I've actually thought a lot about this too. I play in a band so I've had some time to reconcile what I hear when we play live versus a good recording of a live performance. Obviously the quality of the recording will make a huge difference, so let's just take that as a given along with the fact that electronics and listening rooms play a huge roll in what we hear as well. I'm focusing on speakers here mainly because ultimately that's what couples the music to the space we're listening in. A couple of my observations:
- Live, unamplified instruments emit sound in all directions -- front, back, up, down, etc. -- but not necessarily at the same volume level in all directions. These sounds continue to expand into space and mix together into the "ether" of the room in a complex fashion along with reflecting off the room boundaries and the things in it.
- The majority of dynamic cone box speakers primarily emit sound in a forward direction. Some have a rear-facing driver or two. Then there are dipole planar, ribbon, dynamic cone designs that mostly propel sound both forward and backward at similar volume levels. Then there are a few omnidirectional designs that send out sound in all directions.
My thoughts have mainly focused on how these two observations come together as sound reproduction in a listening room. I find traditional cone speakers can do a good job of capturing the heft and dynamics of a live performance, and those with rear-firing driver(s) can produce an added sense of spatiousness and atmosphere. But these designs (except for a larger line array types) don't always capture the size and scale of a performance, and they often portray individual instruments, vocals, etc. in a very well-defined but relatively small size. Like some mentioned above, this is not how instruments image in a live setting -- probably because their sound continues to radiate outward in all directions.
The dipole planar and ribbon designs, conversely, can do a good job capturing scale and project individual images in a larger way like in a live setting, but they often cannot project the full dynamic force and heft that cone drivers seem to do better.
I haven't heard too many dipole cone speakers, but I'd guess this design falls somewhere between the other two by adding some heft but lacking some scale. And I've only heard one omnipolar design at a show, and it was an uber-expensive MBL. It sounded great. Maybe the closest thing I've heard to a live performance, but it's an exceedingly small sample.
I'm not sure we'll ever fully capture the total experience of a true live and unamplified performance. But at the same time, I marvel at how much of it good systems can capture and portray. I once read that a theoretically perfect speaker driver design would be like some plasmatic orb, which kinda makes sense and maybe why the MBLs sounded like they did.
Where I am currently given all this? Hell I don't know. I was 90% sure I'd end up with Joseph Audio, Vandersteen, or ProAc speakers -- all of which I love -- for a long time. Now, largely because of this "live" sound issue I'm thinking more along the lines of something like a Nola (not sure the omnis I can afford will suffice). But here's one thing I'm 100% sure of -- whatever speakers I ultimately choose, I will also have at least two high-quality subwoofers. Having heard good, properly set up subs in several systems, I find them to provide a good dose of the "ether" of a live room that I find absolutely essential. With the subs disengaged, the sound goes flat and a lot of the "liveness" disappears. Anyway, I've gone on way too long. Sorry. Nice thread @prof