The left and right volume is not balanced when the macbook is plugged in.

In 2009, Apple issued a patent, which will automatically adjust the volume of the computer or mobile phone according to the surrounding conditions, such as voice. This shouldn't be a problem with your computer. Please recall whether there are any changes in the computer, such as changing headphones or changing places, which may cause automatic volume recognition.

One more thing, Macbook Pro (beginning with15 inch, 20 1 1), Macbook Pro (middle of15 inch, 20 10), MacBook Pro( 15 inch, 20/)

Even if you move the left and right volume balance sliders in the sound preference panel to the left speaker as far as possible, you can still hear the sound from the MacBook Pro.

Issue on the right side of. This sound comes from the subwoofer, but because of the position, it seems that the sound of the subwoofer comes from the speaker on the right. Due to the position of the subwoofer, it is normal for sound stage to move slightly to the right speaker. You can adjust the left and right volume balance control according to your own preference, so that the sound stage can move left and right.

The subwoofer is located to the right of the blank key. This will also cause the left and right volume balance to shift.