Turn everything on and set the frequency generator to its lowest range.  You'll want to do a sweep from about 10 hz to 100 Hz.  Start at 100 Hz and get the signal flowing.  Set the meter to a usable voltage scale, somewhere around 400mV.  If you have an auto scaling DMM, it might jump around a little but it should still work fine.  This part is sort of confusing so pay attention.  To calibrate your meter so that it reads "impedance", flip the switch on the IA (Impedance Analyzer) to "calibrate".   You'll want to set the amplifier volume output so that the voltage reading on your meter is equal to the actual resistance of your 8 ohm resistor.  Let's say it was 8.1 ohms.  Turn the amplifier volume up until you read 0.81 volts on your meter.  Or better is to use a lower scale and read 8.1 mV.  Don't try and get 8.1 volts!  Remember there is a 100 ohm resistor is series with your whole circuit.  You would need 108 Volts from your amp to get 8.1 V across that resistor.  Use the lowest scale you can to get the most accurate readings.  Now that the meter is calibrated to measure 8.1 ohms (as volts), sweep the frequency generator up and down and see how much variance in voltage there is.  There should not be a whole lot of change, but it may vary a little bit, depending on the quality of your frequency generator and how linear it is.  That is why you have the switch.  To change easily between measure mode and calibrate mode as you sweep throughout many different frequencies.  Now flip the switch to "measure".  This loads the amp with your speaker's impedance so the current will remain the same but the voltage drop across your speaker will change, hence you will see the voltage on your meter change as well.  Whatever the voltage says, that is your impedance at that particular frequency.  For example,  6.78 mVolts  = 6.78 ohms because you calibrated the meter to measure impedance in terms of volts!!  Note it should change continuously with frequency.  Especially at low frequencies.  You may even notice a peak in the voltage (i.e. impedance).  These peaks are very important.  If the speaker is in free air (no enclosure) then the peak will be at the speaker's resonant frequency or Fs.  This is how you find Fs.  The peak impedance, where you measure the highest voltage across your meter.  It's so simple!  If your meter peaks at 15.67 mV with a 32 Hz sine wave for example, then the Fs of your speaker is 32 Hz and it's impedance at Fs is equal to 15.67 ohms.  Get it?  If the driver is mounted in a sealed enclosure, the impedance peak will be at the fB of the enclosure and not the fB of the driver.  This is how you measure the fB of a sealed system.

To find the Fb of a tuned ported box you need to do as sweep across the 10 - 100 Hz range.  You should notice TWO peaks on your meter.  Record the one peak as F_L and the other peak as F_H.  Then you must cover the port with an airtight seal, making your speaker essentially into a sealed enclosure.  For PR enclosures you will need to remove the PR and seal the opening with a board and make sure the seal is tight.  Use weather stripping if necessary.  This time measure the peak again, there should only be ONE peak this time.  Record this frequency as F_C.  Now use the formula:    F_B = square root of (F_L² + F_H² -  F_C²) . This should give you a very accurate measure of you actual box tuning frequency.  Up next will be details on how to find all the Thiele/Small parameters of any speaker as well as how to find the resonant frequencies of bandpass speaker systems.   Oh yeah, Fb of a sealed speaker is where you get the first and and greatest peak in impedance between 10 and about 150 Hz.  If you have any questions or suggestions about this method of measuring speaker impedances, feel free to write me.  I think I had a hard time trying to explain in an orderly simple fashion how to do this.  It really isn't as hard as I made it out to be.  Honest. Just try it out a few times and you'll get the hang of it.  Don't forget to switch over to "calibrate" mode often while doing impedance checking because the voltage may change a little.  It will throw off your impedance tests by enough to be significant.  My thanks to Speaker Builder Magazine for printing the article about the Impedance Analyzer and to Radio Shack for actually carrying the parts I needed.  Also thanks to David B. Weems for his formulas in The Great Sound Speaker Manual.