I have recently designed a 4-speaker driver circuit using a simple NPN darlington (TIP120). Each speaker is driven individually by a TIP120 and is connected with one terminal on 24Vdc and the second terminal to the collector of the TIP120. The emitter of the TIP120 is connected directly to ground with the base driven by the output of a 555 via a 1k resistor. I have four TIP120s driven by a single 555. The aim of the circuit is just to make a LOT of noise... speficially around 30Wrms of 'noise' with the waveform generated by the 555. The problem is right now, this circuit does not seem to be loud enough but my calculations and simulations show me that there should be around 30+W dissipated by the speakers right now. Can point me to the right direction on how to increase the volume of the sound generated? Thanks in advance.