Trebam duži kabel, jer želim priključiti drugi zvučnik na računalo.

Trebam is the 1st person singular present of trebati: I need.

So:

• trebam = I need
• želim = I want

In this sentence, trebam duži kabel means I need a longer cable.

A learner may also notice that Croatian uses trebati in more than one way, which leads to the next common question.

Yes — Treba mi duži kabel is also very natural and very common.

The two patterns are:

• Trebam duži kabel = I need a longer cable
• Treba mi duži kabel = literally something like A longer cable is needed to me, but in natural English still I need a longer cable

The difference is grammatical structure:

• in trebam duži kabel, duži kabel is the direct object
• in treba mi duži kabel, mi means to me, and duži kabel behaves like the thing that is needed

In everyday Croatian, both are used.

Because duži is the comparative form of dug:

• dug = long
• duži = longer

So duži kabel means a longer cable.

That makes sense here because the speaker is comparing it with the cable they already have, or with the length they currently need.

Yes, they are objects, so they are in the accusative. But for masculine inanimate nouns, the accusative singular is usually the same as the nominative singular.

So:

• kabel → accusative kabel
• zvučnik → accusative zvučnik

That is why they do not visibly change.

The same thing also affects the adjectives:

• duži kabel
• drugi zvučnik

Both adjective + noun combinations are in the accusative, but for masculine inanimate nouns they look the same as the basic dictionary form.

Jer means because.

So the structure is:

• Trebam duži kabel = main clause
• jer želim priključiti drugi zvučnik na računalo = subordinate clause explaining the reason

In standard Croatian, a comma is normally used before jer, just as English often separates a because clause in longer sentences.

Because after želim (I want), Croatian usually uses an infinitive to say what someone wants to do.

So:

• želim priključiti = I want to connect
• literally: I want connect

This is very normal Croatian structure, just like:

• Želim kupiti kabel. = I want to buy a cable.
• Želim slušati glazbu. = I want to listen to music.

Priključiti means to connect, to attach, or to hook up, especially to a device, system, or power/source.

In this sentence, it fits well because the speaker wants to connect a speaker to a computer.

A few useful nuances:

• priključiti = connect/attach to something
• spojiti = connect/join, often a bit more general
• uključiti = turn on, switch on, include — not the same thing here

Also, priključiti is perfective, which is natural here because the speaker is thinking of one completed action: connecting the speaker.

It can mean either, depending on context.

Drugi can mean:

• second
• other
• another

In this sentence, drugi zvučnik most naturally means a second speaker or another speaker.

If the context is about a pair of speakers, English might prefer a second speaker. If the context is just adding one more, another speaker also works well.

Because na can take different cases depending on meaning:

• na + accusative = movement toward, placing onto, directing to
• na + locative = location, being on/at

Here, the idea is connecting something to a computer, so Croatian uses na računalo with the accusative.

Compare:

• priključiti zvučnik na računalo = connect a speaker to a computer
• zvučnik je na računalu = the speaker is on the computer (location; this would sound odd in most real contexts, but it shows the grammar)

So the accusative is used because there is a directional/target meaning, not simple location.

Because Croatian has no articles.

So:

• kabel can mean a cable or the cable
• drugi zvučnik can mean another speaker, a second speaker, or in some contexts the second speaker

Croatian relies on:

• context
• word order
• adjectives like drugi
• the overall situation

to show what English would often express with a or the.

Not completely. Croatian word order is more flexible than English, because case endings carry a lot of grammatical information.

The given sentence is very natural:

• Trebam duži kabel, jer želim priključiti drugi zvučnik na računalo.

But some parts can move for emphasis. For example:

• Jer želim priključiti drugi zvučnik na računalo, trebam duži kabel.

That is also correct, but it sounds more deliberately structured or emphatic. The original sentence is the most neutral everyday version.