Protection Circuitry; Limiting; Overexcursion Protection; Thermal Protection - Mackie Thump 18S Owner's Manual

Protection Circuitry

The Thump18S subwoofer employs a built-in limiter
for less distortion at peak levels. Additional protection
includes automatic thermal shutdown should the amp
overheat. However, with Class-D amp technology, which
is highly-efficient, this should never be a problem.
The protection circuits are designed to
protect the subwoofers under reasonable
and sensible conditions. Should you choose
to ignore the warning signs [e.g. excessive distortion],
you can still damage the speaker in the Thump18S by
overdriving it past the point of amplifier clipping.
Such damage is beyond the scope of the warranty.

Limiting

The driver has its own compression circuit which
helps protect it from damaging transient peaks.
The compressor is designed to be transparent and
is not noticeable under normal operating conditions.

Overexcursion Protection

A subsonic filter circuit just prior to the power
amplifier prevents ultra-low frequencies from being
amplified. Excessive low-frequency energy can damage
the woofer by causing it to "bottom out," also know
as overexcursion, which is equivalent to a mechanical
form of clipping.

Thermal Protection

All amplifiers produce heat. The Thump18S is
designed to be efficient both electrically and thermally.
In the unlikely event of the amplifier overheating,
a built-in thermal switch will activate, muting the
signal.
When the amplifier has cooled down to a safe
operating temperature, the thermal switch resets
itself, and the Thump18S subwoofer resumes normal
operation.
If the thermal switch activates, try turning down
the level control a notch or two on the mixing console
(or the back of the subwoofer) to avoid overheating the
amplifier. Be aware that direct sunlight and/or hot stage
lights may be the culprit of an amplifier overheating.

AC Power

Be sure the Thump18S subwoofer is plugged into
an outlet that is able to supply the correct voltage
specified for your model. It will continue to operate
at lower voltages, but will not reach full power.
Be sure the electrical service can supply enough
amperage for all the components connected to it.
We recommend that a stiff (robust) supply of AC
power be used because the amplifiers place high
current demands on the AC line. The more power that is
available on the line, the louder the speakers will play
and the more peak output power will be available for a
cleaner, punchier bass. A suspected problem of "poor
bass performance" is often caused by a weak AC supply
to the amplifiers.
Never remove the ground pin on the
power cord or any other component of the
Thump18S subwoofer. This is very dangerous.
Owner's Manual
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