What exactly is PRaT???

Most audiophiles seem to live in the frequency domain.  Mid-range this, bass that, treble something else.  But music exists in the time domain, as a waveform.  Our ears have evolved (as our primary danger sensors) to be incredibly sensitive to the arrival time of sound waves. Our pinnae are shaped to give us a 3D aural image giving the height and orientation of the source sound, even if it behind our heads.

There is a Chesky recoding of a repeated chirrup which on a good 2-channel system appears to rise vertically from one speaker before moving in an arc across the ceiling and descending to the other speaker.

I cannot think of much in nature that works in the frequency domain, apart from resonances and ears.  The tuned hairs in our snail-shaped cochlea fire nerves when they resonate.  The sequence in which they fire feeds our neural network which processes in the time domain.

Our systems on the other hand typically take the waveform and decompose it into frequency bands before feeding each band to a dynamic driver - tweeter, mid-range, bass etc..  We then desperately try to time-align these drivers to get back the original waveform, but physics gets in the way.  Unless the drivers act as a point source (not a line source) reflections from walls, floors and ceiling will not be time aligned at the listening position.

Time domain waveforms can be converted to frequency domain using Fourier transforms, and vice versa.  Start with a square wave, which contains all higher harmonics of the base frequency, and produce the frequency spectrum using a Fourier transform.  Take that spectrum and Fourier transform it, hoping to get the original square wave back.  Well, you get a square wave but it has a pronounced leading spike, mathematically and practically.

Linn was all about trying to avoid spurious resonances in the table / arm / cartridge source, with the subjective outcome that listeners were more likely to tap in time with the music.

The most coherent loudspeaker was the Quad electrostatic ESL-63, designed in 1963 to emulate a point source of sound about a foot behind the flat panel.  It took a further 18 years of development before the ESL-63 was offered to the market. The final test of each production speaker was to compare it to a reference speaker with a microphone exactly equidistant.  A square wave was played to the reference speaker and the same wave with opposite polarity went to the speaker under test.  If the microphone gave no output, the speaker passed.  These speakers and their descendants have specifications that read like amplifier specifications.  Peter Walker said of them "if you don't like what comes out, pay more attention to what goes in".

Try some.  If you don't get PRaT, you probably never will!

Brits and Aussies would say that anyone who doesn't get PRaT must be a prat!

Of course, the actual music does not really slow down, nor change in pitch, nor timing (unless stylus drag actually slows a turntable down!)..

But our perception of when the beat starts is affected by the arrival pattern in time of the first transients of a note.  If the leading edge is sharp, not smeared in time, your brain will snap into recognising the start of something special.  I am suggesting microseconds here!  Get this right, and you'll likely find your foot tapping ... 

... what smears out transients in time is poor driver alignment, cancellation between drivers around cross-over points, and interfering reflections from room surfaces.  These are all reduced if your speakers behave like point sources.

@yoyoyaya "... The irony is that the ... LP12 of the mid eighties had dreadful micro timing stability due to the movement of the subchassis/armboard relative to the platter. Linn’s mantra was pitch and rhythm."

I lived in the UK before Linn, when speakers were regarded as the dominant factor in audio quality. Ivor’s argument was that distortions introduced at the start of the audio reproduction chain were also important.

His starting point was that any sloppiness between the cartridge and the record would be amplified by the cartridge. His engineering solution was to couple the cartridge to the platter as tightly as possible in the direction of the arm tube. The bearings that allowed the arm to track the groove, and the platter to rotate, had to have minimum play.

If different materials were used, which expanded at different rates, changes in temperature would open up gaps. So every mechanical connecting component was made of the same grade of stainless steel. The soft floating suspension allowed the entire platter, sub-chassis, arm, cartridge system to move as one, keeping the relationship between the cartridge and the record consistent.

The most obvious difference from competitive players was the response to transients, especially scratches in the record itself. Others exhibited lengthy mechanical ringing whereas scratches were much less obtrusive with Linn. Ivor the showman illustrated this through his casual handling of records in demonstrations, often throwing them around. Elsewhere I have tried to emphasize the importance of transients for our perception of PRaT.

My recollection is that specifications were notably absent from discussions of Naim products!  The same went for the specifications of Rolls Royce car engines, where the output was described as "sufficient".

I've posted that in my opinion PRaT relates to the time domain, not the frequency domain that we usually talk about.  To the person that never listens to symphonic music, I would ask if that extends to films which use such music to underscore the drama?

Classical music almost always does have a beat, it is just not as in-your-face as some other genres and can be very complex and rewarding if you get it.  A big orchestra faces a big timing problem though - the visual clues from the conductor travel at the speed of light (near instantaneous) but sound is much slower.  It takes almost 1/10th of a second to travel 30-meters.  The Sydney Opera House Concert Hall stage is about 19-meters wide and is small for a major concert venue, because of the concrete shell surrounding it, although it is comparable with the Berliner Phiharmoniker  I pity the organist sitting high towards the roof looking in his rear-vision mirror down at the conductor in the distance!

Nevertheless conductors like John Wilson can make a good orchestra rock ...

Ah, Chris Rea.  First heard "The Road to Hell" in a clapped-out army truck descending into the Great Rift Valley in Kenya, with truck wrecks littering the landscape.

Later I was MC for a conference and had a copy with me.  Played it as attendees drifted in, the morning after the big dinner.  A colleague rushed up: "the sound system is broken".  All he could hear was raindrops and windscreen wipers.  Then the first crescendo hit.

Chris really cares about the quality of sound, and all his recordings are studio-made.  I heard him live in Melbourne and he was absolutely mortified that he could not get the exact sound he wanted.  He never toured the USA

@dogeardaudio

As a teenager I was air-conducting (might even have been to Pierre Monteux’s Elgar) when I accidentally hooked a vase on the mantlepiece and hurled it across the room. Mind you, Georg Solti (the Screaming Skull) got so carried away, he stabbed himself with his own baton ...