Tinny bluetooth mic input sound

I'm using the philips SHB7000 bluetooth headphones with my MacBook. They paired fine, but the audio quality over bluetooth was terrible. I remember having this issue on my previous macbook, and promptly found that the preferences for BluetoothAudioAgent need to be adjusted:

defaults write com.apple.BluetoothAudioAgent "Apple Bitpool Max (editable)" 120
defaults write com.apple.BluetoothAudioAgent "Apple Bitpool Min (editable)" 80
defaults write com.apple.BluetoothAudioAgent "Apple Initial Bitpool (editable)" 120
defaults write com.apple.BluetoothAudioAgent "Apple Initial Bitpool Min (editable)" 80
defaults write com.apple.BluetoothAudioAgent "Negotiated Bitpool" 100
defaults write com.apple.BluetoothAudioAgent "Negotiated Bitpool Max" 120
defaults write com.apple.BluetoothAudioAgent "Negotiated Bitpool Min" 80
defaults write com.apple.BluetoothAudioAgent "Stream - Flush Ring on Packet Drop (editable)" 30
defaults write com.apple.BluetoothAudioAgent "Stream - Max Outstanding Packets (editable)" 15
defaults write com.apple.BluetoothAudioAgent "Stream Resume Delay" 0.75

This seems to have addressed the tinny output quality. Problem now is, that input quality is still tinny. Does anybody know what I can try or do to address this?

Summary: bluetooth headphone input quality is very low with Macbook.