General :: Error - Su: Authentication Failure

i have been running Ubuntu for about 3 days now, finally getting all my files moved back to the drive and what have you.I came from running windows, and an Android phone with full su access, and done up all custom-like..I am loving the speed, etc. great experience so far. BUT: the headphone port on my laptop is broken, and so I run [ran] and external soundcard, a Creative X-fi 5.1 USB SC. I have found linux drivers for this unit, and am trying to install. I have googled the crap out of how to do this, yet am getting stuck.

Here is where I'm getting stuck. I have extracted the package, entered into the sub folder, and am trying to run the Make install:

...laptop:/tmp/xfi-0.0.0.0$ cd ./xfi
...laptop:/tmp/xfi-0.0.0.0/xfi$ su -c "make install"
Password:
su: Authentication failure
...laptop:/tmp/xfi-0.0.0.0/xfi$

what in heck do i type at password... have I NOT done something, am I doing something wrong.... it does not accept my normal password, so I am lost.