The Secret Life of the Signal

Some people actually think of stereo imaging as a “parlour trick” that is very low on the list of desirable attributes that an audio system should have. They ‘rationalise’ this by saying that in the majority of recordings, any stereo image is an artificial illusion, created by the recording engineer either deliberately or by accident; it does not accurately represent the live event – because there may not even have been a single live event. So how can it matter if it is reproduced by the playback system or not? Perhaps it is even best to suppress it: muddle it up with some inter-channel crosstalk like vinyl does, or even listen in mono.

At the top of the list of desirable attributes for a hi-fi system, most audiophiles would put “timbre”, “tonality”, low distortion, clean reproduction at high volumes, dynamics, deep bass. All of these qualities can be experienced with a mono signal and a single speaker – in fact in the Harman Corporation’s training for listening, monophonic reproduction is recommended for when performing listening tests.

Because their effects are not so obvious in mono, phase and timing are regarded by many as supremely unimportant. I quote one industry luminary:

Time domain does not enter my vocabulary…

Sound is colour?

We know that our eyes respond to detail and colour in different ways. In the early days of colour TV (analogue) it was found that the signal could be broadcast within practical bandwidths because the colour (chrominance) information could be be sent at lower resolution than the detail (luminance).

There is, perhaps, a parallel in hearing, too: that humans have separate mechanisms for responding to sound in the frequency and time domains. But the conventional hi-fi industry’s implicit view is that we only hear in the frequency domain: all the main measurements are in the frequency domain, and steady state signals are regarded as equivalent to real music. A speaker’s overall response to phase and timing is ignored almost totally or, at best, regarded as a secondary issue.

I think that this is symptomatic of an idea that pervades hi-fi: that the signal is ‘colour’. Sure, it varies as the music is playing, but the exact nature of that variation is almost incidental; secondary in comparison to the importance of the accurate reproduction of colour, and that in testing, all that matters is whether a uniform colour is accurately reproduced.

There has, nevertheless, been some belated lip service paid to the importance of timing, with the hype around MQA (still usually being played over speakers with huge timing errors!), and a number of passive speakers with sloping front baffles for time alignment. Taken to its logical conclusion, we have these:


Their creator says, though:

It’s nice if you have phase coherence, but it is not necessary

So they still fall short of the “straight wire with gain” ideal. It still says that the signal is something we can take liberties with, not aspiring to absolute accuracy in the detail as long as we get a good neutral white and a deep black, and all uniform (‘steady state’) colours reproduced with the correct shading. It says that we understand the signal and it is trivial. Time alignment by moving the drivers backwards and forwards is an easy gimmick, so we can go that far, however.

Another Dimension

I think that with DSP-corrected drivers and crossovers, we are beginning to find that there is another dimension to the common or garden stereo signal; one that has been viewed as a secondary effect until now. Whether created accidentally or not, the majority of recordings contain ‘imaging’ that is so clear that it gives us access to the music in a way we were not aware of. It allows us to ‘walk around’ the scene in which the recording was made. If it is a composite, multitrack recording, it may not be a real scene that ever existed, but the individual elements are each small scenes in themselves, and they become clearly delineated. It is ‘compelling’.

I can do no better than quote a brand new review of the Kii Three written by a professional audio engineer, that echoes something I was saying a couple of weeks ago: imaging is not just a ‘trick’, but improves the separation of the acoustic sources in a way that goes beyond the traditional attributes of low distortion & colouration.

I think he also echoes something I said about believable imaging giving the speaker a ‘free pass’ in terms of measurements. As in my DIY post, he says that the speaker sounds so transparent and believable that there is no point in going any further in criticising the sound. A suggestion, perhaps, that conventional ‘in-room’ measurements and ‘room correction’, are shown up as the red herrings they are if a system sets out to be genuinely neutral by design, at source.

Firstly, the traditional kind of subjective analysis we speaker reviewers default to — describing the tonal balance and making a judgement about the competence of a monitor’s basic frequency response — is somehow rendered a little pointless with the Kii Three. It sounds so transparent and creates such fundamentally believable audio that thoughts of ‘dull’ or ‘bright’ seem somehow superfluous.

… it is dominated by such a sense of realistic clarity, imaging, dynamics and detail that you begin almost to forget that there’s a speaker between you and the music.

…I’ve never heard anything anywhere near as adept at separating the elements of a mix and revealing exactly what is going on. I found myself endlessly fascinated, in particular, by the way the Kii Three presents vocals within a mix and ruthlessly reveals how good the performance was and how the voice was subsequently treated (or mistreated). Performance idiosyncrasies, microphone character, room sound, compression effects, reverb and delay techniques and pitch-correction artifacts that I’d never noticed before became blindingly obvious — it was addictive.

…One of the joys of auditioning new audio gear, especially speakers, is that I occasionally get to rediscover CDs or mixes that I thought I knew intimately. I can honestly say that with the Kii Three, every time I played some old familiar material I heard something significant in the way it performs…

…Low-latency mode …switch[es] off the system phase correction. It makes for a fascinating listening experience. …the change of phase response is clearly audible. The monitor loses a little of its imaging ability and overall precision in low-latency mode so that things sound a little less ‘together’.

“The Kii Three is one of the finest speakers I’ve ever heard and undoubtedly the best I’ve ever had the privilege and pleasure of using in my own home.”


Kii Three Review

Just saw this review of the Kii Threes by mastering engineer Bob Macc. He seems rather pleased with them:

…everything is just tight, accurate, and not smeared in time or pressed-sounding. Kick drums on these speakers are ridiculous in their tightness and accuracy. Acoustic and electric basses are the very definition of the word ‘articulate’. The time-coherency extends, of course, across the whole spectrum. Transients are, well, transients.

The imaging on these speakers is also absolutely unbelievable, in all dimensions. The front to back depth is unreal; room information is conveyed incredibly well. You’re there. In fact it might be the depth that astounded me more than anything else. The stereo image is absolutely enormous, involving, and everything sounds real. Drums pop out like drums do (or don’t, if they don’t). The main acoustic guitar in Holland and Habichuela’s ‘Hands’ was unbelievably real. The sound is huge, and absolutely pristine in all regards.

They are incredibly revealing – I heard things in tracks I know extremely well that I have never heard before. I heard micro-movement inside tracks from compression/sidechaining that I’ve never heard before. I heard mistakes in work by very famous engineers in tracks I’ve listened to a million times. I heard mistakes in my own work (tiny ones, I promise!) that I absolutely would not have allowed to pass had I heard them previously. That kind of says it all.

The whole time though, you’re thinking; ‘how do those tiny little speakers make all that sound?!’. With eyes closed and a good-sounding track playing, the room is absolutely full of sound. When you open your eyes, it’s almost as if the illusion is destroyed – there’s simply no way those little things can produce all that sound. But they do, and they do it easily and effortlessly.

I really am going to have to get in touch with the chap at Purité Audio (who posted this review on HiFi Wigwam) and see if he’ll let me have a listen…

Light entertainment

Here’s a little controversy from the archives of Stereophile magazine.

Stereophile has an interesting policy whereby an equipment reviewer writes up his subjective experience of testing a device, and only then is it measured for distortion, frequency response and so on. It seems that the magazine has the integrity to publish the two reports whatever the outcome.

Have you ever seen a more polarised review than this one from 2005?

The reviewer says:

The CyberLights represent one of the greatest technological breakthroughs in high-performance audio that I have experienced in my audiophile lifetime….

…for the first time in your life you’ll hear no cables whatsoever. When you switch back to any brand of metal conductors, you’ll know you’re hearing cables—because what’s transmitted via CyberLight will be the most gloriously open, coherent, delicate, extended, transparent, pristine sound you’ve ever heard from your system…

The measurements person says:

If this review were of a conventional product, I would dismiss it as being broken. …I really don’t see how the CyberLight P2A and Wave cables can be recommended. I am puzzled that Harmonic Technology, which makes good-sounding, reasonably priced conventional cables, would risk their reputation with something as technically flawed as the CyberLight.

You’ll have to read the full review for yourself, because the contrast between the two opinions is almost comical. The measurements are quite something to behold.

You see, I sometimes worry that perhaps I just don’t ‘get’ this hi-fi business. £80,000 analogue systems don’t sound anything special to me. Vinyl doesn’t sound as good as digital to my ears but everyone else says it is much better. Designing and building my own system was really quite straightforward, yet the internet is full of intense discussion about how difficult it is; people spend their entire lives building their own speakers and are never happy with them yet it’s almost three years in and counting, and I haven’t felt motivated to modify mine yet. Are the experts hearing something I am not? Perhaps this review sheds some light on the answer.

Analogue enthusiasts often claim that the signal-modifying effects of whatever product they are listening to actually improve the sound. The usual line is that the indefinable magic of valves and vinyl is down to what those devices add: they are serendipitously restoring something that is supposedly missing from the recording. ‘Poor’ measurements are simply an indication of an harmonious combination of factors that enable the leap from clinical, neutral signal to real music. There is no argument possible against this assertion.

However, in the above review, the writer cannot make that claim. Clearly he has confused high levels of distortion and noise plus extreme frequency response variations as an absence of colouration. For him, replacing metal cables with “light” was all about removing “grunge” and other “well-known problems”. Because of his extreme analogo-philia, I don’t think he actually knew what ‘neutral’ sounded like. When he heard something that was different from anything he had heard before, he automatically assumed that it must be because cables really are the sonic quagmire he thought they were and that the product was doing what he assumed it was designed to do. For once, it actually was a “night and day” difference but his understanding of what he was hearing was 180 degrees wrong. In the scheme of things, it doesn’t really matter, but it reassures me that 99% of the ‘expert’ opinion based on listening is very dubious indeed – I do think there are people out there who would find much to like in a pair of yoghurt pots linked with string as long as they cost enough.

Stereophile, it appears, doesn’t normally measure cables when they are reviewed. I think we can guess why: there is nothing to measure. Each and every review would feature the same distortion and noise measurements at the very lowest depths of the test equipment’s range, plus a ruler-flat frequency response when using the cable in normal circumstances. It wouldn’t matter if the cable cost £1 or £10,000 – which, absurdly, they sometimes do. To arrange anything different would actually be quite difficult. It is this complete, boring neutrality that Michael Fremer and other cable mythologisers are convinced is plagued with “grunge” and other problems. The justification for the Cyberlight product, so appealing to Fremer, is that it replaces a short section of metal with light and fibre optics, and is analogue – you still connect to the input and output with those awful grungy wires. It is no different from becoming excited about the audio quality of headphones that use an analogue wireless link rather than a cable. Just as with those headphones, there is a little “background hiss” but this is a small price to pay, apparently. And just like those headphones, the signal goes through a link of dubious quality. Very dubious. At least there is a valid justification for wireless headphones, though.

If you gave me about £20 to buy a few parts, I could build you this device in an afternoon, probably. But if I did, I would try to make it work properly. I would certainly try to convince you that the whole product was unnecessary and was corrupting the signal, and that if we really had to use fibre optics we should digitise the signal and send it as pulses. I might also point out that the commercial product is a mess: various “wall warts”, $400 battery packs and “pigtails” that could, depending on what equipment you’re using, destroy your speakers.

And don’t ever unplug or plug in the power to the cables with the amplifier turned on or you’ll send a horrendous THUMP through your system.

For people who might dismiss active speakers and DSP as too complex, there are no limits to the Heath Robinson-esqueness that they can tolerate in the name of ‘analogue’.

Kii Three


Here is a review (translated from German) of the new Kii Three active DSP speaker.

…a family friendly compact speaker that scores far higher on all significant audiophile fronts than any we’ve had here at AUDIO in our thirty plus year history.

Designed in concept by Bruno Putzeys of Grimm LS1 fame and incorporating some of his highly-renowned Class D amplifiers, it accomplishes the feat of controlling the dispersion of the bass using clever DSP and multiple bass drivers. This means it is not choosy about placement in corners and near walls, and it sounds like a much larger speaker. In common with other advanced speakers, the combination of DSP, active amplification, and correct time domain behaviour produces astonishing results.

For the Three we can suffice with the shortest ever listening report. Its essence is one of superb accuracy that grabs one immediately and releases no-one from its thrall. It takes only a scant few seconds for the listener to grasp what sets this speaker apart from classical speaker and amp combinations. It sounds as pure as crystal, it’s spatially and dynamically right on the mark and its magnificent authenticity alone will make customers sign the order form well before the dealer has managed to produce the compulsory cup of coffee and line up the leaflets

It is compact, but the bass reaches down to 20 Hz through the use of EQ and, as a result, much greater power is required to drive it than a larger box. However, this is handled by the internal power amps so the user need not worry about this. For many people the size will be much more acceptable than conventional humongous boxes (like my speakers).

Basically, it looks as though the Kii Three could be the best speaker ever made (I am not exaggerating) and costs about £6500. And of course it includes DACs and amps so no external gear other than a laptop or other digital source is necessary to make a complete system. A future option will offer wi fi.

On the same magazine cover is an image of the ‘new’ Harbeth 40.2 which costs much more. As the Kii Three reviewer says:

Wild times are afoot for Kii Audio’s competitors.

Dynaudio Focus 600 XD


Another speaker in the list of digital actives that attempt to do things more-or-less right: DSP linear phase crossovers, sealed enclosures.

A magazine review of this model contains the familiar descriptions of incredible bass, clarity, dynamics and coherency that seem common to all such speakers. No negatives are mentioned. Why would anyone want to do it any other way?

Kyron Audio

kyronI saw this on the Ultimist web site. Kyron are another Australian company doing the DSP thing.

Vinyl-ophile Michael Fremer writes the following:

Kyron Audio’s Kronos system … is everything I can honestly say I hate about audio: the amplifiers are Class “D”, the system uses DEQX™ digital room correction and there’s enough processing going on here to befuddle a mainframe…

…what I heard from this system absolutely astonished me. There was nothing ‘digital’ about the presentation. Nothing. The top end was about as perfectly rendered as I’ve heard from all of these tracks as was the detail resolution…

…Instrumental textures and timbres were as accurate and realistically portrayed as I’ve ever heard them. The amount of true detail revealed in very familiar records was unprecedented. I swear I don’t usually blather like this as anyone who knows me can attest but there was no denying what I heard.

…I’ve never before heard the drum sound so realistic and life-like and I mean never. But that was just the start of what I heard from the many tracks I played. …”Can’t You Hear My Knocking” just about made me faint.

Can we detect a similarity between this description, and reviews of other DSP-based systems such as this and this and this?

On the Kyron Audio web site it tells us that the DEQX is used for phase correction of the speakers.

Rather than being just an equaliser however, the DEQX engine is able to simultaneously repair the timing of every frequency so that the group delay is repaired. The effect is not subtle and is just not possible in the analogue domain.

And of course it also performs the basic crossover filtering prior to a dedicated amp for each driver.

The price of the whole system? To you, $100,000. Again, this is one of those systems where the significance of the DSP is disguised amongst the ‘high endness’ and eye-watering price. Fundamentally, the DSP aspect is basically free, comprising some well-established algorithms that (as in my system) can be run on any bit of processing power lying around, like an old PC – though obviously it is much nicer to have a dedicated box like the DEQX. It is ironic that this transformative, low cost technology seems only ever to appear with ‘high end’ hardware. The implication is that while DSP correction is useful for fine tuning already-top notch hardware, using it on lesser hardware would be like putting lipstick on a pig. If so, I don’t agree. This technology reduces the requirements on the amps and drivers, allowing lower cost hardware to be a viable substitute for ultra-hardware. I think that DSP should be the first thing the designer turns to, rather than the last.

Meridian DSP7200

meridian dsp7200

It would be remiss not to mention the Meridian line of DSP-active speakers. I have to admit that I love the very idea of Meridian as a company (or do I mean as a concept?). I’ve only heard one pair in my life, and they didn’t impress me, but this was at some audio show and they were being played at top volume with nondescript music – I hope to be able to hear some properly at a dealers in the near future. On paper, you could get a formidable bargain buying some secondhand on eBay, even though they might be quite a few years old, and you might, therefore, expect that their technology is out of date. But of course the technology to do this has been viable for a long time, and the basic maths hasn’t changed unless you believe that you can hear the improvement of ‘apodising filters’ (I wouldn’t like to bet on it) or higher ‘res’ (ditto).

Martin Colloms reviewed the DSP7200, and his impressions tally with other people’s reviews of DSP-active speakers:

It’s unquestionably ‘active’, with the grip, near effortless dynamic range, convincing integrity and authority that is typical of the breed. The stereo image was simply excellent, in depth width and focus. There was no aural confusion here, as it sounded almost effortlessly clear, with crisp stable imaging of believable width, coupled with stable off-axis placement where obviously phase displaced content so dictates.

The bass is unusually good, as powerful at very low frequencies as the two hard working 8.5in (216mm) bass units could supply… The bass clearly sounded ‘different’, even compared with very large and extended low frequency alternatives. Something about the 7200 got closer to the truth, with tighter control, better tune playing, and an ability to differentiate confidently between percussive and sustained bass sounds. Tracks combining both at once can tend to blur into one sound, but not so with the 7200.

Overall it sounds essentially neutral, if marginally rich and comfortable, giving a slightly distant effect that caresses rather than assaults the ears, even when playing very loud.

In the review Colloms has a moment of doubt, but resolves it by changing from the Meridian CD player to a different brand using standard S/PDIF (- I’m saying nothing…). He then says:

The sound was now so special that any thoughts about colorations, response errors et al paled into insignificance. It was fascinating to hear a speaker which so well commanded one’s emotional responses that any debate over objective criticisms now seemed nonsensical and irrelevant.

…which is somewhat similar to something I said in the post about my homebrew speakers i.e. that this DSP-active malarkey is so special, that it shows up that the things passive speaker users are imagining to be wrong with their speakers are, perhaps, red herrings; their problems go much deeper!

Piraeus DSP-based speakers

piraeus speaker

Another ‘rational’ system I didn’t know about, reported on here. I have to say that the looks don’t appeal to me all that much, but it seems that other people disagree.

Are the mid and tweeter tilted backwards..? On passive speakers this is often done for time alignment of the drivers, but of course with DSP it can be done in software.

The enclosures house the DSP crossovers (phase linear and all that) and the amplifiers.

 piraeus innards

 [Pictures from the manufacturers’ web site.] 

Quadrature DSP 5 Speaker review

quadrature DSP model 5

Quadrature DSP Model 5 []

A review of an early DSP speaker system (1996) written by someone who knows what he’s talking about when it comes to the theoretical and technical side of things. It contains a very interesting nugget (highlighted) that answers a question I asked in my piece on building my speakers, and it includes some by-now-familiar accounts of the sound of DSP…

The Model 5 presents a startling, almost shocking amount of detail without having even a hint of excess treble. Moreover, it produces similarly startling stereo image quality. The Model DSP 5 simply vaults to near or at the top in these qualities. How is this possible? The answer seems to be in the phase linearity attainable by DSP.

Everyone knows that phase linearity above the midbass is of highly secondary importance as far as tone quality and tmbre are concerned.’ Tonally, moderate phase irregularities are essentially inaudible as far as timbre is concerned. But it is important to realize that the oft-quested researches on ‘Inaudibility of phase” in the higher frequency were about timbre only. When it comes to resolution and imaging the story could change. And I am becoming convinced that it does.

Not to head too far into theory, let’s just recall for a moment that localization of sound sources involves interaural timing differences down to a resolution level of one one-hundred-thousandth of a second. In this context, it seems unsurpnsing that time-correct behavior of speakers could be important for imaging…

…  All you have to do is listen. If your experience is like me you will be something like flabbergasted to hear, say. each individual member of large choruses standing before you, as it were. “Veils removed” is some nonsense cliche, and not really the right description. The effect is more of bringing a pair of binoculars into focus. Bingo—with focus achieved, there is the sharp picture. But the sharpness is not that of edginess, of the pseudo-detail of rising top end. This is clarity as clarity is in reality, natural but defined.

I’m fascinated by the various types of speaker cabinet that exist, this one being half way between the traditional monkey coffin and slim floorstander. Those razor sharp square edges, yet it sounds amazing – can edge diffraction be as detrimental as some say it is? It may be possible that the grille (not shown in the picture) provides a smoothly-shaped surround, but the veneer on the baffle suggests they’re meant to be used without grilles if desired.

What does a DSP active system sound like?

Legend Acoustics Tikandi

It looks as though the Legend Acoustics Tikandi system is pretty much an ideal speaker by my criteria (sealed enclosure, active DSP crossover & correction). The following extracts are from this review:

…DSP works so well it has ruined me for anything else…

…I’ve barely listened to my system in the many months since the Tikandi system left my room. At the next CES I attended, with a few exceptions, I could barely sit through most of the demos because I had grown so accustomed to the natural and lifelike sound of the Tikandi system. Everything sounded broken to me….

…There was a vividness and palpability to the presentation that was unlike anything you will likely hear without the benefit of DSP. The localization of not just instrumental images but also ambience cues brought not just the music to life but brought the entire event to life. A “you are there” quality would transport you to the recorded space in a remarkably seductive way…

…The phrase “instruments well placed within the sound stage” doesn’t even begin to describe what I heard. Each instrument became distinct in a whole new way. One of the advantages of DSP, and I think this has mostly to do with correcting the phase response, is things just come into focus in a way that only happens in the most expensive, most painstakingly set up systems (which includes dealing with the room acoustics)…

…The bass was exceptionally well defined with an almost luminescent quality. It was at the same time both thunderous and well controlled creating some of the best bass I’ve ever heard in my room. In fact the bass drum on this recording didn’t even sound like the same instrument I had been hearing… so many nuances were revealed that had been previously masked…