The speakers in your Forcite MK1 helmet were hand selected after much model testing, and provide an excellent audio experience when positioned correctly + the correct settings are applied to your handset. If you are experiencing generally low audio levels, there's a couple of easy steps you can take:
Phone volume settings
Be sure to check your phone to make sure the volume levels on your handset are turned up for media and call volumes. These are separate controls on Android and iOS, independently controlled depending on whether you are playing media, on a call or when the phone is on standby. You can usually tap an icon under the volume slider display on your phone to see all your volume levels.
Answering a call from the handset on iOS
If, when using an iPhone, you use the button on your screen to answer a call, rather than the phone button on your controller, the call audio will default play to your handset instead of the helmet. This is a deliberate feature in iOS. For this reason, it's recommended that you always answer calls from your controller.