Product: All audio products, including sources, amplifiers, loudspeakers and your ear-brain interface
Price: your enjoyment of music
Mains spur & leads: possibly but unlikely
Support/Feet: oh yes, even these
Hypothesiser: Mark Wheeler - TNT UK
Typed: Summer 2008
I was first introduced to the idea of PRaT in about '74 in a long established hifi shop where I'd hang out after school or on a Saturday playing with new stock, presumably tolerated by the proprietor as a future customer or future employee. Here I met a representative of a company I'd only vaguely noticed 'cos they'd had a mention in a SME (Plinth System 2000) advert in HiFi News. The company was Linn Products and the Scottish bloke (possibly Michael Something? can any Linnies elucidate?) was in the process of convincing the proprietor of this shop that he should add the Linn Sondek LP12 to the shop's roster of turntables, that already included similar looking subchassis examples like Thorens and AR. This is the same Sottish bloke who first introduced 2 callow schoolboys to the concept of 'PRaT'.
I don't recall if the actual term 'PRaT' was used on this occasion, but its elements were described and emphasised. Those elements were among many in the Pantheon of musicality Gods worshipped that day, in direct contradiction to the pseudoscientific objectivity of the hi-fi comics of the day.
As an English teenage boy at an all male school, I was no stranger to b*llsh*t:. Let's face it, at my school everyone claimed to have seen top bands live, claimed to have tried drugs and claimed to have enjoyed sexual encounters at the nearby girls' skool, and these activities were obviously the products of fertile imaginations rather than fertile loins. Hence, the hyperbole expounded in this Scotsman's refreshingly original sales-line was equally obvious.
However, some of what he said also fitted our experience of audio experiments better than the pseudoscience of 70s comics HiFi News and HiFi Sound. We 15 year-old audio-neophytes did recognise some of the arguments put forward as being grounded in the familiar skool physics curriculum, like simple Newtonian mechanics etc. However, we also recognised some of the early LP12 sales pitch as being way out there and I do recall a moment when my friend Roy & I were deliberately out-bulling the rep to encourage him to excel himself with his claims for what we thought looked like a one-speed Thorens TD150. This poor chap's claims about coefficients of expansion of aluminium, steel and rubber being considered to ensure speed stability at all operating temperatures are sadly the reason I can still remember the event.
On the other hand, we were seduced by the idea that we were in at the cutting edge, the start of something new that the magazines did not yet acknowledge. These ideas may become established wisdom, a metanarrative for which we could claim early insight. As youngsters we were sufficiently encouraged by the attention paid to our opinions by an audio professional, and sufficiently open-minded, to share with him our own experiments (unheard of in the UK audio press then) of cable experiments (with 6mm^2 mains cable and RF co-ax cable in both speaker and interconnect locations) and in return, he suggested to us, tricks for improving our own turntables (very-well-used Thorens TD150 and Transcriptors Saturn respectively, my Saturn having been bought for £15 not working) that we tried and heard improvements from this chap's suggestions. Ideas like removing the arm grommets from our SME3009/II-imp and early Hadcock Unipoise.
We took with us that man's suggestions to try felt turntable mats after Linn found that that the flat felt mat (offered for "tag cueing" in Linn's early brochures) outperformed the original conventional ribbed rubber mat. Thus my friend Roy tried felt mats and plain rubber mats against the standard lumpy rubber mat of the Thorens TD150. I had a perspex disc cut to cover the 5 rubber nipples of my Transcriptor Saturn platter. I tried this with a felt mat, no mat, a standard dimpled turntable mat and a thin sheet of plain rubber. In all cases we could hear differences; which was heresy in those days in Britain. In those days in Britain folk were burnt at the stake of a soldering-iron tip for suggesting anything mattered in turntables except rumble and wow & flutter.
So musicality, Linn and the PRaT argument had some credence for me and my circle of music & audio freaks in that adolescent time of fanatical enthusiasm, but what did it mean?
During the years 1974-1978 I heard the term PRaT defined in a variety of ways by various shop
sales-people, manufacturer distribution representatives or hifi journalists. In the earliest days only the
folk involved, one way or another, with Linn or Naim (or latterly, Pink Triangle or Exposure) mentioned
the elusive and as yet unmeasurable parameters involved in PRaT, which was obviously an acronym...
so what does the 'P' stand for?
Well now it is universally accepted to represent
P for PACE,
but back in the day it was also described as
P for PITCH.
Linn made much of the ability of their turntable (then their sole audio product, although their reps described an experimental loudspeaker that turned out to be the 'brik) to maintain accurate pitch compared to their competition. One of their key claims to superiority over their many rivals was the capacity of a Linn LP12 to maintain better dynamic pitch stability, compared to other turntables of that period. They argued that during heavily modulated passages, the demand for more stylus deflection (to generate more electrical in the stylus/coil motor assembly of the cartridge) created more drag against the turntable platter rotation. So PITCH was a big deal at that time among that fraternity who would later be termed 'flat earth'.
We were all VERY aware of the limitations of hifi systems to portray pitch accurately; this was the period of audiocassette dominance in hifi shops. Even if I have never owned one outside of a car I have heard otherwise potentially capable audio systems in hifi shops demonstrated with the horrible output of a cassette player. No cassette-recorder less than a Nakamichi TriTracer700 or TT1000 ever managed pitch accuracy tolerable to anyone, particularly anyone who regularly heard a live piano, speshully the old Steinway evry morning in skool assembly. So while Pitch was a good starting point for the basics of audio reproduction it has now become universally usurped by Pace.
Now that Pace is the commonly used 'P' of the PRaT acronym, what does it mean? It refers to the speed at which a piece is played. It is the first piece of information we usually have after the title of a piece of music on a sheet of music. In the past, when sheet music outsold recordings and were the sales on which the music charts were based (and downloads are the most recent sales paradigm shift), the title might be followed by a descriptive clue to the rhythm and pace, for example "slow foxtrot" to indicate to players the speed of the dance and what dance steps the audience might hope to fit to the music. Speed is described first as "slow" and Rhythm next as "Foxtrot". On the example below, the mark showing crotchet=120 (quarter-note=120 in some cultures) indicates the engine speed of this piece. 120 refers to one-hundred and twenty beats-per-minute or 120bpm. This is a metronome marking so that players can set their metronome to that speed for practice. There are 4 crotchets (quarter-notes) in each bar in this time signature so that equates to 30 bars every minute; the bars are the vertical divisions across the stave.
The 'R' in PRaT seems to be the only umambiguous letter in this acronym. It is always described as
'Rhythm' so that's simple enough then, isn't it?
Sadly for the long suffering audiophile, it isn't.
Rhythm is what moves music along, it is the relationship with time that defines music as fundamentally different from other art forms like painting and sculpture. Rhythm is not musical speed, it is not the rate of progress but the relationship of successive notes and where the beat is emphasised.
The except from a transcription of the double-bass part from Ben E King's classic Stand By Me (which must be familiar to almost everyone in the Northern Hemisphere - hence its use here) clearly shows this. Unless otherwise instructed, the first note in any 4/4 time bar is the emphasised beat, the down-beat (the conductor will often bring the baton down for this beat), the kick-drum is often on this beat in rock tunes. In Stand by Me the dotted crotchet that opens each bar (the keynote A in the first bar) is emphasised. Because it is one-&-a-half beats long (that's what the dot after the note does, it adds 50% to whatever value the written note has) the following note has to be written a half-beat long (quaver or eighth-note), then tied to a crotchet to make it sound equal length to that opening note. This second sound in the bar does not start on the beat which is why it almost sounds like it hesitates when it is played. The rhythm is borrowed from the Cuban Rumba. The final beat in each bar is divided into two quavers (eighth-notes) to provide the spring back to the emphasised down-beat of the next bar. Ask many non-players to sing the bass riff of Stand by Me and they will start on the E that is the first quaver of the final beat of the first bar, but if the downbeat moves there all the danceable Cuban vitality falls away.
Some people are as impervious to rhythm as some people are to pitch (the latter are therefore referred to as 'tone deaf'). Rhythm awareness can be learned, which is why music teachers encourage pupils to clap in time to music. When I suffered a severe brain injury in 1998 I completely lost my awareness of time and my sense of rhythm; I couldn't tell a cd player from my Linn Sondek except by its tonality. At the time I was suffering from loss of income due to not being able to work and was forced to sell many of my possessions including my Linn that had lost its key feature to my ears. It was an interesting insight into the experience of others for whom rhythm is unimportant and demonstrated to me how timbre, tonal accuracy and low colouration become far more significant under such circumstances. The experience of listening to familiar music without a well developed sense of rhythm; I found that different recordings became my favourite daily plays. I practiced bass guitar to try to regain some of my sense of rhythm and timing as well as my left-right coordination. I am glad to say that I succeeded in recovering my sense of rhythm & time even if I didn't succeed in learning to play bass, but now I demand timbre, tonal accuracy and low colouration as well as PRaT. Tough. The search for the turntable that does both is still on.
The 'T' in PRaT was once defined to me as "Tune" by one dealer who would now be called a 'flat earther' who seemed to sell mainly Naim and Exposure amplifiers and Linn and Rega turntables. That dealer droned on about "tune following", the ability to separate out one instrument from an ensemble and follow its tune alone. He attributed this to British gear in his shop being better than expensive American imports at accurately resolving the components of tune, which seems to be more a matter of flag waving than listening. Naim dealers made much in their early days of this 'tune following' lark, that capacity of a system to allow the listener to pick out the tune being played by any one instrument in an ensemble and follow its tune alone.
However, nearly everyone else now uses the 'T' in PRaT to stand for 'Timing'. Timing is not the same thing as Rhythm or Pace, but it is related. Timing is the accuracy of reproduction of a wavefront comprising many frequencies. Hence a strike of stick on ride cymbal simultaneous with the other stick on the floor-tom should arrive at the hifi listener's ears in the same relationship as they would had the listener been sitting in front of the drum kit rather than their loudspeakers. The most sinful adulterers of timing tend to be multi-way loudspeakers. One glance at the phase graph of a single drive unit would suggest this is already a problem for 1 driver, but combine 2 drive units with a crossover whose filter is derived by phase shift and we realise how tough a task it really is to make music in the home.
At the beginning of any musical score we can see marks to define the Pace and the Rhythm. These parameters of performance are important enough to be the first pieces of data any player is offered by the composer or arranger, after the title and the composers name!
Only after a sense of the Pace (crotchet=120 for example) and Rhythm (4 crotchets - or quarter notes - to each bar, known as march or common time because it is easy to walk to this rhythm with arms swinging in time) have been set up in the performer's mind do they learn the key signature and then the mode that together might imply the mood of the piece. The example shown below is chosen as a familiar one from school assemblies, where I first learned what music really sounded like, Parry's setting of Blake's call to revolutions, perhaps turntable revolutions. Timing can be upset by sources (especially jitter in cd and phase shift in cartridges), amplifiers (especially at the bandwidth extremes) but mostly in speakers. I suspect the superior timing performance of many panel loudspeakers is one of their big attractions. Timing particularly affects the capacity of a system to create a convincing illusion of soundstage from just two speakers. The term Stereo actually translates as 'solid' and the solidity of a stereo image depends on accurate timing from microphone to speaker. How many listeners have noticed that many systems reproduce cymbals in nearer than the drums of the same kit? How long are the drummer's arms? This is usually caused by crossover timing errors between midrange (or mid-bass) unit and tweeter, on top of their individual & inherent errors.
PRaT are the most basic building blocks of musical performance. In domestic audio they are essential for appreciation and enjoyment of music. If your home audio is purely for home cinema it is probably not important to you, but TNT-audio.com is a magazine dedicated to domestic reproduction of music.
Sheet music prioritises these elements for good reason. Without them you've got nothing musically.
© Copyright 2008 Mark Wheeler - www.tnt-audio.com