I have played well over 1000 different banjos and it never ceases to amaze me how each part makes a significant difference in the sound.
Even the strings and bridge will change the sound of a banjo quite a bit. The resonator however is much more significant and not only increases volume it improves tone.
The resonator is a wooden bowl that is attached to the banjo pot and is on the back side of the banjo. The resonator leads to extra projection because sound that would normally be lost with an openback is redirected and pushed out in front of the banjo. I have taken banjos without a resonator and put one on and the volume alone could easily be more than twice of the banjo as an openback.
In addition the resonator will add a layer of tone to the banjo. The sound which is projected forward will have an opportunity to enrich with the wood of the resonator and will sound different. A good quality resonator can make the difference between a banjo sounding hollow or empty and having a rich and beautiful tone.
There are plenty of openback banjos that sound great and have good volume but I have consistently found that a resonator banjo will have stronger tone and more volume and yes a resonator does make a difference
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