A quick question, i am thinking of buying the Beyerdynamic RSX 550 wirless headphones or the Beyerdynamic DTX 900.
My question is, being the Beyerdynamic RSX 550 a wirless headphone using FM frequency, is there a loss in sound quality when compared to wired headphones ?
In your opinion which is the better pair of headphones

I listen to all types of music and action movies)
Beyerdynamic RSX 550
Wireless Headphone
System: 40mm Mylar-500 High-Tech System
Transducer Type: dynamic, closed-back
Frequency response: 20 Hz- 20,000 Hz
THD at 1 kHz: < 1%
Max. SPL: 100 dB
Battery: 2x NiMH rechargeable batteries
Operating time: 8 hrs.
Weight inc. battery: 290 g
Transmitter:
Modulation: FM Stereo
Operating Distance: up to 100 m
Signal-to-noise ratio: 70 dB(A)
Switchable RF frequencies: 863, 3 MHz/ 863,9 MHz
Connection: 3,5mm stereo phone plug & 6,3mm adaptor
Dimensions: 180 x 100 x 100mm
Beyerdynamic DTX 900
System: 40 mm Mylar-900-TopClass-System
- Transducer type: Dynamic, open
- Frequency range: 10 - 22,000 Hz
- Sensitivity: 108 dB
- Impedance: 32 ohms
- Maximum power input: 1500 mW
- Cable length: 3 m
- Weight without cable: 180 g
- Connector: 3.5 / 6.3 mm stereo jack plug
Sony MDR-7506 Studio Monitor Headphone
Type: Circum-aural, closed
Drivers: 40 mm dia., dynamic type
Impedance: 63 ohms at 1 kHz
Sensitivity: 106 dB/mW
Rated power: 0.5
Power handling capacity: 1 w
Frequency response: 10-20,000 Hz
3 m coiled litz cable with gold plated 1/8, and 1/4 inch plugs
Weight: Approx. 230 g minus the cable
Comes with carry bag and 1/4 inch adapter plug