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REL Subwoofers with AHB2 Power Amplifier

by John Siau November 05, 2020 3 min read

REL Subwoofers with AHB2 Power Amplifier

Many Benchmark customers are using their AHB2 power amplifiers with REL subwoofers. This application note shows how to connect one or two AHB2 amplifiers to one or two REL subwoofers using the speaker outputs on the back of the AHB2 amplifiers.

Benchmark AHB2 Rear Panel

AHB2 Rear Panel Connectors and Controls

The MODE switch in the lower right-hand corner sets the AHB2 to stereo or mono mode. In stereo mode, the outputs of the AHB2 are conventional unbalanced outputs. In mono mode, the output of the ABH2 is balanced.

The two red binding posts (1+ and 2+) on the AHB2 are driven by the amplifier outputs. The black terminals (1- and 2-) are the ground returns for each of the two channels. We will use one of these speaker ground returns as a connection point for the REL ground wire. Notice that the SpeakON connectors provide access to the same set of outputs. In stereo mode, the left speaker is connected between 1+ and 1- using the binding posts or the SpeakON connectors. The right speaker is connected between 2+ and 2-.

Notice that the 1+ post is labeled M+ and the 2+ post is labeled M-. These are the outputs for mono operation. The speaker is connected between M+ and M- using either the binding posts or the SpeakON connectors. In mono mode, M- is an inverted version of M+.

REL "Baseline Blue" High-Level Input Cable


REL supplies a cable with yellow, red and black wires that connect to the speaker output terminals on a power amplifier. The SpeakON connector plugs into the back of the REL subwoofer. The yellow and red wires deliver speaker-level inputs to the REL, but draw no power from the amplifier. The black wire is a signal ground reference for the speaker inputs. The yellow and red inputs are summed together in the REL. This summing allows the input of a left and right channel which will be summed to a single subwoofer. The yellow, red and black spade terminals will need to be connected to the binding posts on the back of the AHB2 power amplifier. We recommend connecting your speakers to the SpeakON connectors on the back of the AHB2 while reserving the binding posts for the REL cable.

Please read these instructions carefully because the yellow, red and black connection assignments will vary according to one of the following system configurations:

System Configurations

Caution: Never connect the REL BLACK wire to a RED binding post on the AHB2. This will short the output of the AHB2 ground and put it into protection mode. It could also damage the REL subwoofer.

One Stereo AHB2 amplifier feeding one REL Subwoofer

  • AHB2 1+ to YELLOW (left input)
  • AHB2 2+ to RED (right input)
  • AHB2 1- to BLACK (ground input)
  • Set the AHB2 MODE switch to STEREO

One Stereo AHB2 amplifier feeding two REL subwoofers

  • AHB2 1+ to YELLOW and RED of Left REL sub (left input)
  • AHB2 1- to BLACK of Left REL sub (ground input)
  • AHB2 2+ to YELLOW and RED of Right REL sub (right input)
  • AHB2 2- to BLACK of Right REL sub (ground input)
  • Set the AHB2 MODE switch to STEREO

Two Mono AHB2 amplifiers feeding a single REL subwoofer

  • Left AHB2 M+ to YELLOW of REL sub (left input)
  • Left AHB2 1- to BLACK of REL sub (ground input)
  • Right AHB2 M+ to RED of REL sub (right input)
  • Note: It may be necessary to extend the RED wire if the left and right amplifiers are not stacked.
  • Set the AHB2 MODE switches to MONO on both amplifiers.
  • Caution: Do not make any connections to the M- binding post

Two Mono AHB2 amplifiers feeding two REL subwoofers

  • Left AHB2 M+ to YELLOW and RED of Left REL sub (left input)
  • Left AHB2 1- to BLACK of Left REL sub (ground input)
  • Right AHB2 M+ to YELLOW and RED of Right REL sub (right input)
  • Right AHB2 1- to BLACK of Right REL sub (ground input)
  • Set the AHB2 MODE switches to MONO on both amplifiers.
  • Caution: Do not make any connections to the M- binding post

Final setup

Adjust the level of the REL subwoofer by turning the control on the back of the unit.

Additional Information


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