Wow, this is something new to me. I always had better results when the sub (REL S/510) was placed in the middle of the room between the speakers which is contrary to REL’s recommendation of corner placement. Nevertheless, I was forced to place the sub in the corner of the room due to practicality issues.
If I have a new room, I’ll surely place a single subwoofer in the middle between speakers.
Try it with a stereo pair in the middle, but don’t expect it to work better. Maybe it will. I recently moved my stereo pair of S/510 from just inside each speaker to just outside (like REL recommends) and it was significant improvement for bass response and soundstage.
When I had a single, I ran it in the middle of the room, but it ended up better in the corner, just outside my right speaker. I’ve been running stereo pairs now for about the last 8 years anyway.
My gut feeling is that putting both stereo subs on top of each other between the speakers might negatively impact the soundstage benefits of using a stereo pair of subs. But it looks like with those two #25s there isn’t a lot of room otherwise.
But…YMMV…and trying it is proof in the pudding.
I suppose one might argue I also have a woofer in the middle. 
Thanks for the post. In my small room there’s only space for one sub. The sub is placed very close to wall boundaries behind the speakers.
Perhaps that is the reason the result of corner placement in my room isn’t that good as it’s placed very close to wall boundaries.
Oh, I don’t know. Every room is different. Yoiu have to go with works best for you in your room.
BTW: I corrected my post to note a single sub in my room was better more in the corner just outside my speaker, than it was in the middle between the speakers.
Point taken that one sub in the corner of the room sounds better than it was in the middle between speakers. Perhaps I need to get the volume and crossover frequency on the sub dialed in more accurately to achieve better results.
I spent a lot of time getting my subs dialed in when I upgraded from two REL R-328 to the two S/510 I have now. I didn’t measure my room. I started with a basic setup based on REL’s recommendation for setup, and tweaked over time. I now have a xover/gain/phase setup that doesn’t need to be touched. It works great for all the music I play: classical, jazz, rock. It’s all good now. The best part is the soundstage for large scale orchestral music is really amazing.
My S510’s sit on the outside of my speakers but not right in the corners… despite following the instructions I found mine worked better with much lower settings than Rel recommends. Cross over is set to 4 and output about 7, not sure if low settings are specific to Naim…
The subs are stacked in the middle because there isn’t any room on the sides as you have pointed out. I’m in the process of building a dedicated room so this is a temporary solution.
I will try them in the sides in the new room, but one thing I’ve noticed is that stacking them opens up the soundstage with my system. As REL promote with their six pack the bass is 3 dimensional when stacking.
What you have can’t really be equated to a REL six pack array though. In those arrays each of two stacks are for the same channel and there are always stereo pairs. Within each stack, each sub is tuned differently, with the middle being the main sub. The high-level connections in an array stack are also daisy-chained, not independently connected to speaker terminals. A REL array requires a minimum of four subs (four-pack) but stacks should really be in odd numbers (six-pack, ten-pack).
At was at my dealer when John Hunter was there to talk about about and demo it all, building up with a stereo pair to a full six-pack.
Your settings are specific to your room and speakers, not to the fact you use Naim amps. With my pair of S/510 I have crossover set to 2 and gain set to 10.
Legend! looking forward to hearing about these, how long do they take to arrive?
i went from sopra 1 to diablo utopia and the difference was crazy, the dealer im buying my 552 has a pair of Scalas coming in within the next few months, im going to get them
I don’t have an issue with speaker placement as such as there’s only on place they can go in the room. They’re in front of a bay window, there’s no back wall so that rules out a good load of speakers, they’re not really as far apart as I’d like as I wouldn’t be able to open one of my built in LP storage cupboards. The left hand speaker is sort of behind the arm of one of the sofas, so speakers have to have few enough divers and be tall enough to hear over that. To be fair I’m a lazy individual so not being able to move them about is a blessing.
I’spose I ain’t a serious audiophile 
Understand, it’s just when watching the video help guides on Rels website they say in most case the settings will be around 12 +/-3.
I have found settings that work for me and good to hear others have settings that are different to the guides.
Gary
I’m looking forward to hearing them too, super excited! I think it’ll take another week or so for the arrival, then there’s the logistics of dealing with huge and heavy stuff again 
Happy to share the initial observations, I’m also curious how they’ll deal with the room and sound with the NC300 stack. Thanks for encouraging me for the Dyn to Focal transition and sharing your experience.
They will take a while to run in, I have heard people say a good 500 hours. im defo interested to hear how it pans out, they will look awesome in your room. if my utopia are anything to go by, they will sound the business too
Same here, pretty excited about hearing them and run through the break in. Now getting lost in biwiring vs single wire with jumpers. I don’t know how NC series respond to biwiring vs the classic series. There are forum posts that it’s not recommended but is that the same for NC series? @Richard.Dane any insights on this you can share would be much appreciated
I still don’t think it’s recommended by Naim, but perhaps @110dB has some comment to make here.
I’m not at all convinced that biwiring has any benefit with any amps/speakers unless you are using too thin a cable, when simple paralleling up would reduce resistance (also reduce inductance, but increase capacitance, and I think it is the latter that at least some Naim amps don’t like).
Positioning a sub in the corner of the room will increase the degree of interaction between the sub and the room modes by 6dB. It will sound as though there is more bass as some frequencies will be enhanced more than others. The bass will appear louder, but the frequency response will be a lot less even.
(Corner positioning is correct for LFE use.)
