Can't figure out audio distance

[HugoCortell]

I can't seem to get OpenAL (part of OpenTK) audiosources to actually go from 1f to 0f in volume based on the distance from the source to the max distance.

I do use...

SourceRelativere = false
AL.Source(slot.Source, ALSourcef.RolloffFactor, 1f);
AL.Source(slot.Source, ALSourcef.MaxDistance, 35f);

The source position is indeed updated and correctly set. I debug the distance between both and can tell how far I am off the threshold. 

I even tried using:

AL.Source(slot.Source, (ALSourcei)0xD000, (int)ALDistanceModel.LinearDistanceClamped);

But it just does not work.

What am I doing wrong? I can't think of ANYTHING. There has to be something...

[HugoCortell]

Solved: 

You need to EXPLICITLY define MinGain and MaxGain, as well as enable the ALCapability of AL_SOURCE_DISTANCE_MODEL