Resolved iMac audio problem

[steviemacuk]

On my 2011 iMac the internal speakers are fine but as soon as I connect external speakers, the audio on the external ones is badly distorted along with a loud buzz. The sound using headphones on the same audio out is perfect and the sound from the external speakers connected to my 2010 Macbook Pro or my PC is perfect. The display does change from 'internal speakers' to 'headphones' when I look at System Preferences/Sound. A PRAM reset didn't change anything. Any ideas appreciated.

 

[Fishrrman]

I'd suspect:
- cable
- speakers.

 

[steviemacuk]

I'd suspect:
- cable
- speakers.

Thanks but speakers work great when connected to my Macbook Pro or my PC though and I just tried them on the iPhone and they're good there too...

I can plug in my nice Sony headphones into the iMac and the sound is perfect through them so it's confusing (and frustrating).

 

[J.Gallardo]

I suppose they must be active speakers (there's an amp with them).
The next logical cause could be iMac interfering with speakers, due to a poor shielding. That would explain why the sound is perfect in other situations cited by you.
Perhaps the placing is inconvenient with your iMac, plus this machine has a lot of electric activity in a reduced enclosure.
Never knew about something like you describe; there must be specially sensitive amp/speakers... or specially affected by frequencies emitted by your mac.
Definitive answer, after trying with other pair of speakers.

 

[jerwin]

a ground loop?

 

[ApfelKuchen]

If the headphones, which use a different cable and plug than the external speakers, don't have a problem, then it's highly likely it's the cable/connector for those external speakers.

This goes back to my decades of doing live concert/audio recording/broadcast - if the buzz is specific to a specific cable, then the first thing to do is swap out that cable - fixes the problem nearly every time.

 

[J.Gallardo]

Thanks but speakers work great when connected to my Macbook Pro or my PC though and I just tried them on the iPhone and they're good there too...

Well, cable is first suspect (and sometimes they behave mysteriously), but:
Do you connect speakers to MacBook or phone with the same cable? (I supposed so).

 

[steviemacuk]

Thanks everyone - don't believe I never noticed the 3.5" plug wasn't a normal stereo 3.5" jack - when I removed the cable again for a better look, I saw the extra yellow RCA dangling out the subwoofer - I must've been using this 3.5mm to 3 RCA cable for ages on the PC with the yellow video cable just left disconnected.

Looked through the boxes in the cupboard and found a 3.5mm to 2 RCA cable and now my iMac sounds sweet! ???