It is your speakers. The highest fundamental note on the violin is like 2000 Hz so most of the problem is likely in the mid range.Two way speakers are awesome but it is still demanding of a 6.5" driver to cover up to 2.5 Khz. The rigid magnesium cone will likely have high resonance out of band (ringing). Normally a very steep cross over can help reduce this out of band ringing but you may notice the ringing on certain resonant but high pitched instruments like violins. Just a hunch.
Getting rid of harsh, shrill treble
I cannot play my classical cd's at a volume where the midrange and bass come through without harsh, shrill treble, especially the violins. I have bookshelf speakers on stands and subwoofer in a small 120 sq. ft. room. I have no treble control on my pre-amp. I tried a Taddeo passive Digital Antidote II between my CD player and pre-amp with minimal result. I have a solid state integrated amp, will switching to a tube integrated amp cure this problem or is it my speakers?