Learn Hardcore Indonesian: Mikrofon nirkabel di teater itu rusak, jadi sutradara meminta aktor berbicara lebih keras. - The wireless microphone in that theater is broken, so the director asks the actor to speak louder.

It’s formal/standard Indonesian, common in written language, tech, and official contexts.
In everyday speech, people might also just say wireless (borrowed from English), especially for things like mouse wireless, speaker wireless, etc.

So:

mikrofon nirkabel = more formal/standard
mikrofon wireless = very common in casual speech

Why is it di teater itu and not something like pada teater itu?

In modern Indonesian:

di is the normal preposition for at / in / on (location).
pada is more formal and used more with abstract things, time expressions, or pronouns, e.g. pada hari Senin, pada mereka, pada kesempatan ini.

For physical places, you almost always use di:

di rumah, di kantor, di sekolah, di teater itu.

So di teater itu is the natural, everyday way to say at that theater.

What does itu do in teater itu? Does it always mean that?

Itu can mean several related things, depending on context:

That (demonstrative, pointing to something not near the speaker)
- teater itu = that theater (the one we both know about).
The (marking something specific/known)
- Indonesian has no separate word for the, so itu is often used to show the noun is specific:
  - teater itu ≈ the theater (we’ve been talking about).
It can also be used as a vague “that…” in comments:
- Begitu, ya? = Is that so?

In this sentence, di teater itu probably means at that (particular) theater / at the theater in question.

If Indonesian doesn’t have a / an / the, how do we know whether mikrofon nirkabel means a wireless microphone or the wireless microphone?

By default, a bare noun like mikrofon nirkabel is neutral: it could be a or the, depending on context.

To be more explicit, you can use:

A / an:
- sebuah mikrofon nirkabel = a (single) wireless microphone
The:
- mikrofon nirkabel itu = that/the wireless microphone (specific one)

In your sentence, context (plus the fact there’s only one in that situation, like a theater’s main mic) makes it natural to translate as the wireless microphone in English, even though Indonesian doesn’t mark it explicitly.

Why is it sutradara meminta aktor berbicara lebih keras and not meminta aktor untuk berbicara?

Both are possible:

meminta aktor berbicara lebih keras
meminta aktor untuk berbicara lebih keras

meminta + [someone] + [verb] is a common, natural structure in Indonesian and often sounds a bit smoother or more concise in speech.

Usage patterns:

With or without untuk, the meaning is almost the same:
- Dia meminta saya datang.
- Dia meminta saya untuk datang.
  Both ≈ He asked me to come.

Nuance:

Without untuk: slightly more direct and common in everyday language.
With untuk: a bit more explicit/clear, sometimes more formal.

So your sentence without untuk is perfectly natural.

What’s the role of lebih in lebih keras, and can I just say keras?

keras = loud / hard (by itself)
lebih keras = louder / more loudly

lebih is the usual word to form comparatives in Indonesian (more + adjective):

lebih besar = bigger
lebih cepat = faster
lebih keras = louder

So:

berbicara keras = speak loudly (just loud)
berbicara lebih keras = speak more loudly / speak louder (than before)

In your sentence, the director wants a change, so lebih keras (louder) fits better than just keras (loud).

Why is aktor not marked as plural? How do I say actors in Indonesian?

Indonesian usually does not mark plural on the noun itself. Context shows whether it’s singular or plural:

aktor can mean actor or actors.

In your sentence, it probably means the actors (the cast), but grammatically it could be singular too.

If you really want to show it is plural, you have options:

para aktor – explicitly plural, neutral/polite:
- sutradara meminta para aktor berbicara lebih keras = the director asked the actors…
para pemain or para pemeran – more like the performers / the cast, also common.

But in many real conversations/writing, aktor alone is enough; plurality is understood from context.

What’s the difference between berbicara, bicara, and berkata?

berbicara
- More formal/neutral: to speak, to talk
- Used for the act of speaking in general.
- E.g. Dia berbicara dengan pelan. = He speaks softly.
bicara
- A bit more casual/shortened form, very common in speech.
- E.g. Dia bicara pelan.
berkata
- Means to say, usually followed by what is said, a quotation:
- Dia berkata, “Saya lelah.” = He said, “I’m tired.”

In your sentence:

berbicara lebih keras = to speak more loudly
You wouldn’t normally use berkata there, because it’s about the manner of speaking, not the specific words said.

What does rusak mean here? Is it like broken, damaged, or out of order?

Rusak is a general word meaning:

broken, damaged, not working properly, out of order

It’s used for many kinds of things:

HP saya rusak. = My phone is broken / not working.
Mobilnya rusak. = His car is broken / out of order.
Mikrofon nirkabel itu rusak. = That wireless microphone is broken / not working.

If something is physically shattered (like glass), you might use more specific words like pecah, but rusak is the default for “doesn’t function as it should.”

What does jadi do in this sentence? Is it like so or therefore?

Yes. jadi is a conjunction here meaning so / therefore / as a result.

…, jadi … often links cause → result:
- Hujan deras, jadi kami tidak pergi. = It rained heavily, so we didn’t go.
- Mikrofon nirkabel di teater itu rusak, jadi sutradara meminta aktor berbicara lebih keras.
  = The wireless microphone at that theater was broken, so the director asked the actors to speak more loudly.

Spoken nuance:

jadi is very common in speech, also used as a sentence opener:
- Jadi, bagaimana? = So, how is it? / So, what do you think?

Is teater the building or the art form (theatre, drama)? How do Indonesians distinguish them?

Teater can mean both, but in practice:

The building/venue (like the theater in English):
- Kami menonton konser di teater itu. = We watched a concert at that theater.
The art form / drama / theatre as a discipline:
- Dia belajar teater di kampus. = She studies theatre at university.

Context usually makes it clear. In your sentence, di teater itu clearly refers to the venue (the theater building / space) because of the preposition di and the presence of the microphone there.