Speaker Impedance Settings

[venkman]

I am running an Onkyo TX-SR703 with B&W DM 604 S3's and a B&W LCR600 S3 center. The speaker instruction manuals say the speakers are 8ohm (3 ohm min). The Onkyo has two speaker impedance settings, 4 and 6. It says use 4 ohms if any speaker is 4 ohms or greater but less than 6, or use 6 if all speakers are between 6 and 16 ohms. I have been running it at the 6 ohm setting but I am wondering if that is the correct one. Also, if either setting is okay, will I get better performance at the 4 ohm setting? Thanks.

[Dusty Chalk]

If all the speakers' instruction manuals say that they're 8 ohms nominal, 3 ohms minimum, then you're in a bit of a dilemma.

It certainly wouldn't hurt to try it -- especially since your amplifier can specifically handle 4 ohm loads.

The thing is, you normally do want to match impedances. If it weren't for the 3 ohm minimum, I'd say stick with the higher setting. But since it does dip down, then it might improve things to try the lower setting.

Stick with whichever sounds better.

What you're looking for is not too dry and thin a sound -- that usually implies an impedance mismatch.

[kexodusc]

A lot of commercial speakers with 8 ohm nominal impedances have dips down in the 3 ohm range. It's not down there very long, and shouldn't put any undue strain on your amp. That's A lot different than a 6 ohm or 4 ohm nominal speaker, where the impedance is lower over a much larger portion of the spectrum.
A lot of those impedance selectors on receivers just activate current or voltage limiting circuitry to protect against damage. Might not be a bad idea. Chances are you don't play it loud enough for this to be of concern to you anyway. Doesn't hurt to try.

[HAVIC]

I know I do not know much about impedance, but I was reading an article on audioholics about the impedance of my yamaha rx-v2500 receiver and they tested the difference between running the yamaha at 6 ohm and 8 ohm settings. The conclussion was even running 4 ohm speakers that the reciever performed better at the 8 ohm setting than the running at the 6 ohm setting.

I know you are not running a yamaha but I thought it was interesting to note, that just becuase the setting is there it may not be better.

[kexodusc]

I know I do not know much about impedance, but I was reading an article on audioholics about the impedance of my yamaha rx-v2500 receiver and they tested the difference between running the yamaha at 6 ohm and 8 ohm settings. The conclussion was even running 4 ohm speakers that the reciever performed better at the 8 ohm setting than the running at the 6 ohm setting.

I know you are not running a yamaha but I thought it was interesting to note, that just becuase the setting is there it may not be better.

This is exactly because of the current limiting protection circuitry the lower ohm setting engages. It's not that the receiver performs "better" always with the setting not engaged, but at higher levels, with the protection engaged you're amp holds back, which can be problematic to sound. Personally, I believe if you're running any receiver to the point that limiting circuitry engages, you need to start looking at additional amplification. I've driven the snot out of even crappy Technics and Sony receivers before - they'll play pretty darn loud before they crap out.
The B&W's have a sensitivity at 90 dB, (2.83V 1m) which is pretty good. I'm guessing you could engage the limiting circuitry and never know the difference. Unless you rock the free world your system.