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Old 2005-04-15, 05:24 AM
Re: Matrix(ed) recordings

Originally Posted by wazoo2u

OK, here we go again. What are commonly (inaccurately) referred to as "Matrix" recordings are in fact "Blends" of independently recorded SBD and AUD sources of an event. In the audio world, a matrix recording is in fact:

Mid-side Matrix
One cardioid mic (M) points at subject (0°), and a figure-8 mic (S) picks up ambient sound by pointing at sides(90° and 270°).

The signals are then run through a decoder matrix (software or hardware) which creates two stereo channels:
n M+S = channel one
n M - S = channel two

One channel is a mix of M and S and the other be a mix of M and Sų (which means S is 180° out of phase)

n The more S, the stronger the separation.

MS Matrix recording is mostly used in acoustic concert settings to capture the true image of the hall.

One technique that Dan Healy perfected when mixing and recording the Grateful Dead, was to place a MS Matrixed microphone array at the mix position, and record it on a source that was locked to the same source as the SBD recording (assuring that the recordings were speed accurate to each other) What Dan called an "Ultra Matrix" was (as I understand it) actually a BLEND of a Matrix recording and a SBD recording. There are also time coincidence issues that are addressed when combining these sources.

Many "Matrix" recordings in circulation are simply blends of 2 different recordings and present a significant challenge in Post Production in terms of correctly time and pitch aligning the sources. The results of these efforts often sound really good, but are difficult to produce.

The cow has left the barn in terms of correcting the proper use of the term "Matrix", but in fact, it's nice to know the proper terms to apply to these very different methods.
I think that is a technically accurate explanation,though the term has come to mean a mixed recording with dual sources,such as a board feed and a mic or two,with some % of each getting recorded. If it is an after the fact blending,it is often called a merge. There is a Hendrix New Years eve show that was merged,in large part because the board and a couple of auds each had significant shortcomings but blending allowed for a more listenable and complete show. A Source might have low hiss,but very weak bass,another may have hi-freq hiss,but full freq response while another has good vocal presence but is incomplete. With enough time and software it is possible to assemble a recording that is a better representation of the show than any one source.
For a mixed matrix'or "matrix" its about the SBD clarity and detail +the aud ambience,audience reactions.
At one point Healy used Beta HI-Fi with the board going through a PCM unit and an AUD feed going onto the Beta HIFI. That enabled a synched 4 channel recording that later could be mixed to the best ratio. The board rec was digital,the aud,analog,but Beta HIFI-or for that matter,VHS hifi,gives a good 20-20k response with a real nice SN ratio,enough for the job.
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