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Polarity can be altered by miswired input cables, interconnecting cables, mixer polarity switches set incorrectly, just to name a few likely culprits. To make matters a bit more complicated, phasing is also influenced by the position of loudspeakers with respect to one another and by their position in a given room. It is possible to have all loudspeakers polarized properly (electrically) and yet achieve better bass response by having the subwoofer reverse polarized. It is even possible to achieve improved bass response from the system with multiple subwoofers polarized differently. Be aware that perceived bass response also will change with the listener’s position, so move around the room (venue) when testing your setup. Because phasing problems can so drastically effect the bass output of a system, the subwoofers are equipped with a switch marked POLARITY. When set to NORMAL, the polarity is such that a positive going input will cause the cone to move outward. When set to REVERSE, the input signal has its polarity reversed and a positive going input will cause the loudspeaker’s cone to move inward. How to Use the Polarity Switch When using QSC subwoofers and QSC full range loudspeakers, NORMAL polarity will result in the best bass response IF the full range loudspeakers are sitting on or very close to the subwoofers. If the subwoofers are some distance away from the full range loudspeakers, polarity change may be of benefit. Start with all subwoofer POLARITY switches in the NORMAL position. This applies to systems with one subwoofer as well. Then, with your system at or near expected operating levels, change the polarity of each subwoofer INDIVIDUALLY. Then walk around the venue and assess the overall bass response. Select the polarity that results in the best overall system bass response. Polarity switch. IMPORTANT! If using full range loudspeakers from another manufacturer, we recommend they be connected to the QSC subwoofer’s 100 Hz LOWCUT OUT. This will ensure proper polarity of the full range loudspeaker with respect to the subwoofer. Front LED switch. 13 SIGNAL Indicator LED The green SIGNAL indicator alerts the user to the presence of an input signal to the HPR loudspeaker. Normal Indication The green SIGNAL indicator illuminates when the input signal exceeds -25 dB. If No Indication Check Gain settings and increase gain if necessary. Check input connections and audio source for signal. If the red LIMIT LED illuminates, refer to the LIMIT indicator section, below. Abnormal Indication If the green SIGNAL LED illuminates with no signal input, there may be system oscillations or some other malfunction. Disconnect the input or fully reduce the gain. If the green SIGNAL LED remains on, the amp may need servicing. LIMIT Indicator LED The red LIMIT indicator alerts the user to several conditions within the HPR loudspeaker: Continuous Bright Red Light • Indicates protective mute mode. • The speaker normally passes through muting for several seconds after applying power, after which the light should go out, and sound should be heard. • If the speaker enters Mute during operation, it has either overheated or developed a fault. • Overheating should correct itself within 1-2 minutes, after which sound should resume. See below for a full explanation of thermal protection. • Short periods of muting indicate a component fault. In this case AC power should be removed and the speaker serviced. Momentary Bright Red Flashes • During operation, bright flashing indicates clipping (overdrive distortion). This is normally due to excessive volume and may be accompanied by audible distortion. • If the loudspeaker mutes repeatedly during output peaks, there may be a component fault; AC power should be removed and the loudspeaker serviced. Continuous Half-bright Light • Indicates that the internal limiter is reducing gain, due to prolonged clipping and/or excessive temperature. • After several seconds of severe clipping, the limiter will reduce power to protect the speaker and improve the sound. This results in a steady, half-bright red indication. Any further clipping will still result in bright flashes on top of the steady half-bright indication. When the program level is reduced, the limiter will clear after several seconds, and the red indicator will go out. • If the power module overheats, the first response is to trigger limiting, to reduce volume and limit further temperature rise. This results in a steady half-bright illumination that does not clear even after reducing program level. It may take several minutes for temperature to drop and clear the limiter. During this time, the exposed heat sink will feel uncomfortably hot to the touch. If overheating continues, the amplifier will ultimately mute, resulting in a full-bright red indication. When muting clears, the amplifier will resume operation, with thermal limiting still active until it further cools off. • Overheating is usually caused by excessive ambient tempera...

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