Mackie S515 Owners Manual - Page 8

S500 Series Loudspeakers Protection A protection circuit is built into the S512, S515 and S525 to protect their high-frequency drivers from excessive power. When tripped, the protection circuit substantially reduces the power to the HF driver. After the driver cools to a safe operating temperature, the protection circuit resets and normal operation resumes. However, if the protection circuit senses excessive power, it will trip again. In this case, it is necessary to reduce the power to the loudspeaker by either turning down the gain controls on the power amplifier or turning down the master volume control on the mixer or other sound source. CAUTION: The protection circuit is designed to protect the HF driver under reasonable and sensible conditions. Should you choose to ignore the warning signs (i.e., frequent clip LED indications on the mixer or power amplifier, excessive distortion), you can still damage the drivers in the S500 Series loudspeakers by overdriving them past their recommended amplifier power-handling ratings, or past the point of amplifier clipping. Such damage is beyond the scope of the warranty. Amplifier Power Recommended Power Ratings • S512: 500 watts into 8 ohms (250 watts rms x 2) • S515: 600 watts into 8 ohms (300 watts rms x 2) • S525: 1200 watts into 8 ohms (600 watts rms x 2) • S518S: 900 watts into 8 ohms (450 watts rms x 2) Preventing Loudspeaker Damage Speaking of clipping, this is likely the number one cause of damage to loudspeakers. Clipping occurs when the signal at the output of any device in the system (not just the amplifier) reaches its maximum level. The input signal to the device may continue to increase, but the output simply stops, and is characterized by a "flattop" appearance to the waveform. Normal Sine Wave Signal  Clipped Sine Wave Signal  The S500 Series loudspeakers have three powerhandling numbers: continuous, program and peak. So how much power do you really need to drive these loudspeakers? The answer to that question depends on what type of program material you are running through the system and how loud it needs to be. Some audio signals have lots of momentary peaks whose amplitudes extend far above the average overall level of the program. Percussion instruments are a good example of this. Other types of signals, like highly compressed rock music, have a higher average signal level with fewer peaks. Speech reinforcement requires less power overall, but involves large moment-tomoment variations in level. Assuming you want to use the full capability of the loudspeaker, and the program contains at least some momentary peaks, we recommend that you use an amplifier that is rated at twice the continuous power rating of the loudspeaker (into 8 ohms). For the S512 loudspeakers, this would be 250 watts x 2 = 500 watts per channel into 8 ohms. This ensures that the amplifier can reproduce peaks that are 6 dB higher than the continuous (rms) power-handling rating before clipping occurs. Clipping interrupts the motion of the transducer, creating distortion and excessive heat in the driver, which can damage it over time. Some folks think that if they use a power amplifier whose power rating is below the maximum powerhandling rating of the loudspeaker, then they can't possibly damage the loudspeaker. But if the amplifier is driven into clipping, even a lower power amplifier can damage the loudspeaker. The bottom line is that to prevent damage to the loudspeakers, you must have a properly operating sound system. Proper operation of a sound system includes being aware of types of audio signals being reproduced, controlling the output levels accordingly, and operating all the devices in the system so that no clipping occurs within the signal chain. 8 S500 Series Loudspeakers