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

Hello

Please help me understand the relationship between Class A bias and wattage output. I recently bought a used Vincent Audio SV236MK used for a great price. The specs state 150 watts into 8 ohms, 250 into 4 ohms, and the first 10 watts being Class A @ 8 ohms.

My speakers are Sonus Faber Lumina II which are rated as 4 Ohm with 86db sensitivity. Everything is set up in my small cube shaped office. I used a DB meter on my iPhone and found that when I turn the volume up to what I consider to be "loud" the peak measurement I get is 80db and under.

 

Given the specs above, am I hearing mostly/all Class A watts while listening?

craigvmn
erik_squires
16,383 posts
 

Depends how far you are measuring at and whether your iPhone’s DB scale is reliable, but probably. Sensitivity is rated at 1 meter, so you should make sure to measure around that distance.

You’d be amazed how little power most of us actually use while listening.

If you want to be sure, get a 60 Hz test tone and an AC capable multimeter. Turn turn the volume up slowly until you measure 2.83 V AC at the speaker input. That’s 1 Watt at 8 or 2 Watts at 4 Ohms.

Also, if you are playing in stereo you'll get a 6 dB bump.  That is, if you put out 2.83V into 2 speakers you'll measure 6dB more than into 1 speaker.

craigvmn OP
3 posts
 

Both speakers playing, distance is just shy of 2 meters

dlevi67
54 posts
 

Take away another 6 dB for doubling the distance.

Were you doing the test with a pure tone input, or listening to music?

craigvmn OP
3 posts
 

Just music. "Turn turn the volume up slowly until you measure 2.83 V AC at the speaker input" as in the speaker terminals on the speaker? Or should it be at the speaker tap on the amp?

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