The output transformer design of some Audio Research amplifiers use a unique ground scheme where the 4 ohm connection is actually connected to Ground.
Single REL Subwoofer Connection:
When connecting one REL, simply use the standard connecting scheme (the red high level lead to the positive right terminal, connect the yellow high level lead to the positive left terminal) with the exception of connecting the black wire to chassis ground (i.e. a metal bolt or screw, preferably not painted or anodized, on the chassis of the amplifier or receiver), not to the 0 ohm speaker terminal, and then connect into the HIGH-LEVEL INPUT.
Connecting a Stereo Pair to a Stereo Amp or Monoblock Amps:
When connecting to mono block amplifiers, we strongly advocate using one REL per amplifier. To connect, twist together the red and yellow wires of each REL separately and connect each pair to the positive 8-ohm speaker terminal of the corresponding amplifier channel, then connect both the black wires to chassis ground (i.e. a metal bolt or screw, preferably not painted or anodized, on the chassis of the amplifier), not to the 0 ohm speaker terminal, and then connect into each HIGH-LEVEL INPUT.