Yes, you would need to supply somewhere around 9v ideally. You could do this with a voltage divider, 9v from 12v is relatively easy to get, you can just use a 10k R1 and a 33k R2 resistor: http://www.raltron.com/cust/tools/voltage_divider.asp
This would give you 9.2v, which is greater than 8.4 and less than 10, so it should work!
