crusty philtrum
Vintageologist
Laughing Kookaburra asked me how to wire a dual-impedance switch for a cabinet with 2 x 8 Ohm speakers, to give a total load of either 4 Ohms or 16 Ohms. (This would not usually be relevant for 2 x 4 Ohms or 2 x 16 Ohms as there would be a redundant impedance for both of those, i.e. 2 Ohms for the first example and 32 Ohms for the second).
I quickly found a diagram online but some people would have trouble relating the switch in the diagram to the actual switch they were holding in their hand, so i have drawn a 'real world' illustration to go with it.
The switch would be a common heavy-duty 2P2T toggle switch ('Double pole, double throw') type, easily found and not expensive. Please note that most switches of this sort switch in the opposite direction to the terminals on the back .... in my hand-drawn pic below, i have shown the terminals on the back of the switch. The switch lever (toggle type, NOT slider) moves up and down on the other side. So where i have the 4 Ohm position marked, the switch lever would be in the 'UP' poisition, and 'DOWN' to get 16 Ohms.
You can easily check this out with a cheap multimeter before you wire it up, and if you have a low range resistance capability on your meter, you can check it again once you've wired it up.
I have shown only one jack socket, but you can parallel another one (or more) from the one shown, as in the first diagram.
I hope this might be of some help to some of you and give you some options when working out speaker impedance configurations.
You will notice there are 2 wires that need to join either at the + terminal of one speaker and the - terminal of the other, OR those junctions could be made at the jack terminals. I'd recommend the latter to avoid the difficulty of trying to attach 2 wires to the speaker terminals.
I quickly found a diagram online but some people would have trouble relating the switch in the diagram to the actual switch they were holding in their hand, so i have drawn a 'real world' illustration to go with it.
The switch would be a common heavy-duty 2P2T toggle switch ('Double pole, double throw') type, easily found and not expensive. Please note that most switches of this sort switch in the opposite direction to the terminals on the back .... in my hand-drawn pic below, i have shown the terminals on the back of the switch. The switch lever (toggle type, NOT slider) moves up and down on the other side. So where i have the 4 Ohm position marked, the switch lever would be in the 'UP' poisition, and 'DOWN' to get 16 Ohms.
You can easily check this out with a cheap multimeter before you wire it up, and if you have a low range resistance capability on your meter, you can check it again once you've wired it up.
I have shown only one jack socket, but you can parallel another one (or more) from the one shown, as in the first diagram.
I hope this might be of some help to some of you and give you some options when working out speaker impedance configurations.
You will notice there are 2 wires that need to join either at the + terminal of one speaker and the - terminal of the other, OR those junctions could be made at the jack terminals. I'd recommend the latter to avoid the difficulty of trying to attach 2 wires to the speaker terminals.
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