Great arco sound, mediocre piz...

In our orchestra arrived recently a Hungarian DB, fully carved with beautifull tonewood. The instrument is constructed in the 70's and has been found in Austria. It has a magnificent arco sound (strung with Evahs), with a quick bow response. However the piz sound is mediocre. I strung it with Spiros Mittel and it improved a bit, but again the difference between arco and piz sound is huge. I experimented with the soundpost and the bridge to no avail. Has anyone any idea if it is a set up matter or it is something inherent in some double basses? Any ideas are welcome.
Mike