It's true, the acoustics and engineering behind the SE846 are something to behold. It's a huge separation between these and, for example, my beloved Pandoras. Whereas those cans just have the speakers up against your ears, IEMs have a big housing unit that must be dealt with. In the case of the SE846, the SOB's put in a multi-chambered filter system and gave the bottom end a passageway that's about 4 inches long (huge considering the tiny housing) without giving it any awkward or artificial echo/reverb.
QUICK LESSON
In any kind of sound system with multiple drivers, the whole idea of it isn't just to cram a bunch of speakers in there, it's to make the sound clearer by giving a determined range of audio its own dedicated driver. You know this if you have desktop speakers or home theater speakers. The subwoofers only make bass, there are mids for the middle area, and then the tiny tweeters that make all the high pitches.
However, it's not like our laptops or DACs have any idea how many speakers there are (think of the various plugs on a car head unit or the console of a home theater system), so the crossovers are a little piece of hardware that effectively clamps off the frequency range for each little speaker. For example, your subwoofer will handle everything under 120Hz, a midrange speaker from 120Hz to 2KHz, and the tweeter from 2KHz and above.
This is great because the reason audio usually gets muddy is from trying to reproduce an entire spectrum of sound from one speaker. Think about a flat surface that has to vibrate 30 times per second. Look up a subwoofer video to see a speaker moving at that frequency. Now think about having to make that thing also be vibrating at ten THOUSAND times per second WHILE it's doing that. It's incredibly difficult. Splitting up the duties makes each speaker clearer and louder because it's only worried about a specific range.
If you want to visualize it, move your arm up and down slowly but steadily, about once per second. That's a subwoofer. Now do that while "tapping" the air with your hand in smaller vibrations, say, 10 times for each one "cycle" of your arm. That is, in effect, a speaker playing a low and a high frequency at the same time. That's how speakers play music. You can see why it'd be easier to have one speaker doing the slow movement and another doing the fast.
BUT, the handoff isn't like a sharp chop. The low speaker won't play 120Hz at full volume and then nothing at 121Hz nor will the midrange play 121Hz full with nothing at 120Hz. There's a "slope" to it. What Shure apparently did was start the subbass slope at around 75Hz for the lowest driver and have it drop off very quickly from there. That's incredibly unusual for a headphone but it's almost certainly why the things have such incredible sub-bass: it's a subwoofer, not a "bass driver" in the way most would do it. So that little guy fires on all cylinders during the low lows, and then does nothing above that, making it almost like a beefed up SE535 with a subwoofer. Nothing changed, just ADDED.
