User`s manual

We can now save our complete results and proceed with the Delta Compliance. The
free air derived data is already in memory and we can finally deal with the last part
of the procedure, which is nearly the same as before. We will be prompted for
volume instead of weight. Obviously the file we have to choose is relative to the
driver loaded with a known volume (15.1 liters in this case). Here we show the
results for the Delta Compliance method. The two sets of data do agree pretty well.
13.7.5 USING LSE (LEAST SQUARE ERROR)
With this option checked, T&S parameters are calculated in a more sophisticated
way. Basically the parameters obtained in the standard way are used to derive the
starting values for the equivalent electric circuit model. These values are then
changed slightly around the initial value until the best fit between the calculated
and measured impedance curve is found in a large frequency range around
resonance. This procedure works fine and gives an accuracy advantage if the driver
impedance fits the Thiele and Small model pretty well. Unfortunately this is not
always the case. Should the user encounter such cases (if the parameters obtained
with and without LSE differ substantially) the user must be aware that the entire
concept of T&S parameters has lost its usefulness. This often happens with
tweeters or woofers whose impedance has been measured at a high level with
defective devices.
196 13 MEASURING IMPEDANCE AND T&S PARAMETERS