B15S; I owned and used a B15S for over twenty years. Some of those years it was used every day, a few where it was just weekends. Several years were of sporadic use. It spent much of its travel time in an Anvil flight case. My amp had been returned to the store by an accordionist who thought it was too loud. I originally wanted a regular, good ol’ B15F(?). The store replaced the speaker, put in new tubes and gave me a brand new cover (the case was a later investment). While loved, it was occasionally stored in loving status in the band trailer. I signed a note and left the place with the amp and no money down, just a promise to get it in their within the next few days. This would have been around the December of 1974.
Someone once told me the cabinet was basically ½ of the BT140 cabinet, maybe was I do not know.
It will not sound identical to either an N or an F, can’t happen. It will get very close to the F. The sound is maybe closer to ½ of a V4B head.
That amp was pushed with a 1974 P with tape wounds, an Ampeg Baby Bass, an Ibanez Artist(?) with tape wounds, an off brand short scale Decca with Tape wounds, and the majority of the time a Guild JSII with tape wounds.
Dizzy Gillespie’s bassist used one, at least in the winter of 1975-1976.
The only repair needed was it did have a resistor crack, if memory serves it was on one of the power tube sockets, so the shop replaced of with a higher wattage, and they did the same on the other power tube socket.
Yes of course it ran out of power sometimes, but that meant the band was too loud. It never ran out of power in C&W bars, weddings, supper clubs, etc. It did at High School Auditoriums and such. It alway did fine with support.
The speaker it came with was a CTS 15G54B. Later I used a Gollehon which made most everything sound woody and string bassish. About ½ of its life with me it was loaded with a JBL K140, that was a bad match for the cab I think. It would get barky, and lacked note definition. Of course tubes, hum buckers and tape wounds may have influenced that.
As extension cabinets, I have used a 360 loaded with a Pyle, an EV 18” in a Homebrew cabinet, and 2x10 cab.Seldom were extension cabs used.
That amp is way heavy by today’s standards. Back in 1974 compared to many it was average. It is an Ampeg, and they were seldom considered a light amp.
I did not have the tilt back leg, but when placed on top of the case, it was much closer to ear level, and that worked well.
Best of Luck,