All REL input filters are 100% analogue — among the fastest ever offered in a subwoofer. At the centre is REL's famous High Level Input, which connects directly to the speaker outputs of your main amplifier. This does not draw power; instead, it carries the complete sonic signature of your system, allowing REL to blend seamlessly with your speakers, a trait reviewers have celebrated for decades. And for systems where High Level isn’t possible, their low-level input employs the very same filter circuit, available via both RCA and XLR connections, delivering the speed, naturalness, and integration REL is known for. For theatre and dual-use systems, REL allows High Level and .1/LFE to be run together, so music gains natural integration, while movie soundtracks deliver the full impact intended by the mix.