Faishal, the LM383 at 7W output seems overkill for an intercom. and if you're making an intercom, have you thought about using the speaker as a microphone? There is a very simple circuit for an intercom on the data sheet of the LM380 (a 2W amp that does not require a heatsink) here (fig 18) using the speakers as microphones but you'd need to source a 25:1 audio transformer which may or may not be easy.
If you're committed to the LM383, for 1W out it would need a signal of roughly 10mv so would probably work with a microphone (depending on the type) but a preamp is probably not a bad idea, especially if you can introduce a bit of compression (loud inputs are amplified less than small inputs, resulting in a more level output over a wider range of inputs). You can adjust the gain of your LM383 by adjusting the ratio of R3 / R1 (the higher the ratio the higher the gain). If you can't get a loud enough output then try using a preamp.
