ok just got my new speakers in, the are supposed to be 200 watts and 11 ohms, i bought this meter
Amazon.com: INNOVA 3320 Auto-Ranging Digital Multimeter: Automotive
put on speaker wires and says 7 ohms on both speakers that i bought
where can i buy a resister that is 4 ohms that will handle 200 watts so i dont blow up my new siren i just got
You're getting ohms (AC) and ohms (DC) confused. While they may appear to be quite similar, they're not.
Your speakers (that 11 ohms rating) is the impedance rating (
Speaker Impedance Explained - Ohms). To measure this, you need an instrument that measures impedance. This isn't the same as DC resistance.
Your new meter is designed to measure volts (both DC and AC using different settings) and DC resistance. It is not designed to measure impedance.
The 7 ohms you got on your speakers is the DC resistance of the wire that makes up the voice coil (a long string of thin wire wrapped in a coil that's generally placed around a magnet). When an AC signal (nearly always an audio signal) is sent through this coil, it causes a magnetic field to be generated, causing the attached paper speaker cone to vibrate in sync with this signal so you can hear that audio signal.
Had that signal been DC (like when using your meter), the coil will simply move one way or the other, depending on the polarity of the voltage. While you may hear a single thud, you won't hear much else. It's likely that you won't hear much of a thud unless your voltage is fairly strong and if it's too strong, you could easily burn out the voice coil (it's not designed to handle DC).
Yea, it's a shame that both DC resistance and AC impedance both use the term "Ohm", but that's the way it is. If you want more proof that an ohm isn't always an ohm (and additional proof that your multi-meter isn't designed to measure the impedance style ohms), take a good piece of scanner coax and make sure that you just have coax being measured (connectors are OK, but no scanner, no radio, no antenna) and put your multi-meter across the coax. Your 50 ohm coax (or perhaps 75 ohm if you use TV coax) should measure infinite resistance (or an open connection). Short the other end of the coax and you'll get zero ohms (or a very small value depending on how long - how much DC resistance the wire has). That doesn't indicate bad coax, just your tool is measuring something else entirely.
See this for a more detailed explanation (
http://en.wikipedia.org/wiki/Electrical_impedance). With DC, you only have resistance along a straight line, so it's a simple measurement (generally E = I R, solving for R you get R = E / I). With AC, you have resistance, reactance (both inductive reactance and capacitive reactance), and the phase angle between voltage and current causing a much more complex equation (see the link for them, the math is too complex for me to show here, especially the part where they include both the real and imaginary parts of the number system).
