Jul 08

Connector Cable for Stereo Microphones

In my last post I wrote a little about the different connectors and wirings for audio cables. Today I want to share another type of cable I  soldered for myself recently: a y-splitter which divides a stereo audio signal from a (stereo) microphone so I can recored it with an audio interface or field recorder.

 

Background

Normal microphones are in mono and in order to record a stereo image, at least two microphones are needed in a particular set up. But of course, there are also a few microphones, which come in stereo.

A few months ago I bought myself a Sennheiser MKH-418s stereo microphone. The microphone itself comes without cables, but a cable can easily be acquired from Sennheiser. However, as a minor nerd, I decided to solder the cable myself. At least in this way I am also able to decide the length and shape of the cable myself.

Stereo microphone capture two signals, which are combined and sent through the cable. Hence the 5-pin connector to accommodate the two signals on the microphone’s end. However, audio interfaces or field recorders need one siganl per channel. A ‘y-cable’ is needed, to enable plugging each signal into its own channel.

 

How Stereo Microphones Work

Using the five wires of the 5-pin XLR, the microphone sends one signal for the front part of the microphone (mono signal) and one signal for the side(s)—aka ‘MS’ technique if two microphones are used. The side(s) is the signal which needs to be decoded afterwards, since it is a mixture of left and right.

This is what it looks like as seen from the MKH-418s
microphone:
the front is a cardioid (the mono signal) and the side
is a figure of eight. [The same setup could be used
with two microphones; just that the MKH-418s
has basically two microphones built in.]

 

the reason we also want to record the signals separately is so we can decode them for their further use in a DAW.  To decode we can either use a decoder plugin or a  routing matrix such as this one for example:

Three tracks in a DAW are needed:

  • Track 1 carries the mono signal (=front),
    panned to the middle.
  • Track 2 carries the side signal,
    panned to the left.
  • Track 3 carries a copy of the side signal,
    panned to the right AND phase inverted.

But of course, first we need a recording and for this we need a cable…

 

What You Need

  • 6-core wire (in your desired or practical length)
  • 1x 5-pin female XLR connector
  • 2x male XLR connectors

 

What to solder up

The colours of your wires entirely depend on the cable you chose in the first place. In my case, I had a cable with two red wires, two blue and two unshielded. It might as well be that your cable comes with wires in six different colours. Whatever your cable looks like, make sure you connect the the correct colour on the other end using following schematic.

On the 5-pin XLR connector solder up

pin 1 ground wire 5 & 6—in example:
combined unshielded wires
pin 1 of 3-pin XLR
pin 2 cold wire 1 (L-) pin 3 of 3-pin XLR one
pin 3 hot wire 2 (L+) pin 2 of 3-pin XLR one
pin 4 cold wire 3 (R-) pin 2 of 3-pin XLR two
pin 5 hot wire 4 (R+) pin 3 of 3-pin XLR two

L-/L+ corresponds with the mono signal and R-/R+ the side signal. The plus and minus wires do not correspond to separate signal flows but belong together to make up one signal! As explained above, the side signal will be ‘artificially’ duplicated in a DAW.

 

This is what my 5-pin XLR looks like:

 

 

The Result

I marked my 2x 3-pin XLRs with red, respectively yellow tape to be able to distinguish the signals: the red tape is for the mono signal and the yellow one carries the sides.

 

Happy recording and remember to drop me a message if you have any questions, hints or wishes for a next blog entry!

Permanent link to this article: http://www.suzannesoundcreations.com/diy-audio-electronics/connector-cable-for-stereo-microphones/

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