What is the differance in AR18s and AR18? And is one considered superior to the other? The reason I ask is that while surfing I was quite surprised to see the AR18 being used as studio monitors on at least 3 sites. I have the AR18s, and AR91 - and when I bought them in 1982/83, I (my tin ear) couldn't tell them apart (a/;) at lower/moderate levels.