Axiom Home Page Forums General Discussion Home Theater Using 7.1 analog inputs with 5.1 material

I just had an idea yesterday and was wondering if anybody has done it before. I have a 7.1 setup with M60 / VP150 in the front and 2 pairs QS8's in the sides/back. Works wonderful for both movies and music and using Dolby PLIIx or NEO:6 I can use all 7 speakers and enjoy it. When using DVD-Audio with 7.1 analog inputs I can only have 5 channels active and the backs are silent (actually hissing a bit - the inputs are open).
Now my side speakers are a bit ahead of the seating first row and ideally I would like to move them back. So I was thinking of bridging the sides and backs inputs on the reciever inputs (Y-cables or something similar) so that the surround signal is sent to both the sides and backs. This will effectively move the sides a bit to the back and should provide a wider sweet spot. Possibly the directionality will suffer a tad but that should not be a big issue in a fairly small room.
What do you think? It should not take too long to do the experiment, but the stores are closed for Victoria Day and I'll have to wait till tomorrow . I will post the results.
V.

Your idea sounds like it might be a good solution. There's no risk of damaging anything electrically, but you will probably have to bump up the levels in both surround channels to make up for the drop in voltage that will result from splitting the signal.

I had a chance to try it out and it seems to do the trick. I used a RadioShack part - will probably replace it with something nicer eventually however at this length there is hardly any technical justification. I actually had to drop the volume in both the sides and the rears for the 7.1 input setup by about 6dB (twice) to compensate for the added speaker. Splitting the signal is probably not affecting anything - input impedance of the preamps is quite high and does not load the line outputs from the CD/DVD player. On the contrary adding additional amplified channel boosts the signal roughly twice (6dB).
I listened to Hell Freezes Over and the sound certainly opens up. It feels much airier so to say. One thing that was annoying me on this open air concert DTS CD was that the applause was coming slightly from the front (it is mixed into all 5 channels and my sides are slightly in front of the seating front row). Now with the backs working this sounds as intended - from all around you. Makes you look around and check - who is clapping so loud next to you between the tracks. When instruments are mixed hard into the surround channels (like percussion in the right side in Hotel California) they now sound directly from the place in the wall where there is nothing (between the side and the back speaker), but the direction is kept tight. Very enjoyable and lets you almost forget where the speakers actually are. Here is how it all looks now with the QS8's in the sides and the rear: Back of the room.