3D Printed Headphones

The Problem

For years I have been frustrated by the quality and cost of headphones.  Either they are excessively expensive or poorly made, disposable products.  Many times I have attempted to repair a set, only to find they were glued together, made from fragile components or otherwise not serviceable.  At the other end there may not be parts available for some higher quality headphones that might otherwise be serviceable.
I searched some of the downloadable designs available on Thingiverse and found a few options.  I printed one of these options.  But generally each of these designs were lacking in some area.   Ultimately I decided to design a set from scratch.

Parts Sourcing & Design

I started off working in 123Design but quickly switched to Fusion 360. My intent was to create a fairly universal design template that could be modified.  There were a number of parameters that I decided to incorporate into the designed .

• 40mm drivers (speakers) that are readily available from a variety of sources. 
• Foam pads that can be purchased as replacements.
• Removable, plug in style cables.

​My intent was to source parts that were readily available online.  Many of the parts can be obtained through Ebay, Bangoods, Amazon or other vendors.  However, there are some things to consider.  

• Drivers, none of the online vendors provide much in the way of specifications.  Short of impedance numbers, there is little information on frequency range design intent (open back or closed back) etc.
• Foam Pads.  There are a lot of options out there many are intended as replacements for round pads that press on your ear.   I wanted something that goes over the ear and is elliptical in shape but did not want to have the cans be overly large.  I settled on replacement pads for Sennheiser hd202 headphones.  This was largely due to having pads laying around from a broken set of hd202 cans.  
• Cables and connectors. My first plan was to go with a forked cable that has 3.5mm or 2.5mm plugs at the cans.  This was actually more challenging to source than I anticipated but still available.   I also ordered 3.5mm jacks for the headphones.
• Connectors.  I purchased M3 machine screws and nuts at a local hardware store.

More on Cables And Connectors.

So many options:

• Hard wired vs Connectors.
• Y cable vs Straight.

Hard wired cables are the cheapest way to go but ultimately strain on the cables will require the cables to be re-soldiered.  Plug in cables add cost but can easily be replaced without having to disassemble the headphones.  (Assuming the connectors are durable)
Y cables are harder to source but eliminate the need to snake a connector across or through the headband.  Also, if there is a wire between the cans, should it be hard wired or also use connectors...

Prototype

I printed the plastic parts in silver PLA.   The assembly process was a good lesson in constructability.

• M3 Screws and Nuts: Using M3 screws with backing nuts seemed like a good idea but I found the assembly to be a fiddly process with the tiny screws and nuts.  Also the part count gets to be a pain.  I see now why so many commercial headphones use essentially wood screws into the plastic parts.  I am already reworking the design with this in mind.
• Shims: I designed hat shaped shims or washers wherever there are rotating parts.  In practice these worked OK but have a tendency to work themselves loose.  I don't want to use nylon lock nuts on the already fiddly screws so am reworking the shims so they have a hex insert into the opposing part to prevent loosening.  Will also rework the shims for wood screws.
• Headband:  I knew it would take a few tries to get this part right.  In order to be adjustable I designed them to work similar to a zip tie.  First print was too tight, second too loose...   Both could be a little thinker and more springy.
• Cables:  I found a reasonably suitable cable in a junk box of audio crap I keep in my garage. But the 3.5mm connectors I purchased on Ebay are of marginal quality.   Long and short, I am still on the fence about hard wiring the chords or using plugs.