Hi Kieran. I don’t use Bluetooth on the Soundbar, so haven’t encountered this issue myself. Hopefully, you understand that Bluetooth won’t be able to handle audio in the same way as HDMI, as it’s 48kHz and 16-bit, even without compression. There will always be a noticeable drop in audio quality with BT, and in “normal mode” the wireless rear speakers and subwoofer are being fed a signal over WiFi, so I’d expect them to be ‘weaker’ than the actual Soundbar’s speakers (which gets the HDMI feed directly).
In my experience, none of the satellite speakers not *worryingly* weak and I haven’t had any problems using the Soundbar as intended. Indeed, the Soundbar’s rears are clearer and more powerful sounding than my old WIRED home theatre Onkyo!
If you use Bluetooth to stream music over Spotify, etc, it just won’t replicate an ATMOS/7.1/5.1 track from a Blu-ray or SVOD.