mosfet,

you're right.

I think there is again quite a confusion. While bookshelves and paintings/pictures help the diffusion, carpets are known by the amateurs to be effective as absorbers.

What I feel is rediculous are the words  "is as effective as anything else." and "Persian carpets and the like are ideal".

This is just like saying that choosing any two loudspeakers from a catalgue with tha same amount of drivers is the same and if there are 3 drivers in a loudspeaker then it is ideal.