For balanced tone, we recommend placing the piezos under the saddle on the bridge plate under the guitar - as shown in our installation manuals. However, since each guitar has a different tone, you can try experimenting with different placement of the piezos inside your guitar. By positioning the piezos closer to the treble side of the bridge plate (towards the thinner strings), you'll get a brighter tone, whereas positioning them on the bass side of the bridge plate (towards the thicker strings), you'll get a darker or deeper tone. There are some artists who like to use preamp to further alter the tone. We recommend either the EPS001-15K for our OF660 guitars, or the EPS001-05K for guitars with traditional sound holes.