The word you are looking for is latency. My REL wireless sub has a latency of 8 ms (milliseconds) with no audible distraction. My headphones with 50 ms latency definitely echo the tv speakers. Check the latency spec on the bluetooth. Lower is better (obviously).
Transmit to sub
Physical room arrangement makes it difficult to get wire to my sub-woofer. I can put an amp next to the sub.
Looking at Bluetooth transmitters. Is there any appreciable delay that one could hear?
Looking at Bluetooth transmitters. Is there any appreciable delay that one could hear?