Dynamic heads for automotive speakers. Reference data

Encyclopedia of radio electronics and electrical engineering / Reference materials

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The article provides basic information about the electrodynamic heads produced by the Kaluga enterprise "ASA". These heads can be used both in built-in car acoustic systems and in cabinet loudspeakers for high-quality home sound reproduction systems.

Hi-Fi class component acoustic systems used in cars are built on the basis of bandpass (LF, MF, HF) dynamic heads placed in body cavities. The distribution of loudspeakers in the interior space allows you to create spatial sound images in a limited space.

Electrodynamic heads for car audio systems are characterized by increased resistance to vibration, moisture resistance and dust resistance. The dynamic heads presented here are developed on the basis of an optimized calculation of magnetic systems and the technology of manufacturing an anodized aluminum alloy radiant dome.

Component two- or three-way loudspeakers are designed for high-quality sound reproduction through amplifying devices designed for 4 ohm loads. The sizes of dynamic heads most widely used in automobiles correspond to 5- and 8-inch imported counterparts. Diffusers for them are made of anodized aluminum or impregnated cellulose, which improves protection against moisture. The anodized aluminum dome is a foil coated on both sides with the thinnest layer of ceramics. This gives the dome a special rigidity and can significantly reduce dynamic distortion at high power. The developed technology for manufacturing aluminum foil domes ensures the creation of the correct geometric shape and equal thickness of the foil in all parts of the dome.

Low-frequency dynamic heads with a size of 130 mm (according to English terminology - mid-bass) are represented by five models: MB1302, MB1303, MP1304, MP1306, MB 1307.

For the heads of this group, a special magnetic system has been developed, in which a magnet made of strontium ferrite is used. In these heads, the influence of asymmetric magnetic fields on the occurrence of non-linear distortions at large amplitudes of voice coil oscillations is reduced. A steel frame (diffuser holder) with an antiresonant plastic coating and a coil on an aluminum frame with a diameter of 25 mm contribute to an increase in the head's maximum power. The cones of some woofers (MB 1302, MB 1304) are made of long fiber cellulose impregnated to give water repellency. The cone profile provides a sharp drop in frequency response at frequencies above 5000 Hz, which allows you to abandon the use of a low-pass filter and connect these drivers directly to the amplifier.

The diffusers of the MB1303 and MB1306 heads are made of anodized aluminum alloy without a dust cap. The suspension can be made of rubber or polyurethane foam.

On fig. 1-7 show their appearance and frequency response.

In table. 1 shows the technical and design parameters of these heads and their modifications. Connecting dimensions - 100x100 mm.

For all heads, the frequency response unevenness is no more than ±2,5 dB. The rated power for them is set equal to 25 W, long-term - 30 W (for MP1304P, MP1306, MB 1307 - 35 W). Peak power for heads should not exceed 75 watts. Nonlinear distortion at a power equal to 10 W, at frequencies above 250 Hz is not more than 1,5%.

To expand the sound reproduction band in the low-frequency region, larger dynamic heads (8 inches) are designed. 200 mm low-frequency drivers are also represented here by four models: B2001, B2002, B2003, B2004 (Fig. 8-11 shows their appearance and frequency characteristics).

The magnetic system of these heads is based on a ring magnet made of barium ferrite with a diameter of 110 mm. Models B2002, B2003 use a double magnet.

The V2004 head uses a closed magnetic system based on neodymium-iron-boron composite magnets. The steel frame has an anti-resonant plastic coating. The installation dimensions of this series of heads are 200x200 mm.

The voice coil on an aluminum frame or on a kapton in various models has a different diameter: B2001 - 25,5 mm; MV2002-MV2003 - 35,5 mm; MV2004 - 50 mm.

The diffuser for heads B2001 and B2002 is made of impregnated cellulose, and for B2003 and B2004 it is made of anodized aluminum. A stronger magnet system allows the B2004 to be used in a powerful subwoofer.

Technical parameters of low-frequency heads are given in table. 2.

Long-term power of MV2001 heads - 25 W, modifications MV2002-MV2003 - 50 W, MV2004 - 60 W.

Peak power is significantly higher: for MV2001 - 75 W, MV2002-MV2004 - 100 W. Nonlinear distortion does not exceed 3% at a power of 10 W at frequencies above 50 Hz.

High-frequency dynamic heads are represented by one model - NEO-T25 (Fig. 12 shows the frequency response and the appearance of its modification with a protective grid - NEO-T25-1).

This head unit is constructed using neodymium-iron-boron composite magnet and anodized aluminum alloy dome for high sound quality and reliability. The dome of the head is 25 mm in diameter, the magnetic system is shielded. To improve cooling, the voice coil is made on an aluminum frame (in HF heads with a power of more than 50 W, the use of a cooling ferromagnetic fluid is provided). The body is made of black ABS plastic.

The technical and design parameters of this head are given in Table. 3.

Long-term head power - 10, peak - 50 watts. Frequency response unevenness - ± 1,5 dB. Nonlinear distortion - no more than 0,5% at a power of 3 W at frequencies above 3500 Hz.

The head parameters fully comply with the requirements for Hi-Fi audio equipment and can be used in high-quality home acoustic systems. Installation options include a movable mount with the ability to tilt the head at an angle of up to 30 ° or a mortise without adjustment. Connecting dimensions - around a circle with a diameter of 100 mm at three points.

All head models are produced without protective grilles and are intended for installation in regular places of domestic and imported cars.

It can be noted that the presented models are only a part of the heads produced by the enterprise and their modifications; there are also dynamic heads with shielded magnetic systems for home theater, special low-resistance ones (coil resistance - 1 ohm).

Author: Yu.Pukhlyakov, Kaluga

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