How to disable the DSP/ Audio IQ on the Discovery 655 & 665.
Power Saving Mode
Power saving mode temporarily disables the digital signal processing (DSP) or AudioIQ feature of the Discovery 655 and 665 headsets to provide a longer talk time. To enable power saving mode, press both the volume up and down keys at the same time before you make a call. To re-enable DSP, press both the volume up and down keys at the same time. Power saving mode cannot be turned on while engaged in a call.
NOTE: After you turn off the headset, DSP will be re-enabled the next time you turn it on.