protection

Each driver has its own compression circuit, which helps protect them from damaging transient peaks. The compressors are designed to be transparent and are not noticeable under normal operating conditions.

Input Signal Wiring

You should use high-quality, shielded cable to

connect the signal source to the INPUT jack on the TH-12A.

•High quality microphone cables work well.

•Foil shielded cables are commonly used for audio wiring.

•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. You can purchase quality cables from your Mackie dealer.

Placement

The TH-12A loudspeaker is designed to sit on the floor or stage. It may also be pole-mounted via the built-in socket on the bottom of the cabinet. Be sure the pole is capable of supporting the weight of the TH-12A.

WARNING: The cabinet has no rigging

points and is not suitable for rigging.

NEVER attempt to suspend the TH-12A by its handles.

As with any powered components, protect them from moisture. If you are setting them up outdoors, make sure they are under cover if you expect rain.

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