We at Asius have recently launched the ADEL Drum on IndieGoGo, I hadn't posted the link in here because simply this is Empire's thread and I didn't think it was appropriate for me to do so.
The ADEL Drum is an earbud, that uses different speaker configurations at different levels. At the Empire booth at RMAF, we did show a prototype of a Spartan with the ADEL Drum IEM module on it. This module is 10mm wide, that is ported a different want than the current 5mm ADEL module. It's more like a pancake than a bullet you could say. We called it the Drum IEM Module because it's using the same principals that we learned during R&D for the Drum Earbud. As we've already been able to see, this causes alot of confusion for people, so it's been something I've suggested changing the name of before that project really kinda goes any further. I don't have an ETA on that setup, so don't expect it out in the next month or two, that's just not going to happen.
Now I'll explain the difference in approach between the current ADEL Module and the Drum:
The Passive ADEL module and explaining ADEL in general... When you seal an IEM (or closed back headphone) to your ear, you now have a trapped volume of space and pressure. Speakers move like pistons in a motor, moving back and forth to move air, this obviously creates a pressure difference between forward and backward. Balanced armatures work in the same way, just the motion is different, they're much more like billows that you would use to start a fire in your fireplace. Little diaphram moving rapidly to make sound that then gets forced out the snout of the housing.
Sound is being produced, but also the pressure along with it. Your ear drum is simply a membrane that reads those vibrations and then passes it down the line to be analyzed, etc. So pressure gets applied to the only that actually moves, which is your ear drum. As you'd imagine this biases the ear drum since it's being held still, sorta like somebody putting their foot on the scale as you try and weigh yourself. So since the membrane within the ADEL module is more compliant than your bodies eardrum and is ported into your ear sealed ear canal via what's normally a sound tube, it's ported into the trapped space and that allows it to take the pressure. This allows your ear to hear the way it's supposed to (without that foot on the scale), as well letting the speakers to their thing without be hindered by the pressure in the ear canal. So it's a win for sound quality. The health aspect comes in via when your body senses it's eardrum constantly being beat up, it triggers your acoustic reflex and makes your ear drum less sensitive to keep it from damage, this turns down your volume without telling you. This is why many of you have had the urge to turn up the volume after a while because the music doesn't sound the same as it did when you first started listening, so you in turn bump up the volume again, the cycle repeats and you burn out your ears. This cycle and muscles tightening, is the source of not only hurting your hearing, but also this fatiguing feeling of just needing a break from listening. This is called Audio Fatigue. Some people don't listen to iems for long enough spans of time to experience this, but as somebody that listens to iems for a fair chunk of their day, this is a very real thing.
The different ADEL modules offer different tensions/amount of layers of membranes within the modules, netting different performance to the sound signature. Super floppy (like the MAM being untensioned) can be compared to a net around a batting cage, it's so loose that the ball hits it and just falls to the ground. As you begin to tighten it, there's more bounce (you could say), this is especially noticeable with bass. That's why the MAM being tensioned all the way, you get more bass than when it's floppy.
The ADEL Drum... The Passive Module is really like putting ADEL on the ear canal, where as the Drum is much more like putting the speaker within the module itself. The membrane is MUCH MUCH larger and makes up the faceplate of the earbud (there's still a grill to protect it, but you get the idea). Big membrane, then speaker, then to your ear canal. That speaker in the middle, drives BOTH your ear drum as normal but also the membrane on the other side of the housing, effectively turning it into another speaker. We learned that as you tension the membrane, it becomes more springy like a trampoline, bouncing the sound back toward you ear drum and letting the user really control alot of the sound signature. Also, because that membrane is further out than you'd ever place a speaker in the earbud, the sound stage translates to be much much wider. Another perk of that large membrane is it's shire size, it's very fast and can move alot of sound, making it like a very large driver, providing the bottom end that you'd expect from a big subwoofer (comparatively). This has allowed us to have the user experience either very little bass, to enough that on a bassy track, you can feel it in your chest a bit. With our 10mm speaker and the membranes tensioned the way I want, I can get more bottom end response than out of our LCD4s. Granted, I like more bass than most people, I'm simply saying that it's possible if the listener decides to tune it that way.
