The MonkMakes Amplified Speaker 2 is an easy to use amplified speaker on a circuit board.
The board needs a 3.3 to 6V power supply that can be provided by a Raspberry Pi or Arduino. Audio input will normally be to the 3.5mm stereo audio jack socket, which is mixed to a mono signal.
The product includes a separate input with low-pass filter for use with PWM/PCM audio.