The B&W Matrix series have oversize posts and will not accept standard 1/4" spades. I replaced the standard posts on my 802S3s with Cardas posts to solve this problem. I don't know if it was the improved contact area or the Cardas posts, but the improvement in sound quality was quite noticeable. Paradigms also have a slightly larger post then the standard 1/4" and require the spade to be slightly widened with a pair of pliers.
Speaker Posts
In my 12 years as an audiophile audiogear lover, I have gone through over a dozen speakers. Not one has binding posts that fit well with speaker cables spades!! Ive spent nervous hours trying to expand and bend speaker spades so that they make a nice fit into the binding post. I only hope that one sunny day comes where speaker designers and speaker cable makers have a world summit to get it right once and for all.