put your hand on the drivers. see if they feel the same. if you can feel one driver working more then the other (must be same size driver though) chances are something is up.
try doing an SPL check with a test tone disk with each speaker if you are still wondering if the speaker is off. to do this unplug one speaker and read the test tone. if you suspect its the bottom driver, then probably the low test tones might be off.


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