Christian Knufinke SIR2 is described as 'SIR2 is an easy to use native audio-plugin to use for high quality reverberation. It's available for the plugin formats VST and AudioUnit. It offers zero-latency processing with low CPU-consumption and non-destructive audio processing of impulse responses'. There are more than 10 alternatives to Christian Knufinke SIR2 for Windows, iPhone, iPad, Mac and Linux. The best alternative is Audio Ease Altiverb. It's not free, so if you're looking for a free alternative, you could try Reverberate or Rooms!. Other great apps like Christian Knufinke SIR2 are AltiSpace (Paid), Mobile Convolution Reverb (Paid), AudioReverb (Paid) and iConvolver (Paid).