Acoustic system Verna 150-03. Scheme, description

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ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING
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Acoustic system Verna 150-03. Encyclopedia of radio electronics and electrical engineering

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Encyclopedia of radio electronics and electrical engineering / Speakers

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The acoustic system "VERNA 150-03" brought to the attention of readers differs from the previously published models of this brand by the use of new low-frequency drivers DO82C18 of the company "MARK-V" (St. institute. Academician N.N.Andreev.

Structural vibration-absorbing material, from which the speaker cabinet is made, consists of three pressed fibreboards and two layers of graphite located between them. The total thickness of the material is 24 mm.

A sketch of the front panel of the loudspeaker box is shown in fig. 1, and its longitudinal section is shown in Fig. 2. The sloping front panel of the loudspeaker allowed to reduce phase distortion and, last but not least, made the overall structure of the cabinet more rigid.

Acoustic system Verna 150-03

The useful volume of the compartment for the bass head is about 32 dm3. The stiffening bars inside the case are made of beech (you can use oak and other hardwoods). During assembly, the individual parts of the body are glued with PVA-M glue. Mats filled with batting are glued to all panels of the body, except for the front one, with Moment glue (in Fig. 2 they are shown conditionally). The phase inverter pipe is installed horizontally from the side of the rear wall of the case. It is made of 1 mm thick steel, its outer diameter is 72 mm, and its length is 175 mm.

The loudspeaker has a DO82C18 low-frequency head with a large dead weight of 4 kg and a cone diameter of 215 mm. The resonant frequency of the head is 35 Hz, and the phase inverter is tuned to the same frequency.

The MF-HF box is made of chipboard 16 mm thick. Its entire inner surface is covered with soft felt 12 mm thick. The box is filled with cotton wool (about 200 g) evenly distributed over its entire internal volume (3,5 dm3). It is unacceptable to use synthetic materials (foam rubber, synthetic winterizer, etc.) as a sound absorber.

In the MF-HF box, a 30GDS-1-8 mid-frequency head and a 10GDV-2-16 high-frequency head are installed.

The midrange head needs to be improved. But before that, a signal with a frequency of 300 Hz and a voltage of about 6 V is applied to the head and kept in this mode for 15 ... ...20 mm). After 70-10 hours, the dried suspension and part of the diffuser are impregnated with mastic made on the basis of Guerlain. After 12...8 hours after this operation, the PAS is installed on the head, sealing the windows of the diffuser holder with felt 10 mm thick.

The modified head must be tested again by removing the frequency response and measuring the electrical impedance and characteristic sensitivity. Two heads are suitable for speakers, the parameters of which differ by no more than 2 ... 3%.

A thick cardboard 2 mm thick and felt 1 mm thick should be glued onto the mounting part of the diffuser holder of the head.

The HF head 10GDV-2-16 is selected according to the minimum resonant frequency and maximum characteristic sensitivity. Refinement of this head comes down to replacing the sound absorber inside the sound-emitting dome with finely dispersed cotton wool (about 1,5 g), evenly distributed throughout the volume of the dome. To do this, unscrew the fixing screws, remove the acoustic lens of the head and carefully remove the sound-emitting dome using tweezers and a sharp awl. After replacing the sound absorber, install the dome and the acoustic lens in their original place. The modified head is fixed on the front panel of the loudspeaker housing through a felt pad.

A schematic diagram of a three-band AC crossover filter is shown in fig. 3.

Acoustic system Verna 150-03

Coils L1, L2 are wound on rectangular ferrite rods 2000MN with dimensions of 15x85x8 mm. Coil L1 is placed on two such rods folded together, and L2 - on one. The winding of the first coil contains 180, and the second - 110 turns of wire PEL-1 1,12. Coils L3, L4 are wound on standard frames with a diameter of 18 and a height of 20 mm and contain, respectively, 210 and 165 turns of PEL-1 0,56 wire. Capacitors C1-C3 - K73-16 for an operating voltage of 160 V, and C4 - C6 - K73-11. Capacitances of capacitors C1, C5, C6 and inductances of coils L1, L2, L4 are selected with an accuracy of 1%. For coil L3, a deviation from the inductance indicated in the diagram is + 2%. All resistors are PEV.

The filter is assembled on a fiberglass board by surface mounting. The connections between the elements are made with a single-core wire PEV-1 1,8 of the minimum possible length. The filter is connected to the heads with a MGSHV wire. The board itself is attached to the bottom panel of the loudspeaker housing through rubber gaskets.

The AC loudspeaker manufactured according to the above description has the following technical characteristics: rated power - 150 W; maximum long-term (short-term) power - 200 (300) W; total electrical resistance - 8 ohms; reproducible frequency range - 35 ... 20000 Hz with uneven frequency response +3 dB; level of characteristic sensitivity - 88,5 dB/W/m; section frequencies - 500 and 6000 Hz; total harmonic coefficient in the frequency range - 63 ... 550 Hz at a sound pressure level of 94 dB - 3%; 550...6000 Hz at a sound pressure level of 92 dB - 2%; 6000 ... 18 000 Hz at a sound pressure level of 90 dB - 1%; dimensions - 300x840x300 mm; weight - 45 kg.

Author: A. Demyanov, Moscow

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