Audio Systems: Adding headphones, ohm resistors, ohm resistor

Question
I would like to add a headphone jack to my Hammond L112 organ. It has two 12 inch speakers: one 16 ohm and one 8 ohm. I came across a Hammond 'earphone adapter circuit' which applies to the original L100 model which is almost the same as mine except it had two 16 ohm speakers. For the headphone connection, this adaptor circuit uses (apart from the jack) two resistors: 10 ohms 10 watt between the two speaker wires as they come out of the power amp, and 47 ohms in the (+) wire that goes to the tip of the 1/4 inch plug. The power amp's output transformer is 8 ohms with ground on one side and 1.8 volts AC on the other. My question is: to what extent would I have to change the 10 and 47 ohm resistors in order to accommodate the change from two 16 ohm speakers to my model's 8 and 16 ohm ones.

Answer
You don't really want the 8 or 16 ohm load on a set of headphones especially ones that are made today. As soon as you turn up the volume you'll blow them out. The amplified signal to them must be attenuated. Most of them would like to see round a 50 ohm load in which case the 47 ohm resistor is fine.