I'm replacing the diaphragms in a batch of HF108s and discovered they have varying qty and thickness shims under the diaphragms. I tried contacting Faital for the correct procedure in determining the required amount and thickness of shims. I'm pretty sure they're just tweaking the VC offset for lowest THD, but its not clear how they measure it or what their standards are. Has anyone else dealt with this and received any guidance as to the official way of dealing with this?
To eliminate the more obvious possibilities, I've check the clearance between phase plug and diaphragm. There is no appreciable difference in clearances on the drivers in question. I'd think this would be a different story if the machining was sloppy, which it isn't.
Just curious, what is the total shim thickness?
Three 0.1mm or two 0.15mm meet your description of "varying qty and thickness shims under the diaphragms." yet total value remains.
Also check VC winding length and position relative to top plate, in principle both should be aligned.
Three 0.1mm or two 0.15mm meet your description of "varying qty and thickness shims under the diaphragms." yet total value remains.
Also check VC winding length and position relative to top plate, in principle both should be aligned.