Unless you're using an early ParaEq, the answer is no. Most of our pedals regulate the voltage internally down to +8V and then use a charge pump to create a -8V. So no matter if you plug 9V or 18V into the pedal, you're actually getting 16V of headroom! Check the specs at www.empresseffects.com or the user manual for details specifications in regards to headroom.
Early ParaEqs had an internal DIP switch that is set to allow for higher input voltages. These ParaEqs don't have a charge pump, so require higher input voltage for higher headroom. The ParaEqs we currently built (v7 and above) have the charge pump which increases headroom without need for high input voltages.