here is the info pulled from soundpro's website...
Bass Roll off models only
Before making your first important recording, it is suggested that you experiment with your new microphones and battery unit a bit. On the top of the module, you will see the two red switches that select the bass roll-off frequencies. There are 7 different bass roll-off frequencies to choose from: 16Hz, 69Hz, 95Hz, 107Hz, 160Hz, 195Hz and 888Hz. You will find that different recording situations require a different bass roll-off frequency to produce the best results, depending on many factors such as the type of microphone you are using, the venue itself, shape of the room, your position in the room, speaker placement (if any), and many other factors. You should experiment with the different roll-off frequencies to see which one(s) produce the sound that you like the best. To set the roll-off frequency, set the switches according to the following chart:
Your desired Roll-off Frequency These switches set to the “open” position
16Hz (no roll-off) 2,3,4
69Hz 1,4
95Hz 1,3
107Hz 1,3,4
160Hz 1,2
195Hz 1,2,4
888Hz 1,2,3
It is usually desirable to have the left and right switches set to the same frequency; however, they can be set independently if desired. The best way to determine the best setting for a given recording situation is through trial and error, starting off with the 16Hz setting and working up in frequency until the desired amount of bass is achieved in your recording. Remember, setting the switches to higher numbers removes more bass from the recording.
Here are some general guidelines: For louder, bassier situations, try higher settings; for smaller, quieter situations, use lower settings. If the venue has bad acoustics, use higher settings; for venues with better acoustics, use lower settings. If you are using cardioids, use lower settings; for omnidirectional mics, use higher settings (cardioids reduce bass somewhat when compared to omni’s as a function of their more directional pickup pattern). The audible differences between settings are subtle, so you won’t destroy a recording by using the wrong setting. There is no ‘right’ setting…what sounds right to your ears is ‘right’.
and here is the link:
http://www.soundprofessionals.com/instructions/SP%20SPSB%206.doc