bocina – speaker, megaphone
boe-SEE-nah; sustantivo femenino
Quiero comprar nuevas bocinas para mi estéreo.
I want to buy new speakers for my stereo.
El entrenador les habla a sus jugadores por una bocina.
The coach talks to his players through a megaphone.
Las bocinas en su carro son potentes.
The speakers in his car are powerful.
Altavoz is also used for speaker, and may be more technically correct than bocina. An altavoz is the electronic portion (loudspeaker) that amplifies the sound, and the bocina is the cone that projects it. Depending on the country, either term may be correct for referring to a speaker for a sound system.