Thank you all for interesting responses. I'm not sure why RA decided to keep the taps inside, but I assume there must have been a good reason for it. Here's an excerpt from the Cronus manual regarding the impedance setting:
The Cronus also provides options for either 4 or 8 ohm speakers. The impedance selected will depend on the speakers used. Consult either the owner's manual for your
speaker or your local dealer to determine the correct choice. The amplifier is factory set to 8 ohm.
To switch impedance setting:
1) Using a #2 phillips screwdriver, remove the top cover or deck.
2) Using a 5/16 wrench, remove the outermost nut from the positive (red) binding post.
3) Remove the 8 ohm tap (green wire marked 8) from the binding post. Be careful to leave the black wire with heat shrink on the post.
4) Remove the polyurethane tubing from the unused 4 ohm wire (yellow) and lug.
5) Place the 4 ohm wire onto the binding post and replace the outer nut.
6) Place the polyurethane tubing on the 8 ohm wire and lug.
Not looking forward to fiddling with this, I must say. I just hope it sounds more complicated than it actually is...
Another point I wanted to make and see what you guys thought about it is the fact that most speakers' impedance is not linear but varies across the frequency spectrum. Out of curiosity I went through a few copies of Stereophile yesterday and checked the graphs in the tech specs section. All of the speakers reviewed including ones in the $30-40K price range exhibited impedance that was both above and below the specified nominal impedance. If that's the case, wouldn't the arguments about "light loading," considerations about losing power or halving power be rather moot in practice, given the fact that the amp is presented with different loads depending on the frequency?
