I just purchased a Denon AVR 4000. This picture shows that even for one seat that you should take several measurements that are perhaps about 2 to 3 feet or so apart.
How important is to take 6 or 8 measurements vs say just 2 near the sweet spot ear area?
Shouldn't 2 be better since you only have one seat/sweet spot?
If you should take all 8 measurement than would measurements taken much close to the sweet spot (ie within say 1 foot around single listeners ear area) be better?
Has anyone tested the above theory?
Yes - it has been tested to destruction :) See the FAQ link SoM directed you to. Many of us who are only interested in one listening position take all 8 measurements tightly around the MLP - say at 12 inch distances and find that this gives us the best result for just one seat. Our ears and our independent measurements confirm this.
You have to remember how Audyssey works - it is designed to make "every seat a good seat". By definition, that means no one seat is a great seat. In attempting to provide a consistently good result for several seats, it delivers a sub-optimal result for every seat. By clustering around just one seat you can get an optimal result, but for that one seat only. So you need to determine your priorities. If most of the time you are the only listener, or if the other listeners don't care, then measure around the MLP. If you have several critical listeners, then measure a wider area.
But do remember that Audyssey cannot deliver an optimal result for several seats and is not designed to do so.