I’ve just added a soundtraxx DSD-AT100LC EMD2 for my Atlas GP-40. I was able to place an oval speaker (.75) directly under the see through fan in the center of the shell. It fits like a glove, but unfortunately the speaker enclosure I purchased with it was far too big to fit. I refuse to dremel out any weight, so I’m stuck with what I’ve got. It sounds good to me, however I’ve never heard one in an enclosure. Is it the cat’s “meow” with the enclosure or am I OK without it [:D]
If the speaker is completely covering the fan holes and no sound from the back of the speaker can escape out of the loco shell, you may have achieved the same effect as adding an enclosure. The shell of the loco can act as the enclosure.
Anyway, in answer to your question there is a huge difference in sound with and without an enclosure. You may well have created an enclosed enclosure.
Bruce at www.litchfieldstation.com has a nice presentation at http://litchfieldstation.com/lobby/u_sound.htm Click on the desginers notebook presentation link at the bottom of the page.
If you sealed the speaker up against the fan opening, then you have pretty much made the entire shell into the enclosure. If the volume is good, you probbaly have done a good enough job. I have a small Soundtraxx speaker I got with a DSD100LC just to test - sitting ont he bench you can hardly even hear it. Cupping my hand around it to ake an enclosure of sorts, it’s significantly improved. So yes, an enclosure really DOES matter, but there are many ways to accomplish that, not all of them involve a plastic box or bottle behind the speaker.
–Randy
I thought as much that in fact I did create my own enclosure within the engine shell itself. Believe me, its plenty loud!
Besides volume, an enclosure helps bring out the lower frequency sounds. I have heard this many times when I do Loksound installs. I usually wire up the decoder and test it with the shell off and the speaker loose. It sounds very tinny. Then when the enclosure is installed it’s a world of difference, much better volume and bass. Even a small enclosure is better than nothing.