How does imaging with dynamic drivers?

Submitted by GoldflakeTheGoldWing t3_yiwzdd in headphones

How does imaging work? Especially with DDs. If the diaphragm can only move back and forth, I don’t understand how there can be vertical soundstage and depth. Shouldn’t you only be able to hear music in a flat circle centered horizontally at your head, and not a sphere?

edit: ah I messed up the title

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SupOrSalad t1_iul0hii wrote

A lot is based on the recording itself. In the end, we only hear in left and right channels, but the shape of our ear and the timing of the sounds as it reaches our ears all works together to change the Frequency in a way that our brain understands as position.

If the audio has that frequency information and timing in the recording, our brains will decipher positioning as well in headphones

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blargh4 t1_iul7ucq wrote

We only have two ears, so at least in theory, two drivers are all you need to create an arbitrary illusion of sonic space. The 3 dimensional image is created by subtle cues in intensity, frequency response, and timing in the sound both ears receive that are processed by your brain. Presumably headphones can enhance or miscue these perceptions by some aspect of their design.

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dongas420 t1_iulbolb wrote

If you throw marbles randomly into a funnel, some of them will go straight in while others will bounce off the bowl bit first before entering after a time delay. Replace the marbles with continuous waves, and the relative delay results in a dip at a certain frequency caused by phase cancellation/destructive interference.

In practice, your pinna (the part of your ear that sticks out of your head) creates this notch at somewhere between 6-12 kHz. Because your pinna isn't perfectly round, the time lag (and thus where and how deep this notch in the treble is) depends on the location of a sound source, which your brain uses for sound localization.

Since headphones are beaming sound right at your pinna, they can potentially acoustically interact with it in a way that creates this notch, as you can see in dummy ear mic measurements like this. IEMs can also be tuned with dips in the treble that artificially simulate this notch.

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staybythebay t1_iuldtvk wrote

I think it would be similar to how we see 3d with our eyes. If a recording was mono, you wouldn’t get imaging. But with stereo, the left/right levels + delay of an instrument would help create imaging

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audiophile_lurker t1_iuna4ls wrote

Your ears also only move back and forth in 2 spots, practically speaking. We hear in stereo, so a good recording can produce a pretty good illusion (say binaural).

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