Altoparlante vs. cassa
In Italian, both altoparlante and cassa translate to the English word speaker, but they are used in distinct contexts. The choice between them depends on whether you are referring to the technical electronic component, a public address system, or an everyday physical audio speaker box used for listening to music.
Altoparlante
The word altoparlante refers to the technical component that converts electrical signals into sound, commonly known as a loudspeaker. It is typically used to describe public address speakers found in stations or stadiums, as well as the small, built-in sound components inside devices like smartphones, radios, and televisions.
L'annuncio del treno in ritardo è stato trasmesso dall'altoparlante.
(The announcement of the delayed train was broadcast from the speaker.)
Ho messo la chiamata in vivavoce perché l'altoparlante del telefono è rotto.
(I put the call on speakerphone because the phone speaker is broken.)
Il direttore ha chiamato la cassiera tramite l'altoparlante del supermercato.
(The manager called the cashier through the supermarket loudspeaker.)
Ogni televisione moderna contiene almeno un piccolo altoparlante integrato.
(Every modern television contains at least one small built-in speaker.)
L'ingegnere del suono sta misurando le frequenze emesse dal nuovo altoparlante.
(The sound engineer is measuring the frequencies emitted by the new loudspeaker.)
Cassa
The word cassa is the everyday, casual term for a standalone audio speaker, acting as a shortened form of cassa acustica which literally translates to acoustic box. It refers to the physical enclosure or cabinet that houses the sound components, and it is the standard word Italians use for Bluetooth speakers, home stereo speakers, and large speakers at concerts or parties.
Ho comprato una nuova cassa portatile da portare in spiaggia.
(I bought a new portable speaker to take to the beach.)
Le casse del mio impianto stereo suonano in modo fantastico.
(The speakers of my stereo system sound fantastic.)
Durante il concerto mi sono messo troppo vicino alla cassa sinistra.
(During the concert I stood too close to the left speaker.)
Puoi collegare il computer a quella cassa usando il segnale wireless.
(You can connect the computer to that speaker using the wireless signal.)
Abbiamo sistemato le casse agli angoli della stanza per migliorare l'acustica.
(We placed the speakers in the corners of the room to improve the acoustics.)
Summary
To summarize, you should use altoparlante when referring to the technical loudspeaker component, built-in device speakers, or public address systems. Conversely, you should use cassa for everyday, physical audio speakers such as Bluetooth devices, home stereo cabinets, and concert sound systems.