Perhaps you mean to run an extra set of speaker cables and split the input wiring to your loudspeakers, as in the "bi-amp" of your topic title. I'm not sure you'll experience true bi-amped stereo with the 5-Stereo signal matrix modified for an active center speaker. Certianly something you might experiment with if you got the time. The speaker delay/distance settings for all channels involved in the bi-amping might need to be adjusted to the same value.

If you're talking about having two outputs wired in parallel to a single speaker while in a surround mode, you might want pull the reins in and shout "Whoa!" Why?

1) Most receiver output stages simply are not meant to be tied together!

2) Even output stages in some pro gear that will tolerate such wiring must be practically guaranteed to be outputting the same signal at the same amplitude and, ideally, perfectly in phase.

Imagine this scenario: a "whoosh" sound is designed by the audio production team to travel from the front speakers, then envelope the whole area without localization, then sweep out the back.

In the first third of this scenario, the front outputs begin to produce a signal while the surround outputs are by design absorbing any back EMF present thus providing damping to the surround speakers. But wait! The front outputs are supplying a voltage directly to the surround outputs which will "absorb" this voltage into a very low impedance - the fronts are driving a near short comprised of the surround output transistor stage! All output stages are stressed.

In the middle third of this timeline, the front and surround channels are actually attempting to output through shifting phases, including 180° out-of-phase. At some moment in time the fronts are attempting to output 12 volts "positive" while tied to the surround outputs attempting to output 12 volts "negative." If you've got independent power supply stages feeding the output stages, this is akin to using jumper cables on two cars but with plus-to-minus and minus-to-plus - read massive currents! If you are feeding all output stages from the same power supply, this is akin to placing four or more output transistors in a row between the positive and negative terminals of a car battery.

Your output stages had better be "dead short" protected or better.

Third section of this scenario is like the first, except the fronts are at their 'zero point' while tied to the surround channels trying to achieve an output.

I highly doubt you'll hear pleasing sound during such an event.

If you've already tried this, I hope you've kept the volume at very low levels. If not, you will likely need to saddle up and head for either Repairsville or Replacementown.

I doubt you mean to try the output channels tied together, but just in case someone does get that idea, I thought I'd mention these problems.