Problem with side mass not changing T1

[Dolds]

Hi I have followed in Trevor Gores book how to add side mass to a guitar to drop the resonant frequency of the top, but for some reason the top resonant isn’t changing. I glued with 5min epoxy a piece of hardwood with a thread in it and then bolted on some weight (200gms) to the inside of my guitar. The top is showing 207hz so I need move it off this to say 190hz. The guitar has a soundport but I wouldn’t have thought this would impact anything. Any ideas in what I’m doing wrong? Cheers Paul

[Trevor Gore]

Moving down 17Hz would take an awful lot of side mass. The critical thing for making side mass work is to make sure the mass is so firmly connected that it is essentially integral to the sides, because to work the mass has to move precisely with the sides. So if the hold-down bolts aren't seriously tight or if there is any sort of flexibility in the mounts, side mass does not work effectively. An analogy is resting the sides of a guitar on on your thigh when playing. This has little to no effect on the T(1,1)2 resonant frequency because a) the guitar is no where near sufficiently connected to your leg and b) your leg is a "flexible mounting".

[Dolds]

Great thanks Trevor. I will think about what I need to change given your feedback. Cheers