I have a few of the Sierra sound units and I wanted to put one in my USA 44-tonner. Anyone who has opened a 44-tonner knows that space is extremely limited. They also know that USA provides spaces for three speakers in the cab. One faces down in the center with a diameter of about 2-1/2", and required a really flat magnet because of the cab detail, and one in each radiator grill, with a diameter of about 1-3/4". The radiator grill speaker mounts are special in that they slide out so that you can install the speakers. They are cut for a cone and four screws in the corners. These pieces also hold the lights in place.
Even my smallest speakers were too big to fit. (Note that I even had to trim the Sierra unit to get it in.) I measured the screw distances and found pairs of what are listed as JBL speakers with the same screw spacing.
https://www.ebay.com/itm/163001299976?ul_noapp=true
When I tried to align them with the screw holes in the USA speaker frame, the spacing was right, but the headlight protrusion was in the way. Luckily, once you put the frame back in place, you can simply push the speakers up into the recess behind them for a perfect friction fit and floor clearance. Can you imagine a better fit than this?
Here you can see the pair wedged into place. They are 4 ohm so wired in series so the Sierra can take the load.
Of course the magnets now interfered with the floor weights. Rather than just remove the weights, I turned them 180 degrees and trimmed them back on my mill just enough to clear the magnets. This retains the most weight. Milling lead is an experience in itself. It doesn’t “chip” but more “melts” as you trim it.
I fit all of my Sierras with supercaps so I never need to deal with the damn battery. They tuck up to the side just above the floor weight.
And, to keep the caps from going flat when the trains park, I install a relay/cap/resistor so that the supercap will cut out of the circuit just before it goes into motorboating. This engine runs p-t-p and when the power starts, the supercaps are ready to go rather than starting from scratch each time.
