I use a compandor (
http://www.onsemi.com/PowerSolutions/product.do?id=SA575) to do it, though that's a bit extreme for most purposes. I use it because I needed more even input for my color organ.
<iframe width="420" height="315" src="
http://www.youtube.com/embed/jEK11yDzDi8" frameborder="0" allowfullscreen></iframe>
<iframe width="420" height="315" src="
http://www.youtube.com/embed/mH5eU01QFzU" frameborder="0" allowfullscreen></iframe>
I hate to say the same thing that everyone using HB LEDs says, but it looks much better in person
