Yes, 2-4 is the range on the damping knob on the top of the tonearm which the manual recommends for the S-armpipe when using 'low-compliance' carts. Personally, I tend to set it at the low side of what the manual recommends, but it is definitely worth experimenting - it will change the sound more than you expect...
FWIW, I assume your AT 150MLX is 'low' because of the specs shown on vinyl engine (which I had recently looked at). I have not used one of those carts on one of my tables.
FWIW, I assume your AT 150MLX is 'low' because of the specs shown on vinyl engine (which I had recently looked at). I have not used one of those carts on one of my tables.