Mackie 800R Rear Panel, MIC Inputs, MID/SIDE Decode, Closer Look AT MID/SIDE Recording

ONYX 800R

Rear Panel

The rear panel is where you make all your analog and digital audio connections to the Onyx 800R (except for the high-impedance instrument jacks on the front).

14. MIC Inputs

These are female XLR connectors, which accept a balanced microphone input from almost any type of microphone. The microphone preamps feature our new Onyx design, with higher fidelity and headroom rivaling any standalone mic preamp on the market today.

The XLR inputs are wired as follows:

Pin 1 = Shield or ground

Pin 2 = Positive (+ or hot)

Pin 3 = Negative (– or cold)

15. MID/SIDE DECODE

The Onyx 800R has a built-in Mid/Side decoder for stereo mic’ing. The Mid/Side (or M-S) stereo mic’ing technique not only provides a stereo image of the source, but allows you to adjust the width of the image by varying the balance between the Mid (or mono) and Side signals. See “A Closer Look at Mid/Side Recording” below for more info.

When using this technique, connect a cardioid (mid) microphone to channel 1 and a figure 8 (side) micro- phone to channel 2. Push in the MID/SIDE DECODE button, and the left signal from the decoder is sent to the channel 1 output, and the right signal from the decoder is sent to the channel 2 output.

A CLOSER LOOK AT MID/SIDE RECORDING

A number of stereo recording techniques have been developed over the years including Blumlein, ORTF, spaced pair, and coincident pair, of which X-Y and M-S are a subset. They each have their advantag- es, depending on the application. Let’s look at what the M-S method has to offer.

M-S (Mid-Side) requires the use of two micro- phones, one with a cardioid pickup and one with a figure-8 (bidirectional) pattern. The cardioid microphone (mid) faces straight forward toward the center of the sound source, while the figure-8 (side) microphone’s two elements face sideways, perpendic- ular to the mid microphone. It is important that the null of the figure 8 mic aligns with the zero degree line of the cardioid.

			MID
			0°
+	=	+		–
		SIDE
CARDIOID	FIGURE 8

Some microphone manufacturers make stereo mics designed specifically for M-S recording, with all three elements properly aligned in one housing. There’s nothing wrong with using two separate microphones, however, as long as the capsules are as coincident (occupying the same space) as possible.

The M-S technique requires a special decoder that produces a left and right stereo signal. The left channel is the sum of the mid and side microphones (M+S), and the right channel is the difference be- tween the mid and side microphones (M-S).

The Onyx 800R has a decoder built-in, which is activated by pushing in the MID/SIDE DECODE but- ton on the rear panel. Connect the MID microphone to channel 1 and the SIDE microphone to channel

2.The signals pass through the decoder just prior to the A/D converters and the analog line outputs.

Stereo recording reproduces the instruments in the same relative locations within the stereo image as they were in the original performance. The side to side stereo image and, to some extent, the front to back depth of image are preserved.

The M-S stereo recording technique allows you to adjust the width of the stereo image by varying the ratio between the mid and side signals. With the 800R, this is accomplished by adjusting the gain controls on channels 1 and 2.

Notice that the adjustments are made prior to the decoder. Adjusting the ratio of the left and right sig- nals after the decoder will not have the same effect. If you want to adjust the stereo image later during mixdown, record the raw MID and SIDE signals to tape with the decoder turned off. Then, when you are doing the final mix, run the recorded MID and SIDE signals through channels 1 and 2 with the decoder turned on and experiment with the gain controls on channels 1 and 2 to adjust the stereo image to your liking.

Another benefit of this recording technique is that the stereo recording is mono compatible. This is especially important for broadcast and film produc- tion applications.

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ONYX 800R