The BR 50 is a 3-way Ba fl reflex-Box that was manufactured in the Frankfurt / Oder Energy Combination. It was developed from the experience gained with the BR 25 by VEB Musikelektronik Geithain. Compared to the BR 25, however, some technical changes have been made, which allow a higher sensitivity and resilience with improved sound.
The first to be mentioned is the housing, which is much more complex and of high quality compared to the BR 25. It is made of chipboard and covered with real wood veneer. On the front panel there are milled beads for the 4 loudspeakers and the reflex tube. Furthermore, to mechanically isolate the midrange speaker from the air volume of the woofer, a small chipboard housing is also glued into the box, onto which the crossover is screwed at the same time.
The mounting of the individual loudspeakers in the box is unusual. They are mounted on the front of the baffle without the screws being visible. Black molded plastic parts are used for this, which enclose the loudspeakers, but leave their membranes exposed, and are screwed into the box from behind (with a total of 30! Screws). For this reason, the BR 50 has a removable rear panel that is held in place by 8 screws and thus enables access to the box from behind.
In order to achieve a nominal load capacity of 50 watts, two woofers had to be used in the BR 50, which were connected electrically and acoustically in parallel. The 8-ohm version L 7114 of the L 7102 known from the BR 25 with the same acoustic parameters is used as the woofer. It has a very soft foam surround, which enables large membrane deflections and high rise times for undistorted playback, e.g. of drum beats. The membrane, which is light but still stiff due to the embossing, also contributes to this. The voice coil is wound on an aluminum support for good heat dissipation, whereby a high load capacity of 25 VA can be guaranteed. The generously dimensioned drive allows a pulse load of 50 watts.
In connection with the bass reflex system, which is matched to the technical parameters of the two woofer chassis and the speaker volume, a lower limit frequency of 45 Hz is achieved. As a result, the BR 50 has, compared to other, similarly large loudspeakers in the GDR range of speakers, a lower lower limit frequency, a higher sensitivity and realizes less distortion and better impulse transmission behavior.
In the mid-range branch, the L 7113 with 4 ohms, acoustically slightly different from the basic type L 7102, is used. It has a slightly shorter winding, which means that it has a higher sensitivity in the middle frequencies, what for
use as a mid-range speaker is useful. It works in a small, separate volume in order to be acoustically decoupled from the woofers.
In the tweeter branch of the BR 50, the 25 mm dome tweeter of the type L 7101 known from the BR 25 is used, which has a soaked fabric membrane. It also has a high load capacity of 25 watts. This was specially designed for use in the BR 25, as it not only has to emit high frequencies, but also a large part of the important mid-range down to 2600 Hz. Compared to the L 9801 dome with polycarbonate cone, which is otherwise used, it sounds a little softer, but at only 87 dB it has a relatively low sensitivity. In addition, a horn attachment was provided to improve the radiation behavior, in the case of the BR 50 with a plastic cover.
The three loudspeakers are interconnected via an electrical crossover with a slope of 12 dB / octave for the bass and mid-range, or 18 dB / octave for the tweeter. The crossover frequencies are 800 and 2600 Hz. In the low-frequency and mid-tone branches, coils with a ferrite core are used, in the high-tone branch only MKT capacitors are used. All components of the crossover are housed on a circuit board. The tweeter also has overload protection in the form of a PTC thermistor (21 watt light bulb).
The visual design of the BR 50 is very idiosyncratic and can be traced back to acoustic rather than optical aspects. Designed as a large shelf box, the housing is not very deep, but has a fairly large baffle. The front has a very three-dimensional effect thanks to the molded plastic parts and the slightly offset front panel. The box was labeled with gray and green screen printing on the plastic parts. The membranes of the box are not covered by a grid or ‰. Protected, there is no additional front panel.
The aluminum-etched type plate on the box and the real ash-wood veneer look very high-quality. Almost all of the BR 50s produced are colored black, only a few boxes are made of light ash.
