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Amplifier current vrs watts; why is current more important?

Lately when talking to knowledgeable people in the audio industry I’ve been hearing how current delivery is more important than watts in determining weather an amplifier will drive a speaker.
So what exactly is current and how does it effect speaker performance? How can a amplifier rated at 150 watts into 8 ohms vs one rated at 400 watts into 8 ohms be a better match for a hard to drive speaker?
hiendmmoe
hiendmmoe
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atmasphere's avatar
atmasphere
11,800 posts
 
But a monoblock amp like the "Legendary" old Mark Levinson ML2 monoblocks that are only 25w!! into 8ohms, will sound better into them, because it’s said they double their wattage for each halving of impedance all the way down to 1ohm with the current it can generate, so they will stay flat in frequency response, where the 500w’ers will sound like a tone control.
What is important is that the amp behave as a voltage source, not whether it can double full power as the load is cut in half. The latter is a subset of the former.

Of course, a good number of loudspeakers in high end audio don't even expect the amp to behave as a voltage source. That is why there are so many successful  zero feedback tube designs, which behave more like a power source.
georgehifi's avatar
georgehifi
10,312 posts
 

Doesn't matter what "spin" is put on it, when you have good current, the amp stays flatter in frequency response, instead of looking like a tone control.
An amp needs current along with the watts, as these frequency response graphs show, of the same "wattage" amps with and without good current ability into the same easy speaker load.
https://forum.audiogon.com/posts/1730185

Cheers George


 
mijostyn's avatar
mijostyn
8,570 posts
 
Hi atmasphere. I love your amps by the way. If I had reasonably normal loudspeakers I'd have a pair for sure. I have my eye on a pair of Soundlabs which I understand do wonderfully with your MA 2s.
I am not sure I understand your last statement. Are you saying that zero feedback amps can supply more current and would do better driving low impedance loudspeakers?
atmasphere's avatar
atmasphere
11,800 posts
 
I am not sure I understand your last statement. Are you saying that zero feedback amps can supply more current and would do better driving low impedance loudspeakers?
No. I am saying that some loudspeakers (like Sound Labs) don't need a very low output impedance in order for the amp to sound right on them. Other examples are most horns, most full-range-driver loudspeakers (like Lowthers) and other speakers where the designer found that he preferred the smoother sound of tubes.
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