Speaker loudness

See image below re how to improve output from 555 timer to increase loudspeaker power

Thanks Mark! I have to confess that this design has me thoroughly confused. As you can probably tell, I am a hobbyist, not a professional engineer. Can you explain the principles of your circuit so I can do the same for my son?

Thanks again!

My 13-year-old son is building a metronome for a Boy Scout electronics merit badge. We built the basic timer out of a 555 with a diode across the R2 resistor so we can control the duty cycle of the circuit. The idea was to have the 555 emit a short (~-50 ms) pulse at a regular interval. We then run the pulse through a 2N3904 transistor that drives a small (2") 8-ohm speaker. This is all driven by a battery pack of 4 AA batteries in series, or a single 9V battery.

The circuit works GREAT, with one exception. The "tick" from the speaker is not loud enough to be useful while he is playing hi instrument.

The question: how can we increase the amplitude of the audible 'tick' from the speaker? Should we change to a different (louder) speaker, or is there another solution that will work?

Thanks!