Can I mix and match 8 Ohms and 6 Ohms speakers

Yes you can, I'm doing it right now with a mix of Energy and Jamo speakers.

Just leave the setting on 8 ohms. Most receivers don't even have a 6ohm/8ohm switch. Non of my 3 receivers do and none in the past did either including one Yamaha receiver.

If you had 4 ohm speakers then yes your receiver might overheat but not 6 ohm speakers.

The RX-V667 is a very capable receiver, I wouldn't worry about it. Especially since the BS-21s will be surrounds which don't get nearly as much content as front three speakers.

You can switch it if it makes you feel better but I don't think its necessary.

Just run YPAO again after you connect the surround speakers so they'll be calibrated correctly.

You asked for it, you got it! Macrame plant hanger

I ran 4 ohm surrounds in a 6.1 setup with 8 ohm L/R/C via a Pio VSX-01 for several years with no problems at all.

what if its the other way around, receiver is rated at 6ohms and you have speakers rated at 8ohms. Is that a danger to the receiver/speakers?

Any receiver rated for 6 ohms can also handle 8 ohm loads. 8 ohm speakers are easier to drive...

There is fish hook $4 a pack -just my made up name- I bought at Home depot near paint section or picture hanger, it's a half circle and extended arm, just poke it into the wall and can hang up to 80 pounds.

They say a picture is worth 1k words, have any to share?

People say the darnedest things. There's a guy who posts over in the Paradigm forum that seems to want to convince people that hooking a Paradigm speaker to an AVR is like taking your foot and kicking in the cones of all of the drivers.

That's because there is usually nothing to notice.

The leading cause of AVR overheating is lack of ventilation.

The leading cause of blown speakers is trying to play them too loud, and tolerating way too much distortion. Being intoxicated seems to be an enabler.

No.

Read this:
http://www.audioholics.com/education/amplifier-technology/impedance-selector-switch-1

Unfortunately it contains the following audiophile myth:

"Amplifier clipping is bad because it takes the undistorted waveform and essentially clips off the top and bottom of it. This creates high frequencies not present in the original signal, in a word, distortion. When done to extremes, the original signal can be converted from a sine into a square wave. The square wave includes high frequencies not originally present in the signal, which represent a real hazard to the loudspeakers systems high frequency device(s) voice coil(s). Clipping is therefore especially dangerous to small light and delicate high frequency loudspeaker components in a system as the square wave contains far more high frequency energy than was found in the original music signal. It can take an unclipped musical signal sending 5% of the energy to the tweeter, and suddenly send 25% of the increased power available to the tweeter. Clipping, despite what you have read on the blogs, is rarely damaging to woofers by comparison."

The following is a spectral analysis of a fairly ordinary piece of music as compared to a square wave:



The point being that regular music can have more high frequency information (blue) than the allegedly damaging square wave (green). If I cherry picked my music, for sure!

No what clipping does is cause the overall power output of the amplifier to continue to increase in ways that may not be expected.

The true and relevant rule about not damaging speakers is to avoid turning the volume up past the point where the music sounds impaired to an unimpaired listener. ;-)

That's 100% factual. What's a myth is when the key phrase 'high frequency devices' is omitted, and the facts are corrupted to the simplistic phrase 'clipping kills speakers'. Your posted chart doesn't show the difference between an ordinary piece of music at a nominal 1% THD as opposed to the same piece with a potentially tweeter busting 20% THD, so it's not relevant.

One trick we used to use in pro-sound to make sure we weren't clipping any gain stages, back in the days before there were clip indicator LEDs at every point in the signal chain, was to use a piezo tweeter as a clipping detector. We'd run a 100Hz signal with only the piezo hooked up to the amp, with the amp at a low level. The piezo would not reproduce a 100Hz signal, of course. But when you turned up a gain stage enough to clip it harmonics of that 100Hz signal would be created and you'd hear them through the piezo, kicking in around 1kHz.
Edited by Bill Fitzmaurice - 4/26/13 at 9:08am