I have a pair of M80 ti speakers, which were probably the first edition. The tag in the back says they are rated at 6 ohms. The current model literature says the M80 v3 is 4 ohms. I called the company and the person I spoke with suggested the M80 was never built with anything but a 4 ohm rating. I am installing an Onkyo NR929 which tells me to set the speakers at either 4 to less than 6 ohms or greater than 6 ohms. Does anyone know when the specs changed? I am tempted to set up the receiver in the 4-6 range. Any thoughts?

Changing that setting protects the amp from exceeding the amount of current going to your speakers. A 4 ohm will potentially draw more current than an 8ohm speaker. The M80's have a minimal 4 ohm spike and should not present any problems for your receiver. Just leave it at default and you will be fine.

In other words set it to greater than 6 ohms.

In other, other words. Never change the impedance switch on a receiver no matter what speakers you have.*


*If the speaker's impedance is so low that the amp shuts down, only change the switch long enough to save up for a new amp, or a different set of speakers.

DP, as some of the previous replies indicated, despite the language in the manual, never switch the receiver to the lower impedance number. This language is legally required because of UL(Underwriters Laboratories)testing for overheating and fire prevention. To minimize the possibility of the receiver overheating with a lower impedance load, setting the receiver to a lower impedance number reduces the voltage output of the receiver's power supply section. Following Ohm's Law, when the voltage is reduced so is the current and power. So the chance of overheating is reduced because of the lower current, but at the expense of reducing the designed maximum power capability of the receiver. Tests have indicated that it's cut roughly in half.

As to the impedance spec on your M80s, it's possible that at one time the spec was based on an average impedance(for which 6 ohms would be a reasonable number)rather than a minimum 4 ohm impedance. In any case, it's nothing to be concerned about, and the setting should remain at the higher default number.

The receiver is now set up and using the greater than 6 ohms setting. It sounds great. Thanks for the input.