After complaining about this for over a year I finally got a service tech who agreed that there was a problem and found the cure! The front sub frame was loose and had to be dropped and retightened/torqued.

The front right would clunk going over a speed bump. The last tech went for a drive with me, I heard it clearly, and surprise surprise, he said it was normal for a sport suspension. Glad I finally got a tech who knew what he was doing!

 

Awesome! Glad it was taken care of. The clunk must have been really annoying.

 

I have a 2008 TLS and now hear a clunk from the left front suspension. It's when I hit potholes, bumps around 20-25mph (yes I try to miss them, but in the city, its not easy..). I hear it clearly when I have the window down. Car has 24K miles on it. Is this similar to what you had, or witt the speed bumps you heard it going 5-10mph (I don't hear the noise then, when going slowly)?