Recently I bought a SHZ-84 helmet, only to find that its headphones didn't work... so I changed them.

Step 1: Removing Ear Muffs

Materials:
1)SHZ-84
2)knife
3)old headphones
4)glue
5)soldering iron
6)music player (my phone)
7)black tape
First you have to cut off the yellowish ear muff things. Do this very carefully by simply cutting the yellow muffs from the fur and rubber. Now you should see the speakers inside their rubber casing, just pop them out. Unscrew the red and green wire from the speaker-tablets and pull the wires from the helmet.

Step 2: The Hard Part

Now that the Helmet is just a an empty shell of a padded hat, we can start inserting the headphones. you should get a pair of old headphones (the kind that cover your ears completely). Remove the speakers & the cord with the jack that goes into the music player.
The wire with the jack should not at this point be connected to the speakers. When you remove the wires from their respective places, you should take notice of where they should be. Thread the wires first through the provided black rubber tube. The red and green wires from the original speakers can be discarded, while the yellow and white wires should be left alone (this is purely cosmetic and optional). thread the wires through the holes designed for the old wires. This can be frustrating but don't give up.
When the wires are through to the rubber part of the helmet, its time to solder the small wires back to their respective places. When you finish soldering, you should check that the connections all work by turning on some music.

Step 3: The Last Mile

Now you just have to glue the speakers to the rubber (I put some cotton into the ears behind the speakers to eliminate extra space) and glue the ear muffs to the fur. be careful to glue it back into its original place.