Hi everyone.
I thought I'd post a photo of my latest installation in a DCC-ready Atlas RS-11 to both illustrate the techniques I'm using today and to show how I do this for a DCC-ready frame.
Here's the photo:
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In this photo, the front of the locomotive is to the left, the rear is to the right. The decoder is in the front; the speaker is in the rear, and is a 9x16mm (this one is a Knowles Fox, no longer made, but you can still get 9x16mm speakers from CUI and Soberton via Digikey and/or Mouser). Just in front of the speaker are two 16v, 220uf tantalum chip caps that I use for keep alive. The wires go in the channel, along with my tiny piece of circuit board that has two 1K, 1/8w SMT resistors for the front and rear LEDs. You can see the front LED at the very left end of the decoder - I just tape the wires of the LED on the decoder to hold it in place.
There's not a whole lot of frame milling on this. I milled down the rear shelf even with the phosphor-bronze piece that holds the bearings (well, in this case, bearing - singular - since I have Beardenized this loco). This gives about 7.25mm of height on the rear shelf for the speaker. The speaker is set in a sealed enclosure made of .020 styrene; the sides are 6mm high, with an .020 styrene base, making the speaker/enclosure overall 6.5mm high, by 17mm long, by 10mm wide.
This kind of arrangement, with the decoder in front and speaker in the back, should work for pretty much any DCC-ready high-hood diesel. The RS-11 is about as short as you can go in a DCC-ready frame, so anything else actually should have more room.
I have to say that with the progress manufacturers are making on sound installations, the days for doing custom installs like this may be numbered, except for retrofits in older locos. I think that pretty soon, installing sound in a diesel will consist of popping a new board on the top of the frame and popping a speaker/enclosure in the pre-milled slot in the fuel tank. So my RS-11 may represent the end of an era - a good thing, overall, but I'd be lying if I said there wasn't a tinge of regret . . .
John C.
