What exactly is PRaT???

@audition__audio 1+

@dogearedaudio There are several aspects to stereo imaging that help define a systems performance. Imaging specificity is essentially the "focus" of the image. With the best systems and recordings each instrument and voice is sharply defined in 3 dimensional space with "blackness" (no sound) in between. In most systems the individual sound sources blend into each other. With a large number of instruments, like a symphony orchestra there is a solid wall of sound. Instruments still occupy a location, but they blend into each other whether one likes it or not.  Imaging the third dimension is not where in instrument is located in 3 dimensional space it is the sensation that an instrument or voice is not a flat object on a painting but a three dimensional object in space. This is the sensation that the singer is in the room with you. This is the hardest aspect of stereo performance to achieve. Very few systems will do this and only with a limited number of recordings. A 3D soundstage is imaging in 3 dimensional space. Some instruments are up front and others behind. In many instances this is artificial. The recording engineer is doing this with echo. It is best to evaluate this with a live recording as fewer tricks are used in their production. A good recording of a symphony orchestra should easily demonstrate that the tympany is at the back of the stage. 

Sometimes audiophiles will refer to a soundstage as being wide and will relate that their system images out beyond their speakers. You can throw an image beyond the speakers with phasing tricks, but in the absence of these the system soundstage should be defined by the distance between the speakers and the listener's distance from the speakers. Imaging beyond the speakers is due to reflections off the side walls and always represents a problem that diminishes image specificity. For a system to have the best image specificity the frequency response curve of the two channels has to be identical. This is very difficult to achieve usually due to room issues. This is not to say the frequency response of a system should be flat. To the contrary systems tuned to be flat sound bright and bass less.    

As a former musician PRaT never clicked with me in home audio until a full Krell class A system with Thiel CS3.6 cycled through here.  @soix , I can only relate my experiences playing in bands like this.   When everyone is locked in perfect synch with tempo, perfect attack and release, volume and balance, there is an undeniable completeness to the sound of the group.  No early flams, no hangover notes, no smearing of staccato passages, running musical phrasing is in lockstep to the point that every note is heard but none stand out in any way.   The band speaks with one voice.  
I have listened to recordings of myself with excellent musicians and always hear the original performance to some degree or another.  We had a few sessions that were “tic-less” or without error for those non band / drum corps folks understanding of that word.  Tic = timing error.

The combo of class A and phase coherent speakers opened my ears to the most accurate presentation of music I was intimately familiar with.  No smear of any sort.  With that system in place and only speakers rotated through, I became aware of crossover / driver anomalies that slowed the edges of notes, broke the synchronization of percussion with brass and slowed the output of ranges from treble on down.  The music was all there, shading and dynamics etc etc, but the recordings lost that lockstep timing or unison, a Slight blurring of instrumental notes that is normally undetected.  Speakers have been the bigger culprit in the change or lack of PRaT for me.  Electronics and cabling can have some deleterious effects but driver and crossover implementation tend to wave a bigger flag for me when it comes to decreasing PRaT.   For me full range speakers that marry woofer, mids and tweeters in phase and speed offer that sense of unity or unison

@soix - not knowing PRaT in audio components may be a blessing - one less thing to detract from the music

I find this interesting.  I'm with soix as I too have difficulty pinning down the understanding of PRaT in audio components.

I understand what is musical drive, but cannot put into words. I understand when orchestra timing is off, but when it focuses music beauty and drive take over.  I get the gist of @atmasphere in that increasing component sonic errors leads away from emotional engagement towards the analytical as we're wired to single out things that don't fit.  

When evaluating components, I do the usual test tracks: own familiar songs, test cd songs, acoustical instrument reproduction, etc. specifically paying attention to voices, piano, violin, bass definition, etc.  When choosing a component, I choose one that "resonates" with me (sounds great top to bottom, pulls me into the music) like Magico, MBL, YG.  Likely PRaT is a subcomponent of "resonates" that I simply haven't isolated separately

OP…. As the old line goes about jazz… Of you have to ask, you’ll never know….

To me, PRaT is a subjective (although not stupid) term.  To me, it refers to how realistic the music sounds, i.e., does it sound like you are there?  Does it give the illusion of a performance right in front of you, with depth, width and proper tone?  Since that is so dependent upon system, synergy, room size and treatment, etc., it can only be subjective.  I never refer to PRaT for that reason — I just say that my system makes me feel that I am there witnessing the performance, wide and deep soundstage, etc.  Those are terms that although they are subjective, they have some general understanding among the audiophile community.