A funk bass for MuLab. It's a mix of two audio sources:
1. A filtered waveform-based oscillator for the basic bass sound
2. A sample player for the slap sound
The slap noise will only be heard in the upper velocity range and is slightly randomized in sensitivity and pitch. You can switch off the slap sound by turning down it's volume.

If you're mainly mastering for headphone listening, binaural panning is right for you. Positioning an instrument in a stereo panorama is a combination of at least a difference in volume and also a little delay (below 0.5 ms) between the stereo signals.
(You'll even get a realistic panning effect without panning the volume, only with that delay. Google for 'binaural' panning.)
I have built this patch for MuLab giving a more realistic panorama sound for a reproduction via headphones.