Basically what i did was to combine the following materials:
-a pair of hearing protectors
-two pairs of 5$ headphones i got at Walmart
-a 1/16 audio splitter (7$ at Radio Shack)
-oxygen tubing i had lying around
To sum it up, I stripped the speakers out of the headphones, and glued them into the hearing protector, being sure to put both the Right speakers in the Right side, and same with the Left, to preserve the stereo audio. Then I wrestled with the wires until both headphone wires were coming out of one side of the hearing protector. I drilled holes and ran the wires through them. I then slit the oxygen tubing along one side, ran the wires through that, and taped them in ( I could have done a better job of that. This is a work in progress). I plugged both of the headphone plugs into the audio splitter, reducing the input to one plug. Finally, I put Sugru around the place where the wires enter the headset to prevent them from coming out.
-excellent passive noise cancellation
-great sound quality
-look pretty good and get lots of attention
-i can remove the audio splitter, and plug the plugs into different audio jacks, enabling me to simultaneously listen to two separate things in a sealed environment. this makes gaming amazing, since i can hear the game sound effects from my Xbox 360 and whatever music is playing on my computer simultaneously.
-large bulky plug gets in the way
- the cord looks kind of junky
-i ran out of Sugru, so i could only reinforce one end of the cord, not both
-i used two identical headphones, both of which dont have good bass capability.
-they get uncomfortable after an hour or so
-Replace headphones with ones of higher quality, enabling better bass
-try to combine all four speakers into one wire to simplify wiring and get a longer cord
-paint and make more amazing
-get or make better ear pads.
-built-in volume control
-reinforce better with more Sugru
Okay, so I know that these aren't TRUE quadrophonic headphones. I know that true quadrophonics have a more integrated system using electronics that i am ignorant of. However, these are ETYMOLOGICALLY quadrophonic because they have 4 speakers (quadro-) and are made using headphones (-phonic). there you go.
This is a work in progress. As I said before, I cannot claim this idea as my own entirely, but as far as i know, no one on this site has made a pair of jackhammers with FOUR speakers.
Oh, and that thing in the pictures is a cheap MP3 player built into an Altoids tin. A project from a bored afternoon.
At some point I may make an Instructable of these, if i ever have reason to make a whole new pair.
Live Long and Prosper