The voice quality was me buying mainly important. This headset is not to beat. Whether one speaks directly on the phone or use this headset makes the comparison no difference.
Currently I use the headset with the Siemens SL565. It was possible to combine easy and makes no problems. However, there is one small catch: The dial Language. Unfortunately, there is not in the manual, how this would work. Did it then after a few Minunten himself found. Simply connect Hold 1-2 seconds and immediately press it again and you can choose by language. ;)
Conclusion: A super headset that I can recommend to anyone and its processing justifies the price.