Community VLF Series – Operation Manual - Page 13
SELECTABLE HIGH-PASS OUTPUTS: VLF212P
The VLF212P subwoofer is equipped with an industry-standard NL4-compatible locking connector wired in
parallel with a ¼” jack. A second NL4-compatible locking connector is provided, also wired in parallel to a
¼” jack. This second set of connectors is intended as
OUTPUTS
and are associated with the subwoofer’s
SWITCHABLE HIGH-PASS OUTPUT
.
When the selector switch is set to the
PARALLEL INPUT MODE
(the
down
position), both the NL4-
compatible locking connector and the 1/4” jack function exactly as loop-thru connectors; in other words they
are simply wired in parallel with the
INPUT CONNECTORS.
Conversely, when the selector switch is set to
HIGH-PASS OUTPUT
(the
up
position), a 1
st
order high-pass
filter (6 dB per octave) is inserted into the circuit. The filter has a corner frequency of 125 Hz with an 8 ohm
load.
Using the
HIGH-PASS OUTPUT MODE inserts the HIGH-PASS FILTER as mentioned above, but it also
presents a higher impedance load to the amplifier. This can become quite important, particularly if a pair of
full-range loudspeakers and a subwoofer are being powered from a single amplifier channel. In the
PARALLEL INPUT MODE, the impedance of the combined load could become dangerously low for some
amplifiers, potentially causing the amplifier to shutdown or fail.
The following graph shows the difference in the total load impedance with the high-pass switch in the HIGH-
PASS and PARALLEL INPUT MODE positions. The lower line depicts the response with the switch in the FLAT
position where the load drops below 2 ohms between 30 – 50 Hz and again between 100 – 200 Hz,
potentially causing early clipping, amplifier shutdown, or even amplifier failure. The upper line depicts the
response with the switch in the HIGH-PASS position, where the load impedance has been
increased
by about
50% by the subwoofer’s internal crossover circuit, thereby protecting the amplifier from premature clipping
and potential failure.
Figure 12: Graph Depicting Response of HIGH-PASS / FLAT Switch
(Note: upper line depicts HIGH-PASS; lower line depicts FLAT)
FLAT position
HIGH-PASS position
