There are three causes of sound misalignment to the parent device: time difference, accuracy, and latency.
【Time difference】
CPU time stamp counters are used for timing adjustment of the music playing of the parent device and the child devices in this application.
Since the CPU time stamp counter is relative time from the power ON of each device, it is impossible to share the same time between devices.
So this app temporarily uses the clock of each device and recognize the difference.
Therefore, when using multi speakers, it is necessary to connect to the Internet in advance and adjusts the clocks of each device.
It is possible to get nearly accurate time by matching to the Internet time, however, it still has slight difference for each device so that this will cause the initial sound misalignment.
【Accuracy】
CPU time stamp counter is very accurate, however the error is not zero.
If you continue playing for a long time there will be sound misalignment due to stack of errors.
【Latency】
It occurs when connecting to AirPlay or Bluetooth compatible speakers.
It is a sum of delay because of…
・until the sound data arrives at the other speaker with wireless signal from the iPhone
・the arrived data is converted to sound by internal processing.
More sound misalignment will occur compared to the above time difference and accuracy.
TIME DIFFERENCE in Mixer can totally absorb sound misalignment due to these three.