Why does the bass range of phase mismatched speakers show more interference than the treble range? If stereo speakers are connected to the amplifier "out of phase," one speaker is moving outwards when the other is moving inwards.This results in a weakness in bass notes, which can be corrected by reversing the wires on one of the speaker connection. Why are only the bass notes affected in this case, and not the treble notes ?
 A: I believe the premise of the question is incorrect.
If the speakers are connected in the manner specified, the sound waves for all frequencies will be out of phase, as observed at the surface of each of the speaker cones.
If a single observer is located equidistant from the two speakers, he/she will also observe destructive interference for all frequencies.
However...
Assume that the observer is not on that equidistant plane.
Then the phase relationship at the observer will depend on the path length difference divided by the wavelength of the sound waves.
Bass notes, say $60$ Hz, will have a wavelength of about $5$ metres.  It would take a lot of movement to make the path length difference get as high as $2.5$ metres.
On the other hand, a sound at $6,000$ Hz has a wavelength of about $5$ cm.  A small movement, of the same order as the size of your head, will shift the interference from destructive to constructive, and back, and forth... and so on.
This site, http://phet.colorado.edu/en/simulation/wave-interference has a simulator that allows you to adjust frequency, source separation and observer location, for sound, light, and ripple tank experiments.  The only thing you can't do is change the phase of the two sources!.
