how much voltage is generated by a mic
The input common-mode voltage range of an opamp is the voltages where the inputs work.
For the 741 opamp it is 3V above the negative supply and 3V less than the positive supply. So with a 6V supply the inputs barely work if they are biased at half the supply voltage. It will not work with a supply that is only 5V.
When the supply is only 6V the output of a 741 opamp can swing only 2V peak-to-peak when the load current is very low (10k ohms load).
The datasheet for a 741 opamp shows that the open-loop gain is 200,000 with a 30V supply and drops to only 40,000 with a 6V supply.
An active rectifier circuit needs to have an input that swings below 0V. So a coupling capacitor is needed between the output of the bandpass filter and the input of the active rectifier circuit.
The rectifier diode is included inside the negative feedback loop for the opamp to cancel the forward voltage drop of the diode. The active rectifier circuit uses an inverting opamp.
Are you using an electret microphone?
Why are you using a bandpass filter?
Why is the frequency of the bandpass filter set so high?