I was frustrated by the low sound level from my new MTH 20-3357 Camelback from the very first, and finally decided to do something about it. The sound was just a whisper, compared to my K-4 upgrade or any of my diesels, and the first time I took a look in the tender after I bought it a couple of years ago, there didn't seem to be a lot of extra room for a bigger speaker.
A forum member who lives nearby suggested I could add a larger speaker in a car immediately behind the tender. Before going that route, I decided to take another look in the tender and see if I got any ideas.
After studying the situation, I decided I could squeeze in the speaker that is used in PS2 upgrade kits (MTH BF-0000034), if I was willing to sacrifice the switches and pots. Since my layout is 3-rail DCS only, I removed the smoke & sound control pots (for vertical clearance) that are only used in conventional mode, and the switches used to select 3-rail/2-rail & DCS polarity (to clear the speaker diameter). The forward edge of the speaker would just slip under the PS-2 board connector pins, with room for a 10-mil insulating sheet. However, at the rear, I would have to cut or grind off about 1/16" of the speaker OD. That, I was reluctant to do, so I ordered a couple of slightly smaller candidates from MTH. (a forum member had posted an MTH speaker spreadsheet a few years ago, and that was a big help in selecting the sizes)
Both the 039 and the 041 fit ok, but the 041 seemed to have better low frequency response, so I decided to install the 041.
The speaker is offset because that is where the original speaker vent holes are. The two screws fastening the speaker are 4-40 installed in two unused holes that were already drilled and tapped in the chassis - sometimes you get lucky... The speaker is up against the multilayer PCB, so there is a piece of Kapton tape inserted as an insulator.
The results of this little experiment are quite satisfactory, I now have sound almost as loud as my K-4, and, in fact, I don't run the master volume wide open anymore.
Happy camper!
