Aiwa WM5 Operating Instructions Manual page 6

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6
Phase
Depending upon the room or the characteristics of the right
and left speakers, sound from the powered subwoofer may
seem unnatural or unusually loud or soft.
In this case, try changing the PHASE switch setting. Set to the
NORMAL or REVERSE position, whichever sounds better.
Dynamic Bass System
The TS-WM5 adopts a Dynamic Bass System in which port
(1), duct (1), and air cavity (2) compose an acoustic bandpass
filter in front of air cavity (1). By virtue of this structure, the
bass reproduction limit is extended and sounds higher than
middle range frequencies are reduced in the Dynamic Bass
System. This makes it possible for the TS-WM5 to reproduce
powerful bass sound.