The HD Intercom is a unique feature found only on Sena headsets. HD Intercom combines the intercom Bluetooth profile with the A2DP Bluetooth profile for high quality audio during an intercom conversation. Due to the HD Intercom feature using the A2DP profile for high quality audio, this means that the range between the the headsets is reduced compared to the lower quality intercom audio. The range is reduced between the two headsets because of the amount of high quality intercom audio that is being shared between the headsets through the intercom. If the two headsets are too far apart then connection will be unstable because the headsets can't keep the the high quality audio connection constant.
In addition, the HD Intercom feature can only be used in an intercom conversation between 2 connected headsets that support this feature. If you connect more than 2 headsets together for an intercom conversation then the HD Intercom feature will automatically become disabled and will switch to a lower quality intercom audio because the headsets can't share the high quality connection between each connected headsets in the intercom conversation. This lower quality intercom audio is more susceptible to radio frequency interference from the environment but allows for a greater intercom range and can be used between 3 or more connected Sena headsets.
If you use your Sena headset with the Bluetooth Audio Pack for GoPro, you can enable or disable this feature only during Normal Audio Recording Mode. The HD Intercom feature is automatically disabled while in Ultra HD (UHD) Voice Mode on the Bluetooth Audio Pack for GoPro. If two more headsets are connected and recording audio through the Bluetooth Audio Pack for GoPro then the Audio Pack will automatically switch to the Normal Audio Recording and the headsets will automatically switch to the lower quality intercom audio to support the multiple connected headsets.