Loft progressions are a bit tricky, but are mostly driven by the need to achieve a progressive, playable level of distance gapping throughout the set. That being said, the trends that are the result of different companies going strong on lofts to create the illusion that technology is creating more distance (when it’s primarily strong lofts) have had to come into consideration when determining lofts and loft progressions. On the long and mid iron portion, because we have to be able to compete and because lofts have become so strong, progressions tend to get narrower, as you see in the TS1. Because we did a #3 iron in the set, the gap(s) between the 3,4,5 needed to be a little narrower to be able to be where we needed to be on the #6 iron. From there, we can go back to the more conventional gapping of 3.5 to 4 degrees in the 6,7,8. When you get into the short irons, we must stretch them to 4.5 degrees so that by the time you get to the PW and GW, you are in a place that allows better transition gapping into the scoring wedges. If we did not offer a #3 iron, and TS1 and the legacy models TE and DBM are the only models we offer the #3 iron, it would be easier. Without the #3, the gaps will be 3 degrees to 4 degrees throughout the set, usually. In hindsight, the #3 was probably not needed in the TS1. Makes no sense to make a #3 iron with less than 20 degrees, remembering that traditionally they were at least 22 degrees. Obviously when you have 2.5 degrees progressions, the distance gap between the #3 and #4 will be less, probably 10-12 yards vs 12-15 yards, but this will vary greatly from player to player. We are conscious of where the cg location is in the lower lofted clubs and analyze ball flight to insure that the combination puts the trajectory in a good window.
No real formula, but we do look at each design, the category we are designing for, the target window for the vertical cg lcation, and the trends and go from there. Ultimately first articles are evaluated and we tweak from there, if needed.