Apple iMac computers come with speakers. You can also plug a pair of headphones into the iMac by using the headphone jack on the back of the computer. You should hear full stereo sound when the headphones are plugged in correctly. You might, on occasion, realise that your headphones are not producing stereo sound or any sound at all. You can troubleshoot your headphone problems by checking the headphones and also your iMac's settings to get your headphones working again.
Check your headphones for any cuts or breaks in the wiring, especially near the plug and the ear cups.
Use scissors to cut at least a 2-inch strip of electrical tape from its roll.
Wrap electrical tape around the damaged areas to cover them securely.
If your headphones have an "On/Off" switch, make sure it is set to "On."
Plug the headphones into the headphone jack to test your repairs.
If your headphone wires are intact, ensure that the headphones are plugged into the jack with the headphone icon over it on the back of the iMac.
Wiggle the headphone plug and press in on it to ensure that the plug is fully positioned in the jack.
Use a headphone plug adaptor if the headphone plug is too small for the iMac's headphone jack. Push the adaptor onto the headphone plug, and plug the assembly into the headphone jack.
Play music through the headphones to test that the plug adaptor is working.
Ensure that the "Mute" button with the solid speaker icon at the top of the iMac's keyboard has not been inadvertently activated. Press either of the sound buttons at the top of the iMac's keyboard that have a speaker icon with curved lines to the right to turn the sound back on. Test this fix by playing some music through your headphones.
If the "Mute" button is not the problem, adjust the headphone balance to hear sound by clicking the Apple icon in the upper-left corner of your iMac's screen. Choose "System Preferences," "Sound," "Output," and ensure that the headphone balance indicator is placed in the middle of the sound bar. Test the sound balance by playing music through your headphones.
If you can only hear sound in one ear, change the sound back to stereo by clicking the Apple icon in the upper-left corner of your iMac's screen. Choose "System Preferences," "Universal Access," and then click the "Hearing" tab. Uncheck the "Play stereo sound as mono" to return your iMac's headphones and speakers to stereo sound. Test the stereo settings by playing music through your headphones.
Switch the sound to the headphones on an iMac with Microsoft Windows by clicking "Start."
Choose "Control Panel" and "Hardware and Sound."
Select "Manage Audio Devices" under sound.
Choose "Speakers," which is then highlighted with a green check. Select "Properties."
Choose the 3.5mm jack and enable headphones usage. Click "OK."