DIY 70's Style Headphone Bluetooth Modification

I had picked up these Sound Design headphones at a flea market a number of years back for a few dollars.  When I tried them one of the speakers would cut out, sort of a disappointment, but nothing that couldn't be fixed.  I figured they would be used for some project eventually.  I liked the design of them so I wasn't going to throw them away.

Now, more recently I had purchased a pair of bluetooth headphones for my smart phone, and although I loved the wireless concept I wanted them to be practical as real headphones for my non-bluetooth devices.  Otherwise I'd be taking two pairs of headphones to work, a wired pair for my laptop (which doesn't have bluetooth capabilities) and a wireless pair for my smart phone.

What a dilemma, eh?

While browsing around I had found another instructable where a user had velcro strapped a bluetooth adapter to his headphones and I wanted to do something similar, but a little more in depth with the wiring.  Now I had an idea to make headphones that doubled as wired and wireless and I had a pair of headphones I wasn't worried about scrapping in the process.

(I'm aware now that they actually sell headphones that do both jobs, but what's the fun in that?)

I found this HDE Bluetooth Receiver on Amazon fairly cheaply.  Paid less than $15 after shipping and it's interface was simple with just an on/off switch and a 35mm jack output and a mini usb for charging.  Plus the size of it seemed perfect to gut and insert inside the giant headphones
HDE Link on Amazon (If the adapter moves or is taken off of amazon, google it).

The pager-like case opened pretty easily by wedging a screw driver in the crack to separate the top and bottom.

The original idea I had was to wire the speakers and external jack straight to the board, but the circuit there was pretty small so I gutted a male headphone jack off a pair of earbuds and wired that up accordingly. 

These headphones originally had two volume knobs on each side and a switch which converted them from stereo to mono, which was handy then, but I wouldn't need those for this project, so I gutted those parts out.  I converted the stereo/mono switch to a power switch for the bluetooth, which I'll explain in the next step.

Here's the diagram of my wiring for the speakers.  Excuse my 5th grade drawing...

The bluetooth headphone jack out was wired into the speakers, left, right, and ground, accordingly.  Additionally the external jack was wired to these points so both sources go to the speakers.

The female 35mm jack was hot glued to the bottom of the headphones where the original cable was.

On the bottom of the bluetooth adapter were the nodes for the on/off switch.  I just wired these to the stereo/mono switch that was already in place in the headphones.  This will allow me to turn the adapter on and off so the outside of the headphones retain their original look.

After everything was wired and tested I hot glued the items to act as insulation so nothing shorts out when I jam it all together.

The final product is practically identical to what I started off with, aside from the female jack where the original cable used to be.  The only issue I have at the moment is that I cannot recharge the battery on the adapter without having to remove the speaker.  I will need to find a spare female usb mini port and wire it in accordingly.  I have a space where the volume knob used to be where I can mount the port.

Whole project was done in an afternoon.  Now I have some cool looking 70's style headphones that work with any wired or wireless device I have.