Some good information presented by Rlafoone on the processes, but not completely accurate on the current processes that are available on the forging front. On the drivers we forge, we use a precision cast process where the parts are extremely precise and basically snap together before the welding process. The welding process is extremely precise and the amount of material used is way less than what was used in the old method of forging. This process is a little less expensive than casting titanium, but not much. To my knowledge, our factory is the only one that uses this precision forged process. They also cast titanium. The older forms of forging, which I’m sure some factories still use, were significantly cheaper than casting. I can guarantee you that when you see component drivers selling for low prices, they are forged and welded the old way. The advantage of casting titanium is that you can do deeper cuts, more intricate surface designs, etc. However, the technology behind our precision casting is getting close to being able to do the same thing.
As far as the sound, the fact is the process of manufacture has nothing to do with it. The shape, wall thickness, cavities, materials and internal structure have everything to do with it. The head is like a bell, as someone already mentioned. Different shapes and wall thickness will influence the sound. The biggest challenge any manufacturer has in developing a driver is the sound. Trust me when I say that the most anxious I get is when we get first samples of drivers. We can’t shaft them up fast enough to hit them, because no mater how great the ball flight numbers are, if the sound is not acceptable or not in that range we want, we go back to the drawing board. Even though we know what measures to take in the design and manufacturing process to get t a “good” sound, you just can’t know for sure until you get first articles and test them. This is true for every manufacturer. Rarely will any two designs sound exactly the same, but there is range of sound our team accepts, and there is a range that we do not accept.
Also, the process has absolutely nothing to do with performance. Performance is dependent on the mass and dimensional characteristics, the materials and the precise dimensions of those materials (especially the face on drivers) and the overall specifications and how they fit the individual.