I have measured many speaker's T/S parameters in the past and all have come very accurately. I use the method that can be found on diysubwoofers. My problem is that I have two Audax HP130Z2 drivers. I measure them and their fs ends up being near 110HZ., I tried using a voltage of 2.83 @ 100Hz, at the receiver and the fs was 95Hz measured, but the calculated fs would never be within 1 or 2 Hz. I have tried changing everything except for the method. Does the 2 mean that the HP130Z0 becomes a full-range driver? Hence the much higher fs.