Need some help with Yamaha RX-V1 and Mirage OM-5 speakers...

[beekermartin]

I bought a new audio rack and while I was rewiring everything I remembered that I wanted to find out more information about the impedance selector switch on the RX-V1.

I have it in the upper position which basically has all speakers at 4ohms. The lower position is 8ohms. The OM-5's are rated for 6 ohm nominal, 4ohm minimum. All of the remaining speakers (Mirage OM-C2 center, OM-C3 rear center and OM-R2 surrounds) are rated at 8ohm nominal, 4ohm minimum.
The OM-5s are rated at 90db for room effeciency. Which I think is fairly easy to drive.

I left it in the upper position for fear of damaging the OM-5's or the receiver. I have been doing a lot of searching and reading and mostly everything I have found says that I should set it to 8ohms. What do you guys think I should set it to?


BTW, the RX-V1 just fits in the new rack. Sanus makes the rack. Basically it sits on a glass shelf which is open on all sides except for the 3 support legs, two in the front one in the rear. So there is plenty of ventilation on all 4 sides but there is only 1inch above the receiver before the next glass shelf. I am hoping this will be ok.

 

[rschleicher]

impedance switch

I have the same impedance switch on my Yamaha (an RX-V750), and had the same question. My Def Tech speakers are stated as being "compatible with 8 ohm impedance settings", but have a minimum impedance more like 4 ohms.

I saw in a Yamaha review someplace that the lower impedance setting of the switch basically selects a lower voltage tap of the output transformer, thereby reducing the peak current that can flow into a lower-impedance load. This may help to prevent over-heating problems, but it also means that clipping occurs at a lower power level. In fact, in the review I saw, the output power into a 4 ohm load was (as expected) twice the output power into an 8 ohm load, with the impedance switch set at 8 ohms. But, with the switch set at 4 ohms (and the load at 4 ohms), clipping occurred at a much lower power level. My conclusion was that you are best off using the 8 ohm setting for any speaker, as long as you are a little watchful of the receiver getting hot (like really cranking all channels). I would certainly use the 8 ohms setting if you only have a single set of speakers connected to the front channels.

If it's any other comfort, I asked the same question via an e-mail to Yamaha tech support, and got the short reply to "use the 8 ohm impedance setting - it will sound the best".

 

[shadow]

Use the 8 ohm tap for better sound and more dynamics. Stereophile Guide to HT reviewed this receiver a few months ago and found that with difficult four ohm speakers it still put out plenty of power and never shut down on the eight ohm tap.