Posted on: 12 March 2017 by ryder.
I currently have a subwoofer integrated with the Harbeth SHL5 Plus in a novice setup and it does help boost the very low frequencies by just a bit. A subtle but appreciable improvement. Though I only have a single subwoofer which is placed at the centre between speakers. Ideally I think you should have two units at the corners near the main speakers with some sort of Mini-DSP thing inserted somewhere in between.
In my system, the subwoofer (PMC TLE-1) is connected to the Hicap DR. I think this may be the only way you can connect the sub(s) to a Naim system, to have the sub connected to either the Hicap or Supercap.
I am convinced that the results will be stellar when quality subwoofers are used together with proper implementation, with the Harbeth C7ES3. In my case, the PMC sub is a leftover from my Home Theatre setup (now defunct) so the integration is not on a serious level.