Determining Speaker Polarity

i had some work done on my car that required the speakers to be removed... when reinstalled i noticed that they had lost the bass that i previously use to enjoy a lot... asked a friend who is in to electronics and stuff... he told me that they must have mixed the wires and reversed the speakers polarity... that caused the loss of bass... i thought it's worth a try and inter changed the positive and negative wires of one speaker and to my astonishment the bass came back... searched the internet about it and found this article... here goes...

Determining Speaker Polarity: finding the positive terminal
I just bought a new pair of speakers but the terminals are not marked positive or negative, how do I figure out witch terminal is which??

Method 1
Most speaker terminals will have one terminal smaller than the other. The smaller terminal is most ofen the negative terminal as seen below.

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Method 2
to be absolutely sure of which terminal is positive and which is negative we will use a 1.5 v battery to have the speaker react as though it is playing music.
SPECIAL NOTE... DO NOT USE ANY MORE THAN 1.5 V AS IT MAY DAMAGE THE SPEAKER COIL.
As we know, batteries are marked positive, negative, or both... we will use this to our advantage when hooking up the battery to our speaker.

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To start the process temporarily attach the short piece of wire to each terminal of the speaker... be sure to either use wire that is marked, or wire of differing colors to help determine which terminal is which.
In our example, we used standard speaker wire which is "polarized" one wire is made of copper and the other is made from tin... interestingly, this serves no electrical purpose
Once you have connected the wire to your speaker, proceed to briefly tough the free ends of the wire to the battery terminals as shown below. In some cases, extended contact with the battery has caused cancer of the voice coil i e. blown speaker

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if the speaker moves out when the battery is first connected, the battery is connected in proper alignment. Be sure to take note of which wire is connected to the positive terminal of the battery as this is your speaker's positive terminal...