#1
I recently purchased a digital multimeter and still am not sure on how to use it for the most part. I'm interested in finding the total impedance when I daisy chain my two 16-ohm cabinets together, since I am not sure if the one jack is a parallel jack or not.

Where do I connect the two (positive and negative) leads in order to get a good impedance rating? Would it be found by attaching the leads to the sleeve and tip of the speaker cable that is going into the amp head, or something different? Sorry, don't want to sound like a complete idiot..
#3
I've never checked the impedance of a cabinet, but I have on individual speakers.
Put one probe on the positive terminal and the other on the negative. It should be off by a bit, that's normal.

The most accurate way is to take the back off of the cab and do each speaker individually then check the wiring and do all the calculations. You can also rewire it to a different impedance.

The jacks are most likely parallel. The best way to check is looking inside.
..I was watching my death.
#4
you don't measure impedance with a multimeter, impedance is a measure of opposition to alternating current (AC) what you are measuring with your multimeter is the dc resistance of the speaker not the impedance
*edit
probably the easiest way to determine the impedance wouble be to check what it says on the back of the speaker the impedance should be written there in ohms, to tell the difference between series and parallel

note that the equations in the picture are for adding resistors but they also work for simple speaker impedances eg: two 16 ohm speakers in series will equal 32 ohms where as in parallel the total will be 8 ohms
Last edited by tobuei at Jun 3, 2011,
#5
Quote by tobuei

*edit
probably the easiest way to determine the impedance wouble be to check what it says on the back of the speaker the impedance should be written there in ohms, to tell the difference between series and parallel

I completely overlooked suggesting the easiest way.
Oftentimes, vintage gear wont have any labels, just a serial code on the back of the magnet. My '77 Ampeg VT-40 has no notable markings on the back of the magnet, even though I know they are Jensen speakers.

TS, if it's a serial code you may be able to look it up.
Most of the time if a cab has two 1/4" jacks on the back that are unlabeled it'll usually be parallel, but it's unsafe to assume that.
..I was watching my death.
#6
I was looking for what the impedance would be if I daisy chained two cabinets together, not the individual speakers... that's an extremely easy thing to do. But I really haven't seen any series jacks on mass produced cabinets, so I think its safe to say that its a parallel jack and I'd be at 8 ohms when I daisy chain them.
#7
okay - as mentioned before impedance is a measurement for AC currents. a multimeter can give you the DC resistance which will be an ohm or three less than the impedance rating. i can get into the science if you want, but i will restrain myself for now.

if you have already wired them up, plug in a speaker cable to the cab and with the meter's probes, put one on the tip and one on the sleeve of the cable's other terminal.

remember this will not tell you if you wired a speaker backwards or swapped the + and -.
#8
Quote by brentonlatour
remember this will not tell you if you wired a speaker backwards or swapped the + and -.

All that would do would be to put the speaker out of phase. It won't affect any measurements, it'll just mean that when the cones of the other speakers move forwards, that speaker will be moving backwards.
#9
Thank you for all the help everyone, but I think I wasn't explaining myself clearly in the first place. I just wanted to know if you could test impedance by putting the leads of your multimeter on the sleeve and tip of a speaker cable. Thanks anyways!
#10
Quote by polishedbullet
......I just wanted to know if you could test impedance by putting the leads of your multimeter on the sleeve and tip of a speaker cable. Thanks anyways!


sorry...so the short answer is yes but it will be a few ohms less than you expect. i.e. an 8 ohm speaker will read maybe 6 ohms with your multimeter.