I have no experience of using Bluetooth/wirelessWireless audio peripherals on elementary OS, but the following works for standard ones at least:
You can install an application called PulseAudio Volume Control (pavucontrol
) from the AppCentre to get more control over audio in elementary OS.
You could also install it through apt
sudo apt install pavucontrol
Among other things, it allows you to boost the volume levels of specific applications or whole audio outputs over the normal maximum of 100%. Going over 100% might lower the audio quality, though.