The only other person doing with loudspeakers I know is:
See this video from him, it's absolutely awesome!!!
His setups are very complex, microprocessed and all time based... mine are much simpler, triggering with sound trigger circuit to do similar shots is my idea 
Now I want to improve, hopefully Arduino will be the key!
There's also another technique of 2 consecutive water drops... when the first hits a surface and splash upwards, a second drop splash on it. I will try it when I get a solenoid water dropper working.