Three-way loudspeaker for anyone who collected it. High efficiency loudspeaker

Three-way loudspeaker with head W21 EX 001

The goal of developing the described design was to create a relatively small-sized loudspeaker with high electro-acoustic characteristics suitable for repetition in amateur conditions. When choosing dynamic drivers, their electroacoustic parameters were taken into account, as well as the experience of designing several loudspeakers that the author had previously developed. For low frequencies, the dynamic head SEAS W21EX 001 was chosen. At the beginning of development, there was a positive experience of using W21EX 001 in a two-way closed-type loudspeaker, which provided a fairly high quality of low frequency reproduction. For mid frequencies, a SEAS H143 head with a paper diffuser was chosen, for high frequencies - PEERLESS 810665 without magnetic fluid, with a dome made of impregnated fabric.

A drawing of the loudspeaker housing is shown in Fig. 1. The housing has a useful volume of 28 liters for the bass head and 2.7 liters for the midrange head. These volumes are filled with low-density padding polyester. In order to reduce vibrations, the inner surface of the housing is covered with hydroglass insulation.

(click to enlarge)

Overlays are used for additional damping of the side walls. The linings have round recesses in which rubber washers are inserted, the thickness of which exceeds the depth of the recesses by 0.5 mm. The covers are attached to the side walls with self-tapping screws. As the pads are pressed, the washers deform and they fit tightly to the side wall of the case.

The outer surface of the body is covered with cherry veneer, the linings are painted with black acrylic paint. Dark overlays against the background of light veneer emphasize the shape of the structure, giving the body a more harmonious appearance.

It is advisable to pay special attention to the description of the crossover, since it is an important component of a three-way loudspeaker.

Let's start by clarifying some concepts. The frequency interval in which both heads participate in the formation of the resulting frequency response in terms of sound pressure is the region of joint radiation of the dynamic heads, and the crossover frequency is located inside this region. With symmetrical frequency response decays in sound pressure, the crossover frequency can be calculated as the geometric mean of the frequencies that define the boundaries of the co-emission region. For brevity (due to frequent mention), we will call the dependences of the impedance module on the frequency of the dynamic heads and loudspeaker Z-characteristics.

When developing the crossover, the goal was to ensure minimal unevenness in the frequency response of the loudspeaker in terms of sound pressure. To simulate the crossover, the LEAR program was used, which allows you to work with the measured frequency response and Z-characteristics of dynamic heads. This makes it possible to preview the operation of different filter circuits, obtaining fairly clear results, and select the most appropriate option for implementation. The LEAP program has an optimizer that allows you to automatically calculate any filter element according to a given criterion (for example, the minimum frequency response unevenness in a given frequency range).

The initial data for developing a crossover are the frequency response of sensitivity and Z-characteristics of dynamic heads. All these characteristics are measured in the loudspeaker cabinet after adjusting the acoustic design. To select the optimal crossover frequencies, the frequency response of all heads was measured using a microphone located along the axis of the head at a distance of 0.5 m, and the results were averaged in intervals of 0.2 octaves. Z-characteristics were measured in current generator mode. Let us roughly determine the crossover frequencies based on an analysis of the frequency response of the dynamic heads.

The frequency response of the LF head (Fig. 2) has an unevenness of 3 dB in the frequency range 60...500 Hz; further, with increasing frequency, there follows a rise with a maximum at a frequency of 1.3 kHz. This nature of the frequency response is not a problem, since in a three-way loudspeaker you can use a low-frequency head in the frequency range no higher than 600 Hz, where the unevenness of the frequency response is quite small.

The frequency response of the midrange head (Fig. 3) in the frequency range 600...4000 Hz has an unevenness of 4 dB. The unevenness of the frequency response is characterized by a rise at a frequency of 1 kHz and a dip in the range from 1.5 to 3 kHz. When developing crossover filters, it is desirable to reduce the unevenness of the frequency response of the midrange head. To do this, it is advisable to select a crossover frequency close to the dip in its frequency response. Let's choose a crossover frequency of 3 kHz and check how this agrees with the parameters of the RF head.

The frequency response of this head (Fig. 4) in the range of 3...20 kHz has an unevenness of 3 dB, and the resonant frequency is about 950 Hz. When developing a filter, it is necessary to take into account that in order to protect the HF head from overload with mid-frequencies, it will be necessary to provide attenuation of the signal at a frequency of 950 Hz of at least 20 dB. At a crossover frequency of 3 kHz, the required attenuation can be achieved using a third-order high-pass filter.

The crossover circuit is shown in Fig. 5. Low-frequency signals are supplied to the dynamic head W21EX001 through a second-order low-pass filter L4C7, which provides a fall in the frequency response in sound pressure of 3 dB at a frequency of 500 Hz. The R5C8 circuit compensates for the increase in head impedance with increasing frequency. The symmetrical decline in the frequency response of the midrange head forms a first-order high-pass filter in which capacitor C3 operates.

The use of a first-order filter with the required frequency response roll-off with a slope of 12 dB per octave turned out to be possible due to the fact that the beginning of the natural frequency response roll-off of the midrange head turned out to be close to the crossover frequency. The formation of a decline in the frequency response occurred as a result of the interaction of the transfer characteristic of the filter and the natural decline in the frequency response of the midrange head. The resonant peak in the Z-characteristic of this head is compensated by the series circuit L3C6R4. Elements R3 and C5 compensate for the increase in midrange head resistance with increasing frequency. In the compensating circuit, R4 is selected so that the total active resistance of the inductor and resistor R4 is 9 Ohms.

In Fig. Figure 6 shows the results of compensation for the nonlinearity inherent in the Z-characteristic of the midrange head. The second-order low-pass filter L2C4 forms a roll-off in the frequency response of the midrange head, which starts at 2.5 kHz.

A third-order high-pass filter operates in conjunction with the high-frequency head, which provides an attenuation of 5 dB at a frequency of 2.5 kHz. Divider R1R2 matches the HF head in terms of sound pressure level with the MF and LF heads.

The parameters of the crossover elements were selected using the LEAP program optimizer according to the criterion of minimal unevenness of the loudspeaker frequency response in terms of sound pressure.

In Fig. Figure 7 shows the frequency response of dynamic heads working in conjunction with filters and the resulting frequency response of the loudspeaker. For clarity, the frequency response level of the dynamic heads is reduced by 1 dB.

The region of joint radiation of the LF and MF heads is in the range of 400...900 Hz, located symmetrically relative to 600 Hz. Their frequency response in terms of sound pressure intersect at a frequency of 550 Hz. The region of joint radiation of the midrange and high-frequency heads lies in the range of 2.5...4 kHz, located symmetrically relative to 3.16 kHz. The frequency response of the sound pressure of the mid and high frequency heads intersect at a frequency of 2.9 kHz. In Fig. Figure 8 shows the transfer characteristics of the filters.

Let's consider their characteristic features.

The filter, working in conjunction with the low-pass head, creates a slight roll-off in the low-frequency region. The roll-off starts at 50 Hz and is 1 dB at 20 Hz. This is the effect of changing the impedance of the woofer head: the impedance decreases from 30 to 8 Ohms when the frequency changes from 50 to 20 Hz.

The filter for the midrange head is used in addition to limiting the operating frequency band and for adjusting the frequency response according to sound pressure; therefore, its transfer characteristic in the transparency band has practically no flat section. As a result, in the frequency band 1...3 kHz, the frequency response unevenness of the loudspeaker is 1.5 dB, while the midrange head in this range has an uneven frequency response of 4 dB.

The filter, which protects the HF head from out-of-band low-frequency signals, provides an attenuation of 24 dB at a frequency of 950 Hz.

The crossover uses metal film ceramic resistors with a power of 5 W. Capacitors C1, C2, C4 - with polypropylene dielectric for an operating voltage of 250 V from Solen. Capacitors C3, C5, C7, C8 are film capacitors with lavsan dielectric (MKT axial) for an operating voltage of 160 V. C6 is a non-polar oxide Jamicon capacitor for an operating voltage of 35 V.

The inductors are wound on frames made of plexiglass. The diagram shows the maximum permissible values ​​of the active resistance of the inductors. The winding data of the coils is summarized in the table. It uses the following designations: D - frame diameter; H - winding height; T - winding width; N - number of turns; d - wire diameter.

In Fig. Figure 9 shows the Z-characteristic of the loudspeaker. The minimum loudspeaker impedance value is 4.3 ohms at 300 Hz. Above 3 kHz there is an increase in resistance, reaching a maximum of 18 ohms at 7 kHz.

This increase in impedance can result in emphasized high-frequency reproduction when the speaker is driven by a tube amplifier that has a higher output impedance. To compensate for the rise, a series circuit R6L5C9 can be connected parallel to the loudspeaker input terminals (see Fig. 5). The Z-characteristic with lift compensation is shown in Fig. 10.

Those who like to reduce the number of crossover elements can exclude compensation for the resonant peak of the midrange head. In Fig. Figure 11 shows the change in the frequency response of the sound pressure of this head, which is obtained as a result of eliminating the compensating circuit R4L3C6. Without compensation at the level of 12 dB, the frequency response decline acquires a small “shelf” in the range of 150...300 Hz. The change in the frequency response decay occurs mainly outside the region of mutual radiation and does not lead to noticeable changes in the frequency response of the loudspeaker. By ear it is difficult to notice some deterioration in sound associated with the exclusion of the compensating circuit.

Listening to the loudspeaker was carried out with a transistor power amplifier. Everyone who took part in the audition gave positive feedback, noting good bass articulation and neutral sound in the mid and high frequencies. The low-frequency sound of the loudspeaker was considered adequate for its size, but insufficient for high-quality reproduction of programs where frequencies below 60 Hz play a significant role. You can expand the frequency range of the loudspeaker down to 35 Hz by introducing a bass reflex for the W21EX 001 dynamic head.

See other articles section.

The loudspeaker brought to the attention of readers is made on the basis of widespread dynamic heads 10GD-ZOE, 4GD-8E, ZGD-31 and is designed to work with high-quality sound amplification equipment.

Main technical characteristics

Effectively reproduced frequency range, Hz, with uneven frequency response 12 dB 20..25 000

Uneven frequency response in sound pressure dB, in the frequency range -. Guy,

27.. .20 000 ... 4

Rated power. Tue 12

Maximum power, W. . thirty

Nominal electrical resistance

tivlenis. Om....... 8

Dimensions, mm. 500x350x

The acoustic design of the loudspeaker is made in the form of a bass reflex. The dynamic heads are connected to the amplifier through a three-band iLC crossover filter (Fig. I) with crossover frequencies of 0.5 and 5 kHz. A distinctive feature of the filter is the presence of attenuators in it, providing stepwise (in 2 dB steps) adjustment of the loudspeaker frequency response in the high and middle frequencies by ±4 dB relative to the average level.

The attenuator resistors are wound with 0.25 PEMS manganin wire. MLT-2 resistors with a resistance of more than 100 kOhm were used as frames. Switches SJ and S2 are biscuits (PM or PGK).

The required capacitance values ​​of the filter capacitors are obtained by parallel connection of several capacitors of the types MBGO, MBGN, BMT, etc. (preferably with a permissible deviation of the capacitance from the nominal values ​​of ±5%).

Coils LI and L2 are wound on plastic frames (Fig. 2), L3 and L4 are frameless, with an internal diameter of 36 and a length of 20 mm. Winding all the coils. ordinary, turn to turn. Coil L1 contains 312, L2 - 263, L3 - 98. L4 - 82.5 turns of PEV-2 1.84 wire. Autotransformer 77 completed

on magnetic circuit OL 32X28X5. Its winding contains 1000 turns of PELSHO 0.27 wire with a tap from the middle.

The loudspeaker housing is made of 10 mm thick plywood. Front panel (Fig. 3). on which heads and switches S1 and S2 are installed (holes with a diameter of 10 mm are intended for them), spaced from the edge of the case to a depth of 10 mm. A removable wooden frame with a cotton canvas stretched tightly over it (for cross stitching), repeatedly coated with NC nitro enamel (in aerosol packaging) is tightly inserted into this recess.

The dynamic heads are secured with M4 screws and nuts through rubber gasket rings 1.5...2 mm thick. Before installation, the rings are coated with rubber glue on both sides. Screws

ZGD-ZG-1300

inserted from the front side of the panel. Rubber washers 2 mm thick are additionally placed under the washers for fastening the low-frequency head.

It is advisable to separate the separating filter coils as far as possible from each other and from the magnetic systems of the heads. It is best to place them on the back wall of the case.

The walls of the case are fastened with pine bars with a section of I5X I5 mm and screws screwed into the inside of the case. Before installing in place, the bars are coated with synthetic “Mars” glue. All seams are sealed with the same glue.

A wooden spacer with a cross section of 20x25 mm is inserted between the middles of the side walls of the case, and a vertical partition with dimensions 4I0XI20 mm is installed at a distance of 80 mm from the rear wall. adjacent to the side wall with its long side. The partition is covered with foam rubber with a thickness of I0 mm.

There are cotton wool seals in the corners of the box. that its inner surface has a rounded shape. The entire remaining volume is evenly filled with cotton wool (600...700 g) in such a way that there is some passage left between the opening of the bass reflex tunnel and the YUGD-ZOE head (it is formed with a metal mesh or wire arches). Corrugations of head diffusers. 4GD-8E and ZGD-31 are impregnated with a solution of castor oil in acetone (the concentration of the solution for the first of them is 50...70%, for the second - 15...20%). This impregnation reduces the unevenness of the frequency response of the heads by

3...5 dB. The central (up to half the radius) part of the 4GD-8E head diffuser is impregnated with a weak solution of tsaponlak in acetone, and after drying, an additional layer of rubber glue diluted with gasoline is applied to it (the treatment is carried out with a film mandrel inserted into the gap of the voice coil). This two-layer coating is combined with an asymmetrical filling of the cap with cotton wool.

Improving the sound quality of modern loudspeakers is achieved mainly through the use of new powerful dynamic drivers, and this most often entails an increase in their dimensions, weight, and cost. Meanwhile, a very good loudspeaker can be built on the basis of inexpensive dynamic heads.

Main technical characteristics.

Rated (nameplate) power, W....................................10 (30)

Nominal range of reproduced frequencies, Hz............30...25,000

Number of lanes................................................... ........................................3

Section frequencies, Hz................................................... ....................500; 5000

Nominal electrical resistance, Ohm............................6.3

Average standard sound pressure, Pa...................................0.35

Dimensions, mm................................................... ................................620x350x310

The electrical circuit of the loudspeaker is shown in Fig. 1. It is built on the basis of three dynamic heads. The low-frequency (LF) functions are performed by the 6GD-2 head, the mid-frequency (MF) head - 3GD-38E, and the high-frequency (HF) head - 6GD-13 (new name 6GDV-4). The second-order filter L1C1 is used in the low-frequency section, the first-order filter L2C2 is used in the midrange, and the third-order filter L3C3C4 is used in the high-frequency section. To equalize the frequency response of the loudspeaker in the region of medium sound frequencies, the midrange head is connected through resistor R1. In order to improve the sound of the system at frequencies above 503 Hz, the 6GDV-4 HF head is connected to a filter using resistors R2 and R3. It is important to note that this head is turned on in antiphase with the bass and midrange heads.

Fig.1. Electrical circuit of a three-way loudspeaker filter

The acoustic design of the loudspeaker is a bass reflex. Its body is made of chipboard 20 mm thick. The front panel and side walls are connected to each other with 20 x 20 mm slats using EDP epoxy glue. The back wall is removable; it is attached to the body through 2 mm thick rubber gaskets.

The view from the front panel is shown in Fig. 2, a, and a section of the body along line A-A- in Fig. 2, b. The bass and midrange speakers are attached to the outside of the front panel. Between it and the head diffusers there are rubber (polyurethane foam) rings 1.5 mm thick are laid.

Fig.2. Three-way loudspeaker drawing

Before placement on the front panel, the 6GD-2 head must be modified in order to reduce its overall quality factor. To do this, acoustic resistance panels (ARPs) should be installed in the windows of its diffuser holder, i.e., sealed with synthetic felt or, in extreme cases, medical gauze folded in several layers. The mid-frequency head must be placed in a sealed box with a volume of about 2 liters, filled with cotton wool. The diameter of the box is equal to the diameter of the hole in the front panel for the midrange head. The place where it connects to the panel must be carefully sealed (for example, with plasticine). The 6GDV-4 RF head is mounted on the inside of the front panel, and the side surfaces of the hole for its installation should, as it were, continue the cone existing on the head and form a radiating horn with it. A sealing rubber ring should be placed between the body of this head and the panel. The bass reflex tunnel is a plastic tube with an outer diameter of 70 and an inner diameter of 65 and a length of 150 mm. It is inserted into the corresponding hole on the front panel from the outside. The gaps between the panel and the tunnel are sealed from the inside with plasticine.

The crossover filter parts are placed on a getinax board measuring 250 x 150 mm, installed on the side wall of the housing in its lower corner, opposite the bass reflex tunnel. To avoid rattling, a sound-absorbing gasket must be laid between the board and the case. The filter uses non-polar MBM capacitors. MBGO for a voltage of 200 V and wirewound resistors with a power of 2 (R3) and at least 7.5 W (others). Capacitor C1 is made up of six 10 micron capacitors connected in parallel. Coils L1-L3 are frameless. The internal diameter and height of the first of them is 40 mm, the other two are 25 and 30 mm, respectively. Coil L1 contains 260 turns of PEL 1.5 wire, L2-170 and L3-90 turns of PEV 1.0 wire. The inner surface of the case is covered with sound-absorbing material (batting, foam rubber) with a thickness of 10...15 mm. The body itself is filled with cotton wool, but in such a way that an air passage is left between the woofer head and the bass reflex. All connections of the housing walls are sealed with epoxy glue.

The sound of the described loudspeaker was compared with the sound of the well-known industrial model 35AC-012 (S-90). During the tests, a stereo AF amplifier with a rated power of 2 x 25 W and a harmonic coefficient of no more than 0.2% was used. The softer sound of the homemade loudspeaker was noted in the region of low and medium sound frequencies, as well as the absence of unpleasant overtones created by the 10GD-35 head installed in the 35AS-012 in the range of 5...10 kHz.

P.S. Replacing the 6GD-2 head. Instead of 6GD-2, you can use a dynamic head 75GDN-1L-4 (formerly designated 30GD-2) or 35GDN-4 (25GD-26B). These heads have more than half the standard sound pressure (0.15 and 0.12 Pa, respectively) compared to the 6GD-2 (0.35 Pa), but their significantly higher rated power compensates for this disadvantage. The rated power of the loudspeaker after such a replacement will increase in the first case to 50, in the second - to 40 W, the nominal electrical resistance will drop to 4 Ohms. The capacity of capacitor C1 when using the 75GDN-1L-4 head is 80 µF. PAS is not required in both cases. The first replacement option is preferable, since the 75GDN-1 L-4 head has the same dimensions as the 6GDN-2, and greater efficiency than the 35GDN-4, especially at frequencies below 100 Hz.

Yu. DLI, Gorky

Radio magazine, No. 3.9 1989

A three-way dividing line with a crossover frequency of 520–4800 Hz was used (Fig. 1). The presence of attenuators allows you to adjust the frequency response of the loudspeaker in the mid-high frequency region by ±4 dB relative to the average (zero) level. The attenuator resistors are made of Provo-PEMS 0.41 - 0.56. They can be made from iron-tiles.

Separating coils. filters are wound on frames made of wood (birch, ) with. external 0 36 mm, length 24 mm (Fig. 2), and contain: LI, L2 - 260 turns each, L3 - 85 turns, L4 - 170 turns with a tap from the middle of the PEL 1.0 wire.

The loudspeaker body and front panel are made of 16 mm thick chipboard (Fig. 3). The front one (Fig. 4) is deepened by 20 mm. The back cover of the speaker is secured with overlapping screws. Between the back cover and the case for sealing, feathery rubber 5 mm thick is laid. The boxes are fastened with birch bars, pre-coated with EDP-3 or EDP-5 glue. glue seals the loudspeaker.

The dynamic heads are installed on the front side of the front panel. For this purpose, recesses are made in the frame of the dynamic heads. Between the front panel and the bars, and to which it is attached, porous rubber is laid for sealing. Then inside the box, seals are created from cotton wool at an angle so that it becomes spherical. The mid-frequency one is covered with a cap made according to the same technology: a cylindrical blank 0 140 mm, 120 mm high, is machined from foam plastic. Then with one it is given a spherical shape (Fig. 5). A thin (1 - 2 mm) amount of plasticine is carefully applied to the surface of the finished sphere. Then, using the papier-Mrzhe method, pieces of fiberglass impregnated with EDP-3, EDP-S glue, 2 - 3 mm thick, are glued onto it. After the glue has dried, the sphere is removed from the foam plastic blank - the cap for the frequency head is ready. The windows of its frame are sealed with mar- , the volume between the head and the cap is evenly filled with cotton wool.

MAIN TECHNICAL DATA:

effectively reproduced frequencies (Hz) with unevenness of 14 dB - 20 - 25000,

with unevenness 8 dB - 20 - 22,000;

dimensions, mm - 460X350X260.

Rice. 1. Schematic diagram of a separating filter.

An air passage is formed between the low-frequency head and the phase inverter using a metal mesh. The remaining volume of the box is evenly filled with cotton wool weighing 0.9 - 1.5 kg. The phase inverter consists of a glass and a pipe-insert (Fig. C, made of -16T duralumin. They can also be made using fiberglass and ZDP-3 glue.

Rice. 6. Bass reflex: 1 - glass, 2 - insert.

At the exhibition RosHI-End 2013, together with an amplifier by L. Zuev and a DAC by V. Korsakov, a three-way loudspeaker on speakers with metal diffusers was demonstrated. The reproduction of musical material selected by V. Lukhanin by this system has received many reviews, which can be found on the Vegalab website.

The development was carried out with the goal of constructing a compact floor-standing loudspeaker intended for sounding residential premises with an area of ​​up to 15-20 square meters. meters, focused on playing music programs with a dense spectrum and high-quality vocal reproduction against the backdrop of a dense signal spectrum. Below we will consider a version of this loudspeaker, modified based on comments from visitors and exhibitors, as well as taking into account the possibility of repeating the design at home. The increase in the project budget associated with the modification seems to us justified by the increase in the quality of sound reproduction. Below we will talk in more detail about compromises, including between price and quality.

In residential premises with an area of ​​15 -20 sq. m. It is not always possible to optimally place speakers, which leads to problems in reproducing low frequencies and deterioration in the localization of apparent sound sources. This circumstance was taken into account and was reflected in the choice of the main technical solutions of the project.

A drawing of the loudspeaker enclosure is shown in pic 1.

The front panel has a trapezoidal shape, the variable width of the front panel slightly reduces diffraction effects. The low-frequency closed-type acoustic design has a usable volume of 30 liters, which is powered by the RS225 speaker. Inside the low-frequency compartment there is a piece of sound absorber (sintepon) measuring 0.5 by 0.5 m. The choice of a closed acoustic design is due to the desire to obtain the most compact impulse response of the low-frequency section.

In residential premises, as a rule, there are standing waves between the walls, between the floor and the ceiling. In such a situation, it is advisable to favor a compact impulse response over extending the frequency range downward using a bass reflex.

The midrange speakers operate on a closed volume of 6 liters, tightly filled with sound absorber. The use of two W4-1337SD speakers for the midrange leads to an increase in costs, which is justified by the improvement in overload capacity at mid frequencies and allows the construction of an MTM configuration that provides a narrowing of the radiation pattern in the vertical plane. Narrowing the radiation pattern in the midrange seems to be an additional bonus, since it increases the level of the direct signal at the listening point. A simulation of the radiation pattern in the vertical plane is shown in rice. 2. The W4-1337 speaker has a moving mass of 4.6 grams with a cone area of ​​57 square meters. cm, linear portion of the voice coil stroke is 3 mm. The voice coil inductance value of 0.015 mH indicated in the manufacturer's data sheet is questionable.

According to my estimates, W4-1337 has Levc = 0.4 mH, which is quite acceptable for mid frequencies. The low moving mass and rigid diffuser ensure good transmission of dynamic contrasts. This speaker is manufactured in two versions: W4-1337SD has a neodymium magnet, W4-1337SDF has a ferrite magnet. Both versions are suitable for the loudspeaker. Prior to the publication of this work, it was possible to examine 18 specimens of W4-1337SDF and 24 specimens of W4-1337SD. Based on the results of parameter measurements, it became clear that it was possible not to select speakers in pairs for the MTM configuration.

The increase in the budget associated with replacing the Seas H1499 tweeter with a Mundorf AMT 19CM 2.1 is justified by an increase in the quality of high-frequency reproduction. In addition, as a result of the replacement, it was possible to exclude 4 elements from the filter circuit, including those requiring adjustment, since AMT 19CM are supplied in pairs, with a small spread of characteristics.

The choice of speakers for the loudspeaker assumed the use of crossover frequencies of 500 and 3500 Hz. The specified crossover frequencies with a margin ensure that the speakers operate in piston mode.

At a crossover frequency of 500Hz, the two-polar impulse response, which is inevitably obtained when the speakers are turned on in antiphase, does not spoil the sensation of sound perception. I assume that the waveform distortion lasts less than 2 ms. lie beyond the temporal resolution of hearing at frequencies above 500 Hz. A simulation of the impulse response of LF and MF speakers working with filters is shown in rice. 3. The result of the impulse response simulation raises some doubts; this issue will have to be sorted out. For now, you can focus on the listening results, which indicate fast and dynamic sound delivery in the low-frequency range.

The crossover frequency of 3500 Hz is an acceptable compromise due to non-linear distortion of the midrange and tweeters.

The result of the loudspeaker frequency response simulation is shown in rice. 4. The frequency response has been optimized for a listening distance of 2.5 m. The slight increase at the upper edge of the frequency range takes into account the decrease in acoustic power with increasing frequency, which occurs due to a narrowing of the radiation pattern. On rice. 5 shows the phase response of speakers working with filters.

The crossover circuit is shown in rice. 6. At a cutoff frequency of 500 Hz, the filters formed 2nd order frequency response slopes with a quality factor of about 0.5. The LF and MF speakers are switched on with reverse polarity. A wide co-emission region (Fig. 4) and a compact impulse response (Fig. 3) provide a cohesive and dynamic sound delivery. At the crossover frequency of 3500, 4th-order frequency response slopes according to Linkwitz-Reilly are formed. For the AMT 19CM 2.1 high-frequency speaker, the formation of a given frequency response decline was provided by a 2nd order electric filter; for the midrange speakers, a 3rd order electric filter was required.

The tweeter filter places the most stringent demands on the quality of the elements. The option of parallel connection of film and foil capacitors turned out to be a good compromise between price and quality.

The notch filter R5 L4 C5, which, according to a widespread myth, should kill sound, performs the function of protecting the midrange speakers from overload and corrects the phase response at a frequency near 100 Hz. The value of resistor R5 depends on the ohmic resistance of coil L4. The sum of the ohmic resistance of coil L4 should be 4 ohms ± 10%. When repeating a loudspeaker, it is not at all necessary to use the types of components that are indicated in the tables. Crossover filters have a low quality factor and allow deviations of values ​​from those indicated in the diagram of at least 5%, and 10% in the ohmic resistance of the coils. The crossover uses 10 W MOX resistors.

Inductors

L1	Mundorf Aire Core M Coil	0.47 mHn 0.58 Ohm
L2	Mundorf Aire Core M Coil	0.82 mHn 0.44 Ohm
L3	Mundorf Aire Core M Coil	0.22 mHn 0.21 Ohm
L4	ERSE Air Coil ALg 20ga	3.3 mHn 1.37 Ohm
L5	Mundorf Ferrite M Coil BH Drum coil	5.6 mHn 0.62 Ohm

Capacitors

C1-2	Dayton Audio PPF	0.47 mkF 400V
C1	MKP Mundorf M Cap	3.3 mkF 250V
C2	MKP Mundorf M Cap	22 mkF 400V
C3	MKP Mundorf M Cap	10 mkF 400V
C4	MKP Mundorf M Cap	8.2 mkf 250V
C5	Erse Non-Polarized	470 mkF 100 V
C6	MKP Mundorf M Cap	47 mkF 400V

On rice. 8 shows the frequency dependence of the input impedance of the loudspeaker. The minimum input resistance is 6 ohms, the maximum is 13.5 ohms. The phase angle, which characterizes the reactive component of the input resistance, does not go beyond plus - minus 30 degrees in the frequency band 20 - 20000 Hz. The parameters of the input impedance of the loudspeaker allow us to consider it a quite comfortable load for the amplifier.

The transfer characteristics of the filters are shown in rice. 7. Resistor R6 with a value of 22 Ohms was sufficient to eliminate unwanted interaction between the filter and the speaker. This can be judged by the transfer characteristic of the low-pass filter. “Pumping” does not exceed 1.5 dB with a maximum at 70 Hz.

On rice. 9 shows the loudspeaker's frequency response, measured in a room at a distance of 1 m at an input voltage of 2.83 V. The measured frequency response is not smoothed, but is the result of averaging three measurements: along the axis of the tweeter and when the microphone is shifted 5 cm down and up from the axis. This measurement technique allows you to get a clearer idea of ​​the tonal balance of a loudspeaker in a room than a smoothed frequency response along the axis of the tweeter.

In conclusion, I consider it necessary to express gratitude to V. Lukhanin, who resolved all organizational issues and carried out the bulk of the work on modernizing the loudspeaker, to the Difton company, which quickly and efficiently manufactured the enclosures, as well as to all sound lovers for their comments and suggestions on the project.