Speaker cab wiring schema
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The topology is relatively straightforward: a series/parallel arrangement for the speakers, with the Midax horns over the top. The 2uf capactitors filter out the low frequencies, protecting the horns from excesses of bass.
The impedance of the four drivers in the cab was always 15 ohms, as was the total impedance of the cab - never 8 ohms.
A note on the maths underlying the circuit (impedances and so on) to follow.
The arrangement of the wiring is clever. If either or both of the horns fail, all four speakers remain in circuit. In addition, if one pair of speakers fails, the other remains active, though the impedance of the cab rises to 32ohms.