The subwoofer. Theory and practice
Every building should have adequate the foundations. His role in the AV complex plays a subwoofer. Because nothing gives your home theater more charm than a deep, powerful bass.
You know how Murphy's law? Give an example. Having spent a lot hard-earned money on a home theatre system, you buy the latest svergnutoj action. Invite all your friends and acquaintances "enjoy" the achievements of cinema and computer graphics... But, alas, your efforts will be in vain.
What's the matter? Well, at least in the fact that the explosion at the beginning of the "Death weapons-2" is more like the crackling of dry twigs under foot hapless trapper's some parody of a Western, and the pace of the tyrannosaur from "Jurassic Park" is on the timid baby steps. And after another SIP of beer one of your friends in a fit of drunken candor admits: "Yes, surround sound wonderful, that's just not enough bass..." you like salt on the wound: you feel like a complete idiot and it's done half a lifetime to pay for this bass.
"Oh, the bass! How much of this sound for the heart Russian merged!.." That's it, that's what the majority of kenolaba (especially beginners), rests the real sound. The rest, in their opinion, - nonsense. To hell with localization and natural tonal balance. Loud, powerful, resounding bass that "catchy" Amateurs in full the home theatre system. Whether it's a shot from a gun in the film By John, the explosion in the last series of "die hard", the soaring roar of "Apollo 13" or the sounds of the orchestra performing Gavotte in "the Mind and the feelings," really good bass everywhere is the basis of sound, giving its life-giving drama and ability to impact, possible only in the best cinemas.
The reasons for this - psychoacoustic (that is associated with the fact. as the ear hears and how the brain processes this information), In the process of evolution the human ear in a certain way tuned. That's why our hearing particularly sensitive in the midrange to which it relates and other sounds made by people (for example, a crying baby). In the antediluvian times are low, rumbling sounds meant hazard (earthquake, storm. growling giant beasts with sharp fangs, etc.), so they now cause the body to release adrenaline. Thus, our love deep bass is actually a love for the thrill.
However, there is another explanation for the excessive emphasis on bass. As the rule, "to hurt" home theater people begin after visiting one such exhibition or trade salon, and there are usually cut for sub the whole coil is to produce a killer impression on the visitor. Many I think that it should be the same at home.
Dance from the stove
Sounds are vibrations in the air. Their causes, which may cause the air in motion - from the explosion of a nuclear bombs to vibration mosquito wing - and, of course, fluctuations of the diffuser the loudspeaker. Electrical signals make it move forward or back. With every movement the cone compresses or racreset the air, and this compression/rarefaction propagates at the speed of sound. The faster it occurs, the higher the sound. The pitch (or frequency) is the number of cycles compression and rarefaction in a second. They are called Hertz (after the famous the German physicist Heinrich Hertz, and not Herzen, which, according the expression of Lenin, was awakened by the Decembrists).
We perceive sounds that are in the range of from about 16 Hz to 18 000 Hz (18 kHz). Meanwhile, most manufacturers of acoustic systems lead a more easy-to-remember range 20 Hz - 20 kHz, although the sounds above 18 kHz captured only dogs, bats and people, which rarely leave the silence of his home. Unfortunately for men, the highest part of the spectrum ceases to be available to us in the transition to adulthood, with the purchase of the first tube of cream after shaving, women and the average age of well retain the ability to hear high frequencies. But with the opposite end of the spectrum at most people have no problems: even the elderly distinguish frequencies below 20 Hz.
The second, and last, the physical factor that is important for hunters deep bass, is a logarithmic unit of decibels (dB). Decibels, among other things, show the sound pressure level. However, there is a catch: measurement at this level is not absolute, but relative. Worse also, when you change the sound pressure level, our hearing changes the sensitivity. However, there is a generally accepted scale of decibels, which zero accepted the hearing threshold and the maximum of the so - called pain threshold (it exceeds the threshold of hearing is about ten million is 140 dB). Perhaps this is too great a simplification, but if remember that for the average Amateur home movie the norm is 75 - 100 dB and that according to this scale, the addition of 6 dB represents a doubling the volume of the rest can be forgotten.
Asset or liability?
To get a real bass in conditions home theater requires a subwoofer, the bass is the loudspeaker. It can be embedded in either the two front speakers, either in their base, and may be a separate device, allows installation almost anywhere in the room because deep bass - non-directional sound radiation. Due to the last factor, there is no the need for a stereo pair of subwoofers: to obtain excellent sound quality happens often enough one. Everything is clear.
The problem lies elsewhere. What should be the subwoofer - active or passive?
Passive subwoofers are usually developed for a specific set the speakers are usually passed through to the market for low-end systems. Their the main advantages are that they allow you to use smaller main speakers (satellites) and do not require a main amplifier having additional outputs. The most serious the disadvantage of passive constructions is their basic inability to reproduce enough deep bass. However, sometimes to blame should not the subwoofer and amplifier, which lacks a "strength" for to swing or satellites and a subwoofer. That's why the firm already Technics a few years produces not only five-, and six-channel amplifiers for home theater, equipped with a connection inexpensive passive subwoofer (the latest example is the SA-AX7. we reviewed No. 3/2000 on page 79).
Active subwoofer built-in amplifier and the regulators to change the volume and cutoff frequency that gives the opportunity to coordinate the device with any pair of main speakers. The advantages of active Saba before passive - car and small truck. Because the amplifier in this case is built, it is optimal for a particular loudspeaker, that eliminates many potential problems. Active models improve the sound of any speaker, so that the latter can not be changed, and the existing regulators allow to take into account the specific characteristics of your room. The disadvantages are two - relatively high cost and the need for the separate amplifier output. Recently, however, prices are significantly decreased, and if your home theater is not yet active subwoofer, so you're behind the times.
Where to lay the Foundation?
Let me remind you once again: no matter how well acoustically designed your "cinema", he will inevitably become a kind of equalizer, amplifying some frequencies and attenuating others. This the effect is determined by the resonant frequencies of the room (actually the acoustic properties are determined by a lot 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 what is the sound created constant region high and low sound pressure (standing waves). It is easy guess that determining the optimal location for placement of the subwoofer (as well as chair of the viewer) is determined either by trial and error, or requires a lot of computer power and graduate specialist in the field of acoustics.
Optimal the location of the subwoofer. However, try to alienate him from the TV that it did not affect the kinescope.
A good option for oblong room - if you can put the subwoofer at least a few meters from the place of the audience. General advice: keep away from SAB the listeners, but not in the corner (he's not to blame!).Trial and error is extremely simple, but takes a long time. Play a CD or tape with the deepest bass that you just can find, and play it, rearranging the subwoofer from place to place. After each permutation sit in "look-up" chair and evaluate the incident with the sound changes. If you are still in doubt, take the basis of the recommendations of the manufacturer. When you come to the conclusion that there's nowhere better, please see some movies to make sure that you are on the right track, and then enjoy results.
However, let me give you a few "thin-life observations". First, most beginners theater or turn on subwoofers too much volume, or "turn up" the cut-off frequency. In short, if you find that the sound in the movie "the Piano" was more for a tape "Terminator 2" or that the subwoofer emits a fierce growl when play the most modest bass note, reduce the volume. Secondly, if possible, try to arrange sub is about the same the wall where the TV to avoid the phase shift of LF waves from the rest of us. Third, leave a little space between the TV and subwoofer, because hidden inside the last large and destructive for kinescope magnets. Fourthly, most of the recommendations given manufacturers of AV amplifiers and processors, in my opinion, incorrect. These the devices are usually equipped with linear "subwoofer" output, which served pre-filtered through a low-pass filter the signal.
Meanwhile, active subwoofer equipped with a linear input the same a filter. As a result, when connected to a linear signal, the two low-pass filter are connected in series, and the total characteristic will just unpredictable. Best served on a special "high-level" input Saba full-range signal from the "column" exit the amplifier. And the last tip (it applies only to those who really desperate): setting weak subwoofer in the corner of the room maybe a little "tighten up" mid and upper bass.
What we mean by these words? The answer will have to look in Hi-Fi field, as it is the ancestor of home theater. It turns out that the bass are divided into three octaves, and overlapping. To the octave from 20 to 40 Hz are deep bass (here get the lowest notes of the organ), octave from 40 to 80 Hz known as srednemirovogo range (extracted from them bass drum), and octave from 80 to 160 Hz is called the range high bass (listen to the cello and bassoon). Anything below 20 Hz. we feel more than hear, here you will not be able to distinguish the pitch or repeat the sound, of course, if you don't live in Cathedral.
In fact, this fad bass terminology. The word "attack" is not entirely appropriate here, but is because low frequencies are more slow transients on compared to high frequencies. Meanwhile, the difference between "slow" and "fast" sounding bass systems, often otherwise not determinable, it the difference between the system, "pecking on the brain" and forcing entranced to listen.
The majority of adjectives that describe a good bass. you can use as compliments skillful drummer Words that mean the opposite, associated with the concepts of obesity and unwieldy. So, if the sound of an explosion to mind the definition of "fast", "clear", "clean", "live", "busy", "tight" or "accurate" - perhaps you are dealing with a decent system, If I recall the words of "echoing", "fat", "too busy", "thick", "loose", "fuzzy", "slow", "quiet" or "deaf" - it's time "did your feet."
When it comes to the number something, such as bass, we want to apply the term "weight". If the system lacks bass, it's called "skinny" and "skimpy". But if the bass is in excess, say that the sound at the complex "fat" and "inflated". When the bass is fine, the system is called "taut" and "muscular".
If the system is able to discriminate between loud and quiet bass notes, and doesn't sound "of a barrel", then in relation to it used the word "cotton", "udar" and even "energy" - all in positive value. Surprisingly, negative characteristics not here. I'll try to come up with something myself. As you like it, let's say this: "sounds. as glass chews"?
Speaking of subwoofers, the reviewers often use the term "deep bass". It only means how "deep" is the lower limit of the frequency range. System, not able to reproduce the lowest bass, called "stabbed to death", and that this may, is the proud title "extended".
Each set of speakers, includes "Squeaker", midrange speaker and a subwoofer, there are dots the frequency range where there is an overlapping of sound one dynamics on the sound of the other. They are called the points of overlap. So, if midrange "clipped" at a frequency of 90 Hz. and the subwoofer works in the range from 40 to 150 Hz, somewhere in the area 100 Hz most of the sound goes from the mid-range to the subwoofer. This frequency is called the frequency of the slab. Most loudspeakers are equipped with circuitry, the components of which emit a signal that can make a smooth transition from one speaker to another. This scheme is called crossover or the crossover.
Bass to taste
Without quality bass no home theater or noteworthy audio system...
If you decide to purchase a sub, go to his or her choice with all responsibility. Failure is almost useless when it comes to bass response, - it is better to spend the money on a couple of larger and better basic the loudspeakers. Fortunately, today, just overwhelmed great subs for every taste and for any price, only give a hand.
Models under $400
Energy e:XL16 ($300). Despite not a very high price and a 40-inch woofer and 300-watt MOSFET amplifier. Crossover rebuilds for any the frequency in the range 50 - 100 Hz. moreover, if desired, can be connected external EQ or active filter, for which there is a separate entrance. To facilitate coordination with the rest of acoustics provides control phase in a very wide range (from 0 to 180 deg.). This subwoofer is not a lot of competitors, and those either created for MIDI-systems (Aiwa TS-W5), or are about 35% more expensive (Velodyne CT-80). Those who are on a tight budget, I would advised to buy the main speakers of the maximum possible size, however if you have a small bathroom and you have recently purchased new compact loudspeakers, e:XL16 - what you need to the majority of cases.
REL Q-50 ($500). It is the most cheap production model REL. It is unassuming, but reproduces deep bass very well. Her closest rival, more elegant in appearance KEF 20B ($500), equipped with a built-in 70-watt amplifier and unlike 0-50 has magnetic protection. Good bass also demonstrates PSW120 firm Polk ($480). He several preferred due to a better ratio quality/price, since it will make to rumble in the power of any home theatre system.
REL Q-100 ($850). Beautiful, deep bass, good ratio quality/price, acceptable appearance and loud a name that combines the device. He is able to achieve such deep bass that your home cinema system will roar and Sarkozy. However, we should warn REL she's here there are formidable opponents in the face of exquisite Tannoy 625 ALFie ($900), a simple, but bass Mission 75AS ($800) and small in size but great in all other M&K VX-7B ($675). Each of these models is quite a good alternative.
When the price does not matter
Be careful, very careful. "Price doesn't matter" - these four short words can mean for designer more than anything else. If you definitely need the best subwoofer in the world, carefully read opportunities REL Studio ($4000), M&K MX-100 ($2200), KEF AV1 ($3500), Revel Sub 15 ($2800 - 5200), as well as models of firms B&W, Bag End, Linn, Meridian and Muse. The cheapest of these subwoofers ease your wallet at least $2000, but if you really want to overspend, and you can spend twice more. In if you need to save money, and the place, pay attention to EnergyMicrostar 12.1 ($1600). This cube of side 40 cm can snap so, that will not find his power half kW! The Kevlar woofer, digital amplifier plus all sorts sound and custom bells and whistles make it extremely attractive for high class theaters.
RELяция on REL
In the UK among the masters of bass one firm holds a special position - it is not one but a few heads above the rest. It REL. Perhaps no manufacturer of subwoofers has not been met here is welcome and has won many prizes. Why is it so and who is the Creator of successes REL?
Let's look in the late eighties. A man named Richard Lord receive retired with full honors. And instead of start a regular life and to rest on its laurels, Richard Lord let your savings on the development and creation of the simplest bass loudspeakers for Hi-Fi systems. Thus was born the first the REL subwoofers.
Of course, conservative by nature, Hi-Fi industry refused to acknowledge the usefulness of such devices, and formed the view that though they are not the devil's spawn, but only slightly better. Therefore, in the early 1990's the dream of Richard Lord on bass, the bass everywhere, seemed unattainable. Fortunately, in life suddenly broke into a home theater, needing oceans bass, and place of REL subwoofers in history was determined.
The formula REL simple, but devastatingly effective. Each subwoofer has a great bass speaker severe, "tightly knit" housing and the MOSFET. able to receive a signal from the corresponding linear amplifier output, either directly "speaker" outputs. Regulators have a subwoofer quite a bit - they only has control of volume, cut-off frequency and phase. About the last you can forget after the first installation. There are also four "heel" preventing swaying of the machine, regardless of what stood on it on top of. - so the subwoofer with a mind more like an impromptu a table than on the part of the AV system. The formula remains the same at all levels REL-hierarchy: just each "parent" model more size, stronger and better.
In most other subwoofers companies omitted, at least. one of the elements of the formula REL and often this is done in an attempt to keep in check the retail price. This approach inevitably leads to a reduction quality and turns the product into another mediocrity. Refusing such compromises, REL provides its the family more and more popular.
Finally, we should not forget that REL is so successful in Russia, as a real competitor to its products can to be mainly American vehicles, and the journey so respectable person, like a subwoofer, across the ocean does not come cheap. Meanwhile, in the U.S. produced a lot of very cool subs (firms Miller&Kriesel, Bag End. Muse and others), and if not transport costs, we would recommend them to you more strongly.
Author: Vyacheslav Savov, Salon AV; Publication: www.audio.ru/salonav/home.php, www.cxem.net