[. . . ] When you power down, the amplifier should ALWAYS be turned off first to avoid the same problems. MATCH CONNECTOR POLARITY When using two or more speaker systems, be sure match the polarity (+/­) of the speaker system connectors to those at the amplifier. If the polarities do not match, the sounds produced by the speakers will interfere with each other, making it impossible to achieve a well-balanced sound field. When choosing a power amplifier to use with your speakers, make sure that its power output matches the speakers' power capacity (refer to the Specifications on page 6). [. . . ] When choosing a power amplifier to use with your speakers, make sure that its power output matches the speakers' power capacity (refer to the Specifications on page 6). Even if the amplifier's power output is lower than the speakers' PGM (program) power capacity, the speakers may be damaged when clipping of a high input signal occurs. Continuous high sound pressure level produced by electronic instruments. Popping noises caused by turning on equipment, or by connecting or disconnecting system components while the amplifier is turned on. All full-range loudspeakers are fitted with a self-resetting poly switch that protects the high-frequency driver from damage caused by excessive power. If a loudspeaker cabinet loses high-frequency output, immediately remove power from the unit and wait for two to three minutes. Re-apply power and check the performance of the high-frequency driver before continuing with the power reduced to a level that does not cause the poly switch to interrupt the signal. On the SW118IV/SW118IVS sub woofer, the Poly Switch protects the woofer and a similar routine should be followed if its output is lost. This product, when used in combination with amplification and/or additional loudspeakers, may be capable of producing sound levels that could cause permanent hearing loss. dO NOT operate at high volume levels or at a level that is uncomfortable. the SW118IV , SW118IVS subwoofer has a metal socket to allow mounting of a satellite speaker. The illustration below shows audio connections for a standard setup using two speaker systems. DAISY-CHAINING SPEAKERS Since the speaker systems in this series are equipped with two input terminals that are internally connected in parallel, it is possible "daisy-chain" speakers by connecting the output from the power amplifier to one phone jack, and a second speaker system to the other. Since most power amplifiers are designed to provide stable performance at a load impedance of 4 or 8, Yamaha recommends that no more than two 8 speaker systems be daisy-chained together. This will allow the amplifier to operate properly and avoid overheating. PHONE PLUG WIRING The standard input terminals for this unit are 1/4" phone jacks. Caution: Use only unshielded speaker cable with stranded conductors to connect speakers to the speaker terminals on a power amplifier. The use of audio cable not rated as sufficient for the amplifier's maximum output level can create a potential fire hazard. This example shows audio connections for a system using SW118IV or SW118IVS Subwoofers and a PN90 Crossover Network. Do not connect the PN90 between the power amplifiers and the SW118IV, SW118IVS subwoofers, as doing so will damage the equipment. [. . . ] This example shows audio connections for a system using SW118IV or SW118IVS Subwoofers and a PN90 Crossover Network. Do not connect the PN90 between the power amplifiers and the SW118IV, SW118IVS subwoofers, as doing so will damage the equipment. ⷠAlthough the PN90 has a standard load impedance of 15 k, it can be used with loads between 7. ⷠSince the LOW signal polarity is inverted at the crossover point between the LOW and HIGH signals, be sure to reverse the polarity when connecting the SW118IV, SW118IVS input jacks to the power amplifier output jacks. [. . . ]