Question’s re: Output Taps

[miatadan]

A few years ago when I had the MC302 power amplifier, I had the Martin Logan Spires connected to the 8 ohm taps, for whatever reason it sounded better than the 4 ohm taps but the amplifier would run for hours with the heat sinks just getting slightly warm. Do not even matter if I had it at max volume ( 300 watt peaks )

I then sold the Martin Logan’s and purchased Magnepan MG 1.7i speakers.
At first I hooked up the Magnepan’s to the 8 ohm tap , like the Martin Logan’s but after about a half hour the amplifier at just past 30 watts output, shut off and go into protection. Heat sinks would be hot enough to burn your hands. I was forced to use the 4 ohm taps and no more issues with heat sinks getting hot.
But the sound quality was not the same as when at 8 ohms. This goes back to 2016.

Later in 2018 replaced MC302 with MC312 ( part of insurance replacement due to break-in. At that time changed to Magnepan MG 0.7s as moved to apartment with smaller living room . I used the 4 ohm tap, afraid to try 8 ohm tap with past experience.

This January replaced the MC312 with MC462 power amplifier. Noticed that the 8 ohm, 4 ohm and 2 ohm taps had individual + and - post compared to 1 negative post and 3 posts + for 8, 4 and 2 ohms.

Ran the amplifier at 4 ohm taps for about a week and a half. The Magnepan’s did sound better than it did with the MC312.

Last night decided to try the 8 ohm taps again on the MC462.
This time, the heat sinks are just as cool to touch as it was on the 4 ohms tap. Does not matter how loud I am playing music. And yes it does sound better on 8 ohm taps than 4 ohm taps on the Magnepan’s.

What confuses me is why do both the Martin Logan and Magnepan’s sound better with the 8 ohm tap when the recommended impedance for both is 4 ohms.

Why does the MC462 stay cool on the 8 ohm tap with Magnepan’s but the older MC302 when go into protection + heat sinks getting super hot after half a hour?

Any scientific reason for this ?

Dan