Is it possible to hook up bluetooth headphones with the Firehawk FX? in Firehawk Posted June 15, 2020 I replied to Juanfe16 privately, but for the record... The Sennheiser 4.40 BT phones don't use AptX LL (low latency), they use ordinary AptX. The Priva lla BT transmitter is AptX LL capable, but the headphones have to be as well. See AptX.com for an up-to-date list of AptX LL enabled headphones and earbuds.