I have a Denon 5.1 av receiver and have bought some new speakers. The only restriction (from my wife) was on size so I have managed to get hold of a set of speakers for the Sony DAV-IS10 (http://www.trustedreviews.com/Sony-DAV-IS10-DVD-Home-Cinema-System-review) which should work. Five 10ohm satellites and a mid/bass dual driving woofer. The dual driving woofer is required as the satellites are very small and don't output a full range. What I planned to do was have the dual driver run off the receivers sub out. I built a lm3886 dual mono amp from chipamp.com driving each woofer as the old amp was fully integrated and needed to work with the original Sony DVD/receiver. I now realise that the Denon receiver sub out is set to low pass at around 100-250hz which is no good for the dual driver.
What I have at the moment is 5 satellites and the sub working with the receiver but the mid-woofer is not really receiving any signal. What I want to do is to use a line level adapter on the speaker outs to draw a 1v line (speakers are around 27v) to the input of the mid-woofer amp similar to http://www.dougcircuits.com/lineout.html. I believe this is simple enough for a single speaker circuit but then I would have to choose which circuit to use. The left and the right channels clearly have different signals at different times. The center speaker is where the bulk of the dialogue sits but I don't know if it contains all the range and effects the left and right get. Ideally pulling one line off the center speaker would be easiest (if that works then great) but I am considering whether I need an output from the left AND right or even all three to get the full range through to the mid-woofer.
What I have not been able to work out is: can I combine these line level signals into one RCA input for the mid-woofer amp? It would be a separate line level adapter at each speaker output but then combined into the mid amp. Is this even necessary... does the center channel put out enough range to cover the mid for the left and the right?
I know that you cannot do this for speaker level outputs as there will be interference and likely shorting of the amp. I believe that the Denon amps use common grounds so that side of things should be okay.