Hi,
To further complicate matters, some receiver manufacturers (JVC for one) used to wire the "A" and "B" speaker outputs in series--if you wanted A and B running at the same time--to prevent consumers from lowering the impedance to the point the receiver would overheat or shut down. You can't assume A and B speaker selectors are wired in parallel.
If all he wants is okay background music, the series connection will work fine. It's just that with series connection, the impedance curve of one speaker may affect the frequency response of the other, and vice versa. They'll interact with each other with unpredictable sonic results.
Regards,
