Hi folks.
So I decided to try an 11x15 cell-phone type speaker in a sealed enclosure 8mm deep in place of the stock speaker in the BLI Mike. What I found was interesting. First, the stock speaker isn't as bad as I first thought. The bell actually sounds better to my ears via the stock speaker than the replacement, although I think this is the result of having the volume level too high for the 11x15, thus inducing some distortion in the upper octaves. The whistles and chuffs, however, sound noticeably better to my ears with the 11x15. In particular, the 11x15 gives considerably more weight to Whistle 2 and the chuffs. I might try a 13x18 instead of the 11x15; there's plenty of room in the tender for a 13x18, so I might experiment with that. It's also possible that if I took the time to fully seal-up the stock speaker to the top of the tender shell, it would sound better. Right now, the stock speaker is mounted on a flat piece of plastic that press-fits into the top of the shell. There are holes (for the wires, for example) that aren't sealed. Using some silicone sealant to fully seal those holes might make the stock speaker sound better.
I'm going to do more experimenting, but here's a video that compares the stock speaker to my 11x15 replacement:
Here is a photo of the stock speaker from the back. You can see that it is mounted to a flat piece of plastic, which press-fits into the top of the tender shell:
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And here is a photo showing the 11x15 mounted in the tender, firing down toward the decoder board.
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John C.
