Mackie Thump18s Owners Manual - Page 13

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 13