Why do speakers improve with more powerful amps?

One man’s datapoint. Your mileage will vary.

VTL 500 (500 watt monoblock) powering tweeter on a Klipsch Jubilee and VTL 750 (750 watt monoblock) powering the bass on same Klipsch Jubilee. The Jubilee is designed for bi amping and comes with an active crossover. The Jubilee has a sensitivity of 105 db..

https://youtu.be/_7ZGLrOpCQo

https://youtu.be/xUMDlpVu98w

Then the Wotans arrived. Switched the VTL 750 to the tweeter and put the VTL Wotan (1250 watt monoblock) on the bass. It’s not just a bit better, it’s a quantum leap better. Just playing YouTube, man.

Is it headroom or damping factor or whatsoever? Couldn’t begin to tell you. It just sounds fabulous.

Don’t let beliefs stop you. Keep exploring.

Interesting comments about the vtl Monster tube amplifiers above.

vtl website has an interesting few paragraphs about tubes that may be of interest 

https://www.vtl.com/technology/why-tubes/

@chowkwan wrote:

One man’s datapoint. Your mileage will vary.

VTL 500 (500 watt monoblock) powering tweeter on a Klipsch Jubilee and VTL 750 (750 watt monoblock) powering the bass on same Klipsch Jubilee. The Jubilee is designed for bi amping and comes with an active crossover. The Jubilee has a sensitivity of 105 db..

https://youtu.be/_7ZGLrOpCQo

https://youtu.be/xUMDlpVu98w

Then the Wotans arrived. Switched the VTL 750 to the tweeter and put the VTL Wotan (1250 watt monoblock) on the bass. It’s not just a bit better, it’s a quantum leap better. Just playing YouTube, man.

Is it headroom or damping factor or whatsoever? Couldn’t begin to tell you. It just sounds fabulous.

Don’t let beliefs stop you. Keep exploring.

Exactly - keep exploring. And with that in mind, have you tried the Wotans on the midrange/tweeter horns and the VLT 750 on the bass horns? Yes, I know - why the hell would one use the more powerful amp on the HF-section, with the higher sensitivity even? Remember, 750 vs. 1250 watts doesn’t even account for a 3dB difference, and 750W will still get you a mighty long way with the high eff. bass horns. If the Wotans are the better choice on the HF-section, perhaps in triode mode (with the VTL 750 on the bass horns, say, in tetrode mode), then that’s what it is. If found out myself that the more powerful amp on my 111dB sensitive MF/HF horns (>600Hz) was the better choice, though there was only a 50W difference (575 vs. 625W). Common wisdom would’ve dictated the less powerful amp to drive the HF driver, but with so much capacity at hand with 100-111dB sensitivity it really comes down to shuffling the pieces and see what works the best - irrespective of presumptions and numbers. The question of course remains if a further gain in headroom, even with those wattages and very high sensitivity ratings, has a hand in this, and that may bake the noodles around here if people dare to follow that line of thought with the (little) attention typically invested in headroom.

Power supply

Power supply

Power supply

Bigger amps have bigger power supplies. The signal that gets sent to the speakers, is fed directly from the power supply. Bigger power supply, more dynamic headroom. 
 

My 30w class A amp, with a massive power supply - 192uF of capacitance and a 500va transformer, more than adequately drives my 80db 4ohm speakers. 
 

An amp needs a power supply that can handle the difficult passages in a piece of music. 
 

I agree w the comment above where an amp should work within its linear region. And to make a big power amp that is operating in an ideal manner at low power, takes some skill. Having two output transistors per channel vs 16 per channel has some benefits.
 

So many variables when it comes to having great synergy between amp/speakers.
 

There is a dynamic load being presented to a reactive source with an ever changing signal. 
 

Bigger isn’t necessarily better. Better, is better.  

@perkri 

Amazing answer very helpful. Impressive how you drive inefficient speakers with so little. Worthy of study.

That's a really pretty Marantz vintage piece.