The first watts

So your speakers, rated at 87 dB @ 1 watt, should be able to get up to 97 dB in an amp that switches over to Class AB at 10 wpc. Probably most of your listening would be in Class A, unless you are a headbanger.

Sorry, that's not exactly right. The speakers are rated at 87dB/2.83V/m and since the speaker is 4 ohm, that will be 2 watts. Then there is a gain for 2 speakers, and a loss for listening distance greater than 1 meter. So a rough estimate for a distance of 2.5 meters using 10 watts would be ~92dB. Also, even if the average SPL is 75dB, some music can have dynamic peaks of 95dB and higher. If you really want to know, get a sound level meter, and measure the peak SPL when you listen.

If you use an iphone you can download an app with a fairly accurate spl meter. I find I rarely listen much over 70db in a small room. This was a surprise to me.

This makes me think your amp is operating mostly in class A.

I got the app. It seems my listening preference is between 75 and 85 dB. That's 8 to 9 feet away from the listening position to the center of the speakers. I'm not sure what that equates to in Watts

It seems that there is a disconnect between theory and practice here. A speaker rated at 87db is considered to have moderately low sensitivity. I would say that most speakers have a higher sensitivity today.

If 10 watts powers that speaker to 92db, that is loud. Wouldn't a 100 watt amp be a monster amp? They certainly aren't considered that these days. Any ideas why that is?

If 10 watts powers that speaker to 92db, that is loud. Wouldn't a 100 watt amp be a monster amp? They certainly aren't considered that these days. Any ideas why that is?

If 10 watts powers the speakers to 92 db at the listening position, 100 watts will power them to 102 db at that position (assuming the speakers can handle that power level without thermal compression or other problems).

As Tony (Tls49) said, "even if the average SPL is 75dB, some music can have dynamic peaks of 95dB and higher." I have more than a few classical symphonic recordings in my collection which when played at average levels in the 70's will reach occasional brief dynamic peaks of 100 to 105 db, at my listening position.

The ability of the amp to comfortably handle such high volume peaks will be less of a concern, of course, with many or most pop and rock recordings, which are typically compressed to narrow dynamic ranges. Often to the extent of having less than a 10 db difference between the loudest and the softest notes.

Also, I'll add that in the absence of specific technical information about whatever SPL meter is being used to measure these levels, I would not assume that a given meter necessarily responds fast enough to capture the true maximum volume of a brief dynamic peak.

Regards,
-- Al