Well..If you connect ur Woofer with Reverse polarity..this would happen

when the Membrane of woofer was supposed to move Forward..it will move backwards instead..

so if it was to punch sound forward..it will punch sound backward..
i think it wont damage..BUT if u play LOW bass with Loud sound..
Membrane will move backward with a LOT of force and hit the backwall instead of moving forwards..(depends on the design)

dont reverse polarity..theres a reason they marked it +ve and -ve

Hmm yeah maybe

Here's a more Professional Explanation

Audio Signals are not DC, They are Alternating Signals with continuously varying Frequencies,
an Audio Track playing a constant 20Hz tone will make the Polarity of the wire change 20 Times in a second
From this you might say that its okay to connect a woofer in reverse Polarity, since its changing polarity 20 times every second, But ofcourse that is only for the 20Hz tone, and we dont call it music

during a normal song, the frequencies are constantly changing,

so it all boils down to one thing, changing polarity means when the woofer membrane was to move forward, it will move backwards

keep in mind that some woofers are designed to move more in forward direction than backwards,
moving forward is okay, but if you move backwards the coil will hit the magnet wall and create a rattling sound and damage ur Woofer

okay, so WHAT if the woofers are not marked?
then you can do a simple test
take a 1.5V AA Battery, connect its +'ve terminal to one of the terminal of Woofer
connect its -'ve terminal to the other terminal of woofer


if the membrane pushes forward, that means you connected +ve of the battery to the +ve of woofer,
if it moves backwards, it means you connected +ve of battery to the -ve of the woofer

then you can mark its terminals

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Added on October 5, 2011, 10:47 amNo, Markings are there because its supposed to be connected that way
because normally audio signals from songs tend to push woofer more towards forward
(peak amplitudes are on the +ve)

ofcourse you can connect tiny speakers anyway you want, cuz they dont move (or flex) much
but we're talking about huge woofers, and we are supplying a lot of juice (amps)

you can connect woofers oppositely if you dont listen too loud..that wont damage them

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Added on October 5, 2011, 10:59 amI install my woofers myself, cuz i know how to handle the juice properly
i just explained what would happen if you put a sub on reverse polarity, not recommended doing it
ofcourse both ways you can kill your sub with overPower..

This post has been edited by amir_zohaib: Oct 5 2011, 10:59 AM