So, we've done a Free Air impedance test and estimated
the woofer parameters. Now, we can do two things to look at and
evaluate our results.
First, open the driver window and bring up the properties
dialog. Go to the Parameters tab. Mine now looks like:

Everything below the Calculated line has been calculated
by this first Estimate parameters pass. Compliance is also set because
I've cheated and done an added mass test, as well. If you had not
done the added mass (or sealed box) test yet the Compliance value
will not be set.
Of particular note are the total Q (.415) and the
Free Air Resonance (43.67). They matter because they affect the
box size selection significantly (as well as the F3, 3 dB down point).
Also, they are not at spec - which is why you should use a product
like Speaker Workshop.
The Vifa is spec'ed at 39Hz and a Q of .35. We are
measuring a higher Fs and a higher Qts but well within factory specs
(also note that increasing both means that our box design will be
very similar to a factory spec box design).
To check the results, you can compare the Free Air
impedance chart to the .Estimate chart. I don't have that picture
here, but take a look at the subwoofer
test for an example of doing that. As expected the correlation
was excellent.
Next, we'll do an added mass test to calculate the
compliance (VAS) of the driver.. |