George's (TVW Miniatures) plywood enclosures work well however I like to add a coating of Aileen's tacky glue to be sure to fully seal the wood on the outside and when installing the speaker into the box - need a perfect seal.
As for are these big enough to install 1/16" foam tape to the inside - well I haven't tried doing this using his enclosures myself but I would think making a slightly larger enclosure box with the absorbing material lining the inside would be very worth the effort - and of course let your ears tell you if the sounds are better.
I'm using the foam tape that is used by automotive industry as it is a bit denser than the cheap foam tape and a little bit thinner too - saving space and the box size.
If you are serious about using these tiny speakers and really want to let your ears discover how you can make them produce slightly different sounds I suggest you experiment with one or two.
Make the enclosure (box) about 8.0mm deep and use styrene (0.015" thick) for the sides. You glue the styrene around the speaker and make sure youget a good seal.
This leaves the rear cover to be glued onto the box sides.
Try a balsa wood cover but seal the outer side with Aileen's glue or similar to ensure a good seal so air pressure can't push through the wood.
Glue the cover on and let the glue dry completely (overnight). Then hook-up the speaker and have a listen.
If your ears don't like what you hear remove the wood cover and try a cardboard cover. If this doesn't sound right then try a styrene cover - say 1/16" thick.
What I'm saying is trying different side and rear cover materials will give you slightly different sounds.
Next is adding sound wave absorbing material inside the "box" and I just use foam tape.
Of course it will all depend on the available space in a loco to accommodate the speaker with its enclosure.
The best I have so far found is to make the box at least 1.5 times as big as the speaker itself - 2 times bigger is better but will take up more space.
Where Detlef glued the speaker onto the loco body using super-glue if the speaker was to fail then removing it may be a problem.
In my Kato SD40 I use the very thin double sided tape which I purchased from an electrical sales store here in Australia. It comes 3/4" wide in a roll about 5 inches diameter and used to stick electrical signs inside power boxes etc.
It is very thin at about 0.003" thick and being so thin the transfer of sound waves into the loco body is good.
You may find a similar tape in an office supply company in the USA ?
The key is to get a perfect seal on the enclosure box so care needs to be taken when gluing the sides and the rear box cover. I cut the foam tape so it makes a "push-fit" on the rear cover into the box sides and glues I use are Pliobond or Loktite Super-glue GEL to seal the back box cover.
I usually mount in locos using the rear cover against the loco with the thin tape or the 1/16" thick tape.
I know folks here are serious about sounds and desire as good as they can get. I always make my own enclosures to suit the space but I still experiment and try different s tiny speakers and listen to how they sound.
I have 2 plastic kits part boxes full of speakers plus my Sound Sample demonstration panel and I have several speakers with different materials to try. This investment has paid off and I have shared much of this on my YouTube videos.
Do yourself a favor and make a few test speakers up and then let your ears do the talking (Grin)
Regards and good listening .....
Laurie