| # Speaker WorkshopTM # Calibration Setup

> > > Once the volume is set correctly (so recording at 50% seems right), I then calibrate the impedance jig and the sound card.

> > > Keep the same jig setup (reference resistor shorted, using Z input).

> > > Now perform a channel calibration, just in case your input channels have different gains. Do this via Options / Calibrate then click the Test button under the channel difference option. The jig is already acting like a loop cable, so our wiring is set already.

> > > The channel difference is then saved in the system folder as Measurement.Calib. If you want to look at the chart you can... mine looks like:

> > > At first blush this is a pretty big difference, but don't forget that Speaker Workshop autoscales. Looking harder we see that the maximum difference is about -.06 and the phase difference climbs all the way to 0.6 degrees - not much at all. This card has well matched input channels.

> > > Once the channels are calibrated, we then calibrate the impedance jig. Set the Ref switch to the 3rd position (reference resistor in-line and test resistors in-line, now) select Options / Preferences. Set the sample size to 32768 (my preference) and the same rate to 44100. These rates will be used for the impedance calibration. (You may need to click OK now and reopen the dialog). Then go to the Impedance tab and click the Test button in the Impedance Jig Definition section.

> > > When the wizard asks for the first resistor use the ten ohm (or so) in the test resistor set (set the jig switch to use that resistor) and click next. For the second request flick the 10/5 switch to the 5 position, enter the resistor value and click next. If the results look awful and you're sure you did everything right, try reversing your left and right output leads then try it again.

> > > The first time I did this I got 10million as a result for the reference resistor (whoops) and realized I hadn't flicked the 10/5 switch to 5.

> > > Your results may be slightly off at this point. Do the test again (now your starting point will be closer) and the second approximation should be even better. After doing this my dialog looked like:

> > > Press Finish to have the values placed into your Calibration preferences.

> > > I usually leave sound card impedance set to 1000K ohms and 0F. The input impedance is so high that it usually doesn't matter unless you plan to test high impedances with your setup.

> > > I use a 10 ohm reference resistor because when measuring impedance peaks for drivers the peaks is often 20-40 ohms and a higher reference resistor will produce better accuracy.

> > > Speaker Workshop is now ready to be used. Save the file with a real name and then reload it and proceed (just in case you crash).

> > > At this stage I usually check some known resistors, capacitors, and inductors to verify the impedance accuracy. Create a new generator resource, open it, and then select Measure / Passive Component. My accuracy is usually well within 1% for these devices. Resistors less than 20 ohms, capacitors around 1-10 uF, and inductors of around 1mH work best for the checks.

> > > last updated July 08, 2000