| # Speaker Project # Evaluating the initial subwoofer results

> > > 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..

> > > Click here for the next page

> > > last updated August 27, 2000