Simple Ohm/Watts Question

[jokolono]

So I picked up a couple of 2x12 cabs, which have had new speakers put in, and despite lots of googling I can’t get my head around what the ohms/watts are! 

As far as I can see it’s 2x eminence gamma 12s, which are apparently 300w at 8 ohms. 
Not sure if this is wired series or parallel? (Pic below) 

Also as I have a second matching cab - if I were to run the pair, what ohms/power would I be looking at? 

I’m running an orange terror 500 through them which has a 8/4ohm switch, so I’m hoping it’s one of those two! 
 

Thanks and sorry for the noobish question!

Edited November 9, 2019 by jokolono

[itu]

Take a look at the wires. One wire goes to the upper element. Then another goes downwards to the lower element. The third wire goes back to the amp. This is called series. You sum the ohms together (8 + 8 = 16 ohms). Very easy.

Now, the speaker can handle up to 300 + 300 watts.

So you have two similar speakers, but one amp. Your amp probably has two 8 ohm outputs. When two sixteen ohm speakers (the complete boxes with elements inside) are put to the single output (with two parallel sockets), they are parallel from the amp point of view.

So the amp sees one 8 ohm impedance (1/(1/16 + 1/16) = 1/(2/16) = 16/2 = 8 ohms) and you can push up to 4 x 300 watts of power to the system. Enough? Clear?

 

It is quite common, that a transistor based power amp is not so accurate with impedances, especially big ones (>4 ohms). Most of them do not even need the cab.

Valve/tube power amps tend to like some load in their outputs, so it is better to have a 5 inch nail in the output than nothing at all.

These are just basics, and there are many exceptions, so always keep a load in your amp's output, if you even think about connecting the unit to the 230 volt line. And use quality cables.

[ikay]

Looks like the speakers are wired in series which makes each cab 16 ohms. Running both cabs in parallel will bring that down to 8 ohms.

[goingdownslow]

Where is the green and red/yellow wire going?

[jokolono]

Thanks guys, that’s exactly what I needed to know. 
Weirdly the red and green wires go to a separate XLR Input, next to the speakon input. Any logical reason for that...?

[itu]

Someone has used an XLR connector between the amp anf the cab, or an output to DI-box, or a parallel output.

[BassBunny]

If it were me I'd be inclined to rewire them both with the speakers in parallel as it would give you a number of advantages.

Firstly the cabs would then be 8 ohms each so you could run one on it's own if you wanted. At the moment you can't as your amp hasn't got a 16 Ohm option.

Secondly at the moment with the speakers wired in series should 1 fail or the wiring between them, you lose the whole cab. With parallel wiring if 1 speaker goes, you have the other one still in circuit.

Finally, 4 and 8 Ohm cabs are more common than 16 ohm ones making them more attractive should you want to sell them.

Just my 10 penneth for what it's worth.

[Jack]

1 hour ago, BassBunny said:

.... rewire them both with the speakers in parallel as it would give..... 8 ohms each ...

Two 8R speakers in parallel would result in each cab being 4R.

1 hour ago, BassBunny said:

Firstly the cabs would then be 8 ohms each so you could run one on it's own if you wanted. At the moment you can't as your amp hasn't got a 16 Ohm option.

Solid state amps are usually fine with anything greater than their minimum load, so the OP's amp should be fine with 16R, or 32R, or 1047R.... Unless there's something special about the Orange amp I don't know about.

[BassBunny]

1 hour ago, Jack said:

Two 8R speakers in parallel would result in each cab being 4R.

Solid state amps are usually fine with anything greater than their minimum load, so the OP's amp should be fine with 16R, or 32R, or 1047R.... Unless there's something special about the Orange amp I don't know about.

My Bad. I thought they were 16 ohm drivers. should read the OP comments properly before putting keyboard into gear.😀