There are many types of speakers which can be overly bright; ribbons, horns, etc…..
One thing to consider is parametric equalization (PEQ) or low pass filters applied in the digital domain before your DAC.
Additionally it's desirable if you can achieve a "Harman tilt" or "Harman target curve" for a more enjoyable listening experience.
We have a video which overviews one way of doing using miniDSP Device Console