You don't want a low power amplifier almost clipping when there are inaudible infrasonic rumbling "sounds" from traffic and aircraft.
A speaker will not produce the very low frequency sounds. The feedback will be at the most sensitive frequency which is about 4kHz for a cheap little speaker.
You can't close mic brass or reed instruments with electret mics because of overload problems. You really have to be careful how high a sound level they will receive.
Hi, Audioguru,
It was a tongue in cheek reply to the posts further back between Mikebits and Colin55.
One, an American and one Australian both having a spat over the mic answers.