What Is A Subwoofer And Why Do You Need One?

Jul 29, 2020 | 0 comments

When discussing subwoofers, many questions arise. What size to use? What is the ideal position? These give subwoofers a bad reputation among music lovers. Yet they are essential in a surround setup and a nice addition to a stereo setup. Time to dive deeper into the topic of “subwoofer”. What do they do and why do you need one in your house?

This bad image is not entirely unjustified. People who want to keep their living room tidy and free of cables regularly stumble at the size. The interaction between subwoofer and your other speakers does not always go well. This can often be solved with all kinds of settings on an AV-receiver. Enough reasons why this device is not the favorite for many people. Yet much of this aversion has to do with misunderstanding. A well-adjusted subwoofer takes your entire setup to a higher level. Whether it is surround or stereo.

What is a subwoofer

WHAT ARE BASSES AGAIN?

People often talk about “basses”, as if it is one thing. People who listen to their music through poor quality headphones or speakers may think this. Actually, different types of low frequencies can be distinguished, each with different properties. You only hear this difference when you listen through quality equipment. In our article about omnidirectional speakers, we explained that bass sounds have a relatively wide frequency range. A good subwoofer is capable of reproducing this full range well.

The word “bass” is usually used for frequencies from 20 to 200/250 Hz. The very lowest tones, approximately up to 60 Hz, are called “sub-bass”. However, there are few natural instruments that go this low, like the double bass, which starts at about 37 Hz. You will mainly encounter these low frequencies in film music or electronic music. If your sound exceeds 250 Hz, we are talking about the “Bass Presence Region”. These tones are in line with the lower tones, you can see them as higher harmonics of the fundamental bass tones. But these tones are not played directly by a subwoofer. This shows how important it is that your subwoofer fits well with your speakers.

WHAT ABOUT OUR EARS?

Theoretically, our hearing ranges from 20Hz to 20 kHz. This gradually decreases as we get older. Various forms of hearing damage can also occur. The most decrease is in the high tones. It is normal for someone with an age around 50-60 years that the upper limit is around 15 kHz. There is also a small decrease at the lowest tones, but this is a lot less strong. In addition, we not only hear the very lowest basses with our ears, but our bodies can feel these too.

Then there is another phenomenon that is important in the context of this story. The human brain is in fact set up to be able to locate certain high tones by differences of intensity and time between the left and right ear. This is a lot more difficult at low tones, because the long bass waves reach our ears almost simultaneously. The lower the tones, the less well our ears can rely on timing. The intensity at low frequencies is the same for both ears, so our brains can’t use this technique to localize low sounds. This is why one subwoofer is already a good extension of your setup, while you always have to keep speakers in ‘balance’. Of course your sound will be even better with a second subwoofer, if set correctly.

WHAT IS A SUBWOOFER?

In fact, a subwoofer is a speaker like any other. You could even say that it is a very simple speaker, because it usually only has one speaker or driver. Subwoofers only produce bass, so the lower tones. The exact frequency range varies from model to model.

We have previously told what the difference is between passive and powered speakers. This principle also applies to subwoofers. Most subwoofers are powered, which means they have a built-in amplifier. These are connected to the AV-receiver by an audio cable, instead of a speaker cable. Passive subwoofers also exist, but are much less common. You mainly encounter these at low-end sound bars or in exotic high-end setups. There is a good reason why most subwoofers are active. Controlling a subwoofer requires quite a bit of power, sometimes up to 2000 Watt. Every subwoofer driver needs specific electronics to perform optimally. If your AV receiver has to provide that power, then you need to buy a very powerful receiver. 

WHY SO MUCH POWER?

Subwoofers need so much power because they have to move a lot of air. Bass sounds are large soundwaves that can only be produced by a large driver. Eight, ten or even twelve inch is therefore a common size for such a driver. In addition to the power, a subwoofer also requires a lot of control to be clearly audible. It is the easiest to control an amplifier designed specifically for a speaker. A good reason to make a subwoofer active.

DO I NEED A SUBWOOFER?

You probably wonder now whether a subwoofer is a good investment. “Can’t these lowest tones just be played through the speakers?” The answer to this is usually no. Producing basses correctly is extremely difficult. There are column speakers that can fairly reproduce low frequencies. However, these generally have a lower limit of 40-50 Hz. If you let these speakers go even lower, the chance of distortion increases. Small speakers aren’t built to play lower frequencies. If you do this, you have the risk of burning your drivers and destroying your speakers. Not a good idea.

In short, a subwoofer complements speakers that cannot reproduce low frequencies properly. In addition, they are also good to “relieve” speakers from the arduous task of producing low tones. Because they no longer have to play these basses, the speakers perform better at higher frequencies.

A SUBWOOFER IN A SURROUND SETUP?

Where a subwoofer in a stereo setup is a nice addition, this is an absolute must for surround sound. Surround codecs support a separate LFE (Low Frequency Energy) channel, which contains specific layer information. This is also a nice addition for your own film experience. Film music and special effects contain many low frequencies. A subwoofer not only ensures that these are more audible, but also tangible. Something that filmmakers love to use.

Adding a subwoofer also means that you can keep your other surround speakers a bit smaller. This is in a much smaller living room very important. However, we recommend using larger speakers for the front channels (left-center-right).

WHAT PROBLEMS ARE THERE?

Basses contain a lot of energy, so the placement of a subwoofer can quickly go wrong. It is therefore possible that your furniture will vibrate. Another common problem is “room modes“. This means that a certain low frequency is amplified in your room, making it sound louder than the rest. This is possible, for example, if your subwoofer is placed too close to a corner. Then you have an inverse phenomenon called “bass traps”. This attenuates certain frequencies, making the basses sound very thin.

COMPARE A SUBWOOFER TO A POND

Placing a subwoofer is quite a challenge. What can help with this is to imagine that your room is a pond. If you throw a stone into a pond, you will get expanding circles around the point where the stone hits the water. These circles are similar to how the circles of (low) sound waves move. Each stone is then a bass sound that comes out of your subwoofer. These circles are sent in all directions, while speakers send the mid and high tones in a certain direction. That is why you have to point speakers to your listening position, while a subwoofer can theoretically be anywhere in your room.

Back to the pond. Ideally, the circles stay as pure as possible until they reach your ears. However, if you throw a stone too close to the edge, you will notice that the circles bounce back and affect the other waves. However, this becomes a lot more complex in a space with many surfaces. This is the problem with subwoofers placed too close to an angle. The sound waves that come into a corner are amplified and pushed back into the room. This distorts the rest of your sound waves, giving you a distorted view.

WHERE TO PLACE A SUBWOOFER?

The tricky thing about these stumbling blocks is that they are not so easy to identify and solve. In general, larger spaces experience fewer problems than small ones. If you use an AV-receiver with a calibration system, you’re in luck. These can solve many problems for you. But for the heavy issues you quickly need a very advanced model, which you will of course see in the price. Nowadays you see more and more subwoofers with their own measurement and equalization system.

However, this does not apply to everyone. There are some rules of thumb that are a good basis for placing your subwoofer. It is usually advised to place it at the front of your room, not near a corner or against a wall. Because this is not always possible, subwoofers can also be placed in the back of the room. In this case, it is wise not to set the crossover too high.

Many people find it tempting to tuck the subwoofer away in a cabinet. An understandable idea. Subwoofers are often not the most beautiful devices and they take up a lot of space. By placing it in a cabinet, you simply create an extra housing for your subwoofer. A housing that is not designed for music and therefore has a negative influence on the sound.

A measuring system can solve many problems in your room. To do this properly it is important that you know something about audio. In addition, it can be a time-consuming job and such a system is not cheap. However, you can also start with a simple application on your phone or tablet. Before the inner audiophile comes up in you: such an app is a nice start, but it certainly does not solve all possible problems.

BUILT-IN SUBWOOFER

This article focused on external sub woofers. A better solution is to integrate the subwoofer into the speaker. Just like we did with our VEDDAN Origin, as you can see in the image below. This has some nice advantages over a separate subwoofer. First of all, this saves you one device in your space. In addition, it is a great advantage (for many people)that all components connect perfectly. When you use separate devices you will notice that there is a small transition when the frequencies go from the low to the mid tones. 

Subwoofer in VEDDAN Origin speaker

Finally, this means that instead of one subwoofer you now have several, depending on the number of speakers you use. As a result, the sound waves from the subwoofers are less distorted, more evenly spread in amplitude, have a perfect timing between the fundamental bass tones and their corresponding harmonics and therefore appear more realistic.

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