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, except for compliance, which
is still the 1.0 cuft I set it to as verification. Of particular
note are the total Q (.5374) and the Free Air Resonance (19.20).
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 NHT is spec'ed at 16.5Hz and a Q of .445. We are
measuring a higher Fs and a higher Qts.
To check the results, though, the Estimate Parameters
command also builds an impedance chart using these new parameters.
Open that chart (named NHT1259.Estimate) and add (using the red
+ sign or the right button menu Add... command) the NHT.Free Air
chart to compare the two. I've thickened the Estimate dataline substantially
to make it more readable here -
Notice the excellent correlation between the two charts.
There's not much to comment on here. Next, we'll do a sealed box
test to calculate the compliance (VAS) of the driver..