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:

wilson_wamm_master_chronosonic_final_prototype_news_oct

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.”

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Vinyl sales overtake digital

vinyl

It seems that a milestone was passed last week when UK vinyl sales hit £2.5m versus digital’s £2.1m. Vinyl has enjoyed eight straight years of growth.

It’s no skin off my nose, except where new recordings begin to be produced primarily with the vinyl release in mind. This is where dynamics are reduced, bass and treble attenuated, and stereo effects restricted while the recording is being made, rather than a special post-processed master being made for vinyl. We digital listeners are then forced to listen to the less dynamic version as well.

I just had a quick look to see if I could find an actual ‘Top Tips for Mastering Vinyl’ example for the above. The first site I looked at contained this:

Mastering for Vinyl

…For minimalist recordings, you want to try and minimize large phase differences between channels… This means that spaced omnis are really not such a good idea if you can avoid them.

If you can’t avoid them, try and put loud bass sources in the center of the soundstage, as close to the center mic as possible. Even if you are using coincident miking, this is a good idea.

In other words, once vinyl becomes a major consideration, actual recording techniques are dictated by the medium. In the example above, it is not crazy studio effects that are being limited, but the microphone placement used in minimalist recordings that you might have thought were not a problem.