First, i appreciate you taking serious energy to formulate a reply. Sadly, you didn't push through.
The main event:
You have reduced your previous "we can measure it" to "in theory we can measure it". You are almost there.
No, that was always my position. There was no previous different position. Way back at post
#52 I said "in theory".
Ask yourself this:
- If i give you two speaker measurements, can you tell me which has more "meters of soundstage"?
- Is the unit of soundstage meters per instrument or just meters?
Begging the question again. Not a single metric, a complex function.
Back to the optical illusion:
Those parameters don't give you how fast the rings spin or that they spin at all. Maybe 15% don't see it spinning at all.
Are you lost here, or is this just word choice? The illusion (and its popularity as a meme) is about the circles apparently (but not actually) moving in the direction indicated by the arrows. Not about them spinning, or how fast they spin. The latter is just basic animation (yes, basic animation is an illusion too, but we know revolutions/frame and frame rate so if you are stuck back there you'll need to catch up). I'll assume you understand this and continue.
If you ask them, how would they measure the illusion?
- You can not measure the optical illusion in a picture or display. You can only measure physical properties, but an illusion has none.
- All you can hope to ever achieve is statistical analysis asking lots of people, a "optical illusion intensity score". You will agree, that is not a measurement like volts, amps or ohms.
The point was that we can precisely measure the parameters of the graphic that set up the illusion. We don't need to measure the brain activity directly (although it would be fun and likely useful if we did). The graphic works this way:
Here's frame 180, roughly half-way through the sequence. You can see the main rings obviously, with 90º segments of yellow and blue. You should also be able to see the inner and outer rings, just a few pixels wide. The circles rotate clockwise in the animation, and the inner and outer rings are shifted 45º "behind" the main segments. The inner and outer rings are opposite phase to each other, 180º. This creates the illusion of movement (notice they correspond to the arrows). The left and right rings are also opposite phase (so one "moves" up and the other down). I'll assume you can see this, and understand it.
Now imagine you are reproducing the animation but your system isn't so good. Pixel resolution isn't sufficient, frame timing is off, frames are skipped, colours are rendered wrong, and so on. Those factors can be objectively assessed, no problem (the source of illusion has measurable properties). Not one metric though, several. You may have to check them all to see where/why your system is f*cking up. Now consider this as analogous to the sonic manipulations we use to create stereo image in a recording (amplitude and timing between channels, phase manipulation to expand width and depth, frequency shaping and echo/reverb to cue depth, and so on, all the things that mimic natural sound behaviour and the way we hear it). We employ these deliberately because we know they work.
Back to soundstage:
When has that sufficient degradation occurred? Is it the same for everyone? Only a person can tell you, but that is not a measurement.
- You can not measure the soundstage in a CD or speaker. You can only measure physical properties, but an illusion has none.
- All you can hope to ever achieve is a statistical analysis asking lots of people, a "soundstage illusion intensity score". You will agree, that is not a measurement like volts, amps or ohms.
You continue to think that illusions in your head are measurable by physical properties in reality, but that is never the case.
Yes, we have to correlate the objective manipulation of the image and performance of the reproduction system to the subjective perception of the illusion (we don't care that it's exactly the same for everyone, it probably isn't). The recording-electronics-speaker-room-listener system is complex, and each element has to be characterised and measured appropriately. You appear to mix this up, assuming that there is no systematic manipulation (which we can measure precisely and directly) or that it is unrelated to the subjective human response (which we can survey). Or that we measure rooms and people the same way we measure DACs and amplifiers. Or both. All incorrect.
You will never be able to measure beauty, soundstage, best guitar, taste, attraction or believability of an actor in a movie.
This is both obvious and irrelevant to the discussion.