Celestion SpeakerMix Pro If you thought IRs were the closest software could come to the sound of a real speaker, think again! Speaker manufacturers Celestion have dipped their toes into the waters of the software world before: they’ve been selling high‑quality speaker/ cabinet/ mic impulse responses since 2017. But while their impulse library is great their new SpeakerMix Pro plug‑in is even more impressive. Celestion tell us that SpeakerMix Pro “doesn’t do any convolution or interpolation of responses — even [with] user‑loaded IRs”. Rather, it’s based on what Celestion call Dynamic Speaker Responses, or DSRs for short.