I own a single M/S microphone: Sennheiser MKH 418s. I don't want to have to use two channels from my recorder to record mono. If I only plug in the left channel of the mic, I'm actually getting the Mid + one of the sides together (am I right here?)...

Is there a clever way using a Sound Devices 702 to decode the mid channel using only the left channel from the mic. This way I can also have another mic plugged in, especially important if I'm location recording.

I hope my question makes sense. Thanks for any input.

  • @Andrew just to be sure I understand you correctly - you mean the mic's output is already X/Y-decoded? because according to the manual, that is not the case...
    – Julian
    Commented Oct 20, 2010 at 8:53
  • @Julian no it's encoded in Mid-Side. So on the left channel I get the Mono channel I'm interested in combined with the left of the side channel. Commented Oct 20, 2010 at 9:05
  • @Julian Sorry, I mean it's not encoded at all, it's just M/S, but once I bring it into the recorder I decode it into X-Y. But I figured it out, thanks so much for your input! Commented Oct 20, 2010 at 9:26

2 Answers 2


I have this mic, and the info going on in the comments section is correct. You need to provide power to both elements, otherwise the mic won't work. That being said, you don't necessarily have to plug in the "Side" component into your 702. If you had a separate phantom power supply (you can find some for under $40 at B&H) that you could plug the "Side" cable into you would then be fully powering the mic, and could record only the "Mid" signal on your 702 and still have the second channel free for a different source.

  • This is perfect, thanks (to all). I just assumed that the reson why it didn't sound good when plugging in just the mid is that it had a phasing issue when it's actually a phantom power problem. In the meanwhile I'll just use my Zoom H4n :-) Commented Oct 20, 2010 at 15:25

The 418 output Mid on the left ch and Side on the right ch, if I remember well.

I'm quite sure that it should work with phantom power to both channels, even if you need only the Mid signal. Maybe you can check the microphone manual.

  • @Andrew the manual :) tinyurl.com/9kxfjh according to this you should beable to record just the Mid BUT you will need to power both the Mid and Side channels.
    – RedSonic01
    Commented Oct 20, 2010 at 9:04
  • Are you sure it's not Mid + left side on left channel and then only right side on right channel? Commented Oct 20, 2010 at 9:06
  • yes, the two channels should be MID and SIDE. when you decode to stereo you'll have: LEFT = M + S RIGHT =M + (-S) The 418 is only a shotgun mic (for the MID) plus a figure 8 capsule (for the SIDE) Commented Oct 20, 2010 at 9:19
  • @Richard @Davide Oh okay, I get it. Was being an idiot. I'm usually good at reading manuals but not this time ;-) Am I understanding correctly that I have I to have phantom power to the sides, even if not using them? Thanks for all your help Commented Oct 20, 2010 at 9:24
  • @Andrew yes, you should power both sides all the time. Maybe will work even if you power only the MID side, but probably the frequency response will be altered Commented Oct 20, 2010 at 9:33

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