What is the difference between an active subwoofer and a passive subwoofer and which one to choose? Bandpass type subwoofers What does a passive subwoofer consist of.

A subwoofer is a speaker system that converts low frequency sound waves. The localization of low frequencies is very poor, as a person can hardly determine where the sound comes from. For this reason, one subwoofer is enough for any audio system, which must be installed in the right place.

You can install a compact device somewhere under the table, so its functionality will not suffer at all. True, when standing waves occur in a small space, it depends on the placement of the subwoofer how effectively they can be dealt with.

Listening to most music does not require the purchase of a subwoofer, as they do not contain bass. The equipment is suitable for those who:

• likes to listen to heavy music, like rock;
• watching blockbusters with powerful special effects.

It is in these cases that the subwoofer is able to show itself in all its glory by adding volume to the sound and a specific resonance.

Types of subwoofers

All low-frequency systems are conditionally divided into two groups in relation to the presence of an amplifier:

• active;
• passive.

The first already have a built-in power amplifier, which helps to dock the different parameters of the subwoofer and the sound source. The latter are not equipped with an amplifier, so they require external equipment connection. Of course, you can do without an amplifier, but in this case, the subwoofer will produce distorted sound waves, often expressed as an unpleasant wheeze.

In a professional environment, it is believed that it is a passive subwoofer that is able to convey a deeper sound of low waves, giving a specific color. But to achieve this effect, you will need to configure the equipment, which not everyone succeeds in full. For ordinary people, it is better to give preference to an active subwoofer, since it can be directly connected to the sound source.

Types of construction of subwoofers

There are several types of subwoofers that differ in their design. So, for example, in a horn device used in concerts, the horn is folded. There is no additional emitter in closed boxes, and the woofer is built into one of the walls of the sealed case.

The phase inverter is a cylindrical ventilation tube built into the housing. This allows sound to be emitted from the rear of the cone. With this component, you can significantly increase the efficiency of the subwoofer, which is accompanied by an expansion of the spectrum of reproducible low frequencies.

A passive radiator has a similar purpose as a phase inverter, only an additional diffuser without a voice coil and a magnetic system is installed in the body instead of a tube. By varying the parameters of the diffuser, you can change the lower limit of the reproducible frequencies.

The bandpass is a box with a phase inverter, divided in the middle by a wall. The speaker in such a subwoofer is inserted into the partition between the two chambers, due to which it is possible to limit the frequency. The efficiency of such a device is higher than that of simple boxes with a phase inverter. There are three types of bandpasses:

• the fourth category (two cameras with a built-in phase inverter in the top);
• the sixth category of type A (two chambers and two phase inverters, each of them in its own chamber);
• the sixth category of type B (two chambers and two phase inverters, while the upper one is common to both chambers).

A quarter-wave resonator is a tunnel with a certain cross section and length. The return of this design is 40% higher than that of bass-reflex, and up to 300% than that of closed boxes.

How to choose a subwoofer?

When buying a subwoofer, there are several factors to consider:

• device price;
• the area of ​​the room in which the device will be installed;
• the intended installation location;
• sound preferences;
• range of output frequencies;
• ultimate sound pressure;
• compatibility with other elements of the system.

Subwoofers are considered good, the price of which starts at 10,000 rubles. When buying a device, you can get excellent upper and middle low-frequency ranges, but it is effective to install the equipment in a room not exceeding 20 sq.m.

Subs with a cost of more than 20,000 rubles are designed for large areas. They are preferred by true connoisseurs of audio. When choosing, you should focus on the power of the system, since the higher it is, the better the sound will be transmitted. True, you should not buy a subwoofer with a power of up to 1 kW in a small room.

As for the frequency range, it is better to give preference to devices whose lower limit starts at least from 60 Hz. The rule works here: the lower the frequency limit, the better bass you can get. It’s not worth chasing the upper limit, since any speakers already sound the range from 350 to 2000 Hz. It is worth remembering that the more limited the sound range of a subwoofer, the better it will transmit it.

When installing the subwoofer indoors, choose a location against a long wall away from a corner. The sound pressure should be from 100 dB, while with an increase in the indicator, the power of the sounds produced also increases. Another parameter is the presence of controls built into the subwoofer. Among the necessary ones are Level (Level), Cutoff frequency (Frequence) and Phase (Phase).

Subwoofer connection

Any low-frequency speaker system is connected either to low- or high-amplitude inputs. When connecting via high-amplitude inputs, it is necessary to connect the device with an amplifier or receiver to the connectors for the second pair of speakers (if the amplifier has such a possibility).

When using high-amplitude outputs, the following connection procedure is allowed: the signal is transmitted to the subwoofer from the outputs to the front pair of the receiver, as a result of which high frequencies are automatically cut and redirected to the front speakers. True, the subwoofer amplifier in this case does not fulfill its function. The above methods are very rare and are used only when it is not possible to connect through low-amplitude inputs or if a passive subwoofer is used.

To connect to low-amplitude inputs, RCA connectors are used, which are marked Sub out or Pre-out, which means the same thing. In the event that the receiver or amplifier has only one input, connection is possible to the left input jack labeled Mono or marked L. The second subwoofer is connected exclusively through low-amplitude outputs.

Thus, if you want to add low frequencies to the speaker system that add volume, you need to add a subwoofer to it. One device is enough, since a person is not able to distinguish where the low frequency sound comes from. True, much depends on what design the subwoofer has and what parameters it has. In order for everything to be connected correctly, it is recommended to read the instructions for use in advance, which will greatly simplify the setup process and will not affect the quality of the transmitted signal.

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The subwoofer is an integral part of any modern system, designed for watching films rich in special effects or listening to music of various directions. This acoustic element is designed exclusively to reproduce low frequencies, the abundance of which gives the music significance and the effect of high power. It is powerful basses that sometimes form the initial opinion about the quality and advancement of acoustics in general. This is understandable, because the bottom of the sound range is just the most demanding on the speakers, the materials and components used. In this material, we will not go into complex technical details, but will try to highlight only the main points that are important for the average buyer who went to the store for a subwoofer.

If you decide to purchase a subwoofer...

First of all, you should evaluate your financial capabilities and the topology of the proposed listening room. It is easy to guess that one of the decisive factors is the cost of a hypothetical acquisition. Any acoustic system works according to the laws of simple physics, which state that the size of the emitter must be comparable to the wavelength. And since for low frequencies it is measured in tens of meters, then the dimensions of the speaker should be measured at least in tens of centimeters. There are a huge number of different technical solutions and tricks, however, getting really high-quality bass from a speaker smaller than 5...6" is simply unrealistic, ideally it should be close to 10...12". Therefore, when purchasing a tiny multimedia subwoofer, it is worthwhile to understand that the resulting bass is unlikely to reach the results of an ordinary average speaker.

Based on this consideration, it is worth once again soberly assessing your budget and the level of available acoustics. If we are talking about "under $100" class computer systems, be it, for example, the classic 2.1 version, then their subwoofers are a pitiful imitation of full-size systems. After all, even the most basic options cost at least $70, and the dimensions of the cases are measured in tens of centimeters and can reach up to half a meter. Therefore, having gathered in the store, ask yourself three questions. Are you really willing to spend money on a quality bass subwoofer? For a cheap option can disappoint from the first minutes. Does your speaker system really need a subwoofer? After all, a subwoofer will not help a lot for budget speakers, but for expensive solutions, a subwoofer may not be required. And is there the necessary space and facilities for installation.

Active or passive?

So, suppose that the decision is made, it remains to decide on the main parameters. Like all acoustic systems, subwoofers are active and passive, i.e. with or without built-in amplifier. It is classically believed that real acoustics should be passive. This improves the parameters of the speakers themselves, and simply allows you to change amplifiers, finding the sound you like best. There are passive subwoofers, but there are still more active models. The fact is that the speakers, at least, are used in pairs when the subwoofers are monochannel. To put it simply, a subwoofer needs an amplifier with one channel, and with non-standard adjustments. Naturally, there are such, but the easiest way is to purchase just the active option. Passive subwoofers are popular only among motorists, which is associated with some subtleties of connection and huge power. Also, we do not take into account various audiophile habits when tube amplifiers or other extraordinary solutions are used for subwoofers. If we are talking about a computer system or a moderately priced home theater system, then we recommend active solutions.

Power

We have more than once that the power figures indicated by the manufacturer poorly characterize the real parameters of the system, because. there are many standards for measuring this parameter, which gives rise to numerous "additives". You can start from numbers, but you need to do this with a certain amendment. Roughly speaking, it is necessary to strive for the declared power of the subwoofer to be close to the power of the satellites used. This is how the necessary headroom and balance in sound pressures are achieved. For example, consider the simplest case. Let's say you have microlab SOLO-6 speakers with a total power of 100 W, and their bass, according to the user, is rather weak. In this case, a subwoofer with a power of at least 80 ... 100 W and a speaker 8 ... 10 in size can radically improve the situation. Buying a subwoofer for such speakers with a five-six-inch speaker is simply pointless.

Types of subwoofers, their main advantages and disadvantages

With a more specific search, any user will immediately realize that there are at least several different subwoofer designs. Of course, I want to know about the advantages and disadvantages. To begin with, let's look at the simplest constructive option - a closed box. With this design, the low-frequency head is simply placed in a case isolated from the external volume.

For all its simplicity, this acoustic design is quite nice, because the column is slightly affected by the room, and the sound is confident and biting. However, there is one significant drawback - the efficiency of such AO is extremely low. In other words, to get high sound pressure, the manufacturer needs to initially use a high power speaker and an appropriate amplifier. For reasons of simple economy, this is extremely unprofitable, because. too many materials are required. If this is acceptable for real Hi-Fi, then for multimedia this option is obviously losing. The user simply does not want to pay money for a subwoofer / speakers that play well, but quietly. That is why there are very few closed boxes among computer systems, and in other areas they are not as popular as even the simplest phase inverters. It turns out that to increase the sound pressure with the same parameters of the head and amplifier, it is enough to equip the closed case with a pipe through which the internal volume will communicate with the external space. The phase inverter helps to change the phase of the oscillations from the rear wall of the diffuser and adds them to the oscillations from the front. As a result, the power increases. The disadvantages of this option is the likelihood of jet noise and peaks in the frequency response. The latter are possible due to errors in calculations or poor influence of the room. However, the power indicators perfectly cover the appearance of possible shortcomings, therefore, most of all subwoofers on the modern market are just phase inverters.

Often, an even more efficient design is practiced, called bandpasses (bandpass resonators). The speaker is placed inside the case and communicates with the external environment through one or more phase inverters. The advantage of this option can be considered that it allows you to "pull out" the bass even from the smallest speaker. Sometimes multimedia subs are built using 3 ... 5 "heads, and at the same time they at the very least bass. However, such an acoustic design is very sensitive not only to the setting and spread of the parameters of the heads themselves, but also to the room. Therefore, inexpensive bandpasses play powerfully, but there is no beauty in their sound, and a cheap bandpass is most likely not the best option in terms of quality.The situation is better with more expensive solutions.

Placement in the room and basic adjustments

It should be noted right away that there are no clear rules for installing subwoofers in rooms, however, like all acoustic systems, they are subject to the influence of the listening room. It is best to choose a place empirically. As a rule, the subwoofer is installed on the floor between the front satellites or near one of them. You can move the low-frequency unit closer to one of the speakers in the corner of the room. Such liberties are due to the fact that low-frequency sound is not localized by the human ear. Naturally, you should not install close to the walls, especially if the phase inverter port is placed on the rear or side panel. To achieve the best option, it is worth conducting several test listenings, choosing the most suitable place. It will be individual even for rooms of the same size, because. a lot depends on the decoration of the walls, the location of the furniture, etc.

More precise adjustment can be made with the help of several convenient adjustments, which are provided in the vast majority of cases. The first is the volume control. Everything here is very individual, because. someone likes a moderate bass, while the other, on the contrary, prefers the prevalence of low frequencies. In any case, the subwoofer-satellite volume balance is the most necessary adjustment, which is always present. In second place is the cutoff frequency, which, as a rule, regulates the upper limit. It helps to match the frequency response of the subwoofer and the main speakers. The boundaries must be chosen so that there is no significant overlap, but also no dip is formed. All this can be done based on subjective feelings. Finally, any more or less high-quality subwoofer has the ability to adjust the phase or, as they say, delays. This function is provided for position compensation so that the sound at the listening point from all speakers arrives at the same time.

Summing up

In conclusion, we can only describe the approximate actions of a user who decides to purchase a subwoofer, and give the briefest recommendations. To begin with, it is worth deciding on the price, because. ultra-cheap options tend to bring nothing but disappointment. Still, buying a separate subwoofer implies a desire to get high-quality bass, and you have to pay for it. Secondly, it is worth deciding on the type of acoustic design and power, paying attention to the dimensions of the case and the possibilities of the room. Finally, thirdly, it is worth conducting a test listening, choosing the optimal location, and adjusting the sub in conjunction with the speakers used.

When choosing, it is worth remembering only one unshakable rule, the sound is very individual, and each person has his own unique preferences. Reading reviews and studying technical characteristics will help weed out frankly unsuccessful options, but you will have to listen to the rest, because. only listening gives a guarantee that a hypothetical purchase will be liked in the future.

From time to time, bandpass type subwoofers come into our field of view. Otherwise - bandpasses ...

Most often, it should be noted, in the form of finished products. Much less often - as an element of a system built on an individual project. The basics (quite the basics) of the theory and practice of this type of design were published with us a long time ago, years, not to lie, 15 years ago. There is an opinion (of the author) that it would be necessary to clarify something on this issue, otherwise, you see, and remind, not forgetting about “newly discovered circumstances ...”

1. Relatively narrow frequency range.

2. Increased complexity of manufacturing and customization.

We see more benefits.

1. The presence of an internal low-pass filter.

2. The ability to reproduce low bass.

3. Acoustic amplification.

4. The security of the speaker from external influences.

The first minus and the first plus are two sides of the same coin, which confirm the well-known wisdom that every thing is good in its place. That is, for the role of a broadband bass radiator (in three-way acoustics, say), the bandpass is of little use, while in the position of a subwoofer it will be very out of place. The second drawback was a factor that largely limited the spread of bandpass designs. Moreover, the problem is not even in manufacturing, after all, the difference between PP and FI lies only in the presence of an additional inner wall. The difficulty is that in the process of fine tuning one of the walls will probably have to be moved, changing the “front” volume. In a single production, this is really inconvenient, but when preparing a series (even a small one) - what's the problem?

Now about pluses. As you can imagine, the presence of a natural low-pass filter has led to a certain popularity of bandpass in the past, when passive filters were considered a natural way to separate frequency bands. A passive low-pass filter, tuned to a typical subwoofer frequency, involves the use of large and expensive coils. With the transition to dedicated bass amplifiers and active filters, this factor became irrelevant. However, given that most truly musical amplifiers in our industry are equipped with second-order filters, the presence of an additional (acoustic) low-pass filter will be very useful.

The ability to reproduce low bass is a good thing, but not for us. For example, a subwoofer for a home theater in WL can play bass from 50 Hz, in design with FI - from 32, and in PP design - from 25, and if you sacrifice the uniformity of the frequency response, you can reduce the frequency border to 20 Hz. However, in our industry, there seems to be no problem with low bass, the subwoofer in the WL plays (in theory) from 0 Hz. We have another problem with mid-bass flatness, as the transition from free field to compression occurs between 55 and 70 Hz (-3 dB boost frequency). All subwoofers with FI give a boost starting at this frequency and going down, a CL tuned exactly to the transition frequency will give a straight-line response, but, of course, without any kind of boost. With all other settings, the WL will either rise in the mid-bass region of 70 - 50 Hz, or, even worse, decline at the same frequencies.

So, a fourth-order bandpass (hereinafter, we will only talk about it, we will avoid unnecessary difficulties) can give rise exactly where it is needed, near the upper border of its working band, and maintain an attractive shape of the frequency response in cabin conditions. I think this alone is enough to take a closer look at it. Well, the last of the above pluses is also worth something.

So, let's start looking. We take some nameless speaker, we are not interested in its characteristics for the time being. So far, we are building characteristics in a free field, so it’s clearer. Let's see how the frequency response changes depending on the size of the "back" (that is, closed) volume.

Rice. 1. Change in characteristics depending on the size of the closed volume

Rice. 2. Change in characteristics depending on the size of the front volume

Rice. 3. Change in characteristics depending on the mass of air inside the port

Rice. 4. Change of characteristics depending on the bandwidth

As you can see, even with a volume change of more than three times (by 10 dB), the bandwidth changes insignificantly. However, as the volume decreases, the rise in the characteristic shifts to the lower limit of the passband. And we don't need it. Therefore, the benchmark will be simple, the first volume should correspond to the EP with the Butterworth quality factor or slightly lower, say, from 0.62 to 0.72 (green curve on the graph). To avoid bulky boxes, we must immediately focus on heads with a quality factor of at least 25% lower than this indicator, that is, no higher than 0.47 - 0.5.

Now notice that all curves pass through some point. This is the resonance frequency of the port and the front volume, we will call it the center frequency. In this case, it is 38 Hz, such a choice is typical for a home subwoofer, in our area the center frequency should be chosen much higher.

The upper frequency limit depends most of all on the value of the second (front) volume.

By reducing this volume, we extend the frequency range upwards while gaining a boost in response. The shape of the high-frequency part of the characteristic is due to the resonance of the phase inverter with a joint elasticity due to the rigidity of the suspension, the elasticity of the rear air and the elasticity of the air in the front volume. A 3 dB boost (orange curve) occurs when the top resonance frequency is an octave above the center frequency. The mass of air inside the port affects the lower frequency limit and at the same time the shape of the characteristic.

The characteristic in this area is due to the resonance of the combined air mass inside the port and diffuser with the joint elasticity of the suspension and rear volume. Luckily, we don't need a lot of mass, just move the bottom resonance 1/3 octave away from the center frequency (brown curve). To understand the nature of the bandbass, it will be useful to see how the shape of the characteristic will change if we keep the port setting, but at the same time change both the mass of air inside it and the volume of the front chamber.

The graphs are shown in an idealized form, which is obtained without taking into account leaks (as well as non-rigidity) of the case. If this is taken into account, the central part of the graphs will never reach the level of 0 dB. However, in the current theory, losses are not taken into account.

Now let's move on to practice. Let's choose two heads from test No. 2 for this year. Their parameters meet the Qts criterion<0,5. Как показало моделирование, чтобы избежать провала характеристики на суббасовых частотах, надо, чтобы частота резонанса головки в ЗЯ (заднем объёме) была не выше 50 Гц. Потому добавляем ещё один критерий: Fs <35 Гц. Вот что мы выбрали:

Head #1. Fs = 31.6 Hz; Vas = 29.3 L; Qts = 0.480.

Head #2. Fs = 33.4 Hz; Vas = 22.0 L; Qts = 0.454.

To calculate the PP of the fourth order, you can use many of the ready-made programs: not all of them give the expected results, but the old JBL Speakershop (aka Bass Box) in this case gives quite correct ones. If, as already mentioned, we discount the possible leaks of the hull. But for meaningful calculations, it is desirable to have some starting points. For example, for the first head, pre-calculate the volume of the IC in which the Butterworth (or slightly lower) quality factor is achieved. For Butterworth, we get 24.7 liters. If, after installing the head in such a box, we measure the impedance characteristic, then it will look something like in Fig. five:

Rice. 5. Characteristic of the impedance of the head No. 1 in the IC

Now we need to determine the front volume. A good starting point would be 1/3 of the rear, in this case 8.2 liters. As a result of the simulation, the corrected value of the front volume is 8.06 liters, which is almost the same. During the calculation, we obtain a characteristic in the free field such as shown in Fig. 6. The graph shows the approximate position of the resonant frequency of the port.

Rice. 6. Subwoofer free field characteristic

However, we are much more interested in the performance of a subwoofer in a car interior. If the standard transfer function of AvtoZvuk is superimposed on the previous graph (it was published in its entirety in No. 8/2000), then we get the picture depicted in Fig. 7.

Rice. 7. Characteristics of the PP subwoofer in a typical cabin. Head No. 1, cutoff frequency 100 Hz

As you can see, the maximum amplitude spread over the entire operating range from infrasound to 95 Hz is less than 2 dB. A similar characteristic can be obtained with the help of the ZYA, but on the side of the bandpass there is also a constant acoustic gain of 3 dB, plus an effective slope of 18 dB / oct on top.

For completeness, see Fig. 8 impedance characteristic. The frequency of the port is 64.3 Hz, the lower resonance is tuned an octave lower, the upper resonance is about 2/3 octaves higher.

Rice. 8. Subwoofer PCB impedance characteristic. Head No. 1, cutoff frequency 100 Hz

What happens if we make a mistake with the volume of the front drawer during production? Say, 10% (Fig. 9)?

Rice. 9. Detuning the volume of the front drawer by ± 10%

Especially terrible - nothing. The upper frequency limit changes by 5%, but the shape of the frequency response does not change radically. But it is not recommended to make a big mistake in the realization of the air mass inside the port, the consequences are shown in Fig. 10.

Rice. 10. Port mass detuning by ±10%

A 10% deviation of the air mass inside the port in each direction (that is, a 5% change in the tuning frequency) results in a frequency response deviation of 1 dB in either direction.

With the head number 2, although not quite identical, but a similar set of characteristics is achieved. In this case, we set the first volume to a quality factor of 0.66, for this we need a box (part of the box) with a volume of 21 liters. The resonant frequency in such a ZA would be equal to 48.8 Hz. The front volume as a result of the simulation was chosen to be 7.3 liters. The calculated frequency response is shown in fig. eleven.

Rice. 11. Characteristics of the subwoofer software in a typical cabin. Head No. 2, cutoff frequency 100 Hz

The unevenness in the entire range is not more than 2 dB, the upper cut-off frequency is about 95 Hz. The steepness of the decline - the same 18 dB / oct. If we now turn to the impedance characteristic (Fig. 12a), it will not be difficult to see that the characteristic frequencies here are almost the same as in the case of head No. 1.

Rice. 12. Subwoofer PCB impedance characteristics. Head #2: a) cutoff frequency 100 Hz; b) cutoff frequency 80 Hz

If we need to work in a narrower bandwidth, then the settings will change in a predictable way (Fig. 12b). To get an upper frequency limit of 80 Hz instead of 100 Hz, we will need to lower the center frequency and the upper resonance frequency by about 10%. In this case, the frequency response takes the form as in Fig. 13.

Rice. 13. Characteristics of the subwoofer software in a typical cabin. Head No. 2, cutoff frequency 80 Hz

The unevenness has increased to 3 dB, although unlike FI, which tend to focus on the lower bass, in the PP design, the decline begins around 30 Hz, where, in fact, the informative bass ends. True, in order to narrow the strip on top, the front volume had to be increased to almost 10 liters. Paradoxical as it may seem, but the bandpass design in our conditions works better in a wider band.

There is very little left to add. That the bandpass, for all its apparent "technocratic" nature, radiates like a closed box, and therefore its transient characteristics are more interesting than those of FI. For the same reason, his (correctly tuned) bass turns out to be more collected, which is important for SQ installations. Finally, in terms of full volume, the bandpass loses not so much to the phase, we can say that the amount of loss is equal to the amount of the front volume. This is the price for uniform acoustic amplification, in other words - for increased efficiency.

From the history of bandpass

In order not to give the impression that the bandpasses came up with “just now”, two illustrations with dates. The first is a US patent issued in the name of a man with a noble French surname d'Alton. He came up with the bandpass as a narrow-band emitter, counting from a multitude of such, tuned to different frequencies, to assemble broadband speaker systems of great efficiency in the manner of a church organ.

The idea is wild and, as history has shown, of little use, but the device, and, as far as one can judge from the lonely schedule, the nobleman understood the characteristics, in principle, correctly.

Twenty years later, when the speaker (that is, the direct-radiation electrodynamic loudspeaker) finally supplanted other means of sound emission, another patent appeared. It already explicitly states that this is a way to extend the bandwidth down with a separate, relatively narrow-band acoustic unit. That is exactly what we today call the word "subwoofer".

Moreover, Henry Lang's explanations already feature sound pressure curves very similar to those discussed in today's publication. “The process started” from that moment.

Choosing the right subwoofer is quite important when creating a personal sound system for your car. Today, different manufacturers offer many models, but in this article we will talk about how an active and passive subwoofer differ, what are their disadvantages and advantages.

So, what is the difference between an active subwoofer and a passive one?

Unfortunately, not all car owners can give a clear answer to this question.

What is a passive subwoofer?

A passive subwoofer is one or more woofers that are housed in a wood, plywood, or MDF cabinet. In order for it to reproduce sounds, an external amplifier is needed, and a sound separation filter, which leaves only low frequencies from the signal.

What is an active subwoofer?

An active subwoofer is a speaker system that has a built-in amplifier, a crossover filter and, of course, one or more speakers. This system is somewhat easier to connect, and by popular belief sounds somewhat better than a passive subwoofer. But as practice shows, it all depends on the overall setting of the speaker system.

Active vs Passive Subwoofer: What's the Difference?

In order to understand which subwoofer is better, passive or active, let's compare the main indicators that, one way or another, all car owners pay attention to:

• Cost - active subwoofers are more expensive, which is not surprising because they have a lot more expensive electronics;
• Ease of Installation - Since passive subwoofers require an external amplifier, frequency filter, etc., they are somewhat more difficult to install. In addition, active systems already have a built-in amplifier, and this can save a lot of space;
• Sound quality - It would seem obvious that an active subwoofer should sound better, in fact, everything is somewhat more complicated. After all, in order for the speaker system to sound good, it must be properly configured. And as practice shows, a well-tuned passive subwoofer can sound better than an active one;
• Ease of setup - on the one hand, active subwoofers have more tuning options, but if you have a good external amplifier, this advantage fades away.

Advantages and disadvantages of passive subwoofers

As already mentioned, a passive subwoofer is, in fact, just a speaker equipped with a special speaker that emphasizes low frequencies. Accordingly, such an element of the acoustic system will cost relatively inexpensively.

But this is far from the only advantage of passive subwoofers. With their help, you can assemble a system in which all components will satisfy your ideas about the right sound as much as possible. Indeed, in order to get the optimal sound, it is necessary to assemble a set of a suitable amplifier, the necessary frequency filters, and a set of speakers in suitable cases.

Also quite important point is that, unlike active, passive subwoofers use different types of cases, namely standard boxes, phase inverters, bandpass. In active systems, the ability to use different types of cases is hampered by the need to place additional electronics in them.

Advantages and disadvantages of active subwoofers

Of course, the main advantage of active type subwoofers is that a speaker, an amplifier and a filter are combined in one housing. This makes it as easy as possible to connect them to car radios, and provides a certain sound quality with a minimum of settings.

Unfortunately, this is their main drawback. Due to the need to fit both the speaker and the electronics in the same enclosure, there are some compromises to be made. In particular, this applies to underpowered amplifiers, which naturally affects the power, sound pressure and responsiveness of the system.

Of course, there are models in which all components allow you to get the highest quality sound. But, unfortunately, their cost is quite high.

In order to reduce the cost of active subwoofers, manufacturers quite often try to reduce the cost of components as much as possible, which makes the sound of most of them somewhat rough. It also affects their reliability.

Separately, it is worth mentioning the power of active type subwoofers. The fact is that in order to ensure sales, manufacturers often attract their potential buyers with a combination of small dimensions and high power. But in fact, really good sound with a powerful amplifier is impossible without a speaker of the appropriate size, namely 10, 12 and more inches.

What is the best choice for a car owner?

The differences between an active subwoofer and a passive one are quite obvious, and based on them, car owners make their choice in favor of one or another option.

People who want to improve their installed speaker system a bit tend to purchase inexpensive and compact models of active subwoofers. They are quite easy to install, but you should understand that in a compact case it will not be possible to place a really powerful high-end amplifier. Accordingly, such a subwoofer will slightly improve the sound, but will not give a really powerful and punchy bass.

If the car owner is disappointed in the sound of an active subwoofer, and the return period has expired, then the question naturally arises - “is it possible to make a passive subwoofer out of an active one?”. Of course, in practice this is possible, but it is worth understanding one simple point. In most active systems, the speaker is somewhat inferior compared to passive subwoofers.

Also, before choosing a subwoofer, it makes sense to check if your radio has a built-in amplifier. Today, many cars are initially equipped not only with a car radio, but also with amplifying equipment. In this case, there is not much point in purchasing an active subwoofer, unless you want to get a very powerful sound, at a power of 250 watts.

A rather important point is that active subwoofers have factory settings that are designed for the most popular styles, in particular, various dance music, etc. Therefore, if you consider yourself a gourmet of sound, then they may not be enough.

Let's summarize. In order to clearly understand which subwoofer to choose - active or passive, you need to clearly articulate your requirements for the car's speaker system. In particular, the following parameters must be defined:

• The presence in the radio of a built-in amplifier of the required power;
• Free space in the car to accommodate the subwoofer;
• Planned budget;
• Free time that you are willing to spend on setting up the speaker system;
• Requirements for the sound of the car's speaker system (want to add some bass, or plan to enter a car audio competition).

As you can see, choosing which type of subwoofer suits you best is not as easy as it seems. After all, in addition to the above factors that affect the choice of model, a lot depends on musical preferences, etc.

Do you know how the law of meanness works? I'll give you an example. After spending a lot of hard-earned money on a home theater system, you buy the latest super-cool action movie. You invite all your friends and acquaintances to "treat yourself" with the achievements of cinematography and computer graphics... But, alas, your efforts are in vain.

What's the matter? Well, at least in the fact that the explosion at the beginning of "Lethal Weapon 2" is more like the crackling of a dry branch under the foot of an unlucky trapper from some parody of a Western, and the tread of a tyrannosaurus rex from "Jurassic Park" is more like the timid steps of a baby. And now, after another sip of beer, one of your friends, in a fit of drunken frankness, admits: "Yes, the surround sound is wonderful, but the bass is not enough ..." And this is like salt on the wound: you feel like a complete idiot - and are ready to give half your life for this same bass.

Fatal attraction?
"Oh, bass! How much has merged in this sound for the heart of the Russian! .." It is on it, according to the majority of film lovers (especially beginners), that the real sound is based. The rest, in their opinion, is nonsense. To hell with localization and natural tonal balance. Loud, powerful, deafening bass - that's what "catches" amateurs in a full-fledged home theater system. Whether it's a gunshot in John Woo's movie, an explosion in the latest episode of Die Hard, the rumble of Apollo 13 taking off, or the sounds of an orchestra playing a gavotte in Sense and Sensibility, really good bass is the foundation of the soundtrack everywhere. endowing it with a life-giving drama and impact that only the best theaters can offer.

The reasons for this are psychoacoustic (that is, related to how the ear hears and how the brain processes this information). In the process of evolution, the human ear has tuned in a certain way. This is why our hearing is particularly sensitive in the mid-frequency region, which includes speech and other human sounds (such as the cry of a baby). In antediluvian times, low, rumbling sounds meant danger (an earthquake, a thunderstorm, the growl of a giant beast with sharp fangs, etc.), so they still make the body release adrenaline. So our love for deep bass is actually a love for thrills.

True, there is another explanation for the excessive passion for bass. As a rule, people start to "sick" with a home theater after visiting the corresponding exhibition or trade show, and there they usually turn on the subwoofer to the fullest - in order to make a killer impression on the visitor. Many people think that it should be the same at home.

We dance from the stove
Sounds are vibrations in the air. They are caused by everything that can set the air in motion - from the explosion of an atomic bomb to the vibration of a mosquito wing - and, of course, the vibration of a loudspeaker cone. Electrical signals cause it to move forward or backward. With each movement, the diffuser compresses or rarefies the air, and this compression/rarefaction propagates at the speed of sound. The faster it happens, the higher the sound. The pitch (or frequency) of a sound is the number of compression and rarefaction cycles per second. They are called hertz (in honor of the famous German physicist Heinrich Hertz, and by no means Herzen, who, according to Lenin, was awakened by the Decembrists).

We perceive sounds ranging from approximately 16 Hz to 18,000 Hz (18 kHz). Meanwhile, most loudspeaker manufacturers list the easier-to-remember range of 20Hz-20kHz, although sounds above 18kHz are picked up only by dogs, bats, and humans, who rarely leave the silence of their homes. Unfortunately for men, the highest part of the spectrum ceases to be available to us in adolescence, with the purchase of the first tube of aftershave cream, while women in middle age retain the ability to hear high frequencies well. But with the opposite end of the spectrum, most people have no problems: even the elderly distinguish frequencies below 20 Hz.

The second, and last, physical factor of significance to deep bass hunters is the logarithmic decibel (dB). Decibels, among other things, show the level of sound pressure. True, there is a catch: the measurements of this level are not absolute, but relative. Even worse, when the sound pressure level changes, our hearing changes its sensitivity. However, there is a generally accepted decibel scale, in which the hearing threshold is taken as zero, and the so-called pain threshold is taken as the maximum (it exceeds the hearing threshold by about ten million times and is 140 dB). Perhaps this is an oversimplification, but if you remember that for the most average home movie fan, the norm is 75 - 100 dB, and that according to this scale, adding 6 dB means doubling the volume, you can forget about the rest.

Active or passive?
To get real bass in a home theater environment, you need a subwoofer, that is, a subwoofer. It can be built into either the two front speakers or their stands, or it can be a separate device that can be installed almost anywhere in the room, since deep bass is non-directional sound radiation. Thanks to the latter factor, there is no need for a stereo pair of subwoofers: to get excellent sound quality, one is often enough. Everything is clear here.

The problem lies elsewhere. What should be the subwoofer - active or passive?

Passive subwoofers are usually designed for a specific set of loudspeakers and are generally addressed to the low cost system market. Their main advantages are that they allow the use of smaller main speakers (satellites) and do not require additional outputs from the main amplifier. The most serious drawback of passive designs is their elementary inability to reproduce sufficiently deep basses. However, sometimes it is not the subwoofer that should be blamed for this, but the amplifier, which lacks the “strength” in order to swing both the satellites and the subwoofer. That is why Technics has been producing for several years not only five-channel, but also six-channel home theater amplifiers, equipped with the expectation of connecting an inexpensive passive subwoofer (the last example is the SA-AX7 model. We reviewed in No. 3/2000 on page 79 ).

The active subwoofer has a built-in amplifier and controls that allow you to change the volume and cutoff frequency, which makes it possible to coordinate the unit with any pair of main speakers. The advantages of an active subwoofer over a passive one are a wagon and a small cart. Since the amplifier in this case is built-in, it is optimal for a particular loudspeaker, which eliminates many potential problems. Active models enhance the sound of any speaker so you don't have to change speakers, and the available controls let you tailor the specifics of your room. There are two disadvantages - the relatively high cost and the need for the amplifier to have a separate output. However, prices have come down a lot lately, and if you don't already have an active subwoofer in your home theater, then you're behind the times.

Where to lay the foundation?
Let me remind you once again: no matter how well your "cinema" is acoustically designed, it willy-nilly become a kind of equalizer, amplifying some frequencies and weakening others. This effect is determined by the resonant frequencies of the room (in fact, the acoustic properties of the room are determined by many more factors, but in this case the simplification does not affect the essence of the problem), which, in turn, depend on its length, width and height. The fact is that in the room when playing sound, constant areas of high and low sound pressure (standing waves) are created. It is easy to guess that the determination of the optimal location for the placement of the subwoofer (as well as the seat of the viewer) is made either by trial and error, or requires the involvement of huge computer power and a graduate in the field of acoustics.

The trial and error method is extremely simple, but takes a lot of time. Put on a disc or tape with the deepest bass you can find and play it as you move the subwoofer from place to place. After each permutation, sit down in the "viewing" chair and evaluate the changes that have occurred with the sound. If you are still in doubt, take the manufacturer's recommendations as a basis. When you come to the conclusion that it can't get any better, watch a few movies to make sure you're on the right track, and then enjoy the results.

However, I will allow myself to give a few "subtle observations of life." First, most novice theatergoers either turn their subwoofers up too loud or turn up the cutoff frequency. In short, if you find that the sound in the movie "Piano" would be more suitable for the movie "Terminator 2" or that the subwoofer emits a frantic growl when playing the most modest bass note, turn down the volume. Secondly, if possible, try to place the sub near the same wall as the TV to avoid the phase shift of the bass waves from the rest. Thirdly, leave some space between the TV and the subwoofer, because large and destructive magnets for the kinescope are hidden inside the latter. Fourth, most of the recommendations given by the manufacturers of AV amplifiers and processors are wrong in my opinion. These devices are usually equipped with a linear "subwoofer" output, to which the signal is pre-filtered by a low-pass filter. Meanwhile, the active sub itself is equipped with the same filter at the line input. As a result, when connected via a linear signal, two low-pass filters are connected in series, and the total characteristic will be simply unpredictable. It is best to apply a full-range signal from the amplifier's "speaker" output to the special "high-level" input of the subwoofer. And the last tip (it only applies to those who are completely desperate): installing a weak subwoofer in the corner of the room can “tighten” the mids and upper basses a little.

bass wisdom

Bass
What do we mean by this word? The answer will have to be looked for in the Hi-Fi area, because it is she who is the progenitor of the home theater. It turns out that the bass is divided into three octaves, and overlapping. The octave from 20 to 40 Hz includes the deep bass (the lowest notes of the organ fall here), the octave from 40 to 80 Hz is known as the mid-bass range (they are extracted from the bass drum), and the octave from 80 to 160 Hz is called the high bass range ( listen to cello and bassoon). Anything below 20 Hz. we feel rather than hear, here you can no longer distinguish the pitch or repeat the sound, unless, of course, you live in a cathedral.

Attack
It's actually a quirk of bass terminology. The word "attack" is not entirely appropriate here, but is used because low frequencies are characterized by slower transients compared to highs. Meanwhile, the difference between "slow" and "fast" sounding bass systems, often not otherwise defined, is the difference between a system that "punches the brain" and makes you listen in fascination.

Most of the epithets that describe good bass. can be used as compliments to a skilled drummer. Words that mean the opposite are associated with the concepts of obesity and sluggishness. So, if the sound of an explosion comes to mind with the terms "fast", "distinct", "clear", "live", "tense", "tight" or "precise", then you may be dealing with a decent system. If the words “boomy”, “fat”, “overloaded”, “fat”, “loose”, “fuzzy”, “slow”, “quiet” or “deaf” come to mind, which means it’s time to “do your feet”.

Weight category
When it comes to the amount of something, like bass, we're tempted to use the term "weight". If the system lacks bass, it is called "skinny" and "skinny". And if the bass is in excess, they say that the sound of the complex is "fat" and "inflated". When the bass is in order, the system is called "tight" and "muscular".

Dynamics
If the system is capable of distinguishing loud and soft bass notes, and does not sound "like a barrel", then the words "pop", "bang" and even "energy" are used in relation to it, all in a positive sense. Surprisingly, there are no negative characteristics here. I'll try to come up with something myself. How would you like, say, this: "sounds like chewing glass"?

Depth
When talking about subwoofers, reviewers often use the term "bass depth". It only means how "deep" the lower end of their frequency range is. A system that is not capable of reproducing the lowest bass is called "slaughtered", and one that can is proudly called "extended".

overlap
Each set of speakers, including tweeter, midrange and subwoofer, has frequency range points where the sound of one speaker overlaps with the sound of another. They are called overlap points. So, if the midrange speaker is "cut off" at 90 Hz. and the subwoofer operates in the range from 40 to 150 Hz, then somewhere around 100 Hz, most of the sound passes from the midrange driver to the subwoofer. This frequency is called the overlap frequency. Most loudspeakers are equipped with circuitry whose components produce a signal that allows for a smooth transition from one speaker to the next. This circuit is called a crossover or crossover.

Bass - to taste

Without high-quality bass, neither a home theater nor a noteworthy audio system is possible ...

If you decide to purchase a sub, approach its choice with all responsibility. An unfortunate model turns out to be practically worthless when it comes to bass reproduction - it's better to spend money on a pair of larger and better main speakers. Luckily, today's stores are littered with great subwoofers for every taste and every price, just reach out.

Models under $400
Energy e:XL16 ($300). Despite the not very high price, it has a 40 cm woofer and a 300-watt MOSFET amplifier. The crossover is tuned to any frequency in the range of 50 - 100 Hz. moreover, if desired, you can connect an external equalizer or an active filter, for which there is a separate input. To facilitate coordination with the rest of the acoustics, a phase control is provided in a very wide range (from 0 to 180 degrees). This subwoofer doesn't have many competitors, and those are either designed for midi systems (Aiwa TS-W5) or cost about 35% more (Velodyne CT-80). For those on a tight budget, I would suggest getting the largest possible size main speakers, however if you have a small room and have recently purchased new compact speakers, the e:XL16 is the way to go in most cases.

<$600
REL Q-50 ($500). Today it is the most inexpensive model produced by REL. It is unpretentious, but reproduces deep basses very well. Its closest rival, the more elegant KEF 20V (also $500), is equipped with a built-in 70-watt amplifier and, unlike the 0-50, has magnetic protection. Polk's PSW120 ($480) also demonstrates good bass. It is somewhat preferable due to its better quality/price ratio, as it will make any home theater system rumble at full power.

<$900
REL Q-100 ($850). Beautiful, deep bass, good quality/price ratio, acceptable appearance and a big name - that's what this device combines. It's capable of reaching such bass depths that your home theater system will growl and rumble. REL should be warned, however, that it has formidable rivals here in the form of the exquisite Tannoy 625 ALFie ($900), the simple but bassy Mission 75AS ($800) and the small but otherwise great M&K VX-7B ($675). Each of these models is a worthy alternative.

When the price doesn't matter
Be careful, very careful. "Price doesn't matter" - these four short words can mean more than anything to a designer. If you're looking for the best subwoofer in the world, check out the REL Studio ($4,000), M&K MX-100 ($2,200), KEF AV1 ($3,500), Revel Sub 15 ($2,800 - 5,200), B&W, Bag End , Linn, Meridian and Muse. The cheapest of these subwoofers will lighten your wallet by at least $2,000, but if you really want to overspend, you can spend twice as much. In the event that you need to save not money, but space, pay attention to EnergyMicrostar 12.1 ($1600). This cube with a side of 40 cm can bark so that it doesn’t seem a little - its power is one and a half kilowatts! Kevlar woofer, digital amplifier plus all sorts of sonic and custom bells and whistles make it extremely attractive for high class theaters.

REL "ation on REL

In the UK, among bass masters, one firm occupies a special position - it is not one, but several heads higher than the rest. This is REL. Perhaps no other subwoofer manufacturer has been so welcome here and won so many prizes. Why is this so and who is the creator of REL's success?

Let's look at the end of the eighties. A man named Richard Lord is resigned with full honors. And instead of starting a measured life and resting on his laurels, Richard Lord uses his savings to design and build the simplest woofers for Hi-Fi systems. This is how the first REL subwoofers were born.

Of course, the inherently conservative Hi-Fi industry refused to recognize the usefulness of such devices, and the opinion was formed that, although they were not the devil's spawn, they were only slightly better. Therefore, back in early 1990, Richard Lord's dream of a bass, of a bass everywhere and everywhere, seemed unrealizable. Thankfully, home theater suddenly burst into life in need of oceans of bass, and the REL subwoofer's place in history was sealed.

The REL formula is simple yet deadly effective. Each subwoofer has a large bass driver, a heavy, well-knit cabinet, and a MOSFET power amplifier. capable of receiving a signal either from the corresponding line output of the amplifier, or directly from the "speaker" outputs. The subwoofer has very few controls - they only control volume, cutoff frequency and phase. You can safely forget about the latter after the initial installation. There are also four "heels" that prevent the device from staggering, no matter what is on top of it. - so the subwoofer looks more like a makeshift table than part of an AV system. The formula remains the same at all levels of the REL hierarchy: it's just that each "superior" model is larger, more powerful and of better quality.

Most subwoofers from other companies are omitted, at least. one of the elements of the REL formula and is often done in an attempt to keep the retail price in check. This approach inevitably leads to a decrease in quality and turns the product into another mediocrity. By refusing to make such compromises, REL is making its family more and more popular.

And finally, we should not forget that REL is such a success in Russia, since the real competition for its products can be mainly American devices, and traveling across the ocean for such a solid person as a subwoofer is not cheap. In the meantime, there are a lot of very cool subs out in the USA (by Miller&Kriesel, Bag End. Muse and others), and if it wasn't for the shipping costs, we would recommend them to you more strongly.

Viacheslav Savvov
Salon AV

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