Altavoz vs. parlante vs. bocina
The Spanish words altavoz, parlante, and bocina all translate to speaker when referring to an audio device. The main difference between them is regional, as different Spanish-speaking countries have adopted different standard terms for this exact same piece of technology.
Altavoz
This word is the standard term used in Spain to refer to an electronic speaker. It is a compound word combining alta (high) and voz (voice), and while it is understood globally, it is primarily Spaniards who use it in everyday conversation for things like Bluetooth devices, home stereos, and public address systems.
Mi ordenador necesita un altavoz nuevo porque el sonido es muy bajo.
(My computer needs a new speaker because the sound is too low.)
Ellos compraron un altavoz inteligente para controlar las luces de la casa.
(They bought a smart speaker to control the house lights.)
El concierto tenía un altavoz gigante a cada lado del escenario.
(The concert had a giant speaker on each side of the stage.)
No olvides traer el altavoz inalámbrico para la fiesta en la playa.
(Do not forget to bring the wireless speaker for the beach party.)
Parlante
The word parlante is the most common term for a speaker throughout South America, including countries like Argentina, Chile, Colombia, and Peru. Derived from the verb parlar (to speak), it is used for everything from tiny phone speakers to massive concert sound systems.
El parlante derecho de mi equipo de música está roto.
(The right speaker of my stereo system is broken.)
Conecta tu teléfono al parlante para que escuchemos la nueva canción.
(Connect your phone to the speaker so we can listen to the new song.)
Los vecinos se quejaron porque el parlante estaba a todo volumen.
(The neighbors complained because the speaker was at full volume.)
Me regalaron un pequeño parlante portátil para mi cumpleaños.
(They gave me a small portable speaker for my birthday.)
Bocina
In Mexico, Central America, and the Caribbean, the word bocina is the standard way to say speaker. It is important to note that in Spain and South America, bocina usually translates to a car horn or a megaphone, but in Mexican and Caribbean Spanish, it refers to any device that plays music or audio.
La bocina de mi cuarto tiene luces de colores que brillan con la música.
(The speaker in my room has colored lights that shine with the music.)
Necesitamos una bocina más potente para llenar este salón grande.
(We need a more powerful speaker to fill this large hall.)
Ayer compré una bocina recargable para llevarla de campamento.
(Yesterday I bought a rechargeable speaker to take on the camping trip.)
La bocina inteligente dejó de funcionar después de la tormenta eléctrica.
(The smart speaker stopped working after the electrical storm.)
Summary
To summarize, the choice between these three words is entirely based on geography rather than the type of device. You should use altavoz if you are in Spain, switch to parlante when traveling through South America, and use bocina when communicating with people from Mexico, Central America, or the Caribbean.