First attempt at assigning convolution filter in Roon: too much vibration and a bit too visceral. Time to take crossover frequency back and gain down a couple of notches.
Lol ironically my answer is very similar, just a single sub behind my right speaker stand at the same toe in angle. Quite close to the wall and corner.
My turntable is on the left hand wall so keep the sun on the right.
I’m sure a pair will improve things but I’m happy with the one.
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I notice the peak at around 40Hz on your graphs gets bigger each time. I’m no expert on this stuff, but I wonder if the novelty of having that extra bass is making you turn up the gain on your sub, perhaps a little higher than it really needs to be.
Either that, or your room maybe has a bass node at that frequency which is exaggerated rather than cancelled by the sub.
All just idle speculation on my part. If you really want to understand what’s going on and optimise it buy a USB mic and use REW.
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Good points @ChrisSU i did a bit more tweaking when I was waiting for the cricket highlights. Crossover dialled down a few clicks and the gain reduced too. My companion had to take her hearing aids out, but the dog was happy.
I think I need to put some of my books back, just in front of the sub bass unit. I did not expect to see a room node as the walls as not square.
You could also try switching the phase of the sub. It may help get rid of the bass hump.
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Good suggestion … I followed the instructions on checking phase, I.e. which sounded loudest. But not quite the same as placing speakers facing each other as in the old days!
I’ll check it out once my companion has left so as not to disrupt her hearing.
I have two BK P12 300 sub woofer, one per 1028be focal speaker in a 24m2 room. I took some time to adjust them but now they are well integrated, not more bass but bass of better quality as well as a better stereo image and richer highs…
The sub is set to 45 hertz, the phase to 0. I have a sub on each side outside the Focal with the sub hp on the same line as the speakers.
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Anyone any idea why adding subs seems to often improve imaging?
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The sound of an instrument has various harmonics, for example a large organ can give in the bass but its pipes also resonate harmonics in the medium.
A double bass that plays high notes also plays in several registers.
A subwoofer perfectly fused with the rest can’t be understood properly, it adds harmonics that were missing without it.
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I was once told whilst attending a REL training session that the sub-bass systems (subwoofers in normal parlance) energise the air in the room, allowing the main speakers to work more efficiently.
I certainly raised an eyebrow at the time, but whether it’s this or something else that we can’t yet put our finger on, it certainly does just as you say. In fact, I tend to find this the biggest improvement a sub brings, not the bass, which surprises people. Countless numbers of customers who gave me that look of understanding after I’d demonstrated the effect, before parting with their hard-earned.
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Thanks @registlse @BBWan - appreciate the responses 
I’ve never tried a sub, and was interested in this aspect in particular.
Is this a ‘spot the difference’? While looking for differences I noticed that your speaker cables are coiled. They would be better in a z fold.
The graphs seem to show that you get a vastly superior response without the sub.
At what frequency are you cutting the sub? The graphs seem to show that you should cut at 25-30 Hz to avoid boosting the bass hump further or increasing overall bass response to a level far above the rest of the spectrum.
Switching the phase, and perhaps playing around with placement, may get the sub to cancel at the room resonant frequency.
I have three subs and cut them at 30-35 Hz, I also use two active bass traps to absorb excess bass energy.
Good luck
Hans
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Thank you Hans for your observations. I’m slowly dialling back to a sweet spot with the crossover. My gut feeling was to use 30 Hz but I thought I would follow instructions.
As an aside, I’m disappointed that my dealer did not offer to help me tune the sub-bass unit in; perhaps this was because they don’t offer Naim. My choice of dealer was skewed by their relationship with REL. Lesson learnt.
Crossover now set at 30 Hz with gain turned down but not bottomed out. The curve still not quite right to my ears as it’s a bit boomy.
Just as an experiment I’ve added in a convolution filter based upon the above curve which has evened things out for today as cricket awaits. I can see I can lower the gain further. It’s a pity I don’t have space to try different positions for the sub-bass unit.
Question……my SN3 has a left and right sub out, if only using one sub how best is it connected?
Looking at your posted pictured I can see that you have both the S-600 and sub close to the front wall and corner. This is probably the main cause of the boominess. If you can, I would suggest moving the main speakers out. REL recomend corner placement of the sub. Naim recommended placing the n-Sub against a side wall. You could also try this. I have placed all my subs their distance to the listening position is approx. the same as for the bass units of the main speakers.
/Hans
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Most subs have a 2 channel input, so a standard stereo RCA cable would work.
Some cheaper subs only have a single input. Best avoided for HiFi use, although it would still work.
Many subs have a high level input which takes the signal from the speaker sockets, so then you wouldn’t be using the sub out RCAs at all.
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Thanks Chris, so the sub ‘monos’ the two channels?
Yes. Deep bass is less ‘directional’ than higher frequencies, which is why you can still get good results with a single sub
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Leave the Phase alone. You do understand why. Try taking the grill off. In your picture it looks like you could move it out and even rotate it some. Not sure about the room but a nice area rug in front of the system might help .
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