How do I test an 8-0hm speaker or horn with a digital multimeter? Help!

What? You can take a friggin multimeter, stick it across the terminals and if it does nott give you any resistance back you fryed the voice coil. If you get 0 ohms it means you fired the voice coil. If you get 4, 8, 16 ohms then your good to go.

To be honest, a multimeter isn't going to tell you a whole lot more about the state of the speaker than your game with the 9V battery (although it's less likely to damage a small speaker). The main reason for this is that speakers are designed to have quite different ac and dc resistances (technically, the ac version is called "impedance" - though both are measured in ohms). The multimeter measures the (dc) resistance - which varies depending on the size and quality of the speaker, while the 8 ohm spec applies to the (ac) impedance. Remember also that a lot of the bad things that can happen to a speaker are mechanical, and won't show up on an electrical test. The only really reliable way to test a speaker is to insist on hearing music - preferably something with a broad frequency range - played through it at a range of volumes before you buy. If the vendor is reluctant to oblige, then you can probably guess what state the thing is in. (If you still want to try the ohm meter out, then one lead in "common", the other in "ohm" is a good start (doesn't make a lot of difference which goes where). With an analog meter, switch between the ohms ranges until you find one that puts the needle near the middle of the dial (remember, the ohms scale reads backwards). With a digital meter, use the lowest range that doesn't give you an error. You aren't going to damage either speaker or meter in any of the ranges.)

Zeusfaber partially answered your question and there is not a set measurement for measuring speaker resistance. If the speakers have a crossover network it will also affect measurements at connections. The impedance of speakers is an in use AC measurement with an applied signal. Impedance measurements requires the use of an impedance meter versus an ohm meter. Sound signals are generated from an amp in an variable AC wave form so they are measured in AC impedance. This variable AC wave form is what causes the speaker magnets to vibrate back and forth to produce sound. When using an ohm meter on a speaker it will only measure the resistance of the windings on the speaker core and these windings are of different length according to manufacture and speaker type, tweeter, woofer, midrange, wire size, magnet, etc. In short, measuring with ohm meter is not reliable and it's best to listen to with high freq and low bass freq, then inspect cones and speaker mounting for damage, movement or looseness. Physical damage to speakers cannot be measured by any meter so in use is the best test. Using a 9v dc battery on ac speakers and crossovers could cause damage also unless it is a very high wattage speaker, which most are not. Speaker signals in home and car speakers are usually in milivolts, which is a very low voltage, so be very cautious. I'm no electrical engineer but over the years this is what I've learned about speaker science and not getting burned on used speakers.

• burn your speaker with lighter
  
• throw your speaker to your neighbor
• bring your speaker to the nearest service station and say eat this you *********
  
• i hope this 21th century solution will help you
  
• 
  

TEST IT WITH A DIGITAL MULTIMETER THE SPEAKER ITSELF NOT WITH THE CROSSOVER IT SHOULD READ AROUND 6 OHMS. SPEAKERS WILL ONLY READ ABOUT 75 PERCENT OF THERE REAL IMPEDANCE ON A MULTIMETER