It’s hard to deny that the external speaker sound quality on most devices is quite underwhelming nowadays. If external speakers or accessories may not be an option for you, a few Samsung devices have Samsung Group Play, an app that allows for sound synchronization among multiple Samsung devices. However, this may not be the most fitting remedy when you have unsupported devices.
Thankfully, XDA Forum Member jekatt has developed SoundSeeder. The app is modeled on the core concept of Group Play, which is to share one’s music on other devices. Extending support to any Android phone or tablet, the app allows devices running Android 4.1 or newer to stream songs to multiple Android 2.2+ devices. This is done over a shared WiFi connection, enabling you to connect up to 16 different devices and remotely control playback and volume on all devices. Additional features include:
Appreciatively, jekatt has also provided a solution for users suffering from WiFi disconnections upon sleep and other known issues in the form of a simple and brief guide. If you would like to give it go, you can learn more in the original thread._________