Description

The AT933Rx/ML is a wide-range miniature condenser microphone with a MicroLine® polar pattern. It is designed for quality sound reinforce- ment, professional recording, television, and other demanding sound pickup applications. The AT933Rx/ML is furnished with a vinyl-coated steel hanger adapter that allows it to be adjusted for correct positioning.

The microphone features a 50' (15.2 m) permanently-attached miniature cable. Its free end connects to the provided AT8533x power module via internal solderless screw terminals for simple cable-length adjustment in the field.

It can be powered from any external 9V to 52V DC phantom power supply. A recessed switch in the power module permits choice of flat response or low-frequency roll-off to help control undesired ambient noise.

Four additional interchangeable elements are available to permit selection of angle of acceptance from 90° to 360°.

The microphone is enclosed in a rugged housing with a low-reflectance black finish. It is also available in white as the AT933RWx/ML.

Installation and Operation

The combination of small size and excellent response makes the AT933Rx/ML ideal for suspension over choirs, instrumental groups or theater stages. A uniform 90° angle of acceptance provides well-balanced pickup over a narrow area. The microphone should be located forward of the front-most source, above the rear-most source, and “aimed” between them (Fig. 1). Increasing the height of the mic above the sources will tend to equalize sound levels between them, but may also increase background/reverberant sound pickup. Whenever possible, the distance from the mic to the rear-most pickup should be no more than twice the distance to the front source, to maintain front-to-rear balance (Fig. 1).

Width of pickup is approximately 1.5 times the distance to the closest performer. If additional mics are needed for wide sources, they should not be closer together laterally than 1.5 times the distance to the front source, to avoid phase cancellation (Fig. 2).

To orient the microphone in the proper direction, twist the housing slightly in its wire holder (clockwise rotation moves the microphone to the right; counterclockwise rotation moves it to the left). Adjust the vertical angle by changing the number of loops the cable passes through in the steel hanger.

The provided foam windscreen simply slips over the MicroLine element, effectively reducing noise from wind or ventilation air currents.

Output is low impedance balanced. The output connector of the power module mates with XLRF-type cable connectors. The balanced signal appears across Pins 2 and 3, while the ground (shield) connection is Pin 1. Output is phased so that positive acoustic pressure produces positive voltage at Pin 2, in accordance with industry convention.

To shorten the cable, remove the three screws from the base of the power module and slide the outer case up the cable to reveal the cir- cuit board and screw terminals. Loosen the three terminal screws and remove the cable from the module. Next, slide the case off the cable, cut the cable to the desired length (allowing a few extra inches) and slide the case back onto the cable. Tie a single knot in the cable about two inches from the cut end. Following Figure 3, cut the cable off 1" down from the top of the knot and carefully remove 1/2" of the outer jacket. Strip the mic cable wires and attach them to their respective terminals (Fig. 4). Make certain

that the terminals are clamped on the conductors, not on the insulation, and that there are no loose strands of wire which might

touch other terminals. Replace the case, being certain that it goes over the case grounding contact and that the roll-off switch is accessible. Finish by replacing the three base

screws and testing for proper operation.

While a modern condenser microphone is not unduly sensitive to the environment, temper- ature extremes can be harmful. Avoid leaving the microphone in the open sun or in areas where temperatures exceed 110° F (43° C) for long periods of time. Extremely high humidity should also be avoided.

	Frequency Response (Typical)
									in dB
								10 dB	Response
50	100	200	500	1k	2k	5k	10k	20k
			Frequency in Hertz
LEGEND		12" or more on axis (flat)
		Roll-off

AT933Rx/ML

MicroLine®

Miniature

Condenser

Hanging

Microphone

	LESS
DISTANCE	THAN 2	TIMES “X”
DISTANCE	“X”
	“X”
90°
ANGLE OF
ACCEPTANCE

90°	90°
MIC A	MIC B
	1.5 TIMES
	DISTANCE “X”

Terminal screws

Case grounding contact

Shield

Yellow-Yellow

1/2"Red-Red

1/8" strip reds

and yellows

Shield strands, fully twisted

Yellow-Yellow

Red-Red

S Y R

PC board

switch side

Figure 1

Figure 2

Figure 3

Figure 4