Tannoy Revolution Signature DC-4 : review said placement issues?

In your review of the Rev Sig DC-4 you mention that they are finicky about placement.

Could you please expand, finicky in what way? What situations are they OK in, and what are they bad in?

Here's the review URL  http://www.whathifi.com/Review/Tannoy-Revolution-Signature-DC4/

Five stars which is awesome, but the finicky placement comment - what does it mean?

Thanks,

Rick