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M21 Sound Sources Header Graphic
The M21 family is comprised of flexural disc projectors, commonly known as benders. The result of our decade of development is a highly-reliable, efficient, economical low-frequency source suitable for pulsed or continuous use.

A bender can be used individually as an omnidirectional source, or multiple benders can be used in one, two, or three-dimensional arrays at traditional array spacing to produce a directional source. Furthermore, multiple benders can be used with milli-╬╗ separations to create a MPS, with even lower resonances and greater power and bandwidth.

The resonance frequency, bandwidth and other characteristics of a bender are determined by its size. GeoSpectrum maintains an inventory of ceramic sizes and by changing the size of a machined plate, can quickly manufacture a projector ideally suited to your requirements.

Resonance
Frequency
(Hz)
Acoustic
Power
(kW)
Bandwidth
(-3dB)
(Hz)
Operating
Depth
(m)
Mass
(kg)
Diameter
(cm)
Thickness
(cm)
266
0.7
18
50
4.3
27
2.8
436
0.6
34
70
2.8
22
2.6
860
1.0
90
160
2.8
19
3.1
1000
1.1
170
290
8.3
27
5.5
1320*
1.0
230
330
4.7
22
4.7
1320
0.5
140
200
1.0
13
2.6
1410
0.2
150
170
0.5
11
2.2
2000
0.5
250
300
0.7
11
2.6
2110
1.4
430
590
4.2
19
5.3
2400
0.6
410
480
1.3
13
3.5
3450
0.5
680
660
0.9
11
3.5
3900
0.6
1000
1010
1.7
13
4.8
5160
0.2
2070
1170
1.1
11
4.5

The table to the left provides an indication of what can be achieved with a single bender. The two benders that resonate at 1320 Hz provide an indication of the performance-versus-size trade-off.

* The TVR and admittance of this bender are shown below. The electroacoustic efficiency of this and other benders exceeds 80% at resonance.


GeoSpectrum also sells M21s with impedance-matching circuitry that minimizes the reactive current. The figures below are the TVR and impedance of an 1800-Hz bender with a series inductor.

The GeoSpectrum M21 Sources are available with 3 types of cable exit: Radial, Axial, & Tangential. Each is designed to meet a different mounting configuration and can be requested at time of order.

Available Specification Sheets:

PDF Document Icon Download the M21-100-5160 Specification Sheet

PDF Document Icon Download the M21-100-1800 Specification Sheet

PDF Document Icon Download the M21-100-1950 Specification Sheet


PDF Document Icon Download the M21-120-1320 Specification Sheet


PDF Document Icon Download the M21-203-950 Specification Sheet

PDF Document Icon Download the M21-203-1000 Specification Sheet

PDF Document Icon Download the M21-203-1200 Specification Sheet


PDF Document Icon Download the M21-254-270 Specification Sheet

PDF Document Icon Download the M21-254-1000 Specification Sheet

Please contact us for further details or to discuss your specific needs.