Out-of-phase stereo speakers suffer reduced bass from acoustic short-circuiting.

Evidence

Dipole effects could be degrading the performance of your sound system. There are two wires leading to each speaker. If you switch the two wires on one speaker, the speaker cone will reverse the sense of its motion, moving out when before the switch it would have moved in. If one speaker is wired correctly and the other one not, the speakers are 180 degrees out of phase. The consequences for higher frequencies are not great, although there will be some distortion of the apparent placements of different instruments. There is a serious consequence for bass response, however, which will be reduced by acoustic short-circuiting. One speaker cone is moving in, while the other is moving out, partly canceling the pressure undulations for frequencies whose wavelength is longer than the distance between speakers. — Eric J. Heller, Why You Hear What You Hear- An…, 612

Categorization

• CANDY: While never tampering with the speaker wires is the immediate lesson, the acoustic short-circuit concept is a fun, concrete takeaway.