8 Ohm Output into 4 Ohm Speakers

The amp will make less power and greater distortion. By cutting the impedance in half at the output, you are also cutting the load that the power tubes see in half as well.

If you drive the amplifier hard, that will result in shorter tube life.

Check your owners manual. There is a procedure for switching the impedance setting on the amplifier to use with 4 ohm speakers.

Thanks!  I know I can change the leads inside the amp, but it is a mighty pain.  But that is the way to go.   

I did it on mine; it was easy.

My speakers are rated at 6 ohms.  I first tried the 8 ohm setting on the Cronus Magnum for a few months, then switched to the 4 ohm setting for a month and when I switched back to the 8 ohm setting again, I felt that gave me the best sound.  You won't ruin anything by putting the 8 ohm speakers on the 4 ohm taps or vice versa.  I got this directly from Rogue Audio.  They told me to experiment and what sounded best to MY ears was the best way to go.