With the "Multi-output device" feature in audio midi setup in MacOS, we are able to use a MacBook's internal speaker and an external bluetooth speaker **simultaneously** to play the same music. 

However, the issue is that the external speaker might have a larger latency, so that the sounds are not in sync.

**Is there a way to increase the latency of built-in speaker by an amount via some software so that by adjusting a bit, we can match the internal and external speakers?**

**Also:** how can I adjust the **relative** loudness of each device in a multi-output device?