How A Hi-fi Speaker Conquered The Studio World Monitors / Monitoring By Phil Ward

Love or hate the Yamaha NS10, this unassuming little speaker has found a place in the studios of many of the world's top producers. We trace its history, and investigate why a monitor whose sound has been described as "horrible" became an industry standard.

What is it about the Yamaha NS10? If any piece of pro audio hardware deserves that over-used term "industry standard" it has to be the NS10. In a professional audio world continually seduced by the next big thing, where plug-ins can provide a near instantaneous GAS (Gear Acquisition Syndrome) fix, where products live or die thanks to their quantity of bells and whistles, and where the number of contemporary nearfield monitors that could apparently do the job of an NS10 is almost beyond count... the venerable, tired old Yamaha is the one piece of kit that still appears in almost every photograph of a smiling engineer posed at his desk.

You don't have to hang around long in the SOS Forum for a thread to appear that features the Yamaha NS10. Even in threads that begin with some other monitor subject, the NS10 seems to possess a gravitational influence that inexorably results in discussion of its merits, or otherwise. Few subjects excite so much passionate opinion and, as is the way with passionate opinions, you don't find many in the middle ground: nobody says they "quite like" or "slightly dislike" the NS10; it's a definite case of love or hate, as evidenced by the SOS Forum quotes I've included in the 'Love 'Em Or Hate 'Em?' box. Within that context of polarised opinion, the NS10 generates a phenomenon that at first glance seems a little odd. You find those that, in professional terms can't live without it but often don't particularly enjoy listening to it, and, similarly, those that refuse to give it studio room but are often happy to admit that professionally it does a job.

So what's going on? Not only should the NS10 by rights be nothing but a small footnote in the history of recorded music, but also there is precious little consensus or understanding about why we respond to it in the way we do, and why it's still found in almost every studio. That's where this feature comes in — so if you've ever wondered why you're still using NS10s, even though you don't particularly enjoy the way they sound, and if you're prepared to forget some of what you thought you knew about monitors, read on...

Part of the NS10's problem is that the general understanding of how we respond to monitors is coloured by their apparent technical simplicity and by manufacturers, sometimes innocently and sometimes intentionally, encouraging this phenomenon. In reality, the psychoacoustics of the perception of music reproduced by loudspeakers, and how this relates to their technical performance and specification, is an immensely complex subject that doesn't take kindly to simplification by marketing departments. By the time it lands on a sales brochure, a frequency-response curve, for example, is typically meaningless in terms of providing any information that's useful to an end user — even if it was measured competently and had any technical value in the first place. But then, in some respects, it can suit a manufacturer of monitors if their customers don't know too much.

Misunderstanding also tends to breed misinformation, which is often disseminated by well-meaning amateurs: those whose knowledge of a subject is sketchy are always prey to the intuitively plausible but utterly wrong explanation for one phenomenon or another. The hi-fi sector is well known for enthusiastically buying into the plausible (and often the implausible) as opposed to the factually correct. But we serious audio practitioners shouldn't start feeling smug, because the pro sector is not by any means squeaky clean on that front, especially where monitors are concerned. Occam's Razor, the principle beloved of physicists, which says that the most likely correct explanation for any phenomenon is probably the simplest one, never seems to have reached the audio business!

NS10 Variants During the NS10's 23-year life Yamaha manufactured a number of different versions (or perhaps just used a number of different logos): NS10M: The original domestic hi-fi speaker designed for vertical orientation (its front panel logo reads correctly with the speaker mounted with tweeter above woofer). This is the speaker that was too bright for Bob Clearmountain, leading him to resort to tissue paper over the tweeters — although, of course, it had to be the right kind of tissue paper. NS10M Studio: Some time after Yamaha got wind of the NS10M's popularity as a nearfield monitor (and around nine years after the original product launch) a version badged 'NS10M Studio' was produced. This version was designed for horizontal orientation (the logo and connection panel text were turned through 90 degrees), incorporated a redesigned tweeter and crossover to address the HF tonal balance issues, featured a more rugged cabinet design without grille-mounting sockets, and had improved connection terminals. Others: Web searches on NS-10 or NS10 will reveal some variants. There are versions badged NS10M Pro, NS10MX, NS10MC, NS10MT, and a miniature version that was sold in a 5.1 home-theatre package called the NS10MM. I've been unable to establish whether the NS10M Pro and NS10MX offer anything different (my guess is that they don't, but if anybody out there knows anything about them I'd love to hear it), but the NS10MC appears to be an NS10M Studio with a front grille, and the NS10MT appears to be a magnetically shielded and vertically oriented NS10M Studio with symmetrically arranged drivers and, wait for it... a reflex port. Aaaargh! There are also obviously NS10-inspired products out there, by which I mean nearfield monitors with black cabinets and white cones. In the absence of any independent technical appraisal I'd be very wary of purchasing one on the assumption that it will offer anything like the performance of the genuine article. If you really want a pair of NS10s, eBay is probably your only real option, and you should expect to pay anything up to £350 for a pair in good condition.

Before we get into the electro-mechanical and psychoacoustic nitty gritty that I know you're gagging for, let me take you through a little NS10 history. The Yamaha NS10 was designed by Akira Nakamura and launched in 1978, and it was as technically unremarkable then as it is now. At that time Yamaha were also producing the more extraordinary NS1000 (also designed by Nakamura). With its beryllium mid-range and tweeter domes this speaker is technically advanced even now, and if you ever come across a pair in good condition, worth selling your own mother for. The NS10 began life as a domestic hi-fi speaker, but it was relatively poorly received and quickly faded towards obscurity. How the NS10 was rescued from hi-fi death and resurrected as a nearfield monitor, single-handedly inventing a product sector as it did so, is a story that has probably been told slightly differently almost as many times as it's been told, but the version I'll tell here is, I believe, as close to the truth as makes no difference.

To understand the history you first have to appreciate its context. The late '70s, when NS10s began to appear perched on meter bridges worldwide, was a transitional time in music recording. The divide between the engineer and the artist was blurring, as if the glass between the control room and the studio was melting. Desks were getting bigger as track count increased on tape. Outboard gear, driven by the possibilities offered by the mix and editing potential of that higher track count, became more sophisticated and ambitious, and the possibilities for recording engineers to become more creatively involved in the process of producing a record multiplied.

This new-found creativity in the control room meant that those recording engineers who embraced and learned to deploy the rapidly increasing capabilities of recording technology discovered they could call the shots with the record companies. Suddenly they held the power and some of them, initially in the US but pretty quickly in the UK also, became minor stars in their own right. The freelance life beckoned as a result, but a freelancer needs their own tools, and the new breed of 'name' recording engineer/producer travelled reasonably light from studio to studio, with a few items of favourite outboard, a few microphones —and, after a while, a pair of Yamaha NS10s.

Actually, it might not have been the NS10. On both sides of the Atlantic it might have been the Acoustic Research AR18, and in the UK it might have been the Mordaunt-Short MS20: hi-fi speakers that offered similar technical characteristics and were occasionally to be found in studios (I was working at Mordaunt-Short in the early '80s and developed a 'pro' version of the MS20, but a lack of effective distribution scuppered its launch). But it was the NS10, thanks in part to its cool white cone and, it is often said, to Bob Clearmountain...

The usual story goes that Bob Clearmountain, one of the first of that new breed of 'name' engineers wanted a pair of monitors to carry with him from studio to studio so that he had a consistent reference, and he wanted something that he felt was representative of typical domestic hi-fi speakers. It is sometimes also said, usually by those for whom the abilities of the NS10 are a closed book, that he chose the NS10 because it was the worst-sounding speaker he could find. That, as I say, is the usual story. The trouble is, it's not true: the real story, recounted by engineer Nigel Jopson in a letter published in Resolution magazine in 2007, does involve Bob Clearmountain (see Note 1), but is different in almost every other respect.

Bob Clearmountain's Tissue Bob Clearmountain's other significant claim to fame is probably that he was the first to use tissue paper over NS10 tweeters in an attempt to dull their over-bright balance. He resorted to tissue paper after the maintenance staff at The Power Station had refused to modify the speakers by wiring resistors in series with the tweeters (why he didn't simply put an HF shelf EQ in the monitor chain is a question for which I don't have an answer). Yamaha's second-generation NS10, the NS10M Studio, had a less bright balance, so removing the need for tissue paper. There's a technical analysis by Bob Hodas examining the effect of covering the NS10 tweeter with various types of tissue paper here: www.bobhodas.com/tissue.html

Jopson believes he was one of the first engineers regularly to use NS10s in the UK. His first pair was given to him by a producer just back from mixing a project at The Power Station in New York, after hearing that Rhett Davies and Bob Clearmountain had used a pair there while mixing Roxy Music's Avalon. However, Jopson goes on to say that Clearmountain himself recalls that NS10s were recommended to him by Bill Scheniman — who was the first engineer to bring a pair to New York, having used them at either Motown or Sunset Studios in LA. Bill Scheniman recollects that the pair of NS10s at Sunset (or was it Motown?) belonged to Grag Ladanyi, but that he had been convinced of their worth earlier, while working in Tokyo. Scheniman remembers using NS10s at two studios there: TakeOne, and another studio long-since forgotten. So, the most likely seed of the NS10's world domination was probably an unknown engineer at TakeOne studios in Tokyo — and not Bob Clearmountain looking for the worst speaker he could find!

The rest, as they say, is history. Clearmountain in particular was (as he is now) a first-call producer and engineer for the biggest projects, and once he and a few others began to rely on the NS10, the phenomenon grew like a virus inhabiting a welcoming host: studios began to buy NS10s in their thousands in an effort to attract name engineers. Of course, in order to thrive, a virus needs a host to which it is particularly well suited, and this was provided by the rapidly increasing number of freelance engineers I described earlier.

But in what respect was the NS10 so well suited to the nearfield monitor role? What was it that the unknown Tokyo engineer, Scheniman, Clearmountain, Davies, Jopson et al, heard to convince them that the NS10 was worth overturning their previous monitoring practices (predominantly Aurotones on the desk for AM radio/TV mixes, and big horn-loaded main monitors in the wall in front of the desk) for? If the NS10 had truly been, 'the worst speaker Bob Clearmountain could find' it wouldn't still be with us, which means it must have had — and must still have — something special.

Fast forward to 2001 (ironically, the year in which Yamaha discontinued the NS10), when studio and monitor designer Philip Newell, Julias Newell, and Southampton University's Dr Keith Holland presented a research paper to the Institute of Acoustics that constituted probably the first objective investigation of the NS10 phenomenon.

The Newells/Holland paper was based on acoustic measurements of 38 different nearfield monitors, carried out in the UK's premier research anechoic chamber at Southampton University. The acoustic measurements taken included frequency response, harmonic distortion and time-domain response (how quickly

Further Reading The paper, The Yamaha NS10. Twenty Years A Reference Monitor. Why? is no longer available from the Institute of Acoustics but some of it is included in Philip Newell and Keith Holland's book, Loudspeakers For Music Recording And Reproduction. Anyone who gets to the end of this article without losing the will to live could do much worse than get hold of a copy. Ed — Since this SOS article was first published, the authors have kindly given us permission to host the research paper PDF on our web site: ns10m.pdf Having said that the Newells/Holland paper was the first analysis of the NS10, Andy Munro presented a paper to the Audio Engineering Society in the early '90s, in which he examined in passing the acoustic effects on the NS10 of placing it on the meter bridge of a big desk. The paper showed that the NS10's frequency response flattens in such circumstances — reflection from the desk reinforces output in the upper bass and low-mid region.

a monitor starts and stops in response to an input). At the end of the exercise it's no exaggeration to say that one monitor stood out like the proverbial sore cliché: the NS10. While its frequency response wasn't particularly flat, and its low-frequency bandwidth was restricted in comparison to many others, in terms of time-domain and distortion performance it was outstanding.

During my work with Acoustic Energy on its recently launched AE22 nearfield monitor, we repeated some of Newell's and Holland's time-domain measurements of the NS10 and found similar results, and I've reproduced some curves that illustrate it. The measured data was generated by Phil Knight using the MLSSA acoustic measurement and analysis package, together with a calibrated B&K measurement microphone and custom-made power and microphone amplifiers. The relatively small measuring environment allowed for acoustic accuracy only down to around 150Hz — so, in Figure 4, reproduced later in this article, data below that frequency was generated through analysis of the NS10's low-frequency electro-acoustic parameters and calculating its response (see the explanation below). Before I get deeper into the acoustic measurements of the NS10, however, I'll first touch on one fundamental reason, as Newells and Holland pointed out, why its time-domain response is significantly better at low frequencies than most nearfield monitors: it's a closed box speaker.

Frequency Response & Time Domain In electro-acoustic terms, at low frequencies (say, below 200Hz) a speaker is a classical high-pass filter and, just as in classical electrical filter theory, if the appropriate parameter values (driver compliance, moving mass, cone area, box volume, magnet strength, voice-coil resistance, and so on) are known, the frequency response and time-domain response can be calculated with (almost) 100 percent confidence.

Thanks to its two reactive elements — the mass of the cone/coil and the combined stiffness of the driver suspension and the air in the cabinet — a closed-box speaker displays second-order (12dB per octave) high-pass filter characteristics. A reflex-loaded speaker, on the other hand, thanks to the extra mass element of the slug of air in the port and the slug's own reaction against the air in the box, behaves as a fourth-order filter (24dB per octave). All reactive filters display a delay in their response to an input that increases with their complexity. In-phase movement of the air in the port of a reflex-loaded speaker must occur a half cycle (180-degree phase shift) after movement of the driver cone. This kind of time delay is known technically as group delay; it's actually the phase change with frequency expressed as time.

To illustrate a comparison of a closed box and a reflex speaker I've generated two low-frequency response simulation curves showing frequency response and group delay. The simulation in Figure 1 is based on the cabinet volume and driver parameters of the NS10. The NS10's limited low-frequency bandwidth (-3dB at 70Hz), slightly humped response and slow roll-off are clearly apparent. The group delay reaches a maximum of around 3.5ms at 70Hz.

Figure 2 shows what might have happened if Akira Nakamura had decided to aim for maximum low-frequency bandwidth (retaining the characteristic slightly humped shape) when he designed the NS10. The simulation in Figure 2 is again based on the NS10's 12-litre box volume. I've had to tweak the driver parameters slightly to make the system viable, but they are broadly similar to the genuine article. So if Nakamura had decided to go all out for LF bandwidth (as many contemporary nearfield monitor designers do) he could easily have reached -3dB at 57Hz — but look what would happen to the group delay. It increases to just under 11ms at 60Hz, which is around three times that of the closed-box NS10.

Group delay is not some imaginary construct that helps acousticians feel important, it's real — and it means, for the reflex-loaded NS10 option, that a bass-guitar fundamental at 60Hz will arrive at the listening position around 9ms after the second harmonic at 120Hz. Put another way, and expressed as a distance, the low fundamentals of the bass guitar (and parts of the drum kit) will sound as if they are nearly four metres behind the rest of the band (you can insert your own bass player gag here). Low-frequency group delay doesn't only influence mix decisions: it also varies widely between speakers and, unlike low frequency level, which can be adjusted via EQ, once its influence on tracking or mix decision has been 'printed' to the mix, it can't be undone.

A reflex-loaded NS10, however, would not just have had significantly delayed low-frequency output. As well as delaying the arrival of low-frequency output, reflex loading also results in its output continuing significantly after the input signal has stopped (something that takes time to get moving generally takes time to stop), and in a multitude of dynamic compression, pitch-accuracy, noise and distortion mechanisms that simply do not occur in closed-box speakers. These again are effects that come without an 'undo' function once a mix is printed — so one of the best decisions Nakamura made when developing the NS10 was to make it a closed box.

Closed-box loading explains why the NS10's time-domain response is good at low frequencies but, as Newells and Holland discovered, the excellent performance also continues into the vital mid-range. Figure 3 shows a 'waterfall plot' of an NS10M from 200Hz up to 20kHz. These plots illustrate how quickly the output from a speaker dies away after a full-range signal stops suddenly. Imagine instantaneously switching off a source of pink noise. That's not quite how the waterfall plot is generated — one of this type is actually generated by taking sequential windowed snapshots of the speaker's impulse response and applying a Fourier transform to each — but it's a useful mental image.

Time runs in the waterfall plot from back to front, and a perfect speaker would display just one line (equivalent to its steady-state frequency response) at zero milliseconds. At the left-hand side of the plot there's a combination of the tail of the NS10's low-frequency fundamental resonance (even closed-box speakers don't stop immediately), and the unavoidable artifacts of a relatively small measurement space. Moving to the right, there are a couple of obvious discrete features — one at just under 2kHz and one at just under 3kHz. These are resonances in the NS10's bass/mid driver cone (or possibly its surround or dust-cap), and while they may look a little ugly they actually die down very quickly, and in subjective performance terms are relatively innocuous. The second resonance is at around 3kHz, which is actually above the NS10's 2kHz nominal crossover frequency, and illustrates that driver performance is important, even outside its nominal operational band. And speaking of the nominal operating band, the NS10's unusually low crossover frequency of 2kHz (made possible by a larger than typical tweeter, able to operate at relatively low frequencies) provides another clue to its time-domain performance. Any paper-cone bass/mid driver such as that used in the NS10 will become pretty badly behaved, in terms of resonance, above about 2kHz. Above the 3kHz feature in the waterfall plot is an area of general hash: this is the bass/mid cone in what's known as break-up mode, where its output is really just the result of one resonance after another. If the NS10's crossover frequency was an octave higher, at 4kHz, this cone break-up region would reflect in the time-domain performance and the waterfall plot would look very much worse. Moving further to the right, the NS10's tweeter performs very well and shows very little delayed output. Generally, the NS10's waterfall performance reveals a speaker that achieves -40dB within 6ms. Most speakers will take twice that long and many, especially those designed to maximise bandwidth, longer still. With just two small resonant features in the waterfall plot up to 3kHz, Nakamura could justifiably consider his design for the NS10 bass-mid driver a success.

The Heat Is On Measurement of the low-frequency parameters of the NS10 bass/mid driver revels that it has a very high mechanical Q. This means there's no eddy-current damping from the voice-coil former, which in turn means that it's almost certainly made from non-conductive Kapton (polyimide film) rather than the more usual, and conductive, aluminium. A Kapton fomer, while able to withstand pretty high temperatures, dissipates heat very poorly.

I suspect that the success came from the NS10's only really unusual feature: its iconic white bass/mid driver cone. The cone wasn't just unusual because it was white, of course, but thanks to the way it was manufactured. The vast majority of paper-based speaker cones are pressed from pulp using a mould — partly because moulding gives the designer the ability to specify a curved cone-profile, to enable a degree of tuning of the driver's frequency response and resonant behaviour. A cone with a curved profile will generally become less rigid towards its outer edge, so as frequency increases its effective radiating area and output level reduces. Designers often use this technique to delay the onset of directionality in bass/mid drivers, so allowing a higher crossover frequency than would otherwise be possible

The NS10's bass/mid cone was not pressed but 'curled-up' from flat paper sheet and then glued (look closely at the picture and you can see the join). The cone is straight-sided as a result, and the curl-and-join technique had two consequences for the performance of the NS10 bass/mid driver. First, the straight-sided form generally results in a driver with a rising frequency response, and second, while straight sides maximise rigidity, which would normally result in a cone with a strong 'bell-mode' resonance, the glued join acts as a damper (imagine a bell with a glued sawcut down the side: it won't ring much).

The characteristic rising response of a straight-sided cone is clearly apparent in Figure 4, which illustrates the NS10's frequency response measured at one metre on an axis halfway between the bass/mid unit and tweeter. Figure 4 is correctly calibrated so the NS10's sensitivity for a 2.83V (nominally 1W into 8Ω) input can be read from the vertical axis — somewhere between 87dB and 92dB. The NS10's relatively restricted low-frequency bandwidth, and the low-frequency roll-off slope of 12dB per octave, can also be seen. The 15kHz 'suck-out' in the response is most likely caused by diffraction from the tweeter's wire grille and, as it makes only a fleeting appearance in the waterfall plot is probably of little significance (it fades away in off-axis measurements too, which suggests its root cause is one of geometric symmetry).

Love 'Em Or Hate 'Em? This selection of opinions that I've pillaged from the SOS Forum (www.soundonsound.com/forum) gives you an impression of the strength of feeling both for and against the Yamaha NS10 — and it is very rare to find anyone's comments keeping to the middle ground! "I don't find the NS10s fatiguing to listen to at all, quite the opposite. The more I use them the more I love them!" "They're brutally unflattering to mixes, but that's their job. But never, ever use them as a sole pair of monitors. Just a cross check." "...their forte is to exaggerate low-mid ugliness in your mix. If you monitor on NS10s and your low-mids sound clean, then they are." "NS10s were bloody brilliant, I can't believe Yamaha stopped making them." "I keep NS10s in the studio, because it gives bands and producers a warm feeling. Ten minutes into the session I switch them off and not once has anyone questioned it. I track and mix on better monitors and get better results." "The NS10 phenomenon may have more to do with the 'Emperor's New Clothes'. In my opinion they sound nasty and I don't feel that I can trust them." "Nobody in their right minds likes the sound of the NS10s for enjoyable listening!!! They do not do that very well!!!" "The old cliché is that if it sounds good on NS10s then it'll sound good on anything. I think it's precisely because they sound so bad that they are used so widely." "NS10s are totally incapable of reproducing a double bass or the bottom octaves of a grand piano with any sort of accuracy, and have a harsh high-end that can really numb your ears after a while." "I've never really got on with them and can gladly live without them in the studio. However, I've seen experienced visiting engineers produce good mixes on them and I've seen inexperienced people produce terrible bass-heaving mixes on them." "They may sound horrible but they do highlight problems with your mixing." "I totally hated the NS10s initially and wondered why they were industry standard, until I checked back some mixes on a pair. All the problems instantly jumped out." "They really are somewhat unique in their ability to let you hear the mids in a relatively uncoloured way, and I can tell you that they have improved my mixes greatly, and I'm able to get a mix to translate better in a much shorter period of time, especially with busy mixes." "Run out and buy a pair of NS10s... like the sound or not, that is not the point."

Why have I included a frequency-response curve here? I mentioned earlier that the frequency-response curves in a sales brochure are typically meaningless in terms of providing information that's useful to an end user. Actually, though, I'd go further than that, and suggest that in many respects making any judgment about the worth or likely value of a monitor by examining its frequency-response curve is not far short of pointless. I often read opinions on the SOS Forum arguing that to be of any value monitors require a 'flat frequency response', but numerous recordings made during what many would consider the golden age for musical sound quality (the '60s and '70s) were monitored on speakers that were all over the place in terms of frequency response — and I don't know why recording engineers seem to believe so strongly that a monitor should be anechoically 'flat' when so much end-product evidence suggests that this isn't particularly important.

A frequency-response curve appears to tell you if a monitor is going to reproduce different elements of the audible bandwidth at the same level, which intuitively seems vitally important. But a simple frequency-response curve tells you no such thing, and the psychoacoustics of human hearing is more about the time domain than the frequency domain.

When we measure a monitor's frequency response in an anechoic chamber, the microphone 'hears' the output at just one position in space. However, when we listen to a monitor in a room we hear a combination of the monitor and its interaction with the room boundaries (and big items of furniture). Reflections from the walls, floor and ceiling are integrated over time by the brain, to create a composite tonal balance. When I design a typical 'box speaker', I've learned through experience (and reading Dr Floyd Toole's work on the subject) that a frequency-response curve taken at between 20 and 30 degrees horizontally off-axis is likely to be most representative of an appropriate target tonal balance. For a speaker tonally voiced for domestic free-space mounting (not up against a wall or sat on a meter bridge), this off-axis anechoic curve should be reasonably flat up to around 2kHz and then fall slowly at around 3dB per octave for the rest of the range. This is a long, long way from 'flat', but it will sound neutrally balanced in a typical domestic room at average playback levels.

And speaking of 'average playback levels', in addition to the room effects that influence our perception of tonal balance, listening level plays a significant part too. The brain's perception of tonal balance is level dependent. At low levels we're far more sensitive to mid-range than bass and treble — hence the 'loudness' button beloved of '80s Japanese hi-fi amps. So, again, expecting a frequency-response curve measured at one position in space and at a single arbitrary level to reveal the full story on the worth of a monitor is to simplify reality to the point of nonsense.

Moving swiftly on to the second assertion I made a couple of paragraphs ago, we humans have evolved to respond more to the transient than to the tonal elements of sound. Try a little experiment: find a sample of something like a clarinet and a flute, each playing the same continuous note, drop them onto two tracks in your DAW and listen to them in turn. It's very easy to tell which is which. Chop the first, say, 500ms from the front of each so that the characteristic beginnings of the notes are suppressed, and listen again. They'll sound much more similar: the brain uses the characteristic transients to differentiate the instruments, and without them it struggles. Now, go back to the un-edited samples and apply the same severe EQ to each and listen again: despite the EQ, you can still differentiate them. A similar illustration of the use the brain makes of transient rather than tonal information is that a familiar voice remains familiar in wildly different acoustic environments — environments that imprint different tonal characters on the sound. So, concentrating on the 'flatness' of frequency response is to miss a hugely important point: if a monitor handles transients accurately, its frequency response is much less important than you probably think.

Before I wrap up this epic (and promise never, ever to write about the NS10 again), there's just one more issue that probably deserves to be kicked around a little. If the NS10 is so good, why do people so often express their dislike of listening to it? I suspect that there are both practical and emotional answers to this conundrum.

First, the emotional. Thanks to its time-domain accuracy and mid-heavy balance, the NS10 is an extremely revealing speaker that takes no prisoners. In other words, if the recording is poor, the NS10 will tell you in no uncertain terms. You have to work harder to make things sound good on the NS10 not because it sounds bad but because recorded music, even today, is often a poor approximation of the real thing, and the NS10 reveals it. I found a familiar comment on the SOS Forum that reads: "If it sounds good on NS10s then it'll sound good on anything." Again, that's not because the NS10 is inherently poor, but because it is effective at revealing the fundamental compromises inherent in recorded music. If you've worked hard on NS10s at a mix and overcome those compromises, or perhaps cleverly disguised them, the mix will translate well to other systems because it is a good mix. Put another way, the NS10 better enables you to get to the nub of a mix by more accurately reproducing its fundamental time-domain information — and it is this which can make the task of mixing seem more challenging.

And the practical? Well, it's certainly true that the NS10s have a mid-heavy balance and little bass extension. This is especially so if they are not mounted close to a suitable boundary — such as a big desk or a rear wall — to provide low mid-range reinforcement. They're also just as revealing of any shortcomings in the monitoring chain as they are of the mix, and they don't take very kindly to being driven loud. While Newells and Holland showed they have very low levels of distortion, they do suffer from thermal compression, which will not only cause wide-band dynamic attenuation in response to high levels of drive, but will upset the characteristics of the crossover filters as the voice-coil resistance of the drivers increases. As temperature rises, the bass/mid low-pass filter frequency will increase significantly (and the tweeter high-pass filter frequency will reduce), and begin to give prominence to the resonances at the top end of the bass/mid driver's response. When NS10s are driven too hard by a poor amplifier, fed by a sub-standard monitor output, and mounted without any boundary reinforcement, you might well find that they sound horrible to the point of being unusable.

Where does all that leave us? Why do we still use that old monitor? We use it because it does a job, even if it sometimes doesn't sound very nice while doing the job, partly because, if it's installed or driven inappropriately, it will reveal such shortcomings without mercy, and partly because it sometimes reproduces elements of our work that we don't particularly want to hear. But we also use it because nearfield monitor manufacturers seem to have suffered a 20-year blind spot and failed to identify why the NS10 works and remains so popular. Go figure.

Thanks to: FX Rentals for the loan of a pair of NS10s; Acoustic Energy for permission to use their NS10 data; Phil Knight for doing the original measuring; the SOS Forum members whose words I've borrowed; and to Chris Binns for advice that (hopefully) ensured I've not written anything really dumb.