If the surrounds are rated 90Hz-20KHz with no +-dB range provided, then the rating is fairly worthless. My speakers extend to 20Hz. Of course, I can't hear anything at 20Hz but I'm sure it can be measured.
Even if it is, for example, +-3dB, you want to set it ABOVE the F3 point, not at the F3 point. So, set it to 120Hz or even higher. If 100 is as high as your receiver goes, then set it there.
Change your center's x-over as well.
In the future, adding some details like what brand and model speakers you have would allow us to answer more precisely.
Cheers,
Bill
Even if it is, for example, +-3dB, you want to set it ABOVE the F3 point, not at the F3 point. So, set it to 120Hz or even higher. If 100 is as high as your receiver goes, then set it there.
Change your center's x-over as well.
In the future, adding some details like what brand and model speakers you have would allow us to answer more precisely.
Cheers,
Bill
