Hi Guys, Just a quick thought. Thinking back to my car audio days. When we built speaker enclosures we stuffed them with polyfill (pillow stuffing). This would fool the speaker into thinking it was in a bigger box. This always would improve the bass both cleanner and deeper. I don't know if it would help our small speakers much but some help is better than none. Has anyone tried this?
I do the same. I don't really know if it is just myth from my homebrew stereo days that the bass gets better. It does help to kill resonances, at least with 2 inch speakers in O-scale. One thing that definitely does increase bass with Soundtraxx DSX decoders and O-scale speakers is to increase the DC blocking capacitor from the supplied 33 uF to 200-300 uF. Also, rigorous attention to sealing the back of the speaker cabinet so that there are no air leaks helps immensely.
I don't know anything about DCC speakers (please forgive my ignorance), but I do know a little about speaker design and acoustics. You're correct about the effects polyfill can have on a speaker's bass response. Polyfill slows down the flow of air through the box, tricking the speaker into thinking it's in a bigger box. This works if the speaker is in a box that's too small (as often happens in car audio). Used in proper amounts, polyfill can make a speaker perform as if it's in a box up to 40% larger. Polyfill also makes bass sound cleaner by reducing standing waves (like echos inside the box) and helps the speaker produce a flatter frequency response. But polyfill, doesn't work if it's tightly compacted to fit in a tiny enclosure as might be the case with some DCC high-bass speaker enclosures I've seen. Nor does it work when the box is already too large for the speaker and/or may not be sealed well (as might be the case when a bare 1" driver is thrown into a tender car). I'd think building/buying an enclosure to house the speaker that has the proper amount of space for the speaker's Qes value, then making sure it's well-sealed as Bob recommends would produce the best results. It'll also help to reduce unwanted vibrations by securing the speaker box as solidly as possible in it's location and isolating it from the car's housing with damping material.
