Audio power LED

General description:

This is a circuit with a two-color LED indicates how much power an amplifier delivers. The circuit is connected across the speaker terminals. At low power, the LED shows green light, at higher power, the color changes to orange to red. 

Circuit diagram:

Part list:

R1 = 10 k

R2 = 2.2 K?
R3, R4 = 100 Ω
C1 = 10 uF / 16 V
D1, D2 = 1N4148
D3 = duo LED red / green
T1 = BC547B