Would anyone happen to have a copy of the wiring schematic for a mid 70's B25B 2-15" cab? It has a 4-16 ohm selector switch and a 4 pin speaker connector that have been disconected. I would like to re-wire everything to stock without taking my other B25B cab apart. Thanks!
i wired my own series/parallel switch in one of my V4 cabs (it has four 12's and it switches betwen 2 and 8 ohms), but in a two 15" speaker cab, it has to be something like this to switch between 4 and 16 ohms (as long as both speakers are 8 ohm speakers):
Here is the cab schematic, same as what John posted but with the connector. The original impedance switch that Ampeg used was a weak link in the signal chain. Better to get a good quality switch or wire it directly to the desired impedance.
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Last edited by beans-on-toast : 07-21-2011 at 05:00 AM.
Best I can tell this wiring should be correct, but one of my speakers was reading open (thus the readings when playing around with the switch were funky) when I got the cab so I pulled them both and in the process just removed the switch and wired the new speakers straight to the jack for 4 ohms.
Need a Schematic for an Ampeg B25B Cab 
