i looking for headfoon shematic

[guest]

hello who can help me out
i looking for headfoon shematic
i will build it by myself
i have headfoon that i used for shooting with guns
now i will convert it for metall detection
who can help me and can say what i need
i read a need mylar speakers , switch, and potention knobs
who can have me partlist
thanks
sorry for my bad englisch

[Radioactive]

Headphones

Hi did not get your name,

Anyway I think you are trying to build underwater headphones, am I correct? I built a pair using a piezo (crystal) earphone and Mylar diaphragm. You will also need to pot (epoxy) a user-selectable impedances (8/600 ohm, etc.) for compatibility with all water detectors, only if will use with different detectors. You will also need to buy the special headphone connector. I filled mine with mineral oil. This made it very tough to maintain a seal, until a friend showed me how to place a plastic ring over the Mylar. I epoxy the little piezo (like the kind you get with a transistor radio) earphone in the headphone, then placed a dab of epoxy on the face of the crystal (this also covered the contacts to seal them) and placed a plastic tube over it and let it set. Then after it set I took the Mylar and epoxy it to the end of the tube. I left the tube hollow! This is important, since underwater pressure will not compress it as much as the commercial units speakers do. Then after that is dry, I level the headphone cup, pour mineral oil till it just comes to the lip, and then slowly place the Mylar over the cup, leaving about an inch overlap. I then take the plastic ring that just fits over the cup and force it till it seals. You need to make sure there is NO air inside. I found that a second layer of Mylar should then be epoxy over the other Mylar membrane around the edge. Then seal the rest of the cup around the ring with epoxy. You will find that the volume underwater is louder than the comercial units because of the small amount of air in the sealed tube between the earphone and Mylar diaphragm. The oil keeps the pressure inside the same as the outside underwater pressuse. More signal is able to pass this way. I hope that info helps you.

Robert

[Yves]

thanks for the information
sorry i was logged in but i have deleted my coekies
now you can send mail
i looking for make this one or simular headfoon
see photo's

[Radioactive]

Yves,

They look home made and use standard speakers that are covered with Mylar to make them waterproof. How are they sealed? I use Mylar speakers in waterproof walki-talkies. Now these are small, about 2" to 1.5" in diameter. Go to All Electronics. They have a few mylar like this:

1.75" 32 OHM SPEAKER $1.25 each but don't know how waterproof they are, but are at ALL Electronics. This is a closeup view.


these are only $0.75 at HSC Electronics

As you see there are air vents behind the mylar to allow movement. Now as you go deeper underwater, the pressure will press the mylar untill no movement and no sound is produced. If you are in shallow water it won't me a problem. As you go deeper, every 33 feet is one atmosphere surface 14 pounds per square inch, 33 feet deep 28 pounds this is in salt water. So press with 28 pounds with your thumb and you will see that is a lot of pressure for these speakers to push to make sound. That is why I used mineral oil, to balance the pressure. Hope that helps you Yves.

Robert