CH2-SC Semi-closed DIY Headphones

A semi-closed back headphone design using the Peerless 50mm drivers, the tuning of these hits close to my open back CH2 design with the same ear pads. Measurements are provided below.

The project has gone through a lot of changes, which I have tried to document along with what I have learnt here https://www.head-fi.org/threads/diy-3d-printed-headphone-journey.979090/


The size of the cups was intentionally scaled so that they would fit the wonderful Capra Audio headband and Satyr3 yokes and a wide range of other third-party headbands.
I have also modelled my own yokes to fit these cups and the Capra headband. 


BOM:
Drivers - Peerless 50mm
Pads -      Soulwit Hifiman PaliPads                                    
Cable Connectors - PJ392 3.5mm
Screws - M3 FHCS 8 and 10mm, 6mm m3 pan head
Threaded Inserts - M3 Heat Set
Other materials - Cotton Wool, 1-2mm thick 30% wool-blend felt.


Instructions:
- Print from the .step files if your slicer supports them, they are higher quality than .stl
- Setting "ensure vertical shell thickness" to critical only in your slicer will help reduce the weight of the rear cups if you had it enabled fully.
- The blocked-out portion of the driver's grill is to be towards the front.
- Attach the Gasket part 2 to the bottom of the Gasket part 1
- Fill the rear cup with cotton wool, optionally, you can also add a thin fine mesh fabric to prevent dust etc getting near the driver.
- You have two options to choose between to ensure a proper seal for the Pads, 
          1. Print the Hifiman Pad Gasket in TPU and insert it inside the earcup as shown, the wider brim                            should be at the top and sit between the pad material and the plastic frame.
          2.  Place a disc of 1-2mm 30% wool-blend felt slightly larger than the opening within the earcup and                    tuck it between the plastic frame and the pad.  This smooths out some peaks and is a smoother                   presentation overall.
- The rear cups can be sanded and painted for a smooth finish

Measurements:

The Measurements provided are from a custom rig and so aren't directly comparable to anything else other than the measurements given, as such, I've provided and overlaid measurements of the HD650 in grey to act as a known reference.
The measurements were also taken with the headphones made from PETG; I am unsure if other materials will impact the sound.

Standard Rear Cups

Slim Rear Cups

TPU Rings

Felt inserts