Nova connection to a subwoofer

[Bodhisattva]

I have a Nova and I have purchased a subwoofer. What connection would deliver the best sound? Connecting the left and right analogue RCA outputs to the RCA left and right line level inputs on the sub? Or a single cable RCA connection from the Nova to the sub?

Are the outputs on the Naim both mono? If so, in effect is there is no benefit connecting both outputs to two inputs on the sub? In which case just connect a single cable from the Nova to the sub?

[Mike_S]

@Bodhisattva

Connecting the left and right analogue RCA outputs to the RCA left and right line level inputs on the sub?

This one, or the DIN analogue output.

[anon4489532]

The phono outputs are stereo, so you’d need both.

[Xanthe]

The best solution:

Instead of using speakers that excite all the primary acoustic resonances of a room, use main speakers with a limited LF extension, then use a sub to give the required bottom end. The analogue feed to the sub can be passed through a DSP unit without causing the degradation of signal quality in the midrange.

With this approach, the signal for the (more critical) upper bass, midrange and HF goes straight to the main speakers, unmolested, without any change; the signal to the sub (to which our ears are much less sensitive) is corrected to reduce the over-excitation of the room resonances. The crossover to the sub can also be accurately controlled to ensure good integration of frequency response AND timing, and the delay through the DSP an be finely adjusted to allow different positions for the sub while making allowance for its group delay.

First, and importantly, get an instrumentation mike such as a miniDSP UMIK-? (1 or 2) and a copy of REW.
Then check to see if the excitation of the room resonances from your existing speakers is too large (i.e.the bass peaks quite sharply defined and are already too large); if so, the sub only room correction method won’t work for you with those speakers in that room.

If you choose to proceed:
You need a minDSP 2x4.
Connect the inputs of the DSP to the RCA outputs of the Nova (both), connect one output cable to the low level input of the sub.
Use REW to setup the mimiDSP to do the crossover to the sub:

1. Sub level setting: you’re looking for a reasonably even frequency response through the crossover region with possibly a small rise into the deep bass.
2. Sub positioning phasing and & delay: do not invert the phase, move the position of the sub closer to the listener until the minimum phase plot shows a smooth transition through the crossover region.
3. Set the miniDSP to combine both input channels into the output channel (i.e. mono out operation).
4. Room correction: apply parametric cut filters to reduce the sub’s output in places where it is excessively enhanced by the room resonances.

[ChrisSU]

The sub will combine the L and R channels into a mono signal, so as already mentioned, that is what you should use. A single RCA connection will only give you one channel (either L or R) from the Nova.
Alternatively if your sub has a high level input you can use this from the speaker terminals. Naim tend to recommend this as being best for sound quality, but either way is fine.