For whole house audio, I have my amplifier (Harmon Kardon 3490 with 120 watts per channel) connected to three pairs of speakers in parallel. Each set of speakers is connected to an impedance matching volume control. Two of the three pairs of speakers are identical 20-100 wrms in-ceiling speakers (Polk RC80i). The main speakers are a pair of Bose powered through an accoustimass calling for 10- 200 watts/channel.
This set up worked fine with the Bose and only one pair of Polks. When I added the second pair of Polks (and adjusted the impedance settings on each of the three volume controls) I found that the second pair of Polks was louder than the other two speaker pairs (even when its volume control is set to minimum and the other speakers' volume control is set to max) and the amplifier switches itself off intermittantly to protect itself.
What do I need to do to get these three pairs of speakers to match approximately in volume and have an appropriate level of impedance?