Measuring impedance with multimeter

So is there no instrument that can be acquired without breaking the bank for nonEE to broadly measure impedance, or in this hobby where snake oils are rampant does everyone blindly except vendor claims?

You need a sine wave generator and probably a 100 ohm potentiometer in addition to your meter.


The sine wave generator drives the speaker, which is wired in series with the potentiometer; the latter only uses the center lead and one other lead.

Set the meter to AC volts.


You adjust the pot so that your meter reads the same voltage across the speaker terminals as the across the pot. Then remove the pot from the circuit and measure the DC resistance- that is the impedance of the speaker at that frequency.


So you need to do this a bunch of times but with a bit of graph paper you can draw up the impedance curve.

You can measure speaker impedance using Room EQ Wizard and a home made harness.


https://www.roomeqwizard.com/help/help_en-GB/html/impedancemeasurement.html


I personally recommend DATS V2 as a complete, out of the box solution:

http://www.daytonaudio.com/index.php/dats-dayton-audio-test-system.html
Around $99 at Parts Express

As said above, the 'resistance' that you measure with your ohm meter is in DC, i.e. direct current. Impedance is an entirely different measurement that uses an alternating current (The music signal happens to be just that, AC). It might like understanding the horsepower of a car. The stated horsepower isn't exactly what you will be experiencing in driving, at least considering differing speeds, roads, driving habits, etc. It gives a baseline for you to consider. 

If its the m3 and its $300 in Eminence drivers that DC of 4.2 is about right. 4.2DC is about 8 ohm average. If you want a 16 ohm loudspeaker front horns and a few Fullranges are about the only choices I can think of off hand.

This is an area of interest for me too.  A close friend's church had lots of PA gear stolen.  I'll be doing the installation and don't want to be attaching a new power amp before testing the long speaker cables.  Strangely another friend's church needs work on their 70v system with 8 speakers in the ceiling.   I've been running sound for churches for decades, not doing installations.  So I need to purchase something reliable. 

There are relatively inexpensive devices available that will test AC impedance for audio applications--not DC resistance. 
https://www.ebay.com/sch/i.html?_from=R40&_trksid=m570.l1313&_nkw=speaker+impedance+meter&_sacat=0&LH_TitleDesc=0&_osacat=0&_odkw=impedance+meter

The more expensive ones will test impedance at various frequencies.  Some will also calculate "watts" for those testing a larger number of ceiling speakers running on a commercial 70v system, etc.  
http://www.gold-line.com/zm1.htm

There is a software based app that has lots of bells and whistles.  The package is very pricey due to the required $500 audio interface plus the app
https://www.studiosixdigital.com/audiotools-modules-2/speaker-test-modules/impedance-meter--sweep.ht...

The inexpensive  Chinese impedance meters only test at 1khz.  
https://www.ebay.com/itm/Digital-Audio-Impedance-Tester-LCD-Display-Speakers-System-Resistance-Ohmme...

The choice of 1khz seems strange to me.  My understanding is that the standard frequency for testing woofer impedance is 400hz. 

You can see why 400hz is more suitable for testing speakers since impedance varies greatly according to frequency!
https://www.studiosixdigital.com/_Media/impsw5.png