I figured I'd post some clarification on the different ways you can configure the "B" speakers, as you have several options with the flexible Denon setup:If you are using the "B" speakers for dedicated two-channel music, and want to automatically turn OFF the regular 5.1/7.1 setup when you engage "B" speakers:
Hook up your 2-channel speakers to "FRONT B" terminals, and set the FRONT SPEAKER SETUP (pg 27 of manual) to:
2. DIRECT/STEREO = "B"
3. MULTI CH = "A"
With this arrangement, whenever you are in a multichannel mode (Dolby Digital, Pro Logic, Multi CH IN, etc.) the Denon will use the main 5.1/7.1 speakers (with Front "A"), and if you switch the receiver to "Stereo" or "Direct" mode, it will AUTOMATICALLY turn off all the speakers except for the two "B" speakers.
The "Speaker A/B" selector button will be deactivated with this setting, and the ONLY way to switch between "A" and "B" is by selecting Stereo/Direct vs. a multichannel mode. It will happen automatically, you no longer have manual control outside of selecting a Surround Mode.
With this setting, the big advantage is that you can independently control your speaker size / bass management settings for the "B" speakers by using the "2CH DIRECT/STEREO" menu if you have a dedicated 2CH music setup.If you have two pairs of front speakers and want to manually switch between them:
Leave the FRONT SPEAKER SETUP on "Normal" mode, hook up your "B" speakers to "FRONT B". The "Speaker" button on the receiver will now be active for manual control and you can choose: "A" only, "B" only, or both "A+B" simultaneously (see pg 42 of the manual).
In this mode, the "B" speakers will share the same channel level / speaker size settings as the "A" speakers.
Note, however, that the "A" and "B" speaker posts share an amplifier, so if you try to run them at the same time you will be presenting a parallel load on the amps (as SoundofMind points out above) and will half your effective impedance.(ALTERNATE OPTION) If you want to run A+B simultaneously and are only running 5.1:
If you are only running 5.1 and aren't using Zone 2, you can utilize the two spare SURR.BACK/AMP
ASSIGN channels to power the "B" speakers.
Set AMP ASSIGN to "FRONTB BI-AMP".
1. Hook up "A" speakers to FRONT A
2. Hook up "B" speakers to SURR.BACK/AMP
The SURR.BACK amps will now power the "B" speakers separately from the "A" speakers, and can be switched on/off using the "Speakers" button on the unit.
Again, in this mode, the "B" speakers will share the same channel level / speaker size settings as the "A" speakers.