My design is for a subwoofer system consisting of a mixer stage mixing the stereo input feeding an equalizer, with LPF further down feeding the compressor/limiter. When tested using AP equipment, the THD goes to the roof. But, when mixer is disabled THD is acceptable. I wonder how can this be solved knowing mixers introduce harmonic noise that is too bad for the overall noise response.
On the other hand, mixing the stereo signal outside the DSP requires only simple hardware (this has been tested and worked well), but that is not an option since the aim is to do everything inside the DSP, and that seems to add more to the overall cost as well.
Is there any way to limit the THD with mixers involed? Attached is the project file from sigma studio and related AP graphs for THD (with and without MIXER).
Thanks a lot in advance for the help!!!