Are you able to run the voice command on all your HP switches? You might not be able to do it on the web managed ones but the fully managed ones you should, if not then a firmware upgrade might help.
Straight from the HP manual "A voice VLAN is configured for voice traffic. After assigning the ports that connect to voice devices to a voice VLAN, the system automatically modifies quality of service (QoS) parameters for voice traffic, to improve the transmission priority of voice traffic and ensure voice quality"