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Friday, January 18, 2019
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  Stereo Polarity & Sweep Test

Background Information

Depending on how a speaker has been wired internally or connected to the amplifier, it will either move in or out in response to a given input signal. As long as a single speaker is concerned, this direction has no influence on the percieved sound. Our ears are simply not sensitive to the absolute phase. However, when using two (or more) speakers, polarity defines how these speakers interact with each other. Speaker polarity then becomes a very important parameter to check.

When polarity is wrong, the speakers will be out of phase. One will move in, while the other moves out. At the listening position (right in between the speakers) the displaced air from one will be cancelled out by the other. This effect - stronger at lower frequencies - will result in a loss of bass. It also drastically distords the stereo imaging.

The Audio Files

  1. monoral low frequency rumble "in phase"
  2. monoral low frequency rumble "out of phase"
  3. 75Hz sine tone "in phase"
  4. 75Hz sine tone "out of phase"
  5. logarithmic sweep (20Hz - 20kHz)
In Phase, 10sec
Out of Phase, 10sec
Tone 75Hz
In Phase, 10sec
Tone 75Hz
Out of Phase, 10sec

Identify Channels: Is Right Right and Left Left?

Starts on the Left Channel and after a 1 sec. pause the sound should come from the Right Channel (1.8kHz, 10 seconds)

This audio file scan all audible frequencies from 20Hz to 20kHz in a 20s time span.
Logarithmic Sweep
20Hz-20kHz, -3dBFS, 20sec

How To Use

From a central listening position, listen to the "in phase" and "out of phase" versions. If your speakers are correctly set up, the "in phase" versions will
  • produce more bass with the low rumble tone
  • play louder with the 75Hz sine tone
If you experience the opposite, simply flip the connecting wires of one of your speakers (not both) to correct the problem.

To check if the loudspeakers are connected the right way, listening from the central postion.
First you should hear the tone (1800Hz) from the left loudspeaker and after 5 seconds from the right loudspeaker.

Logarithmic Sweep
When checking by ear, the sound should evolve smoothly from the lowest frequency to the highest. No strong frequency dips or peaks should be present.

Please note that due to the increased sensitivity of our ears in some area of the audio spectrum, some frequency ranges - particularly in the upper medium - may be perceived louder than they actually are (the so-called Fletcher-Munson effect).

For this sweep test, don't pay attention to this phenomenon, but rather to strong and localized frequency dips or peaks.