Members Logieberra Posted January 22, 2013 Members Share Posted January 22, 2013 I'm new to heads and cabs and I bought a used fender tonemaster 2x12 with upgraded cannabis rexes but I forgot to ask what ohms they are each 8 or 16 ... the cab is wired in parallel so if they are two 16 ohm speakers then the load would be 8 and if they are both 8 then the load would be 4 ... my head has a 4 ohm and 8 ohm out I guess my question is when using a multimeter to measure the cab will it show the ohms of the individual speaker, the total ohms of both speakers added together or the ohms of what the head should be (8 ohm or 4 ohm etc) thanks in advance Link to comment Share on other sites More sharing options...
Members ENdtime Posted January 22, 2013 Members Share Posted January 22, 2013 It will measure the ohms of both if you take the measurement from a cable plugged into the cab, which is how I would do it. So basically plug in the cable you the cab and touch the tip and the sleeve.. If it's an 8 ohm load you week see sumthin between say 5.5-7 ohm. You will rarely, if ever, see the actual resistance that's listed on the speaker. If it's a 4 ohm cab, it'll be anywhere between 2.6-3.4, etc.. Link to comment Share on other sites More sharing options...
Members onelife Posted January 22, 2013 Members Share Posted January 22, 2013 If you measure the impedance of the cabinet with your ohmmeter it will give you the same impedance your amp will see.It will be a result of the combination of the two speaker which, if they are wired in parallel it will be half the value of each individual speaker (assuming both speakers are of the same impedance) and if they are wired in series, the total will be twice that of each speaker (again assuming theyey are both the same). Link to comment Share on other sites More sharing options...
Members Kazinator Posted January 22, 2013 Members Share Posted January 22, 2013 Logieberra wrote: I guess my question is when using a multimeter to measure the cab will it show the ohms of the individual speaker, the total ohms of both speakers added together or the ohms of what the head should be (8 ohm or 4 ohm etc) The impedance of speakers is only a nominal value, and it is not a DC impedance. The actual impedance is frequency-dependent. If you look at speaker curves that are published (e.g. on the Eminence website), you will see that only at around 1Khz do so called "8 ohm" speakers have an 8 ohm impedance.The same speaker will have a much higher impedance at around its resonant frequency peak, because the speaker generates counter-EMF at resonance, and also a rising impedance with rising frequency (because the voice coil is an inductor).Measuring the DC impedance is largely pointless, except as a check that the speaker isn't shorted or open.Yes, if you measure the terminals of the cab as a whole, then that is the equivalent resistance of the entire speaker circuit. For instance if you have four identical speakers and their DC resistance is all X, then if they are wired in parallel, the resulting resistance will be X/4. That is a common wiring for 16 ohm speakers to make a 4 ohm cab. If they are all in series, then the resistance will be 4X (not a common wiring for guitar speakers, as far as I know). and if you make two pairs which are in series, and put those two pairs in parallel, the total resistance will be X (common wiring for 8 ohm speakers to make an 8 ohm cab). Just do not expect X to be 8 ohms for an 8 ohm speaker. Link to comment Share on other sites More sharing options...
Members Logieberra Posted January 22, 2013 Author Members Share Posted January 22, 2013 thanks guys... so it laymens terms it will show what the amp head should be set at,well close to it anyways ..thanks! Link to comment Share on other sites More sharing options...
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