Multi receiver transmission transmitter supports up to two pairs of headphones simultaneously (optional HDR 185, sold separately) 2 year warranty when purchased from an authorized Sennheiser dealer. Signal to noise ratio: [Analog input] ALC typ. 85 dBA at 1 Vrms, MLC ≥ 90 dBA, [Digital input] > 90 dBA Frequency response is 17 – 22,000 Hertz.
https://www.amazon.com/Sennheiser-RS-185-Wireless-Headphone/dp/B00TOT9G1W