What wattage is enough for a layout speaker?

@Mannyrock I worked as a professional Audio Engineer for 30 years, designing, repairing, and operating live and studio audio systems.  Without going into too many details, to informatively answer your original question, would require knowing how loud and how bassy you want these background sounds to be, the driving amplifier's output capability (in Watts) and its output impedance (in Ohms).  Using an overpowered amp with a small wattage speaker, can easily kill the speaker.  One can sometimes get by pairing an amp with pretty much any speaker, but the results can often be problematic.

Unless you already have an amplifier that you really want to use with whichever speaker you choose, the simplest way to do what you're talking about is to buy a Powered Speaker (built-in amp) with 1/8" stereo and/or Bluetooth input and mount it under the table.  Probably the least expensive one you can find would suffice, unless you want strong bass from it.  More bass requires more Watts = more $.

@Mannyrock posted:

Looking for a speaker to hook to an MP3 or CD player...

Don't you also need some kind of amplifier?  Don't most MP3/CD players have "only" a headphone jack output (1/8" diameter) that drive a stereo headset/earbuds?  Those headphone outputs do not have enough power to drive speakers.

2-3 Watts is plenty for room-filling background sounds.  The best thing you can do is build a chamber for your el cheapo speaker which could be a yogurt cup or whatever.  There have been many threads about the importance of a speaker chamber.  If you look at some of the vendors that sell sound effects modules for trains, their speakers are typically 1 Watt or less.

What is your source of power to amplify the MP3/CD signal?

Powered speakers are great and if you can get a good deal on them so be it.  But I think of powered speakers in the $10 and up category.  I am a cheapskate and would be looking at a DIY solution in the less than $5 range!

I have installed PA systems as adjuncts to office telephone systems, and the self-amplified PA speakers for an office environment are usually in the 5 Watt range. (You've heard them, I'm sure: "Mr. Flacksworthy, call on line 2.")  For a big parking garage or repair shop 10 to 15 Watts is more than enough.  Why not try to use, at first, a pair of computer outboard speakers, which I seem to find in the garbage or at yard sales for a few bucks, when someone buys a new desktop computer.  They are small enough to be hidden in a building or mounted under an opening in the table,

If you have access to a store called "Five Below" in your area, they have dozens of powered speakers between 5 and 10 dollars.

I can dig it up if there's interest, but I think I posted this on OGR.  For less than $10 you can cobble together the total package.  Provide 14-16V Accessory AC power and this will blast out Watts of audio for hours/days or as much MP3 "material" as you have!

This eliminates the MP3 player (or CD player) which might save another power cord or occasional battery changes.  Obviously if you have an MP3 player you have the MP3 sounds so you'd simply transfer the MP3 file(s) to the microSD memory card.  If you have a CD player then you'd need to rip the CD and save the audio as MP3 file(s) and transfer them to the microSD memory card.  Note the speaker is in a chamber (baffle).  It's actually quite remarkable how such a small chamber (I think it's a vitamin bottle cap in photo) can dramatically improve the bass/volume of the audio.  Laundry detergent caps also make for good chambers!

Thanks for all of this great information.

If I want to go the (i) buy cheap CD (or MP3) player, and (ii) connect inexpensive/cheap but adequate sound level powered speakers, would these powered speaker be enough?  (They would have to go underneath the table.)  These are not true Micca speakers, but cheap knock off "Mica" Speakers.  Apparently not much bass, but would I really need that for just background railyard sounds?

Mica PB20i Compact Bookshelf Speakers

Reliable Performance

The PB20i powered bookshelf speakers has combined a retro look with a modern sense of audio quality. If you’re looking for affordable and versatile bookshelf speakers with uncompromising sound the PB20i bookshelf speakers is your go-to 2.0 speaker system. Featuring a 3-inches bass driver and a calibrated, flared bass reflex port, this bookshelf speaker system delivers robust, rich bass notes that are full of presence and depth.

@Mannyrock posted:

...

(At present, I only own a 20 year old Sony Bookshelf stacked CD player with two powered speakers.   I don't own and don't currently have a use for MP3 or Micro MP3 cards.)

Hmm.  A bit confused here.  If you already have a Sony CD system WITH powered speakers then aren't you good-to-go? 

Are you saying you have a CD disc with train-related background sound-effects? 

@Mannyrock posted:

Thanks for all of this great information.

If I want to go the (i) buy cheap CD (or MP3) player, and (ii) connect inexpensive/cheap but adequate sound level powered speakers, would these powered speaker be enough?  ... Apparently not much bass, but would I really need that for just background railyard sounds?

Mica PB20i Compact Bookshelf Speakers

Reliable Performance

The PB20i powered bookshelf speakers has combined a retro look with a modern sense of audio quality. If you’re looking for affordable and versatile bookshelf speakers with uncompromising sound the PB20i bookshelf speakers is your go-to 2.0 speaker system. Featuring a 3-inches bass driver and a calibrated, flared bass reflex port, this bookshelf speaker system delivers robust, rich bass notes that are full of presence and depth.

• Channel: 2.0
• Signal-to-noise ratio: 83dB
• Output power: 2 * 4Ω 5W
• Frequency range: 150Hz - 20KHz
• Power supply: 5V USB
• Interface: 3.5 mm audio / USB Tepy-C
• Net weight: 3.3 LB (52.9 OZ)
• Size: 4.2in(L) * 4.5in(W) * 7.0in(H)

Thanks for all advice.

Mannyrock

Manny, I suspect you'll find that these have more than enough volume as well as enough bass to suit you for RR background sounds.   If realistic sounding thunder is what you want, maybe so so.

Steve, thanks for that info.   I won't be needing thundering sound.  :-)

Stan, sorry for the confusion.  My Sony CD player is on the shelf in my living room.  We use it to play music, so I can't sacrifice it to the train.

Also, Stan, the components you so thoughtfully listed are so cheap, that I am going to go ahead and buy them, as a back-up (or a future project), in case the cost of a cheap (but reliable) CD player and speakers is just too much.       It looks like there are some train sound CDs online that are available on micro memory cards.   If I can't find what I want, then I can probably find a technically proficient 14 year old somewhere you can copy the CD to a micro card.  :-)

Mannyrock

Do you have an old C.B. radio they run on 12 -13 DC volt and would drive any speaker.

When it was time to add real sound to my Starlite Diner and my gentleman's club, I chose to use small 3 inch Bluetooth speakers like these:  https://www.amazon.com/gp/prod...00?ie=UTF8&psc=1

That way I could control what sounds I wanted played from an old iPad or iPhone.  Plus, you can hardwire them in, of just recharge them.  Mine last about 3 weeks per charge.  They are USB, so you could just leave them powered up and wired for power too.  Plus, you control the volume on the speaker AND on your phone so you can dial in the perfect ambient sounds to fit the scene.

Just an idea...

Gunrunnerjohn used to sell (and maybe still does) an audio player/recorder module with enough output to do any of the tasks suggested. It's a very versatile little guy. It didn't come with a speaker as I recall, but the speaker of your choice should work well I think.

I use 2 of these for local sounds played close to the source (tinplate Lionel backshop and 0 scale Lionel crane) and I am happy. For overall background, I use an old surround sound receiver with speakers under the layout, playing ambient sound CDs from Green Frog and elsewhere. I love those, especially the night time sounds.

When I am working on the layout, I use a separate old stereo system with radio, tape and etc. I often listen to old time radio shows or whatever on tape or CD. That has been VERY convenient.

Surround receivers are $40 or so at flea markets. Speakers are $5 each. Heck, the wire might cost more than the system.

Good luck!

Don Merz