BBE BBE DI-100 user manual BBE Process ‘What it is’

The BBE Process - ‘What it is’

Loudspeakers have difficulty dealing with the electronic signals sup- plied by an amplifier. These difficulties cause such major phase and amplitude distortion that the sound reproduced by a speaker differs sig- nificantly from the sound produced by the original source.

In the past, these problems proved unsolvable and were thus delegat- ed to a position of secondary importance in audio system design. However, phase and amplitude integrity is essential to accurate sound reproduction. Research shows that the information which the listener translates into the recognizable characteristics of a live performance are intimately tied into complex time and amplitude relationships between the fundamental and harmonic components of a given musical note or sound. These relationships define a sound’s “sound”.

When these complex relationships pass through a speaker, the proper order is lost. The higher frequencies are delayed. A lower frequency may reach the listener’s ear first or perhaps simultaneously with that of a higher frequency. In some cases, the fundamental components may be so time-shifted that they reach the listener’s ear ahead of some or all of the harmonic components.

This change in the phase and amplitude relationship on the harmonic and fundamental frequencies is technically called “envelope distortion.” The listener perceives this loss of sound integrity in the reproduced sound as “muddy” and “smeared.” In the extreme, it can become dif fi- cult to tell the difference between musical instruments, for example, an oboe and a clarinet.

BBE Sound, Inc. conducted extensive studies of numerous speaker systems over a ten year period. With this knowledge, it became possi- ble to identify the characteristics of an ideal speaker and to distill the

corrections necessary to return the fundamental and harmonic frequency structures to their correct order. While there are differences among var- ious speaker designs in the magnitude of their correction, the overall pattern of correction needed is remarkably consistent.

The BBE process is so unique that 42 patents have been awarded by the U.S. Patent Office.

The BBE Process - ‘How It Works’

The BBE Process imparts a pre-determined phase correction to the high frequencies where most harmonic information exists. This is done by breaking the signal into three sub-bands or groups: a.) LOs (20Hz - 150Hz), b.) MIDs (150Hz - 1200Hz), and c.) HIGHs (1200Hz - 20kHz). The low group is delayed about 2.5 ms (milliseconds) via a delay within the passive low pass filter. The front panel Lo CONTOUR con-

trol allows for either a flat response or a boost at 50Hz.

The mid-range group is delayed only about 0.5ms and passes

through an active band-pass filter while the high frequency group is passed through a VCA (Voltage Controlled Amplifier). The high group is used as a point of reference to make dynamic amplitude corrections to the high frequencies.

The RMS average loudness detectors continuously monitor both the mid-range and high frequencies to compare the relative harmonic con- tent levels of the two bands and apply the appropriate amount of control voltage to the VCA, thereby determining the amount of high frequency harmonic content present at the final output of the BBE processor.

2 - BBE DI-100 INSTALLATION INSTRUCTIONS