Popping noises when streaming with SSM3582A configured in standalone and mono mode.

SSM3582A DAC high frequency filter ?

I would like to use the SSM3582A to design a 1.1 audio system. a tweeter and a woofer. but the 3582 only has a I2S input and not a DSP built in 3582, so how to mix L and R into a tweeter and a woofer ?