If your like me and was thinking to yourself that the earphone/speaker volume on your k800i was a little low then this is the hack for you. (Apparently this also works on other models such as the k750i etc.)
press * right * left left * left *
Its best to do this from the idle screen, once done you should be in a screen called “Service”.
Go down to service tests, then earphone/speaker. You should see a barchart kinda graphic the default is level 3 out of 7. Just crank that badboy up!
WARNING: If you re-enter the earphone/speaker screen, your volume will revert to its default. In my case I had to press the back button rather the ok in order for my change to be saved but what a difference it makes lol.
** This also works on the W995 and SE Elm / J10 (Thanks to Thomas and Rainer) **