With PZM's the boundry size affects the bass response. The larger the boundry, the more bass. I used to record some local bands in a few clubs by taping them to the walls, floor or ceiling near the stage. I probably have a few of those recordings still... I'll have to look. I modified two of the Radio Shack ones with balanced XLR outputs so I could use the home-made pre-amp i had at the time. The way I remember it, they had a very flat natural sound.