My understanding of the relationship between path angle and speed comes from a biomechanist and coach I worked with for many years from France who worked for the FFT and ATP and also from my own empirical evidence from years of working with players on court. Essentially for the same swing path (assuming the same contact point on the ball) a more closed face will create a lower launch angle than a vertical racquet face.
Obviously as Tight Lines says, all three variables are inter linked, but in my experience racquet face determines launch angle and path determines spin (that is to say has a greater bearing over).
Here comes the (not very) science bit..!
If a ball hit with heavy topspin hits your racquet which is stationary and in a vertical (neutral) position the ball will leave the racquet above the angle of incidence due to the spin. If you hit said ball with a low to high path bit maintained the racquet face as neutral you would impart counter spin, but the launch angle is still higher. Repeat with a closed racquet angle and the launch angle is lower.
As for tennispeed - happy that he has "proven" that the pro's have a closed face at contact. Not convinced he has proven that this factor is the major contributor for topspin production, at least above racquet path.
Don't be upset by the results you didn't get from the work you didn't do...
talkcoaching on wordpress, come check it out :)
Last edited by Ash_Smith; 08-01-2013 at 11:18 AM.