Boogie S.O.B. speaker hookup combinations

[lisamerrittjohn]

My S.O.B. has one 8 ohm and two 4 ohm outputs to speakers. If I disconnect the 8 ohm speaker and connect two marshall cabinets rated 4 ohms into both 4 ohm jacks simultaneously am I running at a 2 ohm load, because that could that damage my amp? How do I correctly understand the three speaker jacks in relation to the load each will put on the amp under different combinations of more than one speaker hookup? I understand the S.O.B. can run safely at 4 ohms but was designed to run at 8 ohms.
lisamerrittjohn

 

[RR]

You may have to wire your Marshall cabinets to a different impedance.

If your SOB is like my Mark II (same era) them two 4 ohm impedance jacks are actually both used for 8 ohm speaker each simultaneously, thus 4 ohms. e.g. You currently have an 8 ohm speaker, now if you got another 8 ohm speaker, you would plug each in those 4 ohm jacks.

Now if you have one 4 ohm speaker enclosure, then you plug into one 4 ohm jack and leave the other 4 ohm jack alone (was well as the 8 ohm jack [left alone]).

(I maybe wrong but I thought I read this in the manual).

Now is your Marshall cabinet 4x12" or 2x12"? If you have a 4 ohm 4x12" Marshall cabinet and its wired all speakers in parallel, then you could rewire the cabinet to get 16 ohms.

If you Marshall is 2x12", then you could wire the speakers in series (I'm almost sure its wired in parallel if its a 2x12") to get 16 ohms.

With two 16 ohms cabinets, hopefully one or both cabinet has an extra jack or you need a speaker y cable, one plugs into the other and the remaining speaker cable plugs into you SOB's 8-ohm speaker jack.

sounds confusing? Sorry, I'm typing this on the fly so it maybe confusing but others while chime in either to correct me, or confirm and clear it up.