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Impedance for a fool


JamesLawrence
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I have the Orange OB1 500 and I am playing through an orange 4x10. I am looking to add another cab to the mix and have a good deal on an Ashdown 6x10. 

I am finding this to be a minefield for an answer. The amp says MINIMUM impedance of 4 ohms. The orange is an 8 ohm cab, the Ashdown 4 ohm. I've calculated it that at an amp power of 500w the total impedance will be 12 ohms (Ashdown at 166 watts and Orange at 333)

Does this seem correct? Any help will be greatly appreciated. 

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I think you have calculated for a connection in series; i.e. 8 + 4 = 12ohm.

But bass cabs are connected in parallel, so the calculation is 1 ÷ (1÷8 + 1÷4) = 2.7ohm, which I'm afraid is below the minimum for your amp.

Your only cab options are: one x 8ohm, two x 8ohm, or one x 4ohm.

There is a calculator here with explanation: https://geoffthegreygeek.com/calculator-speakers-in-parallel/

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No, sorry that's not correct.

Your amp has a minimum load of 4ohms.

If you connect an 8ohm cab and a 4ohm cab in parallel (the normal way) you get a total load of 2.7ohms presented to the amp.  Not OK for your Orange OB1.

You could get a series cable which will add the ohm's together and present a total load of 12ohms to the amp.  This would send 66% of the amp power to the 8ohm cab and 33% to the 4ohm cab.

I haven't checked but I guess the Orange is 500w at 4ohm.  That power will be reduced at 12ohms.

The best advice in this situation is to get another 8ohm cab to go with your 8ohm Orange 4x10.  That will present a total load of 4ohms to the amp and give you max. power.

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