The wired micro select is just about half the size the the Atlas board replacement. If they removed the wires and used a spring loaded contact system like is done with SIM cards, you would still have half the length of the hood to fit a 20x9x3mm sound enclosure. Think suggest cube but half the height and twice the length.
Cell phones didn't get really good sound until the engineers got creative with the enclosures. The iphone 4 has this strange "L" shape tunneled baffle with output pipe. I have been toying with the idea of doing the same using an open exhaust stack... Sugar cube hyperbaric chamber - speaker - resonance chamber - output tube/exhaust stack.
Yes, the LokSound Micro is shorted but (at 10.6mm) is quite a bit wider than the Atlas S1 and 73199 decoders which are about 8.2 mm wide. The Micro Select will not fit installed flat in a narrow hood loco (like GP38). Before 73199 came out modelers were installing the Micro Select decoders slanted inside the loco's hood, or in the fuel tank. The 73199 was specifically designed to fit in narrow hood locos.
As far as sound enclosures go, sure the acoustic engineers do get creative, but no matter how the enclosure is shaped, it needs certain amount of air volume (space) on one side of the speaker to isolate one side of the speaker cone from the other side (so sound waves produced on one side do not cancel the opposite phase waves from the other side of the speaker). iPhone might have a horn-type chamber which will boost certain frequencies.
