Technical Data
Sketch
Amplitude & Impedance Frequency
| Rated power | 150 Watt |
|---|---|
| Maximum power | 250 Watt |
| Nominal impedance Z | 8 Ohm |
| Frequency response | fu-5000 Hz |
| (fu: Lower cut-off frequency depending on cabinet) | . |
| Mean sound pressure level | 95 dB (1W/1m) |
| Excursion limit | 14 mm |
| Resonance frequency fs | 50 Hz |
| Magnetic induction | 1.1 Tesla |
| Magnetic flux | 1400 µWb |
| Height of front pole-plate | 8 mm |
| Voice coil diameter | 5 cm |
| Height of winding | 1.4 cm |
| Cutout diameter | 28 cm |
| Net weight | 3 kg |
| D.C. resistance Rdc | 6.5 Ohm |
| Mechanical Q factor Qms | 3.13 |
| Electrical Q factor Qes | 0.7 |
| Total Q factor Qts | 0.58 |
| Equivalent volume Vas | 89 l |
| Effective piston area Sd | 511 cm2 |
| Dynamically moved mass Mms | 40 g |
| Force factor Bxl | 10.8 T · m |
| Inductance of the voice coil L | 1.6 mH |
Used in / Accessories:
MB 212/H
For sound reproduction in large halls or in the open, you need loudspeakers with a high efficiency rating. This means that the electrical input has to be converted to sound output with the minimum possible loss. Since the mid- and high-range sound is dampened more than the bass sound as the distance from the loudspeaker increases, the frequency response of a speaker designed for this application has to rise as you move up the frequency scale. Otherwise, the speaker will sound dull at a distance.
The MB 212/H musician's P.A. system has the required characteristics and is therefore well suited to use in discos, as an outside small-volume P.A., or as a vocals and instrument speaker. The two powerful 30-cm musician's subwoofers run parallel up to around 4,000 Hz, at which point the robust, but neutral-sounding HTH 8.7 8 Ohm high-range flare takes over.
The following calculation shows how important it is to have the right efficiency rating for professional P.A. speakers: the MB 212/H speaker generates a mean sound pressure of 98 dB at 1 watt and at 1 metre from the speaker. At the maximum permanent load of 300 W, the maximum achievable at 1 metre is 123 dB. In the open, measured at 60 metres from the speaker, the level is merely 87 dB.
Suppose we were to use a normal hi-fi speaker with a high efficiency rating of 90 dB/1 W/1 m, it would take 1,900 watts (!) to achieve 87 dB at a distance of 60 metres. As you can see, no normal hi-fi speaker is in a position to achieve anything like the required compression-free sound output.