Now that we have the concept of air speed clarified from several angles (A big, special thanks to Kalijah and Erik Veldkamp), let's get down to what is really happening and counts! The magic word is efficiency and that can be our embouchure, our equipment, our body use or any combination! Jens Lindermann had a great post on a new "smaller bore" Yamaha, the Vizzutti model that is supposedly much more "efficient" than other models. I understand efficiency for trumpet players to mean less work to get the SAME job done. Common examples: controlled aperature ("tight corners"), relaxed approach to playing, preference of somewhat smaller mouthpieces, certain model of instruments. The math shows an efficient resonant system as having more playing resistance. That more efficient horn may be harder to play if it is not optimally in tune. My experience shows that many players describe their instruments as "efficient" because they can hear themselves better when playing. That actually means a less efficient system as sound is escaping through of the back of the bell radiating to the player. This constitutes a LOSS of energy to the audience. Of course no energy is ever "lost", only transformed. This means that our description of efficiency can vary according to what we are trying to describe! A player looking for a "free blowing" instrument by definition may not get a very efficient one - but still be able to get the job done. Feel free to add and comment. I'll jump in a bit later with more!