Owner’
s Manual
9
Owner’s Manual
SRM1550 Subwoofer: Rear Panel Features continued...
4. Normal/Invert Switch [Polarity]
This switch reverses the polarity of the signal going
into the subwoofer amplifier by 180˚. It has no effect
on the signal at the outputs.
There is no right or wrong setting for this switch.
Listen to the overall blend of the subwoofer with
the rest of the system and select the switch position
that gives you the best sound for your audience.
In fact, your system may vary when positioned
differently and in alternate venues. Don’t be afraid
to experiment with the position of the polarity switch.
See page 11 for more information.
5. Gain Knob & Sig / Lim LED
The gain knob adjusts the sensitivity of the inputs.
This allows signals from the outside world to be
adjusted to run through each channel at optimal
internal operating levels. There is –6 dB of gain with
the knob fully down (off), ramping up to 6 dB of gain
fully up (max).
The accompanying dual-colored LED will illuminate
green when the input signal is present, indicating
signal. It will remain lit so long as there is signal above
–20 dBu present.
SRM subwoofers have a built-in limiter that
helps to prevent the amplifier outputs from clipping
or overdriving the transducers. The LED illuminates
yellow when the limiter is activated. It’s okay for it
to blink yellow occasionally, but if it blinks frequently
or lights continuously, turn down the gain knob until
it only blinks occasionally.
Excessive limiting may lead to
overheating, which in turn trips the
thermal protect circuitry and interrupts
the performance. See ‘Thermal Protection’ on
page 12 for more information.
6. High Pass Outputs
Typically, loudspeakers are connected to the high
pass outputs to “split” the work with the subwoofer.
The subwoofer handles all of the low frequencies
and the loudspeakers handle the rest. As a result,
it is more efficient and a bit louder.
Balanced XLR male connectors are provided
for the line-level A and B high pass outputs.
The subwoofer’s crossover splits the input signals into
two frequency bands. The low frequency range below
20 Hz – 115 Hz goes to the internal amplifier that
powers the subwoofer. The frequency range above
20 Hz – 115 Hz is sent to these line-level output jacks.
The frequency range depends on where the high pass
mode [9] is set.
They are wired as follows, according to standards
specified by the AES (Audio Engineering Society):
Balanced XLR Output Connector
Pin 1 – Shield (ground)
Pin 2 – Positive (+ or hot)
Pin 3 – Negative (– or cold)
7. Full Range Outputs
Connect the full range outputs to the inputs of
another powered subwoofer, powered loudspeakers,
or to an amplifier powering passive loudspeakers.
Balanced XLR male connectors are provided for the
line-level A and B full range outputs.
The signal at these outputs is a direct copy of the
input signals. These outputs allow you to daisy-chain
multiple subwoofers and/or send the full range signals
to other loudspeakers. It’s a great way to add side fills,
too!
2
1
SHIELD
COLD
HOT
3
SHIELD
COLD
HOT
3
2
1
Balanced XLR Output Connector
4
8
6
7
5
