InterPhone BlueTooth Intercom with two Speakers - DIY

This DIY describes how to install an extra speaker for a InterPhone BlueTooth intercom from

The BlueTooth based InterPhone intercom unit that I bought in 2008 was only available with one single speaker. This means that one ear is loaded with an uncomfortably high sound level and it is often difficult to understand the speach.

I hence contacted the manufacturer and was informed that it is technically OK to load the output amplifier with two speakers in a parallel connection. After mounting an extra speaker from a damaged InterPhone set in my Schuberth C3 helmet I now have a much more comfortable and centered sound level with better understandability at high speed.

Time and Tools

This is an easy DIY task done in about 1-2 hours.

Tools and consumables needed:

Mounting Procedure

1.0 Remove the InterPhone speaker from your helmet as shown on the left photo below.

2.0 Using a scalpel, make a longitudinal cut through the outer insulation layer approximately 2 cm from the speaker. Be carefull not to damage the inner wires. Bend the cable around to get access to the inner black and red wires as shown in the above photo (second from left).

3.0 Using the hot tip of the soldering iron, melt a small opening in the the black wire to get acces to the copper strands inside it. Again be carefull not to melt too much as this might lead to short circuits. Solder one of the wires from a 30 cm long two wire cable to the black wire. Repeat theese steps now for the red wire. As yoy can see on the above photo (third from left) I used a shielded two wire cable because that was what I had available, but a two wire cable without a shield can just as well be used.

4.0 Using insulation tape and optionally also heat-shrink tape insulate the soldered joints from eachother. See above right photo.

5.0 Remount the main speaker in the helmet and route the attached cable to the other side of the helmet. On the C3 it can be routed around hidden behind the neck collar.

6.0 Cut the 2-wire cable to suitable length and solder it together with the wires on the extra speaker. Make sure the red wire from the main speaker is connected to the red wire in the extra speaker, and black wire to black wire.

7.0 Mount the extra speaker in the helmet and then test the system. You will enjoy hearing the sound as originating inside your head instead of next to the left ear.


Front Page

Copyright 2010 FireBladerDk - First version 2010-03-22