Mackie SRM1850 Owner's Manual - Placement
Owner’
s Manual
11
Owner’s Manual
Placement
SRM subwoofers are designed to sit on the floor
or stage. They are not designed to be pole-mounted
or suspended.
When pole-mounting loudspeakers, be sure that
the subwoofers are stabilized and secured from falling
over or being accidentally pushed over.
Please note that SRM750 loudspeakers
should be stacked, not pole-mounted.
Failure to follow these precautions may result
in damage to the equipment, personal injury, or death.
Speaking of stacking, SRM2850 subwoofers have
footholes located on the top of each cabinet. While we
realize that crowds will fall head over heels at their
beauty, believe it or not, these footholes do indeed serve
a purpose.
Should you decide to stack an additional SRM2850 –
creating a monster PA – the feet located on the bottom
of each subwoofer line up nicely with the footholes
located on the top of each subwoofer. The same can be
said of the four feet of an SRM750 and the four footholes
located near the center of the SRM2850.
For either of these stacked scenarios, it is highly
suggested that straps are utilized. To reiterate, failure
to follow these precautions may result in damage to
the equipment, personal injury, or death.
These cabinets have no rigging points and
are not suitable for rigging. NEVER attempt
to suspend an SRM subwoofer by its handles.
The Ins and Outs of Polarity
SRM subwoofers include a switch that allows you to
quickly invert the polarity of the subwoofer’s output
relative to the input signal it is receiving from the
mixer or other sound source. 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.
When the normal/invert [polarity] switch [4] is
engaged, the original waveform is simply reversed 180˚
[see Figure 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 at the
same time.
The normal/invert [polarity] switch comes into play
when the 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. SRM subwoofers are designed to
be used in a broad range of applications. The flexibility
provided by the polarity switch is necessary to ensure
that you are receiving the best possible sound from
your system, regardless of your setup.
Figure 1: Normal [0˚]
Amplitude
Amplitude
Figure 2: Invert [180˚]