@Canyon Runner
Just curious, do you know the specs of the isolation of the manual modules?
1964ears website say that the Auto modules have a noise isolation of -18dB
Is there a spec of the noise isolation of the manual modules when fully open or closed?
Hi Harry, this will probably be a longer response than you had expected to receive. Sorry for it coming late, I was half way through writing it before we had to leave to go set up our booth at CES.
First off, whats important to understand is how isolation tests work, with traditional sealed IEMs and then how ADEL is different, making the ratings very different.
Isolation tests are basically a guy in a soundproof room, with ear plugs/iems in their ears. They raise various noise levels in the room and see at what point the ambient noise is noticeable.
One thing that plays into that is the inclusion effect of sealed ear. If you plug your ears with your fingers, you'll notice that obviously the outside sound drops off substantially, but also that you'll be able to hear your body (your blood flowing, booming inside head voice, your breathing, etc) and it's actually very loud. This effect plays into the isolation effect/rating, almost like a masking of that outside sound PLUS the isolating effects of the stuff in your ears (ear plugs, iems, your finger tips). That inclusion effect also isn't even throughout the frequency range, basically why your foam tip ear plugs work a bit better down low, while letting a bit more sound in around the mid range.
It's also worth noting that a sealed ear with a plug, restricts the movement of the ear drum by trapping the pressure between the drum and the plug. This ALSO plays into how your ear is going to be trying to decode what it's hearing, be it loud or muffled.
Now for ADEL, we'll talk about the Auto modules first because it's a good standard to use. The addition of ADEL to the situation makes your ears no longer sealed, the pressure now has a place to go and gets absorbed by the ADEL membrane. This also lets the ear drum move as it's supposed to, making it a non-ear-damaging and more natural sounding experience. You can throw the best balanced armatures in the world into an IEM's shell and you're still going to be fighting the way its delivering the sound, so the automatic ADEL is the first step in that battle. That's why it sounds far more natural than anything else, because it's how your ear drum is supposed to function by nature.
The ballpark standard figure you see for isolating measurements on IEMs is roughly -25db, plus a masking of inclusion.
Where as with ADEL, you don't have the in head inclusion to contend with and STILL get an isolation rating of -18db.
So you can see how it's almost like comparing apples to oranges at this point.
But to actually answer your original question, you can close the manual ADELs and achieve a sealed rating of -25db (ish), but opening them up, while the number on paper will be lower (probably like -15db if you want a specific number), you'll actually be achieving a more quiet listening experience to your ear since you don't have to contend with all the sounds in your body playing into it.