What exactly is PRaT???

OP,

Just because you don’t get it now, does not mean you will not over time. It took me decades. Then suddenly the lightbulb popped on.

I was in Dallas about twenty years ago. I went to this dealer / home… hobby gone wild. The entire house was completely crammed with high end gear. In the downstairs listening room he had a set of Sound Lab Millennium-1 Electrostatic Loudspeakers. They were powered by a Viva tube amp… 4wpc (?). He said, I know this is ridiculous… but listen to this. It was all midrange and some flabby bass. It brought tears to my eyes… immediately, I have never heard anything so beautiful, emotionally evocative in my life. I was completely shaken and emotionally drained when I left. I really didn’t know what to make of it.

I couldn’t consider buying into that system… nor was he trying necessarily to sell that sound… he was overwhelmed, as was I by the emotional connection. There was no detail… no treble… the bass was absurd. I tucked the experience into my memory.

It wasn’t for another ten years when I had this epiphany that my main system had become sterile and lifeless (a true “Reference” system) that it all came together. Different experiences with certain systems that had varying degrees of PRaT… I got it! One of those lightning bolt experiences. After that, I could detect it nearly instantly and its degree. For me it was the most difficult parameter to “get”, now one of the absolutely most important.

Keep at it. Starting this thread shows your curiosity. There is a long Stereophile article in the 90’s, lots of technical descriptions… did not do a bit of good for me. But trying to sense what that thing is that is making you want to tap your foot is the thing you want to pursue. Not by narrowly focusing, but by the gestalt of the sound.

Good luck.

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.

The type of music you're listening to matters in term of whether PRaT is relevant. I've listened to turntables that sound soft and somewhat indistinct rhythmically (typically high mass turntables), but their reproduction of the weight of orchestral music was stunningly good. For that music, I think pace and rhythm didn't matter much. On the other hand, jazz typically seems to benefit from equipment with some ability to reproduce pace and timing.

@yoyoyaya The Naim version of PRaT is easy to understand because it is focused on emphasizing the leading edge of notes while being harmonically lean. I've since found that the next level to PRaT involves music reproduction that has pace but is also harmonically full. Pass amplifiers fit that bill. I think @ghdprentice also mentioned that Audio Research is even better than Pass amplifiers at conveying both pace and tonal richness.

My short definition for PRaT: You can clearly hear how different voices and instruments are interacting together in music. This is particularly evident in jazz music as a vast generality.

FWIW, electrostatic speakers have PRaT in spades because of extremely lightweight of their moving elements.