When you have more than one speaker, the speakers interact with each other to create a sound field. Sound designers/mixers have the ability to place sounds in various locations within the sound field since they understand the relationship between each speaker. In order for your speakers to faithfully reproduce the sound field, your speakers must all be wired the same way (or in-phase). All negative (-) outputs from the receiver should be connected to the same color (-) input post on each speaker and all positive (+) outputs should be connected to the same color (+) input post on each speaker. If your speakers are out-of-phase with each other, the overall sound will lack the fullness that in-phase speakers reproduce, and you will not hear what the sound designer/mixer intended. Even if only one speaker is wired the opposite way, the sound image will not be correct.
Sounds can be mixed between channels so that they appear centered between the channels or dispersed in nature. If an effect is to sound centered between two channels, an identical level of sound will be directed to each of the two channels desired “in-phase” with each other. The same signal but “out-of-phase” with each other will produce a wide and dispersed sound image. Improper speaker wiring can produce an out-of-phase image by reversing the two wires that feed the speaker. Proper speaker phase is not only important for the front left and right channels, but the center and surround channels as well.
During each Phase Test, the two speakers indicated on the still graphic will emit test tones that alternate being in-phase and out-of-phase. By observing the sound image that is produced by each speaker test sequence, you will be able to determine if your speakers are correctly wired. Listen to these tests by positioning yourself centered between the speakers under test. “In-Phase” will produce a sound image centered between the channels under test while “Out-of-Phase” will produce a sound image that is wide and dispersed and difficult to localize. If you hear an out-of-phase sound image when the image is supposed to be in-phase, and vice versa, turn off your audio amplifier. Next, reverse the wires that feed the speaker highlighted with a red box in the still graphic. Once this correction is made, verify that the correct sound images are now being reproduced, and then proceed to the next test.
Note: This test is most effective for 5.1-channel or 7.1-channel systems only. If your audio system has only two channels, you may reference the left and right front test only. If you have a 7.1 system, the phase tests for the surround channels will appear in the surround back channels during the in-phase test and in the surround left and surround right channels during the out-of-phase test.