Nearfield Extension: NE-X-T™

In the BM Line, the reproduction of mid-and high tone ranges from 800 Hz upwards is handled by a newly designed element radiating cylindrical waves.

In cooperation with the Fraunhofer Institute for Applied Mathematics in Kaiserslautern, Germany, a slit shaped emitter was designed with an extremely powerful driver. With a cylindrical wave, the acoustic energy reduces by only 3 dB when the distance is doubled, with a normal spherical wave from a normal driver this reduction is 6 dB. This means that with the BM Line, even in larger rooms, your listening area is practically anywhere in front of the speakers.

Effectively this means the intensity of the sound in your ears is due to a much higher portion of direct waves and the effect of indirect waves and reflected waves is significantly reduced. Therefore the room characteristics have a much smaller influence on the acoustics. The direction of the cylindrical waves also ensure that reflections from the ceiling and the floor are further minimized. In this way, a completely different musical experience can be enjoyed with an exactly defined sound. For frequencies up to 800 Hz, the linear arrangement of the bass and mid-tone drivers also emit a perfectly matched cylindrical wave.

Horizontal Radiation Characteristics: FIR Time-Filter Technology FIRTEC™

A digital signal processor (DSP) stores a model of the physical characteristics of the speaker and, 44 times every millisecond, calculates the correct equalization of the complete loudspeaker. This means that in mid-and high tone ranges, an exact advance correction is achieved without loop errors or latency intervals. The AD- and DA converters are state of the art and have significantly more reserves in performance and dynamics than the recordings require. The AD converter works with our own proprietarily developed gain staging technology with a fantastic resolution of 27 Bit, representing a theoretical dynamic range of over 160 dB. Utilizing the unrivalled Backes & Mueller DMC™99 control in analogue mode, the bass achieves the very same high quality reproduction as the DSP does in the higher ranges. The combination of digital signal processing and the analogue Backes & Mueller DMC™99 control results in an exact linearization in volume and phase. The BM Line therefore achieves a constant phase of 0˚60. In musical terms, all frequencies leave the speaker at the same moment.

Dynamische Membran Controlle – DMC™ (dynamic movement control)

If you wanted to use the FIRTEC filter to reach a linear phase in the bass range, you would have to accept a latency interval of over 70 msec. Since this delay is unacceptably long, BM 35 and BM 50 flatten the bass with an analogue membrane control: Dynamic Membrane Control ™. This entails the continuous measurement of the membrane’s movement over distance, speed and acceleration. To do this, each driver has a sensor mounted under the dust protection dome which can measure each of these three values; distance, speed and acceleration. The measured and calculated values are fed into a controller where they are compared instantly with the current music signal feed. Only any differences to the expected values are transmitted to the output stage for correction. This enables a continuous assurance that the membrane only moves in exactly the way that is necessary to reproduce the signal input. In this way, decaying oscillations and other errors are ruled out. With sound travelling at 330 meters/sec and the corrective electronics working at almost the speed of light, the errors are corrected even during their formation with zero latency. An exact plotting of the membrane movement also means a zero degree phase situation across the entire transmitted frequency range.With the help of the most innovative technologies in the new BM 35 and BM 50, a loudspeaker system with the highest precision and neutrality has been developed, offering an exactly matched combination of acoustic radiation characteristics and hightech, resulting in an optimum of monitoring control.

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