Pairing of speakers with amplifier considering watts

I enjoy watching reviews of audio on YouTube. Now someone asked in response to video which amplifier he should use, to which I responded that I was very satisfied with the combination with the Naim Uniti Atom (with B&W 703 S2 speakers). To this came the following response, which makes me doubt whether I made a good choice in the past and whether the dealer’s advice was correct?

"I looked up your Naim and it is 40 watts per channel at 8 ohms and the speakers are 30-200 watts. You are about 10 watts over the minimum for your speakers. Your speakers depending on source material can dip below the 8ohm rating down to 3.1 and when you don’t have enough power, or current, the lower bass notes are not reproduced faithfully.

Also your Bowers aren’t as efficient at 90spl, (sound pressure level) which isn’t horrible, but certainly not as efficient as a pair of Hersey IV at 99 spl or some of Klipsch other speakers over 100spl. The higher the spl rating, the lower you can keep your volume control and still get decent sound to fill the room at a lower volume level and not stress your amp."

Any thoughts?

You’ll hear when an amp runs out of current because the speakers distort. If that happens turn the volume down quickly but unless you’re belting out some Mahler at concert hall levels you may never hear it. In fact Simon Rattle’s rendition of the Cooke completion of Mahler’s tenth symphony is a good test piece.

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If you are satisfied enough with your system to recommend it then you made a good choice. The troll who caused your doubts should get out more and get a life.
If you spend more on a bigger amp it will sound better, that will always be the case; but it doesn’t mean that your current set up is broken or your amp is not driving your speakers “correctly”.
Those are my thoughts - relax and enjoy your system.


They are right to some extent, you are probably over-speakered or under-amped. Your Atom is probably having to work hard at even moderate levels to maintain current into the Bowers at the expense of some sound quality loss.
If it sounds good to you though and the Atom isn’t getting hot then it’s OK.

A Nova would be a better match for those speakers.
Speakers with high efficiency tend not to be used with Naim so I doubt many on here are using speaker with 90dB plus efficiency.

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If your Atom isn’t getting unusually hot (or otherwise misbehaving) when you play your system loud for extended periods, and it sounds good, then you shouldn’t really have anything to worry about. If the dealer you refer to was a Naim dealer, I think you should trust their advice over that of some random other person.

The internet is full of strange characters. To ask for advice and then to respond to that advice (given honestly and in good faith) with a list of reasons why the advice is wrong is a good example of such strangeness. I’d be tempted to treat it with several pinches of salt.



Perfect… :grin:

Remember, too - that a NAP250 is ‘only’ 70W (*) per channel into a nominal 8 ohm load. Obviously, this is a load of low powered rubbish, unfit to drive any decent speaker - applying similar logic.

(* - 80 W pc in later versions)

The best, and I would argue only, judge for this are your ears.

If your system sounds good to you, why bother what someone who hasn’t even listened to your system has to say…?


I think you’re right, but considering I’m happy with my current setup I think I’ll save myself the price difference.

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I have never actually felt if the Atom gets hot, maybe good to check that out soon.

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90DB is very efficient compared to 90% of stand mounts.

At the end of the day, you are the best judge . I hope this doesn’t offend anybody , but there are certain trolls on the internet , who will rubbish anything that isn’t made in their country.

If you are enjoying it with your ears and you judged the products a good match , trust yourself and not some sad soul trolling on the web


I don’t know if this helps at all but I have run my SBLs passively, using my Atom and for that matter my Nait 1. The SBL has a sensitivity of 88 dB I think.

Sounded fine in both cases. Actually pretty engaging!

As others have commented there is more to this than just numbers but in my experience unless you are using this setup in a small room and/or listening from a close distance, I think that over time you might find that the Atom and the B&W 703 S2 are probably not the greatest match? In that sense, I largely agree with the reviewer you quote but, again this is not to say you should give up on them unless you personally feel they do not work in your listening space.

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Naim demoed the Uniti range with Focal Sopra Ones at a launch even to which some forum members were invited. The Atom suffered a bit in comparison to the Star and particularly the Nova but in isolation coped pretty well in Naim’s fairly large demo room. The amps up the range resolved more detail and brought out the bass in particular.
The comparison was similar with the rather different sounding Russell K speakers when I heard the comparison at my then local dealership, though the Atom came out a bit better in that context. I’ve even heard an atom playing through Shahinian Hawks and it didn’t disgrace itself, though it wasn’t being pushed to high volume.

If it sounds good through the 703s why worry and if it doesn’t but isn’t obviously distorting I’d suggest playing around with speaker positioning in the first instance, it’s amazing how much difference this can make.


Have a look at the article on the Benchmark Media website about “First Watt” and then, don’t worry.

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Whilst the response you cite in the OP isn’t factually incorrect, it is clearly written by someone who has a fixed viewpoint, and it might be totally irrelevant to you. There are several aspects regarding adequacy of amplifier power being adequate, any or all of which may be relevant, depending on a variety of factors including the characteristics of the amp, and of the speakers, and the room (notably size and listening distance), and type of music to be played, and sound level preference of the owner.

Key factors include:

  1. A speaker manufacturer’s indicated guide to amp power range is just that, an indicative guide. Whilst speaker sensitivity is a factor, I would say yours at 90dB/W are probably slightly above average. More particularly, what would be adequate in a small room, or for someone who only ever listens at low sound levels may be grossly inadequate for playing loud sitting a long way from the speakers in large room.

  2. Of great significance when considering power need is the power available for peaks, both from the angle of adequate “headroom” and from consideration of speaker damage due to amplifier overload (see bullet 3). This is where Naim amps are different from most: The majority of hifi amps have a maximum peak power capability of around twice the rated max RMS level, but many Naim amps are unusual in the maximum peak power being around 5x the Rated RMS. So whereas a typical 80W amp may manage maximum peaks of around 160W, the NAP250, which is rated at 80W, also claims it can manage transients of 400VA (in simplistic terms, 400W). This means that in terms of musical peaks the 250 has a capability more like a typical 200W RMS amp, not clipping the peaks below that power level.

That said, AFAIK Naim hasn’t published the transient capability of the Atom, so it is unknown whether it, too, can manage peaks up to around 5x the rated RMS of 40W, or if it is more like a typical amp, but assuming it has that Naim characteristic it’s peak capability would be more like that of a typical 100W amp.

  1. Using an underpowered amp is more risky than the other way round: If the amp isn’t powerful enough for your use, not compared to the speaker’s rating or recommendation, and you push it too far, so that it clips but keep it there, there is a significant risk of quite rapidly burning out the speaker drivers’ voice coils. The bigger risk may be if it is only clipping on peaks because that may not be intolerable distortion so you might be more likely to ignore it, but if the music has very frequent peaks it still may result in damage. Don’t ever continue to play so loud that any discernible distortion sets in!

  2. Another aspect is not directly to do with power, but more available current to cope with dips in impedance, and also output impedance of the amp. These can be relevant to how much “grip” the amp has on the speaker, insufficient giving ”woolly” or wallowing bass. That is an area where your ears can simply tell you whether it is sufficiently controlled to suit your needs.


BTW, I don’t understand the use or relevance of those! If they play something for you to hear, so much depends on the microphone(s) they use and microphone technique (which can manipulate things if the reviewer is biased), while any associated compression audio format if lossy will lose possibly critical sound information - likewise your replay if not through a full hifi system. And you are forced to go at the reviewer’s pace, which all too often is plodding and time wasting, trying to promote the person not the content. I gave up on youtube reviews (and lots of other youtube content) some time ago - I much prefer the printed word that I can read at my own speed, reread bits easily, and skip nonsense easily.

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Sensitivity is not efficiency. Often incorrectly labelled as such. In truth, most speakers have an efficiency in the 2-4% range and no manufacturer publishes this since it’s useles anyway.

As for sensitivity, it only gives an approximation of how easy it is to drive and there can be massive outlyers. It just gives you a number for 1w at 1n at 1KHz. Other frequencies and off axis response is completely ignored.

To this end, there are 98db speakers out there that are a real challenge to drive and 84db speakers that are totally 15w valve amp friendly.

So the assumption that a 40w Atom can’t drive thise B&W well based on those numbers is rubbish. It might be underpowered, it might not. But if so, other factors would come into play. A 40w/8Ohm amp that can happily drive 2Ohm loads is likely to do far better than a 70w/8Ohm amp that falls apart just under 4Ohms.


Thank you for your comprehensive response. Instructive and certainly appreciated by me!


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