I was surprised to find that a Mid-Side decoder function is included in the H4n, this is usually a feature of high end field recorders but it’s easy to do in the digital realm so the Zoom engineers could “throw it in” without much added cost. I love fooling with different mic arrangements so I had to set up a couple of figure 8 mics and do some recordings.
Alan Blumlein
In 1931 Alan Blumlein applied for a patent on what we now call stereo sound. He described techniques for creating the auditory illusion of placement and depth using two (or more) channels of recorded and reproduced sound. As part of this patent application he described an array of two bidirectional mics in a coincident X/Y arrangement that we today call a Blumlein array:
Two bidirectional or figure 8 mics in a coincident XY
In the same document he described the Mid-Side mic arrangement. Rather than a crossed pair of mics at 45 degrees to the source, the Mid-Side array has the Mid mic pointing directly at the source and the Side mic at right angles to the source. The Mid mic can be any pattern but the Side mic must be a bidirectional or figure-8 mic.
Two bidirectional or figure 8 mics in Mid-Side
Mid-Side Recording
This article from emusician.com discusses the technical details of Mid-Side recording in some depth. Note that the use of different patterns for the Mid mic gives different results after decoding.
When I record in Mid-Side using my home recording chain it’s startling to see the difference in the levels of the Mid and Side channels. With both channels set to the same gain the Side channel barely shows any signal.
Decoding the Mid and Side channels to Left and Right is easy in a multitrack recording program. Simply place the Mid channel on one track panned to the center. Place the Side channel on a track panned hard left. Then place a copy of the Side channel inverted in polarity on a track panned hard right. When you mix the three tracks down you’ll have two stereo tracks.
Here’s a video I made demonstrating Mid-Side and Blumlein arrays with some demonstrations of the stereo field.
There are a few ? ? ? problems with the video, please accept my apologies. The bubble wrap stereo demo is funny (to me anyway), but the clipping caused by the amazingly loud pops wrecked the stereo field. Listen to the incidental noises for a better idea of how these recording techniques work. And the distortion is not there in the my recording, it was introduced by the YouTube compression process.
Mid-Side and the H4n
I also missed several opportunities to actually address some details of the H4n. For instance, the level metering shows levels after the signal is decoded. I think there’s a good chance of clipping the Mid mic and not seeing it in the decoded signal.
When setting up the Mid-Side connections on the H4n, notice that there’s a menu selection to identify which channel is the Mid and which is the Side.
Let me wrap up by mentioning that I sent my H4n back to the seller. I think it’s a pretty interesting recorder, but for my regular uses the H2 does at least as good a job. When I want to do more serious recording I just turn on my home studio system. I’m looking forward to continued progress in these handheld recorders, though. I just can’t resist the idea of a world class recording chain in my pocket.
April 9th, 2009 - 12:07 pm
I noticed the Blumlein recording of the guitar sounded considerably more diffuse than the MS version. I am guessing this is a function of the relatively poor off-axis response of most circular diaphragm condensors, especially large diaphragm condensors.
Although I know you have returned the unit, a repeat of this test with ribbon mics would be enlightening, as ribbons have very good off axis response – at least horizontal, when the ribbon element is vertical, due to the narrow dimension of the ribbon when compared to the diameter of a circular diaphragm.
With ribbons, the MS should sound more like the Blumlein.
I recorded orchestras and choirs for years with a Royer SF12 in MS and so often found that I decoded it 50/50 MS (which is the equivalent of Blumlein) that I eventually went straight to Blumlein to save the degradation of the decoding, which at that time was done in the analog domain.
Connected with all this (off axis response quality considerations) is the reason ribbons do so well with room tone – the response is pretty constant in a torus around the mic, so everything within that is of good fidelity.
I used to wonder why the room that sounded not bad in real life sounded so lousy when captured by a microphone. Then I figured out that when recording at any distance much of what is heard by the mic arrives off axis, and “LDCs” sound variously lousy off axis.
April 9th, 2009 - 2:41 pm
Russell, thanks for stopping by. I appreciate your opinion on the sound of the recording. I’ve only been doing this for a few years and I don’t think I’ll ever catch up on the listening end of things.
A friend of mine has been using an AEA R88 stereo ribbon, and to me his M/S and Blum sound identical. And gorgeous. I was really tempted by a recent Ebay auction but I resisted.
Do you have an opinion on the Schoeps MK8 compared to a pair of ribbons? That’s another “investment” I’ve been resisting.
I noticed on Gearslutz that you use K&H O300s. Any opinion on the O110?
Thanks again for your comments,
Fran
April 15th, 2009 - 7:44 am
Nice post Fran. I have a question, would the following be the correct way to record MS as well?
Two mics, a cardoid for the mid mic, and a figure eight mic for the side mic. The mid mic is assigned to a mono track, the figure 8 mic to a stereo track. Record my guitar, then invert the polarity on one of the channels of the stereo track using a Logic plugin. Then do you adjust the Mid to Side balance by adjusting the volume of the respective tracks? Or does it involve panning as well.
Anton
April 15th, 2009 - 8:06 am
Hey, Anton,
The setup you describe is exactly what you need. The inverted track is the one on the “back” side of the mid mic. So if the mid mic is arranged with its front side facing right, you invert the left track.
That should do it.
Are you cutting more tracks at home? I need to book some time with Doug myself, so I can try out that R88!
Thanks for stopping by,
Fran
April 16th, 2009 - 8:17 am
Not cutting any tracks at home at the moment, just lusting over some recording gear. A friend might be leaving his MOTU 8pre and some mics in my care for a bit, so perhaps i will have some gear to experiment with. I would like to get an interface and some mics for myself eventually, but with doing the recording for album at Doug’s, it just doesnt make sense at the moment.
I hope to head down to Doug’s in the next few months to finish up the tracks for my cd. Got 4 more to go. Its really nice working at his place, such a relaxing environment, and nice guitars sitting around to play.
Anton