What are the speaker baffles and will I always need them with doing a DCC sound install?
It is usually a thicker paper, plastic, or cardboard tube whose diameter matches the outer speaker diameter closely such that the baffle sits squarely, flush, and can be sealed against the speaker’s rim. This creates a barrier for the sound waves to propogate directionally toward the front axis of the cone…where you want them emitting from the louvres or holes provided in the tender.
For our model locomotives, a speaker baffle is also known as a speaker enclosure – a plastic box into which the speaker is mounted to seal the back and improve the low frequency sound.
Think of it like speakers for your stereo or your computer - you could just have the speakers by themselves sitting on your floor or your desk, but a well-designed speaker enclosure or cabinet can make the sound much better. It’s same thing for our trains. You can make your own enclosures, but a couple of manufacturers make plastic ones to fit different sizes of speakers.
The issue is that when the front of the speaker cone is moving back, dropping pressure in front, the rear of the speaker cone is moving back, increasing pressure. If the front and back of the speaker are in free air, that is, a speaker just sitting there, some of that will cancel out, reducing the volume and ability of the speker to reproduce the input signal.
You can demonstrate this by holding the speaker in a cupped hand - the sound will get louder and a bit clearer. You hand isn’t a great enclosure but it’s better than no enclosure. Depending on the room you have, a 35mm film cannister or a pill bottle can be cut down to make a decent enclosure, if you don’t want to buy one. What BLI and PCM do with their locos is use the tender as the enclosure, the speakers are mounted in the tender floor with a grill below them.
–Randy
[#ditto] So a baffle is anything that prevents this. I call this phenomina an air short circuit. Ultimately a baffle would be a wall of infinite dimension for the speaker to be mounted through. In reality it is usually an enclosure of some type, that allows the air to move only one way, away, from the speaker.
The expanations that the others gave are correct, so I am not going to add more, they did a great job. What I would like to suggest to you, is to do a Google search on the web. I have found this extremely helpful for a variety of questions that I have had, not only for the worded explanations, but many time some great diagrams and pictures that are worth a thousand words.