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The Speaker Project
   
Equipment
 

Setup

Subwoofer
  Testing
  Prototyping
 

Building

The Main Speakers
 

Prototyping

 

Crossover

 

Construction

 

The Main Speakers

Initial woofer tests
Evaluating the test
Doing an added mass test
Evaluating the results

 
  Speaker Workshop Project
Woofer Testing (B)

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..