I would have to agree with Champagne. What makes them much less prone to feedback, especially the Radio Shack model, is its' low-tech lack of sensitivity. However, you must also have it very close to the source to even pick up the bass properly. It works great, at least for me, inside of the F hole. If it's between the bridge feet or under the fingerboard I think it will be much too far away from the sound source to hear much of any real bass. All that will happen is you will need to turn up the volume more to hear the bass and will also pick up more surrounding noise, introducing lots of feedback. I tried it near the bridge and the sound was weak and distant sounding. With it in the F hole, the sound is powerful and deep, and it only picks up the bass.