I have a situation where I have a guitar amp with just one speaker out, and a switch to select the impedance between 8 and 16 ohms. Now, I want to connect two speaker cabinets with 8 ohms speaker inside both of them. I ended up to build up a simple cabinet merger for future use also. When connecting speakers to amplifier, there is two ways to do it, in series or in parallel. Impedances go like this:
So basically, it goes like this:
– In series: Rt=R1+R2+Rn…
– In parallel: Rt=1/R1 + 1/R2 + 1/Rn…
Where Rt=Total impedance, Rx=Impedance of the single speaker
I built up a very simple wiring schematic for cabinet merger with switchable series/parallel -option:
So, no more than three ordinary jacks and a DPDT switch with some wiring.
NOTE!: If assembled inside conducting enclosure, you need to insulate Speaker out 1’s ground from the enclosure. Otherwise it won’t work correctly in series mode. Alternatively you can build this inside non-conductive plastic enclosure.
Always meet your amplifier’s impedance requirements, and don’t even try connect for example 4 ohms load for the amp which expects 8 ohms speaker load. You will most probably fry your output transformer.