Rear Panel Controls - B-52 ACTPRO12M Instruction Manual

ACTPRO
REAR PANEL CONTROLS (cont.)
prevent any unwanted transients (thuds, low-pops)
from coming out of the connected loudspeakers.
IMPORTANT! When you connect ACTPRO full-range
active loudspeaker to HP outputs of ACTPRO-18S
subwoofer, DO NOT engage LOW-CUT switch on
full-range loudspeaker. Input signal for your full-range
loudspeaker has already been processed by
ACTPRO18S's circuitry.
IMPORTANT! If using full range loudspeakers from
another manufacturer, we recommend that they be
connected to the HP OUTPUT. This will ensure proper
phasing of the full range loudspeaker with respect to
the ACTPRO18S subwoofer.
8. INPUT CONNECTIONS
All Full-range models have one female XLR line-level
input marked INPUT. The ACTPRO18S has a second
connector (two input connectors total), one for the left
channel's audio input and one for the right channel's
audio input. Balanced connections should be used as
much as possible to reduce AC hum and interference.
On all ACTPRO amplifiers, the input impedance is
20k ohm for balanced connections.
ACTPRO12M, ACTPRO15 AND ACTPRO1515
Insert the male XLR connector into the jack marked
INPUT. Ensure the connector is fully seated.
ACTPRO18S - For Stereo Operation With
Full-Range Cabinets: From your mixer, insert the
left channel's XLR connector into the left channel's (L)
INPUT connector. Connect the right channel of your
mixer by inserting the XLR connector into the right
channel's (R) INPUT connector on the amplifier. If
a single input signal is used, (for mono operation)
plug into the L (left) channel's input. When two input
signals are supplied to the amplifier, the subwoofer's
gain is automatically increased by 6dB.
9. PHASE SWITCH (ACTPRO18S)
When all of the loudspeakers in a system are op-
erating with the same polarity, a positive polarity
B-52 ACTPRO Active Systems - Instruction Manual
12
THE BEAUTY OF POWER
signal causes the excursion (the forward motion) of
all loudspeaker cones. In turn, this sets up a positive
reinforcement of the sound wave (each loudspeaker
reinforces the output of the other loudspeakers). This
effect refers to the speakers being "in phase" The
effect of proper "phasing" is most noticeable in low
(bass) frequencies. If a loudspeaker's phase is incor-
rect, its cone moves inward while the properly phased
loudspeaker's cones move outward. The inward move-
ment, of the improperly phased loudspeaker, will ef-
fectively cancel the bass response of a similarly-sized
driver in the system. This results in a reduction of the
bass output.
It is important to maintain correct phasing in a
loudspeaker system, in order to operate at maximum
performance. Incorrect polarity can be caused by
incorrectly wired cables, interconnecting cables, and
mixer functions set incorrectly.
Phasing is also influenced by the mutual position-
ing and orientation of the loudspeakers in a system. It
is possible to have proper polarization (of all cables
and equipment) and still achieve better bass response
by having the subwoofer set to reverse polarity, or
having several subwoofers set at different polarities.
Bass response also will change with the listener's
position in the room. During testing, monitor the bass
response from several different locations in venue.
Since proper phase is crucial to a subwoofer, the
ACTPRO18S has a polarity switch labeled PHASE.
When the PHASE switch is set to 0°, the polarity is
such that a positive input will cause the cone to push
outward. When set to 180°, the input signal's polarity
is reversed and a positive going input will cause the
loudspeaker's cone to pull inward.
How To Use The Phase Switch
Start all subwoofers in the system with PHASE switch-
es in the 0° position. This is the same for systems with
one subwoofer as well. Next, with your system play-
ing at or near expected operating level, change the
polarity of each subwoofer, ONE AT A TIME. Walk
around the venue and critique the overall bass re-
sponse. Select the phase setting that produces in the