Help me determine what my cab is wired in..

[Thor Von Clemson]

Because I can not figure it out.

I have a cab with 2, 16 ohm speakers in it. There are two wires running from the speaker jack to the left speaker. The left speaker has two wires running from it to the right speaker. The left speaker has two wires running to it and two wires running from it.. .so four total.

I have attached a picture and will attempt to explain it...



The upper left is #1

The lower left is #2

The upper right (red) is #3

The lower right is number 4

The wires coming from the jack to the left speaker are going to #1 and #4. The wires going from the left speaker to the right speaker are #2 and #3 (red to the red of the right speaker)

I am thinking its wired in series because the wires coming from the jack are only going to one speaker and then they are going from that speaker to the other. Isn't parallel where the wires are going to separate speakers from the same jack?

Finally, if it is in fact wired in series that means I have a 32 ohm cab. I am looking to use it with another cab that is an 8 ohm cab wired in parallel... How many ohms does that give me?


Thanks for any help. I realize this may be a tad bit confusing for some but I appreciate anyone looking at it.

[siggy14]

More then likely your cab is wired in parallel. OK best way to explain this, on the speakers, if the + (red usually) from the first speaker goes to the + (red) of speaker two, and the - (black) of speaker one goes to the - (black) of speaker two then they are wired together in parallel.

Crappy Diagram here.

Jack Positive-------------->Speaker one Positive -------------->Positive Speaker two

Jack Negative------------->Speaker one Negative-------------->Negative Speaker two

[Racerx2k]

Yeah, sounds like parallel.

[Thor Von Clemson]

that sounds like its whats going on... so how many ohms would that give me for the total cab and what would I want to set my head to with my 8 ohm cab? My 5150 can go from 4, 8, or 16 ohms.

About series and parallel... Series is when the wires are running in one continous current and parallel are when the wires are running parallel alongside each other correct?

[Racerx2k]

Two 16 ohm speakers, in parallel, would yield 8 ohms, total.

[Thor Von Clemson]

so two 8 ohm cabs running into the same head would yield 4 ohms right? If thats the case, I would want to set my amp to 4 ohms.

[siggy14]

If both cabs are running in parallel yes, some amps, very few though have series input in the back, most are in parallel.

so two 8 ohm cabs running into the same head would yield 4 ohms right? If thats the case, I would want to set my amp to 4 ohms.

[siggy14]

Yes correct, series is there is one path for current, parallel there are two paths. Advantage of parallel is if one speaker blows there is still a load because of the other speaker to protech your amp.

With series if one speaker blows the whole path is shot and there is no load to protect your amp.

Most Mono 4x12 cabs are wired in a combination of series and parallel, were most 2x12's are wired only in parallel. However i have found some 2x12's wired in series which is not good.

To determine ohms with series you just take the value of both speakers and add it, example 2 eight ohm speakers would equal a sixteen ohm load.

Now with parallel you take load and devide it, exmaple take the same cab with 2 eight ohm speakers and wire it in parallel and you have a four ohm load.

The same concept goes for cabinets, 2 eight ohm cabs wired in parallel equals a 4 ohm load. 2 eight ohm cabs wired in series gives you a sixteen ohm load. Like with speakers if you run your cab in series and one speaker goes out, the whole chain is broken and there is no load to protect your amp.

Now to figure out what to set your amp if you have two cabs parallel that are rated at different ohms, what you do is take the lowest cab and cut that in half.

Example, you have a eight ohm cab and a 16 ohm cab, you would set your amp to 4 ohms. The actuall resistance would be 5.333 ohm, but 4 ohm is close enough.

About series and parallel... Series is when the wires are running in one continous current and parallel are when the wires are running parallel alongside each other correct?

[Thor Von Clemson]

So if I have two eight ohm cabs, regardless of whether they are wired in series or parallel, I would divide the lowest number (in the case eight) by half to find out what to set the ohms on my amp at if I am plugging them into two separate, parallel jacks in the amp correct? As long as the resistance from the cabs is 4 ohms or greater I should be ok if I switch my amp to 4 ohms right? If the cab resistance totaled 8 I would need to set it no lower than 8, etc, etc..

I've heard you can get away with it a little more with solid state heads.

[Chad]

Check out this link, bro. It is great for calculating parallel resistance:

http://www.1728.com/resistrs.htm

Most amp extension cab jacks parallel with the main cabinet jack.

Not saying I recommend it, but I've read that you can generally get away with plugging into a jack one notch higher or lower with most tube amps if they have a beefy enough transformer. i.e. if an amp has 4, 8, & 16 ohm output jacks and you have a total 4 ohm load, you would ideally plug into the 4 ohm jack. But you could also probably go with the 8 ohm jack. If you have a 16 ohm total load, you could probably get away with plugginng into the 16 or 8 ohm jack.

Short answer: if you have two 8 ohm cabs, plug into the 4 ohm jacks.

[Rsmacker]

If in doubt, run your speaker cable from the output of your amplifier set on the lowest impedance (4 ohms). If you have a total load impedance (let's say for example, a single cabinet) of 8 ohms, and your amplifier is set at 4 ohms, it won't do it any harm. It just means that your amp won't be delivering the load as efficiently as it could. In effect it is trying to "push" too much load through a "hole" not big enough to allow it all to pass through nice and neatly.
The result is that when your amp is on number 11, you are not flat out, the amp is not running on "top gear", regardless of the speaker handling capacity, it can't work efficiently. You'll notice it gets bloody warm though!

The thing is not to use an amplifier with a lower impedance load than it can handle (ie. speaker stack at 2 ohms from an amplifier set at 8 ohms). Here, in effect, your amplifier's guts are falling through the over-large "hole"!


Solid State amps are no better or worse than valves at handling mis-matched loads, just less spectacular when they fail mid-show, less blue flame and smoke ( so don't think you can just daisy chain up 4 full Marshall 4x12 stacks just like that, no matter how cool it looks, you must think it through and use a proper loom and power amps.) They still cost a packet to fix, if anything are more of a ball-ache because of surface mount components, and the price of large copper-wound transformers. Pro-audio power amps, switch-mode stuff etc will happily drive 2 ohms these days.

I hope all this advice hasn't muddied the waters too much!

Right, who's gonna explain to him series/parallel 4x12 wiring????:ROTF:

[siggy14]

NO.

In parallel you devide the lowest number by 2.

In series you add the two values.

So if I have two eight ohm cabs, regardless of whether they are wired in series or parallel, I would divide the lowest number (in the case eight) by half to find out what to set the ohms on my amp at if I am plugging them into two separate, parallel jacks in the amp correct? As long as the resistance from the cabs is 4 ohms or greater I should be ok if I switch my amp to 4 ohms right? If the cab resistance totaled 8 I would need to set it no lower than 8, etc, etc..

I've heard you can get away with it a little more with solid state heads.

[Chad]

In parallel you devide the lowest number by 2.

Not always true. With that method, a 16 ohm load paralleled with an 8 ohm load would calculate to 4 ohms. But it actually comes out to 5.333 ohms. There is an equation, but it's easiest to just plug the values in to the calculator in the link I provided above.

[siggy14]

I know, i had mentioned that above in another statement, read all my posts on this subject.

Not always true. With that method, a 16 ohm load paralleled with an 8 ohm load would calculate to 4 ohms. But it actually comes out to 5.333 ohms. There is an equation, but it's easiest to just plug the values in to the calculator in the link I provided above.

[charvelguy]

and in case you're more confused.. this is why you hire a road tech to set up your gear for you.
Then you can blame them when the stuff blows up (I think it was more greenish hued smoke actually)

I actually appreciate you guys adding your input on this as I completely forgot series vs parallel would differ in setting the ohmage for two cabs.
I'm not as careful as I used to be sometimes...which is why I oftentimes only run one cab nowadays.