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2-Ohm Stable: In stereo mode (powering four speakers) the amplifier is stable
down to 2-ohms. The 2-ohm output is 90 Watts RMS x 4 channels.
Bridgeable: The B FOUR can be bridged to two channels, outputting
180 Watts x 2-channels into 4 ohms. You can also wire the B FOUR in three
channel mode, bridging half the amp and running the other half in stereo (60 Watts RMS x
2 channels plus 180 Watts x 1-channel).
Protection Circuitry: The B FOUR offers four protection circuits:
short circuit (or too low an impedance on the outputs), thermal overload, over voltage,
and under voltage.
4-Channel: The amplifier is divided into two sections,
channels 1/2 and channels 3/4. Each pair of channels has independent gain, bass
boost, and crossover controls.
Crossover: The built-in crossovers have three position switches
to select the crossover operation as high-pass, full-range, or low-pass. The high-pass
crossover points are continuously variable from 15 Hz to 4 kHz. The low-pass crossover
points are continuously variable from 40 Hz to 4 kHz.
Note: When a crossover switch is in
the low-pass position, the high-pass frequency dial is also
active. Depending on the high-pass frequency setting, this
creates either a subsonic filter (useful for any subwoofer
and often necessary for ported enclosures) or a band-pass
crossover (with a lower limit from 15 Hz to 4 kHz, and an
upper limit from 40 Hz to 4 kHz).
Gain: The rotary gain controls are continuously variable from
0.2 volts to 6.0 volts to match the source signal.
Bass Boost: The bass boost circuits are centered at 45 Hz and
continuously variable from 0 dB to +18 dB.
Power: The power and ground inputs are set-screw terminals;
they will accept bare wire up to 4-gauge (HELIX recommends 8-gauge minimum) and
are tightened/loosened with the supplied 4mm Allen wrench.
Remote: The remote turn-on input is a set screw terminal; it
will accept bare wire up to 10-gauge and is tightened/loosened with the supplied
2mm Allen wrench.
Speaker Outputs: The speakers connect to four pair of set-screw
terminals; they accept bare wire up to 10-gauge and are tightened/loosened with the
supplied 2mm Allen wrench.
Line Input: Two pair of stereo RCA jacks connect to the output signal from
the head unit.
Speaker Level Input: Use the included harness when speaker
level inputs are needed, or use the HELIX Easy Plug Cable and vehicle specific
adapter harness (both sold separately, see explanation above).
Note: The included speaker level input
harness doesn't use the standard aftermarket color codes,
and there's no color key in the manual (although the pin
positions are labeled on the side of the amp). The colors
- Black: channel 1 negative
- Yellow: channel 1 positive
- Gray: channel 2 negative
- Red: channel 2 positive
- White: channel 3 negative
- Blue: channel 3 positive
- Green: channel 4 negative
- Orange: channel 4 positive
Line Output: Stereo RCA output jacks make adding another
amplifier easy. The settings on the built-in crossovers have no effect on the
Fuse: The amp is protected by two 25-amp ATO-type