The REL No.25 has Landed!

There’s another benefit. Quite a few publications have tested and consistently found that with subs, quantity does beat quality. A single sub requires painstaking positioning and that’s often giving you the best result for your listening spot. But there might be a masive node under granny’s chair. Two lesser and smaller subs give as much oomph and generally provide very simple positioning with far more even response for others in the room.

My dealer was suggesting crawling around like a dog with 40Hz looking for the sweet spot. Which might be a really inconvenient spot to put a sub. Alternative get two and place them in proximity to your main speakers and be done with that nonsense.

Certainly my budgeting for building a cinema/living room is based on two subs rather than one big one.


From the supercap you have sockets 4 and 5 going to the 300 using the DIN to XLR. Socket 3 is an additional signal output which I assume could go to the line inputs of the sub using a suitable DIN4 to RCA. Is that what you are suggesting?

Yes that should work… you will need to ensure however your sub doesn’t clash with your man speakers by using the LP filter and phase control on your sub. This would be the same if you connected the sub to the power amp outputs as well.

Sure I get that if not optimised for a sweet spot, I also think with non attenuated energy below 60 Hz or so bass traps in the corners of the room becomes a must, unless your room is significantly large.
I guess many of us heard systems where we should have been impressed but instead ended up being embarrassed by the deep booming resonance/overhang from the often quite high end Hi-Fi.

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The sub has a switch (in/out) for the LP filter which only works for the line in connection. For speaker level inputs the LP filter is always active. The LP cut off frequency can be selected along with the gain of the line in and speaker level in. Also a phase inverter.
So I just need a suitable interconnect to give this a try.
Two cables input to the SL2 PXO is a real cludge and probably responsible for breaking the solder joint on the crossover PCB.
I guess this should have been obvious, but not from the manuals. Thanks for the heads up!!
Are there more up to date manuals from Naim for the products. I seem to see quite detailed diagrams being circulated that are not part of the standard manuals

Thanks @916SPS
Funnily enough, the suggested optimum cross corner position didn’t work in my room. It just made things sound even more directional.

@feeling_zen - when I got the first sub, I was advised to put the sub in the main listening position and walk around the room listening for the best sound from it. If possible you then place the sub where you found the sweet spot. You should now be able to hear the same when you sit back in the main listening position.
This saves you humping 50kg of sub around the living room.

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That’s the same method I mentioned. But the point is, no one should have to place a speaker like that. What if the sweet spot is next to sofa with a trailing mains lead or in front of a bookcase or 101 place you don’t want to put it?

So much easier to just get two working in unison for even dispersion. Obviously there is still some positioning to manage with 2 but no more complex than your main stereo pair at least.

Still, the OP has a great setup with that gorgeis REL .25 and a marriage of listening position and centre placement. I’m sure it’s quite something.


Just to note a forum search confirmed this answer. There must be so much duplicated information on here…

Adding multiple subs is all about evening out bass response better, both throughout the listening room & also in the primary listening position. If you have the space, adding a second sub is almost always better then one. And yes, adding a 3rd & 4th will also improve things (though obviously not practical for most).

Great post. Has anyone else watched the install and setup of a rel 25 on youtube where they use a Dspeaker for equalisation in a very hi end two channel audio system.

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Yes, understood :+1: and that mighty 25 really is a thing to envy.

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Careful here… it’s turning into a subwoofer waving thread :wink:

:rofl: :rofl: :upside_down_face:

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To ensure there is seamless integration between the sub, satellites and their environment there has to be effective alignment, calibration and dialling in. If this is done correctly then the sub/s will optimally support the system and consistently disappear into the soundstage with a deep, sharp, tight fisted, fast and powerful punchy sub bass regardless of recording/genre.


That’s exactly what I’m hearing, it seems very natural and finishes off the deeper notes that used to just cut off. :+1:


Sorry for hijacking your thread.
I found the following thread on this forum

which is also very relevant to this subject in general. Unfortunately there are very useful details buried in this thread (comments from Richard Dane concerning usage and warnings regarding interconnects) that i would appreciate seeing in documentation (of the supercap) that are rather thin.
Technically speaking the Naim 4 pin DIN to RCA that are available for connecting socket 3 (extra signal output) from he Supercap to the line in of a subwoofer. Is this terminated as standard with the 100R resistor. When one says low capacitance, what are the values for the Naim cable?
If there are no plans to update user manuals and documents then may I suggest that this sort of information goes in an online document.
Could I suggest possibly a Naim wiki for building up the knowledge and useful tips etc…
I appreciate this would take time to setup but most communities nowadays use a wiki as standard. It’s also easier to maintain but again takes some effort to set it up

Hi Mark yes you would only not use the low pass filter if your preamp or home theatre system had the sub eq built in.
It’s a shame your phase control is very limited… many subs have a variable phase control. You might find you need to physically move the sub around if the phase is limited to either 0 or 180 degrees.
This is a harder thing to get right and you are listening for sharp bass aligned transients when working with your speakers… in other words a tight bass punch, as opposed to a slower, smeared bass boom… your room will be affecting this as well and if untreated it will be a case of getting it the best you can within the limitations of your listening room.

In my experience with home theatre this is not crucial, but with quality audio Hi-Fi it very much is.

Good luck… let the games commence :grinning:

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Indeed. However, and I would recommend the subs are mono’d at below 100 Hz if you can and not run in stereo, to reduce channel phase cancellation issues.
This is one reason why many clubs mono their bass subs when playing EDM (and I am told some dance clubs only work in mono across the entire audio band) and these days much pop/rock music and EDM is often mastered with the sub / low base frequencies mono’d, and with a steep cut off around 30 Hz or so… as this is wasted energy in the mix…
Obviously it’s a different proposition for film sub bass channel fx… which often is not about conveying musical information.

Indeed, and unless the room is sufficiently large or well treated for bass, and is about Hi-Fi audio as opposed to home theatre, I think a single centre sub optimised for a sweet spot listening position will likely be best.

Have multiple subs to cancel nulls in certain spots is all very well, but where there is a null there is usually a peak somewhere else… and I think musically there could be all sort of issues of properly phase aligning the subs in such a circumstance.

As said elsewhere for quality music replay (as opposed to home theatre) phase aligning for tight transients with strong bass frequency energy is key… and in my experiences in a domestic setting in many typical UK sized rooms without bass treatment… is difficult to do properly unless focussed on a sweet spot.

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Hi Simon
In most of the subs that I’ve looked at. Admittedly only B&W and REL, they don’t seem to provide a phase control, apart from 0 degree or 180 degree. Fortunately I am not limited with sub placement and so can optimise based on that.
Yes I’m sure let the games commence is very appropriate by adding a degree of freedom.
Let’s see where it ends up.
Anyone? @Richard.Dane perhaps? Any other remarks to my queries about interconnect special requirements?
Many thanks