Class A bias, speaker sensitivity, watts...?

If your amplifier had VU meters your question would have been easily answered.

Yeah, you are still in class A. Unless you have really inefficiant speakers, or a very big room, most of us are only using a couple watts for normal listening. 

Around 80db at my listening spot is also around a watt. 10w is vibrating the house, 100+w is vibrating pictures off walls. 

It’s really easy for me to figure. My amps put out about 10 watts class A into 4 ohms. My speakers are rated at 91db at one meter and my listening position is 2.5 meters from my speakers and seeing as I rarely go past 75-80 dbs, I’m I’m class A most of the time.

@tomcy6

I’ll tell you what I think I know and someone can correct me. Class A watts approximately halve from 8 ohms into 4 ohms, so you have between 5 and 10 watts of class A power.

You invited a correction, so here goes.  (If you were talking about the point where a class AB amplifier starts to move from class A to class B and starts to exhibit cross-over distortion, forgive me!)

Most amplifiers provide voltage gain - the output voltage should be a multiple of the input voltage. When the amplifier is connected to a speaker, current flows which makes the amplifier work harder to keep the voltage the right multiple.

The amount of current flow depends on the impedance of the speaker. It turns out that the amount of power required doubles every time the impedance is halved. For example, my venerable Class A Krell KSA-80 is rated at 80-Watts into 8-Ohms, 160-Watts into 4-Ohms and 320-Watts into 2-Ohms.

Marketers sometimes use this to misinform, by publishing an amplifier’s power into 6-Ohms, or even 4-Ohms. The latter doubles the boast!

Almost all speakers have different impendences at different frequencies, and many have big dips at crossover frequencies where two drivers have to work in parallel. That’s where an amplifier with big current reserves scores. A quick way to check an amplifier’s current reserves is to compare its power into 8- and 4-Ohms. Ideally it will double, but rarely does

@richardbrand

Yes, I agree with what you’re saying.  I was trying to address a different matter.

I was told by an amp manufacturer whom I called (don’t remember which one) that the class A watts are specified at 8 ohms and would approximately halve into 4 ohms. In my case it was 25 watts in class A into 8 ohms, but that dropped to 15 watts in class A into 4 ohms. I assumed other amps operated the same in that matter. Is that your understanding?