A reader sent in a question about headweight and how it affects distance. This is a great question and one that has stirred debate in the golf industry for years. Most people would agree that a lighter club would be better, but if you look closer that answer would need to be qualified.
A typical driver today is 45 1/2 inches long, has a headweight of 200 grams and a swing weight of D-1. If swung around 100 mph the ball leaves at about 145 mph and carries a little over 245 yards. If you could swing a heavier club at the same 100 mph the ball would not go proportionately faster and farther. A 400 gram head (twice the normal weight) swung at 100 mph would send the ball at 160 mph. It has also been shown that lightening the head does not substantially increase distance. As the clubhead is lightened a player can swing only slightly faster.
As a result we can say there are a wide range of weights and will usually produce the same length for a particular player. As the clubhead gets lighter (less mass) the swing speed increases and as the clubhead gets heavier (more mass) the swing speed decreases. Both of these produce approximately the same distance.
Engineers and club manufacturers test a multitude of weight combinations to produce a club that maximizes distance. An experienced clubfitter will then customize the specifications - shaft weight, shaft flex and swing weight - based on each player's swing characteristics.