External speakers for iMac

You don't really need an adapter if your speakers are self-powered. But if you have a set of unpowered speakers like the type used with home theater/home stereo setups, then you need to plug the iMac into an amplifier of some kind.

The iMac has several ways to run speakers.

The iMac has the traditional 3.5mm audio out jack (headphone jack) so you can plug in thousands of inexpensive standard self-powered speakers made in the last 30 years or so. That's how I connected my speakers. I just bought a cheap common 2 speakers + subwoofer set at a generic PC store and plugged it into my Mac. You can also use the 3.5mm audio out jack to connect to an amplifier or receiver that can power speakers. You don't need an adapter this way, just a very low priced common audio cable with the correct connectors at both ends.

The iMac has USB ports, but it is not common for consumers to drive speakers through them. If you have seen listings for USB audio adapters or interfaces, those are typically for audio professionals who need to connect their Mac to USB audio equipment used in recording and mixing music.

The iMac has Bluetooth and Wifi, so if you have one of the increasingly popular Bluetooth speakers, you can send music wirelessly from the iMac to the Bluetooth speaker. Many new audio receivers can take a Bluetooth or Wifi (AirPlay) audio signal from your iMac and send it through a home theater speaker system.

Niku wrote:

Well, I'm sure you don't want to continue this conversation forever, but I understand you to say that I will need a sound adapter plus an external speaker. Is that right?

100% technically accurate completely correct answer: no

The answer you probably need to hear: yes

The answer you have yet to provide, so that useful answers can be provided: what do you want to do

You can use either USB external speakers or ones connected to the iMac's audio output port. Either way you will want to use powered speakers.

An even better idea is to use an Apple AirPort Express or an Apple TV, either one of which can serve as an input to any sound system you design. They both use your wireless network (or, Ethernet if you prefer). There are a mind-boggling array of choices depending on your imagination and what you want to spend. There is no limit to either of them.

Just to add, you can also run a USB DAC directly into an audio system that already has speakers. You can also find Bluetooth speakers although I've never used them myself so have no idea what the quality may be.

Start by describing what it is you want to do. I know you want external speakers, but for what application? Movies? What kind of movies? Music? What kind of music? Games? Which games? Something else? Therein lie the mind-boggling array of choices.

Unless you want to just plug in a headset you need some kind of adapter. There are plenty of headset options also, ranging from poor to very good to off the charts unbelievable.

Personally... I don't like wires, which means an AirPort Express or AppleTV. Then, your options are unlimited and frankly exit the realm of this support site, and enter the audiophile realm. Think Mac users are a different sort? Wait until you get into their world. Want to rattle your walls and shake your seats? You can do that. I hope you don't have neighbors. Want to project an eleven foot image of your 5K Retina iMac's screen with sound worthy of it? You can do that too.

(Or BT audio as dialabrain suggested, but I quickly ruled that out due to BT's audio limitations. If you just want louder iMac speakers they're perfectly OK.)

FWIW, there are powered speakers available that come with a 3.5mm headphone plug that you can just plug directly into the iMac's headphone output. As John says, there are many, many options. One would be budget of course.