serial crossover. Remember all

When installing a modern stereo system in a car, the owner must choose the right crossover. This choice is quite simple if you know and understand what it is and what it is intended for, as well as in which system this device will work. So, let's figure out what a crossover for acoustics is.

Characteristics, purpose

A crossover is a special piece of equipment in the kit, the main function of which is to prepare the desired frequency range for each speaker. As you know, any one is designed for a specific operating frequency range. If the speaker signal is out of range, the sound may be distorted.

So, if you apply a frequency too low for it to the speaker, then the sound picture will turn out to be distorted. If the frequency is too high, then the owner of the system will be able to face not only distorted sound, but also the failure of the high-frequency speaker. The latter simply cannot withstand such a mode of operation.

Under normal circumstances, the function of tweeters is to reproduce sounds only at high frequencies. Low frequencies work separately. Sometimes they are even installed in different places in the cabin. The same applies to midrange sounds. They are fed only to the speaker that produces the mids.

Therefore, for high-quality reproduction of music tracks in a car, it is necessary to allocate certain frequencies and apply them strictly to specific speakers. For this, you need a crossover for acoustics.

How it works

The design of the device is quite simple. These are two frequency filters that work according to the following principle. So, when the crossover frequency is 1000 Hz, one of the two filters will pick out frequencies below that. The second filter will work with a frequency band above the mark. Filters have their own names. Low-pass is designed to work with low frequencies up to 1000 Hz. The high pass will only process frequencies above 1000 Hz.

Two-way devices operate on this principle. However, there is also a three-way crossover on the modern market. The main difference here is another filter capable of handling mid frequencies between 600 and 1000 Hz.

More audio frequency filtering channels and feeding them to the speakers corresponding to these frequencies leads to better sound quality in the car interior.

Technical features of crossovers

Most modern devices are inductors and capacitors. Depending on the number and quality of manufacturing of these elements, the cost of the product is formed.

Why does an acoustic crossover include a capacitor and a coil? These are the simplest reactive parts. They are cost-effectively capable of processing various audio frequencies.

The capacitor can isolate and process the high frequency, while the inductor works with the low frequencies. Manufacturers competently use these properties and make structurally simple, but quite effective devices.

The number of reactive parts affects the filter capacity: 1 - one element is used, 2 - two elements. Depending on the number of reactive parts, as well as the crossover circuit, the system filters differently those frequencies that are not suitable for specific channels. It can be assumed that the more reactive elements in the circuit, the better the speaker crossovers will filter the signal. Filtration schemes have a certain characteristic. This is the so-called "slope slope". In other words, it's sensitivity. Depending on the level of "slope of the recession", all products on the market can be divided into models of the first, second, third and fourth class.

Active and passive equipment

Passive crossover for acoustics is the most common solution. It can often be found in the modern market. As the name implies, this device does not require additional power to operate. Therefore, it will be much faster and easier for the car owner to install sound equipment. The disadvantage of this group of devices is that simplicity is not always a guarantee of quality.

Due to the passive circuit, the system takes part of the energy to ensure the operation of the filter. At the same time, the reactive parts change the phase shift. Naturally, this is far from the most serious drawback. However, it will not be possible to perform the frequency correction as finely as possible.

An active crossover does not have such a disadvantage. The fact is that despite the more complex design, the flow of audio frequencies in them is filtered much better. Due to the presence in the circuit of not only several coils and capacitors, but also semiconductors, developers create high-quality devices with more compact dimensions. An active crossover is rarely found as a separate module. However, any amplifier has such active filters.

How to set up the device correctly?

In order to get the highest quality sound in a car, you need to choose the right frequency at which all unnecessary will be cut off. In the case of an active device designed for three bands, you need to find two cutoff points. The first will mark the edge in the range between low and medium frequencies. The second is the difference between medium and high frequencies.

How to calculate with your own hands?

Crossover calculation for acoustics is an important process. No manufacturer has yet been able to produce an ideal one that could reproduce sound in a different range with high quality. Subwoofers are used for low frequencies. For mids, midrange speakers are used. But when this whole complex begins to sound, a certain confusion may arise. That's what a crossover is for in acoustics - so that a signal of only a certain frequency goes to a specific speaker system.

To obtain a bipolar system or any other, a device that divides the signal is connected to the first channel of the amplifier. This is the filter. Complete with acoustic systems there are already passive crossovers made and calculated by manufacturers.

But what if you need to separate the sound into frequencies according to a different principle? You don’t have to count anything manually - in our high-tech time, there is software for even the simplest operations. So for these calculations there is a program, for example Crossover Elements Calculator.

First of all, the impedance index of the bass and treble speakers is introduced into the program, which is often 4 ohms. Next, enter the frequency that the device should separate. The order of the crossover is also introduced here. Then they press the button and wait for the program to give the result. As a result, it will issue a diagram where the necessary capacitors and coils for the entered parameters will be indicated.

Features of choice

The market offers a wide range of devices that differ in quality, cost, specific manufacturers. Choosing a crossover for acoustics is not easy - you can’t just take and buy what you like. The choice is made according to certain

Imagine that you have a subwoofer that produces a low frequency in the range from 18 to 200 Hz, a midrange speaker reproduces frequencies from 200 to 1000 Hz, and a high frequency speaker from 1000 to 16,000 Hz. At the same time, the amplifier does not have a built-in filter and reproduces frequencies in the range from 18 to 20,000 Hz. In this particular case, you need a three-way crossover capable of filtering in these ranges.

Also, when choosing, pay attention to the number of lanes. Another important parameter is the frequency range. Be sure to consider throughput. Multi-level devices with high sensitivity can significantly improve sound quality.

Conclusion

So, we found out what a crossover is and what functions it performs. As you can see, this is a fairly important element in the car's speaker system.

What is a crossover car audio- the most significant elements in the composition of high-quality car acoustics are considered to be the crossover and the sound power amplifier. Also, one of the most important factors for creating an ideal sound picture in the car interior is the right choice and qualified installation of these devices in the car, otherwise it will be very difficult to get high-quality sound.

crossover

Basically, the device board, consisting of various filters for separating the incoming audio signal into frequencies, is placed in a small case. At a high frequency, when tuning, as a rule, they take a unit from 80 to 100 Hz, and at a low frequency and a band-pass RC filter, they are tuned from 2 to 6 kHz. There are two types of devices - active and passive. p>

What is a crossover car audio- they differ from each other in that the active module is made on electronic elements, such as operational amplifiers, microcontrollers and others, which require a supply voltage. The passive frequency separation device is assembled on components that do not require a power source. In addition, there is some peculiarity in the installation, for example: the active crossover is installed only in the input circuit of the amplifier, and the passive ones are located anywhere, both in front of the amplifier and after it, that is, in front of the dynamic radiator.

It is worth noting an important advantage of passive crossovers, such as its ability to distinguish between audio signals for a three-way loudspeaker, when using only two channels of a power amplifier. The negative point is the impossibility of configuring the device without finalizing the circuit. The opposite is true for crossovers of active use, its controls and settings are located on the outside of the case, so this design solution provides maximum convenience in the operation of the device.

The disadvantage of an active frequency separation device is its relatively high price, the need for a power amplifier for each channel, as well as the existing possibility of distortion from active components. What is a crossover car audio- the choice of crossover is based on the parameters of the speaker system and the number of bands it has. As for the choice when buying and choosing the installation site, as well as fine-tuning it, in this case it would be more expedient to invite an experienced specialist so that there would be no problems in the future.

Amplifier

There are times when, after acquiring even an expensive car radio, the amplifier in it is not of sufficient quality. And why does it happen? One of the important reasons is the small amount of space intended for the radio and, as a result, the impossibility of implementing an amplifier with a higher power in the system. Therefore, car owners who want to get a high-quality sound picture install an additional amplifier.

Amplifiers installed in the car come with both one amplification channel (monoblock), and two-channel (stereo), three-channel (stereo + another channel for the subwoofer), there are also four-channel ones designed to amplify sound in the front and rear speaker system. There are also amplifiers for five and six channels.

What are the criteria for choosing an amplifier?

What is a crossover car audio- the first thing you need to pay attention to when buying a device is the rated power, which should be about 15% less than the power of the loudspeakers. If this dependence is ignored, acoustics may simply “burn out” soon. Another important parameter is the total load resistance that the device can handle efficiently.

A complex of several amplifiers creates the conditions for their inclusion in a bridge circuit, in which the total output power increases in proportion to the connected amplifiers. Basically, such a switching circuit is used for using a subwoofer in its composition. The industry produces a large number of amplifying equipment with already integrated crossovers, however, the use of external devices greatly simplifies the setup and maintenance of car acoustics.

Installation specifics

The relatively small dimensions of the car amplifier allow its installation in various places in the cabin. One of these options can be called the lower part of the rear shelf, where you can fix it with self-tapping screws or in the space of the wing. When self-assembling a subwoofer or making it to order, a great opportunity is created to immediately mount an amplifier inside the case. But at the same time, it must be borne in mind that it heats up quite a lot during operation, and therefore it is necessary to provide the amplifier with sufficient cooling.

In order to install an acoustic complex in your car without incurring very high costs, it would be most reasonable to take coaxial or broadband speakers, installing them in regular places in the car, and use amplifier built into the car radio. In the future, if necessary, the installed audio system can be upgraded by adding an active subwoofer made in its own case to it.

Speakers with a twist: the conciseness of the scheme is combined with the careful execution of the body.

When developing and manufacturing a new model of acoustics, the manufacturer tries to draw a portrait of its listener and evaluate the environment in which this system will be installed. But I want to describe the design, the ideologist of the creation of which was its future owner. Here is a short list of those wishes that we received as a guide to action from another customer. These should be floorstanding speakers for listening to calm music in a cozy home environment. They should be in harmony with the existing interior, but have a twist in the design.

The last, but categorical requirement was the use of the simplest first-order separation filters (it seems that the impact on the customer of many articles about the dangers of high-order filters was greatly affected).

The following picture emerged:

1) the woofer will be made of paper - the order of the filter is obligatory, although an aluminum cone in combination with a light oak finish would perfectly meet the requirements of the apartment design;

2) acoustic design - bass-reflex, because as a result of listening, the client clearly preferred this type;

3) the system will be two-lane;

4) the interior of the room implied the manufacture of a product with smooth lines, and here the unique “monolith” technique developed in our company for the production of cases came in handy. All its faces are rounded, which also favorably affects the problem of diffraction in the high-frequency region.

And they didn’t forget about the highlight: the chiseled oak phase inverter tunnel, brought to the front panel, perfectly complemented the smooth contours of the corners.

About the author

Boris Pukhov is a graduate of the Leningrad Polytechnic Institute, an acoustics specialist at the Peter-Music company. He is directly involved in the development of speakers for individual orders, not only for Hi-Fi systems, but also for home theater. The latest achievement is the launch of automotive subwoofers under the Bloodhound brand.

Having delved into history, we decided to take as a basis the development of a fifteen-year-old Norwegian company SEAS, since now in Russia there are no problems with such brands as VIFA, SCANSPEAK and SEAS. It was nice to note that the H333 8" paper woofer and the H519 fabric dome tweeter are still in production today. The speakers were purchased and the process of bringing the client's idea to life began.

The body is made of high density MDF (side and back walls 19 mm, front - 25 mm). After cutting the panels around the perimeter, they are pasted over with oak bar in such a way that labyrinths are formed at their joints - a 100% guarantee against leaks. The tightness of the structure is also evidenced by the fact that before veneering it is necessary to drill a technological hole, because. fluctuations in air temperature leads to retraction of the walls. In this way, two 39-liter cases were assembled.

Joint "monolith": 1 - oak beam, 2 - MDF panel, 3 - veneer.

A feature of the “monolith” method is that the body is non-separable, and therefore, before installing the last panel, the vibration-absorbing composition “visomat” is hot rolled onto the internal planes and the filter is installed. The presence of internal struts gives the structure additional rigidity. What is characteristic, not a single screw is used during assembly. A three-layer coating with matt varnish reliably protects the body from fluctuations in humidity in the room and emphasizes the relief of the structure of natural wood. M8 countersunk nuts are mounted in the bottom panel for installation on support spikes.

A few words about the filter: inductors with an air core and interlayer impregnation of our own production. Capacitor metal-film polypropylene K78-19, well proven in acoustic filters.

Since these speakers do not require strong displacements of the woofer cone and “winds” are not expected in the tunnel, we limited ourselves to a port with a diameter of 70 mm. The length was selected experimentally by tuning the body to the natural resonance frequency of the head (33 - 35 Hz). At the time of tuning, a plastic tunnel was installed, the length of which was selected experimentally and turned out to be 150 mm. Taking into account the roundness of the edges of the turned tunnel, we made it 160 mm long and glued it into the speaker body. The speakers were installed in the front wall on a specially milled seat belt through a thin rubber gasket and fixed with screws using self-expanding bronze bushings.

The body volume in the lower part was evenly filled with synthetic wool, the volume of which was selected according to the minimum resonant frequency of the system with the tunnel hole plugged. All experiments and settings were carried out on one body, and the second was assembled in the image and likeness, because. SEAS loudspeakers are famous for the high stability of the parameters of the same type of products. The client considered the result of listening as the main criterion for the quality of finished products. It was produced in conjunction with the conservative British Musical Fidelity A220 amplifier. The soft timbre, lightness and delicacy of the sound with a good elaboration of the spatial picture made it possible to listen to music for a long time without signs of fatigue, which suited their owner quite well. Nevertheless, we decided to measure the frequency response for sound pressure in the near field using the Audio Control SA-3055 spectrum analyzer using the built-in pink noise generator. The location of the microphone did not allow fixing the operation of the phase inverter, as evidenced by a clear blockage in the low-frequency region on the LED display (1 dB step), while there were no problems with bass when listening. Sensitivity was at the level of 89 dB.

In conclusion, I would like to note that the emotional perception of music to a large extent depends on the quality of the case, and pleasing the eye is not the last task of modern acoustic systems.

Homemade crossover for acoustics

Homemade crossovers for acoustics are needed to separate the frequency ranges of the speakers. They equalize these very ranges in terms of sound volume.
Making a homemade crossover for acoustics is not so difficult if you know some secrets.

What is a crossover and what is it eaten with

First, let's find out why we need a crossover?
This is a special device designed to separate audio frequencies. Crossovers, as it were, remove unnecessary frequencies, filter them.

For example, there are such speakers (see) as tweeters. If there were no crossovers, then all frequencies would be fed to the tweeters, their full package, along with bass and midrange. It is clear that this will ultimately have a negative impact on the detail of the music.
Tweeters, such as tweeters, are not capable of reproducing low and medium sounds, and the presence of unusual frequencies will become a dangerous problem in this case.

Types of crossovers

Crossovers are usually divided into active and passive, as well as single-lane, two-lane, etc.

Passive crossover, its pros and cons

So:

• A passive crossover filters the signal with its capacitors, resistors, and coils. As a result of this, the first drawback of such crossovers is revealed - the loss of power.

• Passive crossovers are connected directly in front of the speakers. It turns out in such a way that it is enough to use only one amplifier (see), which is an undoubted plus of passive crossovers.

• Passive crossovers are sold as separate units or as a set with acoustics, usually two-way or more.
• Among the disadvantages of passive crossovers, one can single out a limited peak load, which entails a quick failure.

Active crossover, its pros and cons

So:

• An active crossover is used in front of the amplifier. Therefore, the use of one amplifier in this case is simply impossible.
  In the case of an active crossover, each speaker, be it a tweeter or a woofer, uses a separate amplifier channel.

• The advantage of an active crossover is that, unlike a passive one, it allows you to fine-tune the cuts. It is this factor that determines for the most part the cost of such a crossover, which is more expensive than its opponent.

Crossover single-lane

• Designed to cut the subwoofer channel (see).

Crossover two-way

• Designed for two-way acoustics, consisting of a tweeter and midbass.

Crossover three-way

• Designed for three-way acoustics, consisting of a tweeter, midrange speaker and midbass.

Homemade crossovers

It happens that having become the owner of expensive car acoustics, the owner discovers that there are no crossovers in the kit. It is clear that it will be impossible to do without them, since the tweeters can simply burn out.
What to do? The answer is ridiculously simple - make them yourself.

Tools

To get started, arm yourself with the necessary tools:

• Good and handy soldering iron.
• A special device that measures inductance.
• Glue "Moment".
• Ferric chloride.
• Foil fiberglass.
• Heat shrink tubing.
• Silicone sealant.

Step-by-step instruction

We start the manufacturing process.

So:

• First of all, it is necessary to carefully study the technical characteristics of the purchased speakers. It is recommended to pay special attention to the low frequencies of the tweeters, as well as the level of characteristic sensitivity of the bass and tweeters.
• Then you need to choose the right electrical circuit, which involves connecting a crossover.

Note. According to experts, it is desirable to give preference to 2nd order filters, because in a cramped car interior there is a strong increase in the frequency response at medium-high frequencies.

• It must be remembered that tweeters that are connected through a 1st order filter strongly emphasize hiss, and woofers exaggerate bright sounds. As a result, adding together, you get a mess, in which there will be a lot of bright and hissing sound.

Note. At the same time, the wider the interior of the car, the more it will be possible to minimize these shortcomings.

Inductor

So:

• We wind the inductors for the speakers. Note that when doing this for a woofer, it is better to use copper wire with a diameter of 1 mm and insulated with a special varnish.

Advice. In the manufacture of coils, it is recommended to use ferrite cores. This will make it possible to obtain smaller dimensions and weight, as well as reduce the consumption of expensive copper wire. In addition, it will also be possible to reduce the active resistance of the coil.

• The resulting inductance is recommended to be controlled using a unique measuring device.

Advice. When winding the wire, it is highly desirable to make a coil and a coil, and then fix it with glue. This will make it possible to avoid the problems that beginners often face.

Making a printed circuit board

So:

• It's time to draw the board on paper. This should be done based on the size of the resulting coils and resistors.
• We draw a board and transfer it to a sheet of special material.

Note. As such a material, it would be nice to choose foil fiberglass.

• We immediately drill holes for the electrodes of future parts and wires. Be sure to etch the board. This must be done as follows: place the semi-finished board in a solution of ferric chloride.

Assembly

• We assemble the boards of our future crossover according to the installation diagram.

Note. We carefully glue the inductors and capacitors to the board. It is recommended to use a good adhesive such as Moment. Good fixation will allow a home-made separator to work flawlessly for a long time in conditions of vibration and shaking.

Connecting speaker wires

So:

• We connect the acoustic wires using a conventional soldering iron. In work, you need to be extremely careful not to confuse the outputs for the woofer and tweeter. You also need to pay attention to polarity.
• Glue will come in handy here too. It is necessary to fill in the “Moment” with the wires that are soldered, which will again protect against vibrations and possible fractures.

Connection

So:

• We carry out a test connection and make sure that the signal is fed to each speaker from the corresponding output of a homemade crossover.
• If necessary, you can also include a 4 ohm resistor in front of the high-pass filter.

Note. Remember that the sensitivity of tweeters is several decibels higher than the sensitivity of a speaker that reproduces low frequencies - as a result, the tweeters play louder than the woofer.

A do-it-yourself crossover is covered with a heat shrink tube, observing the required dimensions. Be sure to fill the edges with silicone so that moisture or dust does not get inside the crossover.
The presented instructions will help you make a homemade crossover for acoustics without any problems. During the operation, it is recommended to study additional photo and video materials.
As for the price of consumables, it depends on the number of coils and speaker outputs. The material used is also important.

Peter Latsky notes that in most crossovers (crossover filters for multi-band speaker systems) there is a significant (typically 45 to 90 electrical degrees depending on the order of the filters) phase shift between the voltages at the LF and HF outputs at the LF/HF crossover frequency. This leads to significant violations of the integrity of the sound picture at medium frequencies (responsible for the transmission of voice and the main part of the spectrum of most musical instruments), since the same signal is emitted twice: by the HF link and the LF link with a greater or lesser time delay.

The condition necessary for ideal sound transmission is the constancy of the group delay characteristic (GDT). That is, a linear phase characteristic can in principle be obtained only when used in a crossover: a Bessel low-pass filter and an all-passing (phase-correcting) Delianis filter.

HPF for the formation of the frequency response for the RF link cannot be applied at all. After all, they form a phase lead, which is fundamentally not compatible, whatever it may be, with the phase delay of the low-pass filter and the Delianis phase corrector.

In Peter Lasky's phase-linear active crossover (Fig. 1.19), signal generation for the low-frequency link (Low output) is performed by a fourth-order Bessel low-pass filter (op-amps A4, A5). On op amp A2, a second-order Delianis phase corrector is made, which has a linear frequency response, but the same phase response and group delay as the fourth-order Bessel low-pass filter.

The differential amplifier on the op-amp AZ subtracts the signal at the output of the low-pass filter from the signal at the output of the AZ and thus forms a signal associated with the last section of the high-pass filter (High output), supplied to the HF section of the acoustic system. At the same time, the voltage phases at both outputs practically coincide, which ensures accurate transmission of the spatial sound picture.

With the ratings of the elements shown in the diagram, the crossover is used for an acoustic system from an electrostatic HF link and an isobaric ("compression") woofer. The LF/HF crossover frequency can be easily adjusted for other speakers by simultaneously changing the capacitance of capacitors C21, C22, C41, C42, C51 and C52.

Rice. 1.19. Diagram of a phase-linear active crossover

Rice. 1.22. Active crossover circuit with adjustable sub-low-frequency compensator

The crossover filter consists of a U1A buffer and three 2nd order Butterworth HPFs with cutoff frequencies of 4 kHz (U1B), 400 Hz (U2B), and 20 Hz (U3B).

The output of the first HPF through the resistor R9 is fed directly to the power amplifier of the RF link (TREBLE, 4 kHz - 20 kHz), while the signal for the midrange link (MIDDLE, 400 Hz - 4 kHz) is formed by the U2A algebraic adder from the voltages at the outputs 4- x kilohertz and 400 hertz HPF.

Rice. 1.23. Scheme of 3 power amplifiers on the IC TDA1514A

Note. Such a circuit design provides "automatic" ideal phase and amplitude matching at the boundaries of the RF/MF ranges without any selection of elements.

Similarly, a low-frequency signal (BASS, 20-400 Hz) is formed on the resistor R11. The versatility of this solution lies in the fact that resistors R9, R10 and R11 can independently and quickly select the optimal (corresponding to the linear frequency response in terms of sound pressure) voltage level in each of the bands (for almost any speaker), without violating the linearity of the phase characteristic. This is very important for the accurate reproduction of the sound picture.

In addition, the low-frequency channel has an active low-frequency compensator on the U4A op-amp, which expands the lower limit of the acoustic frequency response from 63 Hz to 25 Hz.

The principle of operation of the low-frequency compensator is based on the fact that the own frequency response of a closed-type speaker has a quality factor QTC \u003d 0.66 and below the cutoff frequency fc (thin line in Fig. 1.24) has a decay of 12 dB / octave.

Within reasonable limits, this decline is quite accurately compensated by the frequency response “drift” with a slope of 12 dB / octave, electrically generated by the U4A cascade (EQUALIZATION RESPONSE in Fig. 1.24).

Note. As a result, the frequency response of the entire system turns out to be linear up to 25 Hz (the “thick” line in Fig. 1.24).

Rice. 1.24. Frequency response of the original speaker (thin line), corrector (middle) and resulting (thick)

Rice. 1.25. Compensation for standing acoustic waves in a noisy room

It should be noted that similar compensation in systems with a phase inverter is much more complicated. After all, the latter itself is a filter with its own frequency response and phase response, which cannot be taken into account without careful acoustic measurements. And it is hardly expedient because of the significantly greater steepness of the frequency response decay below the cutoff frequency.

The last stage in the low-frequency channel is the sub-low frequency tone block on the U4B. It is designed to compensate for the rise/fall in the acoustic frequency response caused by the acoustic properties of the room.

The R28 DEEP BASS resistor, which regulates the frequency response in the range from 94 to 23 Hz by ± 12 dB, can compensate for the negative effects of standing acoustic waves of both a small room and a large hall (Fig. 1.25).

Power amplifiers (Fig. 1.23) are made according to the typical TDA1514A switching circuit. When powered by an unregulated ±23V source, they provide up to 28W into 8 ohms and up to 48W into 4 ohms with less than 0.003% THD and a frequency range of 3.2Hz to 100kHz. The article cited below contains all the necessary relationships and formulas for calculating similar systems with arbitrary dynamics and parameters.