Imgur user Peter Clough recently created his own colorful “Magic Box” Bluetooth speaker assembly with a NeoPixel visual display.
If you need a speaker (or rather a speaker with an enclosure) the easiest way is usually to just buy one. On the other hand, if you want something really awesome and unique, why not build it yourself? Clough did just that using an Arduino Pro Mini and a Bluetooth receiver along with a strip of programmable LEDs that react to the emitted sounds–made possible by an electret microphone amp.
Cleverly, the case was sourced from a hobby supplies store, while neodymium magnets were used to keep the lid in place. Clough also employed a “really beefy” 20W 4Ohm speaker, as well as a rotary encoder with push button for volume and play/pause control.
You can find more details, including a schematic, on the project’s Imgur page.