When hit, a golf face acts as a trampoline or spring, which is one reason why the USGA refers to how hot a face can be as its "Spring Effect and Dynamic Properties" rule.
As a matter of physics, the highest trampoline effect always occurs in the middle of a trampoline or the middle of a golf face.
Major brands have used “variable thickness technology” for decades. This technology has the thickest part of the face in middle of the face, where as a matter of physics the highest trampoline effect exists to ensure that the face does not not exceed the amount of time a ball can stay on the face as the more time the greater the ball speed. The USGA Rule limited that time to 257 microseconds and was referred to as the Characteristic Time or "CT" of 257.
Then the major brands thinned the thickest part of center to the outer edges of the face. Why? They do so in an effort to minimize as much as they can the reduced trampoline effect that continuously occurs further from the middle of the face. However, despite this thinning the CT values in the large areas adjacent to the center of the face or the "sweet spot" of the face are much lower. This is why amateur golfers lose so much distance on hits outside the center of the face.
Knuth Golf invented the novel idea of creating
three, largely independent but connected "trampolines" or "3 sweet spots" that covered the entire face in order to take advantage of change in USGA Rule that permitted CT to be as high as 275 outside of the Center of the face. We then invented the novel idea to significantly and immediately reduce the average thickness of the two areas adjacent to center of the face which is the traditional sweet spot and then reduced the thicknesses in the remaining areas of the face for 2 additional sweet spots that has a higher CT which averages 266 higher and is higher than the CT in the center of the face for more ball speed and more distance outside the center than every before.
So why doesn't the higher CT outside the center of the face provide more distance than the center of face with a lower CT ? Good question. The answer is that when hit outside the center of the face it twists which causes a loss of ball speed. However, the higher CT outside the center of the face adds back that lost ball speed from the twisting so the net effect is to have one sweet spot across the face with the same same ball speed and same distance.
By doing so, we were able to create a much higher CT permitted by the new USGA Rule to provide amateur golfers the significant opportunity that the new USGA Rule provided for amateur golfers . . . namely amateur golfers can now for the first time obtain the same distance whether they hit in the traditional sweet spot or the 2 new sweet spots on their driver or on their fairway wood and hybrid approach shots for more greens in regulation for lower scores and more fun.