This thread has become a good example of a very straightforward solution becoming buried.
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Thanks. What’s useful about the thread is the combined experience of everyone who’s tried something. The sub manufacturers generally advise you to use trial and error for positioning, and I’ve also seen 3 different answers on this forum as to how/where to connect, each of which has merits and each clearly can work. I will one day buy a sub (or two, another variable!) and work through this, and will also try facing it/them into the corner as part of the process. Without your input, I’d never have thought to do that!
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I think he’s saying saying facing the opposite back wall, behind the listener, not facing the corner they’re sat it. Apologies if I’ve missed another post or generally just lost the plot
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I have 2 x rel tzero’s. Both attached to my PMC speakers and add just the right amount of bass. Great little things
A little bit about the physics of subs:
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There’s no such thing as a fast sub
A sub (and this applies to all subs) have a low pass filter somewhere in their signal chain. Low pass filters delay the signal slowing the response of the sub.
Subs mainly come in two varieties:
Sealed box (slow; linear phase) either large or with limited power or limited extension.
Ported box (slow,very slow at deep bass; stepped phase) smaller. -
The low pass filter (as above) and the delays in the class D amplifier combine to give the sub a ‘group delay’; this means the acoustic signal from the sub is generated later than the acoustic signal from the bass cones of the main speakers*. If you place your sub beside the main speakers the crossover to the sub will not be time aligned.
Some people are sensitive to crossover anomalies, some people are not so sensitive. -
Putting the sub in the corner of the room exacerbates the room modes (often by more than an order of magnitude); this gives the least smooth response when used for music playback (but it can be good for cinematic x.1 LFE channel).
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The signal seen by any sub connected to the speaker connection (of the amplifier or at the speaker terminals) will be adversely affected by the back e.m.f. of the speakers’ bass cones.
The above are simply the effects of physics, you can pay attention to them in your system design and positioning, or you can ignore them … that’s as you please; but you can’t avoid them (to quote ‘Scottie’ from Star Trek: “Yer cannie beat the laws of phusus Cap’n.”).
(* Unless you put a delay into the signal to the main speakers!)
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The following three are opinions (as opposed to the above which are facts):
a) The easiest way to deal with the group delay is to place the sub closer to the listener than the main speakers.
b) The easiest way to deal with the issue of exacerbating the room modes is to position the sub off the floor and away from the corners of the room and use a device such as a DSpeaker Antimode, or use a sub with a built in DSP.
c) The easiest way to deal with the issue of the back e.m.f. from the main speakers is to use low level connections.
These are the easiest ways, but not necessarily the best for your circumstances.
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Think this is how modern car systems work. My Tesla has a sub in the boot, but delays on the rest of the speakers make the bass sound like it’s coming from the dash, incredibly well integrated. We also have an Audi with an oem sub and it’s a hideous, draws attention to itself thumping away in the boot.
No I was saying facing the opposite back corner of the room. Not the back wall behind the listener, the back corner.
That seems to be correct - it seems to be a concern with REL’s low level input that isn’t present with other manufacturer’s subs (particularly those designed for music replay rater than primarily a LFE devices).
That’s not correct, the back emf of the speakers is transmitted back along the speaker cables until it meet the output impedance of the amplifier, where it affects the output voltage of the amp. The high level input of the sub ‘sees’ this altered voltage.
Sorry but ur wrong john hunter xplains this in a few of his videos …hence i have my Sopra2 connected to the rel 812 s with the baseline blue …as many others have done …and No it doesn’t see the cables and the subs are powered …
Yeah, I just go by what REL (and John) and my very experienced REL dealer recommend.
There was once a thread here where a dealer claimed I couldn’t possibily use my REL correctly if I didn’t insert a crossover between my pre and amp to save my floorstanders from working too hard playing bass frequencies. 
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I have naim bassline blue and it comes with piggyback bananas
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In the past I’ve designed audio amps.
I know what I’m saying is correct.
(From a logical perspective: how does the speaker cable prevent the back emf from the speaker’s bass cone being transmitted back to the amplifier? The speaker cable is a just a wire: it transmits current in both directions, there’s no magic here!).
I didn’t say that it wouldn’t work or that it would completely mess up the signal, just that there is a negative effect. Note also that the interfering signal is generated by the speakers and is affected by the output impedance of the amplifier, so it’s very difficult to calculate the degree of the effect in any particular circumstance. In some circumstances the effect is very small; in other circumstances, less so.
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I haven’t designed an audio amp (yet), but I know (and teach) enough Physics to be able to say confidently that what @Xanthe is saying is 100% in line with my understanding, no matter what anyone on the internet says on a video he might have made.
As it happens, I currently have a paper on the not-entirely-unrelated subject of LCR circuits waiting for me to peer-review it.
Mark
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Not to get in a debate with u but john hunter designs the bassline blue cables with naim …and specs can be viewed on the net …iv heard and have naim amps n rel subs …n i am very happy with tbem as others are also …and were allowed our opinion …what amps did u say u have designed
My BK sub is in the way of the pending Xmas tree (joys of Christmas) and is now disconnected from the setup, to be fair the 552DR/300 into SL2s isn’t too bad
That’s raising a distraction from the points I was making…
I didn’t say that it doesn’t work or that there will always be a serious problem with that type of connection. What I actually said was two things:
First: to some degree, the back EMF from the speakers will interfere with the signal to the sub when using the high level input.
Second: in respect of the interference from the back EMF of the speakers, it makes little or no difference whether the connection is made at the speaker end of the speaker cable or the amp end of the speaker cable.
I didn’t say that this interference is severe enough to always be a major problem, indeed I actually said “In some circumstances the effect is very small…” however, I also pointed out that the effect can, dependent on circumstances be considerably larger.
Yep i understand what you are saying n can aee what ur saying and i agree not all amps are made the same so yep i agree with u that somw anoa will have a problem with the connections and stuff …abd not bien that technically minded i accept what ur sayin …bjt myself personally im only going if a reputable company that only makes high quality subs and only subs …and workjs with naim to actually make a proper cable specifically fir naim gear …wich are also high quality …that’s all rel suggested connecting at speaker ends for 2 subs and amp end for 1 as its easier …and as i said not technically minded …tried it liked it and works for ne and many others …matbe ill send rel an email regarding statement n see what kind of reply i get back
That’s not actually what I’m saying.
Such as Velodyne, BK Electronics, Rel…
I didn’t say that the high level connection can’t work well, just that when using it there is a compromise involved in using it, a compromise that generally reduces the quality of the signal and the integration to the main speakers, to some degree or other. This degradation can range anywhere from unnoticeable to a sense that something’s really not quite right.
If a high level connection works better for your system then continue using it, however that’s not the case for a lot of systems, which is why people should try both connections.
Also note:
Putting a sub in the comer of the room works for Low Frequency Effects but is the worst position for reproducing a music signal.
Putting a sub next to the main speakers works for Low Frequency Effects but is less than ideal for main speaker / sub integration when reproducing a music signal.
If you are putting a sub into a room smaller than 7m in the smaller direction, then a DSP is highly desirable; if a DSP isn’t already built into the sub, adding one (via the low level connection) and tuning it to the room resonances will bring considerable improvement over the high level connection.