I recently purchased the Onkyo TX-NR5009 as an upgrade to use with a new Sony VPLHW30ESB 3D projector. I also wanted to swap out my front speakers (Infinity Studio Monitor 155's) for a pair of the M80 Axioms. Defintely nothing wrong with the Infinity's, but the Axiom's had a smaller profile and I wanted to be able to use as much of the available projection space I had available to me as possible (the Sony VPLHW30ESB is simply an awesome machine!)and the SM 155's cut into that. So, I was thinking about trying the M80's. I contacted Axiom, but they didn't know if I could use them in my system which was basically an 8 ohm system ... two fronts, center, two surrounds, two back surrounds, two front wides, and one sub.
Page 13 of the Onkyo manual states that if any of the connected speakers is 4 ohms or more, but less than 6 ohms, the minimum speaker impedance has to be set to 4 ohms. But on the bottom of page 14 of the manual, it states that you cannot set speaker impedance individually. So, my question basically was this: Is this a bad idea ... to use a pair of 4 ohm speakers in what is essentially an 8 ohm system? (Page 13 of the manual also mentioned that using speakers with a lower impedance might cause the built-in protection circuit to be activated if the amplifer is used at high volume levels for a long period of time ... but, were they referring to all speakers in the system having a lower impedance, or would that happen if one were to use just two lower impedance speakers as I would like to do?)
Anyway, I contacted Onkyo. I didn't get a response, so I contacted them again. This is their reply: Hope it helps.
"You can't use both 4 and 8 ohm speakers onto this unit- doing so will cause damage to the speaker channels. You can use both 4 and up to 6 ohms- no higher and not affect the receiver as much as using 4 and 8 ohm speakers."
