OK, lemme double check. It was late at night, maybe I got it backwards.
Well, I just checked all of my EDR1s, both visually and listening. I even opened all of mine that were still sealed in the white boxes.
Sure enough, it appears KZ changed the location of the vent hole at some point. All of the old black cardboard boxed ones had the hole in the back. I have 2 in a new white box with the vent in the back. The rest of the EDR1s in white boxes have the vent in the front.
So the vent hole is currently not a reliable way to tell the EDSE and EDR1 apart with 100% accuracy. It used to be, but no longer is.
Both vent locations are the same size and both are BEHIND the driver (ie bass vents), so there is no effect on the tuning of the EDR1 whatsoever. This is why the “old” and “new” EDR1s sound identical.
What’s different about the EDSE is not the vent hole itself, but rather the different driver used (or at least USED to be used).
@BadReligionPunk just posted above that his EDSE and EDR1 sound the same, so maybe KZ revised the EDSE at some point and started using the same drivers as the EDR1. Who knows?
And this is why KZ is so frustrating sometimes; because they quietly make changes to models, and it often becomes impossible to know what you’re buying.
So here’s the bottom line as far as I can tell:
1. If you receive an “EDR1” in an old black cardboard box, and it has the vent in the back of the shell (ie behind the wire strain), it is indeed an EDR1 and not an EDSE.
2. If you receive something that looks like an “EDR1” in an old black cardboard box, and it has the vent in the FRONT of the shell (ie forward of the wire strain), it is an EDSE and not an EDR1.
3. If you receive an “EDR1” in one of the new small white cardboard boxes, and it says “EDR1” on the front, it is an EDR1, regardless of where the vent hole is.
4. If you receive a “mystery” IEM loose in a ziplock baggie (ie no box), and it has the vent in the back (behind the wire strain), it is an EDR1. Because all EDSE had the vent hole in the front.
5. If you receive a “mystery” IEM loose in a ziplock baggie (ie no box), and it has the vent in the front (forward of the wire strain), it could be either an EDR1 or an EDSE. There is no way to know which you received.