A lot of people misread the FAQ on the old site, it actually started with words something on the line of…
“If a low level connection isn’t possible…”
It then described the high level connection to the rear of the speakers.
.
Many people got focused on the longer description and forgot about the first few words; this then became received wisdom!
I use a very short (1m) stereo pair lead to a miniDSP 2x4 which then acts as a line driver to drive the longer cable to the sub. (For a non DIY filter approach a DSpeaker Anti-mode 8033 SII can also do the same buffering job.)
In both these cases the DSP box can help to get a much better integration of the sub into the room by reducing the excitation of the acoustic modes of the room (and can also give more flexible and more precise crossover integration of the sub into the main speakers). This configuration results in a limited form of DSP room correction without the consequences of a DSP altering the much more delicate parts of the music in the mid and treble ranges. I find this limited DSP room correction to works really well - it’s almost having the best of both worlds at the same time.
Yes it is potentially superior…
particularly if compared to the performance using long low level leads, which have two problems:
1 If there are no resistors at the source end, then the capacitance of the leads can present an unfair load to the output of the pre-amp.
2 If resistors are put at the source end, then the higher source impedance can lead to interference or signal degradation.
Using a line driver (such as a DSP room mode correction box) fixes both these problems without making the sub vulnerable to the back emf from the main speakers (and can also be use to reduce the effect of the sub ‘driving’ the room unevenly due to room resonances).
Please also note that most people don’t position their subs correctly. Due to the group delay of the sub’s own amplifier there is a significant additional time delay to the signal within the sub. This means that the output from the sub actually comes after that from the main speakers (and this is actually worse for the high level connection as that also has the group delay of the power amp in the chain). The cure for this is to have the sub closer to the listening position than the main speakers. Many people think that the correct position for the sub(s) is close to the main speaker (or even behind them and sometimes even in the room corners); they then find it difficult (in this position it’s actually impossible!) to accurately align the sub and they then frequently claim that subs don’t work well in music systems.
Xanthe I’ve been considering trying one of the anti mode 8033s just to see if it brings any improvement.
Out of interest would the 8033 also increase the group delay as it’s putting another box in the signal path?
Yes it will increase the overall group delay, but only by a very small amount (much less than the group delay of the sub).
It’s probably comparable to the group delay of a typical audio power amp (and maybe even be rather less than that). The group delay from my minDSP 2x4 is about 25-50μs (and the Anti-mode should be similar), by way of comparison the group delay for my B&W ASW610XPsub is 1.1-1.8ms (this is quite typical for the class D amps in subs).
Naim and others do supply a ‘slugged’ low level interconnect for use with a sub, and recommend its use with an N-Sub.
The problem with interconnects is that the length is going to be determined by the required location of the sub, and for many, that’s going to be quite a long way from the amp. In my last room, I needed a 10m lead to reach the optimal position behind the sofa.
Chris,
Sick an Anti-mode 8033S-II into the cable near to the amp and that problem goes away (plus you get the benefit of not overexciting the fundamental room modes!).
Simples! 
Indeed, it’s an idea I have considered trying, although somehow I can’t see the idea catching on widely.
Go on…
Try it…
It does work well!
Thank you so much for your inputs, everyone. I really appreciate the support and willingness to help noobs like me on this forum.
What I learn from this discussion is that despite any inputs/opinions it will be indispensable to use my ears to find the best solution for my room and system. Thanks for the advice.
@ChrisSU Thanks for the picture with the spades.
@johnt Yes, I verified it. They can easily unscrew for the spades to fit in. And the BK P12-300SB and FF have no passive radiator. As @Xanthe already pointed it, only the -PR model has a passive radiator, which I confused it with. That was my mistake.
@Xanthe I didn’t even know that such EQ boxes existed. Will keep them in mind as a next step.
@Simon-in-Suffolk Regarding the aux preamp output: You mentioned that buffering may not always be possible. Under what premises is it possible?
Hi a few of the Naim products have a dedicated sub output, and these I believe are buffered.
After some of the comments in this thread regarding Hi-level and Lo-level connections, I thought I would try the Lo-level connection again. Unfortunately it didn’t sound as good as the Hi-level. Then I bought a DSPeaker Anti-Mode 8033-SII after @Xanthe mentioned it. I connected this between the HicapDR and the BK P12-300SB-DF Sub. This addition has made such a huge difference to the quality of bass and integration, it is just unbelievable what this this little box has done, a very worthwhile investment. I was enjoying the hi-level connected sub before the anti-mode, but I am now completely blown away by the quality of the bass with the anti-mode. Forget Hi-level go Lo-level but do get the DSPeaker Anti-Mode 8033-SII, you won’t regret it.
I made up my mind, persuaded my GF and decided to order a BK P12 instead of the REL T-7i.
There have been many arguments speaking for an input via the low level connection. While I could also read that differences were marginal in some cases, I believe that they will be bigger if a DSP comes into play in combination with the low level connection. I want to try that out. Especially after reading the last reply from @johnt !
@Xanthe already guided me to two of those boxes: “Antimode 8033-SII” and “miniDSP 2x4HD”. I did some googling but couldn’t really find out which of those devices would be better for my use case. From what I found out the Antimode is more like a “plug’n play” device, while the MiniDSP involves many manual settings and thus it might be considered “more powerful”. There is a very good offer for the Antimode at BKelec, but I would still be interested in the advantages of a miniDSP over the Antimode.
Does anyone have an opinion for which one I should go for? @Xanthe maybe? 
I’ve ordered the antimode 8033sii to give it a try and will report back. My subwoofer is between my speakers, closer to the right one which took a lot of trial and error to get right. I just checked the antimode website and their FAQ states that the delay is 2.7ms so am hoping the increased delay will not have any detrimental effects as cannot bring the sub any further into the room.
Indeed the Anti-mode is more ‘plug and pray’ like, whereas the miniDSP requires you to work out the filters needed (it’s a general purpose DSP unit not one that’s already pre-programmed). The main advantage of the miniDSP is the shorter minimum group delay time. Which one you go for depends on your confidence in looking at the in room performance graphs from REW and whether you can work out the necessary filters. (N.B. only try to correct peaks in the response: for mathematical and engineering reasons it’s not really possible to correct for troughs.)
In either case I would strongly suggest putting the sub a lot closer to the listening position than the main speakers, and using the Room Simulation dialogue of REW to try out a few candidate positions for the sub on a theoretic basis, then to try out the best two or three of them in reality.
If you’re using the mini DSP, then you’ll definitely need to use REW to measure the room to work out what filters you need (and to confirm the results and work out the fine adjustments you need to optimise the performance).
It’s worth getting a copy of REW and using the Room Simulation dialogue to explore different positions for the sub, it’s almost impossible to do this by ear and guesswork! Using REW can allow you to test a few candidate positions to see which will work best (i.e. least correction necessary from the DSP).
Strangely enough, antimode actually recommend putting the subwoofer in a corner. They say that there will be less nulls with it there and as the 8033 only corrects peaks you will get a flatter response that way.
I really can’t see this working for me as it would double the distance from my seating position to the subwoofer and it already sounds a bit slow if not between the speakers.
I will give the rew software a go now as I never got round to buying a microphone before in order to try it. If i don’t like the 8033 then at least the included microphone will come in handy.
@Xanthe Thanks for the explanation!
I decided to go for the AntiMode as well, as I’m not so confident that I’ll be able to handle/interpret REW to the extent that will probably be required when using the miniDSP.
But either way, I’ll give REW a try when everything is set up.
Unfortunately in my room only 1-2 positions are available for the sub. So there’s only very little play to begin with. The preferred spot aesthetically would be the one in the corner, right beside the left speaker. So the distance to the listener would be basically the same as the speakers.
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