I was not going to intervene, but I was encouraged…

I can enjoy several systems, 3 of them in room with integrated subwoofer, which brings several advantages: full range system for a much more reasonable budget than using only floorstanders, large opening of the soundstage and better focus (both in quantity and quality).

IMHO the key lies in the quality of the subwoofer and its integration; but if the sub is not of great quality, and preferably sealed if it is to listen to music, or preferably to music, there is no integration that is worth.

After trying several subwoofers, I finally opted for SVS (SB16 ULTRA in the main system and SB2000 in the living) and Jl Audio (D108 in bedroom), which are among the best in subwoofers, although I would also consider Rel and Velodyne.

It is not so complicated, and it is being tuning, like everything:

The bass level: halfway through the level, to finish adjusting it at the end, usually increasing it slightly.

The crossover frequency: start with a frequency between 5-10 Hz above the minimum in the room (-3 dB) indicated by the speakers manufacturer for them, and adjust according to preferences.

Phase: 0º if the subwoofer is firing in the same plane or direction as the speakers, and 180º if they are firing in different planes (for example the sub behind the listening position and pointing forward); anyway, it is easy to try until you discover the one that convinces the most, almost always quite invaluable given the omnidirectional sound dynamics of the bass.

Of the group delay I would not worry given the dimensions of most rooms, the speed of sound and reflections of different order.

This reflections are very important to prevent the sub from exacerbating the room mode resonances; but the only control variable is to play with the positioning until finding the right point of integration. For example, in my main system, I calibrated de big SB16 to sound extraordinary in a sweet spot of around 1.5 square meters, which is where I usually enjoy it, and allows almost 3 comfortable people to take advantage of the sweet spot; in the rest of the room, which is large, there are points where the bass is more intense and another where it is much more subtle, but without awakening the room modes at any point.

A subwoofer is known to be well integrated when you don’t notice that it is or it is acting; but if you disconnect it, the soundstanding and focus are drastically reduced.

Thank you NC that’s an interesting insight.

I’ve orderd two REL S/510s which I believe will work well with my Naim Ovator s800s as they are fast and agile subs. I have a good ear and have manged to tune the room with various treatments to get the best out of it so far.

All the best Pete … always pitch your thoughts and recommendations that’s what this forum is all about :+1:

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Hi @916SPS
I believe they are Supra Combicon.
The dealer provided them with the speakers and speaker cable.

Thanks RG I’ll look for them, they seem to do the job well for you.

Unfortunately the limitations of physics don’t quite agree with some of your conclusions, for instance:

At 50 Hz many subs have a group delay of 5ms, i.e, equivalent of a 90° phase shift. It’s also rather difficult to correct a 90° phase error with a switch that allows 0° or 180° phase settings!
This makes a mockery of the statement


This is true to a limited degree (the only place that will truly eliminate excitation of room modes is exactly in the middle of the room), unfortunately the position in the room also affects the timing integration of the crossover.

Unfortunately the actual lower limit of response of a given pair of speakers is VERY dependent on the room and their position in the room, so this won’t necessary give the right crossover frequency.

Manually trying to work out the best balance of all these competing variables is, shall we say, “challenging”. A much better approach is to measure using a calibrated microphone and a copy of REW.


Hi X,

I can see from your ident that you come from a science background and I’m sure your very aware of physics, but surely with a little experience and intuition a reasonable setting can be achieved. I’ve watched many clips on the ‘tinternet’ that demonstrate how to set up subs. I haven’t seen one yet using instruments. Paul McGowan and John Hunter from the Hi Fi industry are set against using maths
and gauges, tones etc. to find a great setting. Newcomer has just given advice which I appreciate so there’s no need to pick it all apart. If you fancy bringing over a box of tricks and gauges to help set up you’re welcome. :wink:

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If you’re prepared to spend time and effort moving the sub around the room and adjusting gain, frequency, phase etc I’ve found that you can sometimes get very good results by trial and error. It does require a large dose of luck as well though, and if you’re not lucky you will probably never get a really satisfactory result.
At this point I think it makes sense to consider measuring the room and using DSP to optimise the sub integration as Xanthe describes. To do this successfully you will need either a sub with this capability built in, or a low level connection from your preamp via a DSP box.
In my experience if you just stick a sub in a convenient location and hope for the best you are almost guaranteed to be disappointed, so it’s really worth putting in the effort to get it right.

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Hi 916SPS
As You indicate You run a system active with multiple NAP300’s, You’ll have an issue connecting the REL via the high input Speacon connection which is the best. Normally You would connect a REL sub either to the speake routput on the amp or to the speaker terminals on the speaker, for the REL to get the full signal. But in you case - if I understand You correctly, Your active cross-over will split the signal into 2 or 3 frequency ranges. So You somehow have to figure out how to get the full signal from your cross-over and send to the REL Sub. I am sure either your dealer of Naim can help with a solution. I use a REL G2 with my NAP200/Focal Sopra No2 - fantastic set-up.

Normally, should you be within range, I would be delighted to do this for you, however at the moment it’s just too dangerous for me to do so.

In respect of newcomer’s advice, it’s unlikely to give you a setup that is optimum or to match the quality of an active 300 system (there is however, a small chance you could still be lucky and do so).

Thanks for the advice S. I thought I’d just be putting it on the bass amp? I’ll have a dig around for more information.

Thanks Pete


Okay; but it is also true that the best is generally the enemy of the good, balance in this case.

The difficulties you mention are true, but most are quite imperceptible to the human ear from a certain threshold.

I have calibrated 3 subwoofers in 3 different systems in three different rooms without any technical “assistance”, and you are welcome to our home to listen them, and if you want bring a copy of REW and a microphone to check that they are very close to optimization if not in it. In fact, in the living room I started the calibration with microphone and marantz’s REW, and the result was quite disastrous, with a sweet spot of just one head and an insufferable sound in most of the room; in the end, the last ear tuning and with logic is what worked.

It’s not that complicated.

Hi Stenberg, yes you are correct I’ve just had a reply from REL and they advise full signal. I have no idea how I’m going to be able to get one from before the SNAXO. I’ve emailed NAIM so waiting for a reply. One other option I thought is to put a sub on each power amp, but I guess that’ll be impossible to dial in?

Just a thought - if you need to feed a full range signal to each REL, why not just take a line level feed from your preamp (so volume controlled) before it goes to the crossover. I know some insist on a high-level connection to a REL sub (to maintain the sonic character of the main amps) but I use line level and find it works more than well enough. I do not use REL subwoofers, rather BK, who used to manufacture the subs for REL many years ago. From my admittedly limited experience of pre amps and power amps, IMHO more sonic character (tone) tends to come from the pre-amp anyway. The power amp determines depth, control, grip, loudness etc.

As for adding subwoofers, if well integrated they add so much more than just bass depth. For music use I would always go sealed. Positioning is key, dual (at least) is preferable and, from my recent experience, some consideration given to vertical as well as horizontal positioning is well worth it. Exciting room modes is a real possibility but a pair of well-tuned/sited, not too large (for the room) sealed subwoofers worked much better for me than one much larger ported unit. You could think of adding subwoofers as having large full range speakers but with the ability to control volume/crossover to taste/room for better room integration. The best set-up subwoofers appear to add little, until you switch them off…

Thanks Alex,

I’ve checked on the back of my S1 pre-amp and I have 2 XLR outputs so I should be able to use those. I’m looking at a pair of REL S/510s which tie in with your recommendation.

Thanks Pete

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Sounds like it should be a very good combination!

Sounds like an excuse for not upgrading from a 500 series to a Statement! :thinking:
:wink: :rofl:

This makes no sense to me, although I admit I could be missing something. The low pass filter in the sub will be removing the higher frequencies in any case, so why would it matter if the active crossover had already removed some of the higher frequencies first?

I thought that Chris, but REL said they recommend that you give the woofer the full signal. Here’s the reply from REL support:

Full signal is best so that you get better integration. We always try to give the REL full signal as you may have seen in various REL blogs. If you cut the frequencies to the REL you are starving it of the potential to bring extra life to other parts of the music other than bass. I hope this makes sense

From the horses mouth (whatever that means!)

Cheers Pete

Hmmmm! So they are doing something with the full range signal other than just putting it through a low pass filter?