Ingenious Sony Xperia Z1 mod allows you to turn the earpiece into a secondary speaker for a stereo effect
If you happen to own the Z1 and agree with the above statement, then there are some good news for you -- an ingenious new mod, courtesy of xda-developers member dontbelieve allows your rooted Z1 to blast music from both the loudspeaker on the bottom and the earpiece through which you make calls on the top. As you can imagine, this kind of gives you a stereo sound effect, though not completely.
Before you rush and get this, make sure you go through the entire thread and ensure that you have a backup of the files you're about to change. After all, you will be messing around with your device, and it's always a good idea to have a safety net to fall on in case something goes wrong.
source: xda-developers
Things that are NOT allowed: