The position and orientation of the sound post in violin family instruments has long been known to color the sound of the instrument. Small changes in the position of the sound post relative to the top and back plates of the instrument can result in clearly audible changes in the instrument's tone. Quantifying the effect of the sound post's placement on tone requires precise localization of the sound post. Luthiers have developed simple techniques to localize the post relative to the top of the instrument. Precisely localizing the post relative to the back, however, typically requires disassembly of the endpin. This talk will explore nondestructive and noninvasive techniques to localize the sound post relative to the back of the instrument. Results of these techniques will be compared for two cellos – one with a laminate construction and the other carved. Finally, the effects of differences in material properties on these localization techniques will be discussed.