How to add a DryWetMixer or a LinkwitzRiley to a dsp::ProcessorChain

How would I add a DryWetMixer to an ProcessorChain

as of right now my processor chain has a panner and a gain but I wanted to add a dry wet mixer and a Linkwitz-Riley however I keep running into jasserts for example

jassert (drySamples.getNumChannels() <= (size_t) bufferDry.getNumChannels());