This is a modified end cap for the Ploopy Headphone. Personally, I think there's a lot more improvements that could be made to the design and tuning of the Ploopy's, but I don't have the equipment or time to work on it right now. I'm posting what I do have in case anyone finds it useful.

This moves the magnets closer to the driver to diaphragm, which helps with the low sensitivity issue. If you play a very low frequency tone (<30hz) and crank it up, you can make the diaphragm tap against the magnets, but having better sensitivity also makes it so you don't have to crank it up. In practice, I don't find it to be an issue. I've also minimized the surfaces behind the magnets to reduce back reflections.

This design does require the use of a different driver frame modified to allow the magnets to pass through and sit closer.

In case you're curious, I did some measurements of the Ploopy amplifier. On the base EQ setting, I was getting 3.6Vrms output. Boosting up the gain in the EQ, I got up to 4.5Vrms before the amp output began to clip. I believe this is the limit of the voltage rails. Boosting the EQ gain this high does introduce a significant amount of audio distortion.

If I revisit this project in the future, I'll probably start with alternate earpad mounts for better off the shelf pads, and a suspension strap/headband to help with the comfort and aesthetics.