Looks like you caught the face of ghost in that shot.
Down there in the bottom, close to the middle.

An exhaust pipe?

Now I almost hate to do this, but don't be discouraged- try another one, and steer clear of the A/V equipment this time. I'm an A/V tech, so I'd know the reflex port of a subwoofer anywhere (finally had to look at mine, though) - a horn with no driver just behind it  usually means "sub". But this is a great idea for a thread- there are much, much harder ones possible.

Sorry!!