User manual MACKIE HD1501

[. . . ] HD1501 15" Powered Subwoofer OWNER'S MANUAL HD1501 Important Safety Instructions 1. Install in accordance with the manufacturer's instructions. Do not install near any heat sources such as radiators, heat registers, stoves, or other apparatus (including amplifiers) that produce heat. Do not defeat the safety purpose of the polarized or grounding-type plug. [. . . ] If the amplifier becomes excessively hot, the amp is muted until it cools, then the HD1501 returns to normal operation. When the HD1501 is in thermal protect mode, the power LED (2) will remain lit, indicating that the unit is still powered on despite the lack of output. If POWER LIGHT ON (7) is engaged, the front panel power LED will go out when in thermal protect mode. Activation of the thermal protection circuit is an indication that you should take steps to avoid continued thermal problems. See "Thermal Considerations" on page 11. SERIAL NUMBER REVISION TO REDUCE THE RISK OF FIRE OR ELECTRIC SHOCK, DO NOT EXPOSE THIS EQUIPMENT TO RAIN OR MOISTURE. REFER SERVICING TO QUALIFIED PERSONNEL. POWER Owner's Manual 9 HD1501 The Ins and Outs of Polarity Mackie's HD-Series Powered Subwoofers include a switch that allows you to quickly invert the polarity of the subwoofer's output relative to the input signal it is receivingfromthemixerorothersoundsource. But what exactly does that mean?A subwoofer works by literally pumping air as the woofer cone moves in and out with respect to the cabinet in which it is housed. It does so according to the low-frequency portion of the signal it receives from the sound source. The woofer cone is simply following the waveform as seen in the sine wave in Figure 1. As the sine wave rises, the woofer cone pushes out. Likewise, as the sine wave falls, the woofer cone pulls into the cabinet. A musical signal is much more complex, of course, but the same principle applies. Movement of the woofer cone causes air pressure changes that we perceive as sound. WhenthePolarityInvertswitch[6]isengaged, the originalwaveformissimplyreversed180º(seeFigure 2). Again, the subwoofer cone follows the waveform. However, this time the woofer cone starts by pulling into the cabinet followed by the woofer cone pushing out. If you have ever experimented with a subwoofer polarity switch, you may not have noticed any changes to the sound regardless of its position, especially if you are listening to just the subwoofer. This is normal, as our ears perceive them both as the same. The polarity invert switch comes into play when the HD1501 subwoofer is paired with a loudspeaker. Ideally, the woofer cones of the subwoofer and full-range loudspeaker would work together by pushing and pulling in unison. HD-Series subwoofers are designed to be used in a broad range of applications, and with a wide variety of full-range loudspeakers. [. . . ] Symmetrical Linkwitz-Riley 100 Hz Disclaimer Since we are always striving to make our products better by incorporating new and improved materials, components, and manufacturing methods, we reserve the right to change these specifications at any time without notice. "Mackie" and the "Running Man" figure are registered trademarks of LOUD Technologies Inc. All other brand names mentioned are trademarks or registered trademarks of their respective holders, and are hereby acknowledged. All Rights Reserved. Crossover Frequency: 1 Calculated from peak driver sensitivity and amplifier power, half space. [. . . ]