There has been a heated debate going on the last few days, some claim the stalker has a base detection range of 50 which is added to the 30 that all ships have, making its base detection range without sonar 80, that would mean that a stalker would see an enemy sub underwater before it even entered max havok range, and adding sonar3 would give them a detection range of 105.
The opposing view (myself included) believes that the detection range of a stalker with out sonar was 50 (not 50+30=80), and that the only way a stalker will see an enemy sub as it enters max havok range of 75 is if it is equip with sonar3 (+25 detect)
Below is a video I took using a stalker with sonar3 paired with a sw with sfb3 cuts and laser3 against my pred subs with eng1 (no cat drive)
The first run my pred surfaces too soon and was within sfb3 range and was killed while surfaced, the second go my pred was completely submerged and the stalker is stack right under the sw and as Im heading towards it, the stalker does not see me until my havok 4 range circle of 75 hits the stalker/sw location, then the sw fires its missiles and kills me underwater.
So the proof is in the pudding, a stalker with sonar3 has detection range of 75 NOT 105,