Q:

Lower volume on one earbud after fixing it (soldering)

Got one earbud wire ripped out accidentally, but luckily the wire itself was still fine, just had to open the earbud and solder wires again. 
My earphones are Atomic Floyd super darts, high quality (as far as I can judge :-) ), so I could unscrew it to fix properly, or at least I tried. 
Sound is back, but the earbud I fixed has a lower volume than the other one (as well as decreased sound quality). 
Tried several time, to soldering again several times, swapping wires (in case of), but still the same. 
Don't think it would be a ear wax problem (even if I did clean the earbud) as they were working perfectly right before I ripped out the wire, and didn't use them since {~4-5 months). 
Any idea why this would happen?  Bad soldering?  Bad/Wrong tin (Used with 40% lead)? 
Thanks for your help. 
(Sorry if I misused some terms, not English native and not used to electrical engineering language :-) )

A:

Agree with previous poster that you probably have a cold (and highly resistive) solder joint.   Seriously doubt heat damage to the drivers would -only- lower the output.   Heat damage on voice coil/driver that small would distort like crazy.   
You can test this (if space allows) by bypassing the solder joint temporarily) with an external shunt on either side of the soldering point.   Also, look at the DC resistance of both channels.   Cold solder joints are resistive to DC.