Recovery speed too low?
Nah...i use 4.
Gives a better tone.
Too high and the tone is too short and quick.
And too low, it introduces ground noise.
4 is not what I would call too low. I'm not talking about going down a point or two from the defaults (talking 800 here because there is more adjustability), I'm talking taking recovery speed down to 1 or 2 (again, 800 here). There is always a point of diminishing returns as folks try to eek out more depth (or fuller tones) they end up just increasing the ground noise under certain circumstances, which is counterproductive. Of course there are always odd circumstances where you can get away with it, otherwise Minelab would not have put the low end adjustment in there to begin with.
From the manual, p. 51 -
Swing Rate
A good general swing rate is around 2-3 seconds from right-toleft-to-right.
A higher Recovery Speed generally allows for a faster
swing rate with less likelihood of missing targets.
A higher Recovery Speed, for the same swing rate, will help to
reject ground noise, but also decrease detection depth. A lower
Recovery Speed, for the same swing rate, will increase detection
depth, but may increase noise.
Try hunting with a recovery speed of 1 in thick trash and/or mineralized soil and see how that goes for you. So yeah, there is such a thing as having too low a recovery speed.