How many hours does it take to break them in? 100hrs, 200 hrs?
Any techniques that are best for breaking speakers in? Types of music? Volume levels? Should I just let them play day and night at a specific volume until they are broken in?
The download I referred to in that statement doesn't show up because I copied this from the12volt pages where I originally wrote it, but you have test tone resources described on these forums as well. I used test tone generator.
Here's a procedure I learned that is fairly simple to use to break in a woofer. If you are installing your own woofers, be it for car or home use, and have found this thread because you're the type who wants to go about the installation systematically, covering all bases, then this procedure is for you:
You need a test tone CD (here is a download) with a 10 minute track of the tone that corresponds with the Fs of the woofer. You need to be able to hang the woofer up in mid air, through one of the mounting holes in the frame, letting it hang freely. There should be no walls close to the woofer, and the woofer certainly shouldn't be laying on the table on its magnet (as you often see in videos). The nearby table or wall acts to compress the air behind the cone so avoid those types of disturbances.
The idea is to play the sine wave tone through the woofer at resonant frequency in free air. A very slight amount of power will enable the woofer to move at full excursion. You have to first find out what the Xmax is so that you can look at the excursion and gauge (by eye) the approximate excursion you're putting the woofer through. A subwoofer with a one-way excursion of 12 mm would look like its moving about an inch as the voice coil moves back and forth. You'll note that you are allowing only a few watts of power to reach full Xmax, so be careful with the volume control.
If you're working with a car subwoofer, you can prop the trunk lid and hang it from that. If you're working with a home sub, you can hang it from the ceiling of the room near the amplifier. Play the tone at Fs, watch the cone movement while adjusting volume, and let it flap and whirrr for the 10 minute period. It will sound more like a fan than a subwoofer. Allow 10 minutes cooling time, then run it again a few sets. Your woofer is now broken in.
There is only a small percentage of DIYers who will go through this procedure. They are the ones who make sure they have a test tone CD for setting gains, who make sure they damped all the sheet metal while the car is torn apart, who made sure they grinded all the paint off the metal before securing the ground wire. This is just another of the steps to ensuring that when you are ready to debut the system, it will sound the way you had hoped it would.