I have two amplifiers using LM386. One of them I plan to use for normal amplifier and the second one I want it to be a low pass amplifier/bass amplifier and both of them will be connected to same speaker. My question is: is it possible to run two amplifiers in the same speaker with different frequency (there is no high tone in second amp) and how should I wired them, bridge or parallel?
No. Connecting the output of two amplifiers to the same speaker in parallel is not a good idea.
Slight variances in amplified signal at specified periods of time produce a voltage (difference of potential). In this situation you'll have something similar to shortcircuit.
Of course, you could add some series resistors, but this would modify speaker impedance and reduce output power, which isn't too much when using LM386.
You could wire them as a bridge configuration. Something like this:
As you can see, it has only one input. So, you should use a simple preamplifier to mix the different frequency input signals.
You are probably overthinking this. Use passive filters for your tone circuit. Should not affect your battery power. If you are only interested in bass boost...try connecting a 10k resistor in series with a 0.033uf capacitor between Pin 1 and Pin 5 (you should get up to 5 dB bass boost).