The Nova is not balanced, try following the instructions for a regular (unbalanced) amp which would include connecting the black cable to one of the - terminals.
If that doesn’t help you should try either connecting at the loudspeaker end, ot buying a Naim modified cable if you want to connect to the amp.
Before buying a bassline blue cable with stackable bananas/spade (even if not rel original) I’d like to understand some things.
With Rel t/9x + Uniti Nova + kef r7
What are pro and cons between high level connection to the amp e high level connection to the speakers?
Talking about low level connection, what are the differences between this situation:
-2 rca output on the amplifier → 2 rca input on the sub / 1 rca output on the amplifier → 1 rca input on the sub
and
In the last case (my situation) I shoud to use a 2 to 1 cable. What are the cons of this solution? Which type of cable I shoud to use?
Please, read the previous comments on this thread.
You should connect High Level connection wires to the speakers’ terminals not the amplifier’s or you will get hum.
I agree that it’s generally best to use the high level input on a Rel sub, and the speaker end is the best place to connect it if using a standard Rel supplied lead. However, if you are getting hum using a different connection method that almost certainly indicates a grounding problem elsewhere, as this is not normally a problem with Naim/Rel systems.
I understand that High level Is the best solution for rel.
But I’m still confused about the low level connection and y cable that is necessary to connect uniti nova to rel sub
Anyway
If I use the standard High level cable (included )I had to divide it and connect the the black and Yellow cable to a speaker and the Red cable to the other speaker. Is It correct? I can’t See this kind of connection to the speaker on the instruction manual.
And don’t understand why some guys,(I See the photos in this forum) connected the High level cable to only One speaker. (Yellow+ Red to the positive and black to the negative)
Is available A separate bassline cable with spade? Where I can find It?
All reasons why I suggested the RCA connection for a Nova. Nice and simple.
What kind of RCA cable? Coaxial? Y 2 to 1 ? With resistitor?
Or only 1 to 1 rca connected to the left or right preamp Nova output ?
Or a 2 to 2 RCA connected to a device like anti Mode/ Mini disp connected in turn to the rel with 1 to 1 RCA?
I’m curious to try rca connection with the appropriate cable
I’m a Nova owner and It seems absurd I had to modify the only cable included into rel t9/x packaging for using this sub without problems
Now I 've divided the second half of the original cable and connected the Yellow and black cable to the left speaker and the the Red cable to the right speaker.
This to mantein the same lenght from the sub located behind the left speaker.
Now there are no hum noise, and the sound Is Great, but the connection looks like improvised
I’d like to use a pre diveded cable, maybe with spade but I don’t know where I can find It.
I think It Is necessary to connect the sub to the right and left speakers.
All the other High level cable seem to have been designed for An amplifier connection
I suggest you talk to a company called Designacable. They should be able to make you a split cable if you don’t want to use the one supplied by Rel.
Alternatively they can make you a cable with stackable bananas that is specially modified for use with Naim amps if you prefer to connect at the amp end. (Rel also make such a cable, but theirs is very expensive).
As per your photo at post 11 and HH’s reply.
Best placed near the amp, it’s designed to be able to drive fairly long cables.
The main advantage is that it can prevent the sub from ‘driving’ the room modes can causing prominent bass peaks at the room’s resonant frequencies. It also removes any issue with loading the preamp of the Nova (low level) or causing instability of the power amp by connecting a high level cable to the Nova’s speaker terminals.
That means you’ll only get bass from that channel. How well it works depends on how albums are recorded, but if the deep bass is on the other channel you won’t hear it.
When I changed my speakers to Proac I connected to both the speakers but had issues with the distortion same as connecting directly to the naim amp so for checking purpose I connected to only one of the speakers, since then it is there and I left as it is and didn’t got the chance to remove (the cable used for rel is Kimberkable rel subwoofer cable).
The ‘one channel problem’ isn’t an issue if you use the low level connection with a DSP box!
I tried today again to connect the red cable to the right channel on the Proac but had the same distortion issue, I think there is something to do with the electrical properties on the Proac as the issue was not present when connected to the monitor audio silver 300.
I’m waiting for my NC 250 and will try and see if the same problem persists or else I will need to sell the rel T9i and buy a pair of T7x.
It all seems very odd. Have to contacted REL and ProAc for advice? Maybe you could try a Bassline Blue and connect to the amplifier rather than speakers, it’s got to be cheaper than changing subs. Alternatively, rather than two speakers and two subs, you could change speakers.
I have contacted rel and Proac but no solution as I was shocked to see that there are no Proac models in the suggestion column on the rel website. I have changed the speakers just a couple of months back, as I said earlier in my post I’m waiting for my nc 250 and will try connecting them and if still there is issue I will go for baseline blue as suggested by you.
I had a thought of connecting a black wire (negative) from the left speaker along with the red one and will see if there is still issue but I’m afraid to do in case there is some load on the amplifier.
Just a thought 
All I know is that it’s yellow and black to left, and red to right. I wouldn’t try anything else.
Use a miniDSP 2x4 and the low level connection - you won’t get these issues and it can combine the L&R signals for you. You can also use the DSP to sort out room resonance issues.
