[quote name='FretNoMore' timestamp='1448995829' post='2919948']
Do you hear this in all rooms? If not, it could be that the issue is room resonance, boominess, and if so it coud help to get an EQ (parametric preferrably) so you can tame the frequency range that is too loud or resonant.
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We only rehearse in one room so I can't check unfortunately. To be honest it's something I hear on guitars and basses in general - the difference in tone between the same note played on an open string or 5th fret on the next string.
I've been working on my playing style to start using more notes lower down the neck recently because they have more character to my ears so I'm really aware of this difference at the moment. Definitely gonna look into the bass set up as well.