Question about high current amps versus "not high current amps"

To your weight lifter analogy;

I would liken the weight lifter to the amplifier, the weight he's lifting to the speakers, and the power supply to how much muscle (power reserves) he has.

Theoretically, the more muscle he has (capacitance), the more weight (low impedance speaker) he can lift with minimal strain.

@thecarpathian

No, I would not, because they are really two units and both have to be up to par.

I'd say the muscles are the output stages (transistors, tubes, etc.) and heat sinks.  The power supply is the stage he's standing on.  Both have to be strong enough for the weight. 

I'm adding heat sinks because they are a major enabler for Class A and A/B designs.  You will melt your transistors without adequate heat sinks.  Though truth be told the legal requirements to rate an amplifier n Watts may cause many amps to have exaggeratedly large heat sinks for music playing. 

Now I get why you said it the way you did.

A couple more aspirin and I may have this partially figured out..

The topic of "high current" wouldn’t matter if speakers worked like plain resistors - e.g. acting as the same constant 8 ohms value (or 4 ohms, or 2 ohms) at every frequency from 20Hz - 20kHz. But speakers don’t do this; not even close. Hop onto Stereophile’s online archives and look through the measurements for various speaker models - they often include a graph of impedance (ohms) versus frequency. The curves you’ll see are very, VERY far from the straight flat line you’d get from a plain resistor. Of course it’s more complicated than just that, so they also include a phase angle curve.

So what happens when an amplifiers tries to drive one of these "variable impedance" curves? Well, if it’s a:

• "High Current" amplifiers will produce more power into the "dips" of the curve (lower impedance), thus relatively boosting the SPL at those frequencies. The gold standard of these is amps which claim to "double down", which is the theoretical limit for load invariant amplifiers (e.g. produces twice the power into a 4 ohms load verus an 8 ohm load). These amps are also called "voltage sources", becasue their voltage output remains constant (does not dip) while driving loads of increasingly smaller ohms.
• "Low Current" amplifiers (though nobody calls them that) will NOT produce more power into the dips - though in practice they are affected, and will produce some amount that is more or less depending on numerous factors. But they typically will NOT come close to "doubling down". These amps are also called "power sources".

So which is better? It totally depends on how the speaker was designed! The designer has to (somehow) balance these disparete drivers, crossover, and (likely) amplifier behaviors off of each other to produce a result that sounds natural. If they designed with "only" high-current amplifiers, the speaker will surely sound different driven from a tube amp, and vice versa! What’s perhaps surprising is how many speaker models sound good - albeit different - from both high-current SS amps and tube amps.

Most ported speakers will show a HUGE bump in their impedance in the bass region, right around where their actual bass response starts rolling off. That’s due to the port tuning. You’d think this would mean a high current amplifier should sound "anemic" at these frequiencies, from the high impedance (where they produce much less power), but the reality is this bump represents a "resonance" where the speaker system is actually particularly efficient at generating those frequencies. So yeah...a lot of complexity for a speaker designer to juggle...

@thecarpathian  Maybe an easier analogy is legs vs. arms. 

You need both to be able to dead lift.

That’s it, I’m out of aspirin...

Plus I use a leg press machine, better on your back...