The Raspberry Pi Model A-B has a 3.5 mm Audio port which is the blue or black port which is use for sound when you plug in a 3.5 mm plug from speakers, or headphones. with a 3.5 mm audio plug on the sound cable. Using the 3.5mm port on the Pi is useful when you are using a HDMI monitor without speakers. Computer speakers also have a headphone jack and makes it easier to adjust the sound level with the audio knobs on the front. Desktop speakers also sometimes sound better, has more bass and are louder than the speakers which are built-into your HDMI monitor, or TV.
All you need to do is plug in the speakers to the wall’s power outlet, and plug in the sound plug on the speaker to the Raspberry Pi’s 3.5 mm audio port. You may need to configure your Raspberry Pi’s operating system to play audio out of your 3.5mm audio port instead of its HDMI port if you don’t hear any sound. I think Raspbian sets audio to automatically play on speakers, or HDMI port.
A pair of desktop computer speakers with a 3.5mm audio plug like Logitech Z130 Speakers should work on the Pi’s 3.5 mm audio port.
Speakers with a 3.5mm audio plug can also be used with other devices with 3.5mm ports like MP3 players, smartphones, tablets, CD players, portable game consoles, computers, and TVs with a 3.5mm headphone/speaker port.