If you are lucky or have control of your support, the print requires full support. If it is patterned like the second picture it will work as a baffle. Adding some Polyfill behind the speaker might also help. It sounds pretty good to me. I plan to add an eight inch "woofer" to the .1 channel of a 2.1 amp. The speakers are Kenwood 4" car speakers, they come with the mounting rim, a screen cover and all the hardware to affix the speaker to the enclosure for less than $23 at Best Buy, but there are others available for a large range of prices. I have some coming from Banggood too that are a bit more expensive, but I will find out if they are as good. I got a little lvpin 2.1 amp, the kind powered by a wall wart, but I use some 12 volt batteries to minimise power supply noise. I also have a little tube preamp that adds some warmth that was only about $34. Most phones will decode and playback FLAC encoded audio which is lossless. If you have a phoneograph it will sound the same or at least as good as a CD. MP3 made me tired of music. I have found it again. The foam is to fill any gap between the speakers and the enclosure. It looks like if you use the Kenwood, you need a strip of the thin foam doubled and lining the hole before putting in the speaker. You could also print the box at 97% and tighten up the hole a bit. I imagine there is probably a range of hole size needed for various "4 inch" speakers. It takes a while to print. 47 hours on my current printer. I added a 97% version, it fits the four inch speaker better.