Review: Sennheiser's PXC 550 Wireless Headphones Should Put Bose on Notice - MacRumors
Sennheiser PXC 550-II review: Great sound and ANC - SoundGuys
Amazon.com: Sennheiser PXC 550 Wireless – NoiseGard Adaptive Noise Cancelling, Bluetooth Headphone with Touch Sensitive Control and 30-Hour Battery Life : Electronics