I made these feet for my DIY downfiring subwoofer, I found commercial solutions lacking and printed solutions non-existent.

These feet work for subwoofers as well as other speakers, but depending on what you do they might even fit furniture pretty nicely.

To get some dampening, I decided for a two-component system with a solid base (e.g. printed in PLA or PETG) and a tip made of TPU. This tip also hides the screw, so it is invisible from the outside, three little nubs hold it in place (but it's easy enough to remove with a small flathead screw driver). This allows for a little splash of colour-contrast, but both printed in black will also look fine. The base features a little locator-hole for an M5 grub screw or 5mm dowel, this way the foot can't unscrew itself; this is completely optional though. The complete dimensions can be seen in the attached screenshot.

The main screw needs to be 40mm till it sticks out, so in most scenarios 45 to 50mm will suffice; it needs a countersunk head. M5 or 5mm wood screws work fine, any imperial equivalent will work as well.

I recommend gyroid infill of around 25-30% for the base - the TPU tip should be gyroid as well, depending on the shore value of your material and the dampening you prefer an infill of 40-50% might be a good starting point, but you may have to tweak it to your taste.

These settings are already in the supplied printing profiles; there's two different ones, for the base as well as the tip (unfortunately we can't set different printing profiles per plate inside a single .3mf)