[petre]

Yes, it's the frequency and also the amplitude that makes it faster. One could use a lab agitator but it would still be too slow. I think if you pour the water into an ultrasonic cleaner along with the coffee and filter the mix you might get the same result.

[fch42]

That's precisely the thought which has taken hold of me now as well.

The ultrasonic cleaner is always stashed away somewhere safe for its once-a-year use ... I think can't resist to experiment.