But when you connect a synthesizer with stereo out, to a hardware mixer.
You normally connect the left and right to a mono channel, so synth L to mono channel 1 with a panpot and synth R to mono channel with it’s panpot. At that point, the L and R signals are mixed as 1 mono sound
Then you normally turn the panpot on channel 1 to the left and the panpot on channel 2 to the right to get the widest stereo image.
You could also turn channel 1 to the right and channel 2 to the left to invert the stereo image, and narrow it bij setting the panpots anywhere in between.
I thought maybe this was the same concept or at least the same outcome.
Dual pan is a form of true stereo pan, meaning independent pan control for both the L and R channels of a stereo signal, not just mono. When you do narrowing + normal panning(balance), you’re reducing the difference between L and R by blending the two channels, for example, interpolating between stereo and mono: L'(t) = a*L(t)+(1-a)*R(t), R'(t) = a*R(t)+(1-a)*L(t), where a = 1 full stereo, and a = 0 mono. Each processed channel L’ and R’ blends the original and opposite channel. The closer a gets to 0, the more similar they become, narrowing the stereo image. This can degrade the signal, especially if you have effects like reverb or delays. It can cause phase cancellation and make sounds disappear partially or completely depending on the phase correlation between channels
With dual pan, you can still narrow the image, but you can also do things like placing L in the center and R 100% to the left. The way narrowing works is different because the movement of L and R is independent of each other. In this case, we have something like this for symmetric narrowing: L'(t) = cos((pi/4)*(1-a))*L(t), R'(t) = cos((pi/4)*(1-a))*R(t). When a decreases, the argument of the cos increases, causing the cos value to decrease (from cos(0) = 1 to cos(pi/4) ~ 0.707), this represents equal attenuation of both L and R, moving the stereo image towards the center without mixing content between the channels, and the stereo difference is preserved. L stays L, R stays R, but with attenuation and redirection
