Table of Contents
Some General Information
Subwoofer – it’s a separate speaker system for reproducing the lowest frequency sound range. Modern subs reproduce sounds in the frequency range of 20 – 200 Hz, although some models can produce even lower bass. Woofer performs two essential functions:
- it provides bass reproduction on the lower boundaries of the audible range, down to the feeling that the bass isn’t heard by the ear, but felt with the whole body,
- as well as provides a clear reproduction of the remaining sound frequencies due to a lack of modulation of a stronger signal by a weaker one, and a flat frequency response and undistorted signal phase due to lack of vibration of the main speaker system housing.
Main Differences Between Subwoofer Box (Enclosure)
When choosing the best subwoofer for car or home theater, for a start you need to decide the type of acoustic enclosure of subwoofer driver. There are quite a large number of different options, but the most common are three types: closed, vented, and bandpass. Each of the options has its advantages and disadvantages. Let’s consider each type more in detail because housing construction largely determines the acoustic properties of a good subwoofer.
Sealed (closed) box Subwoofer
Models of closed type are the same dynamics, but they are built in the box of a certain volume. This is the most common type of acoustic speaker design. Fluctuations in this box are in a closed volume and eventually, they are extinguished. But as a sound wave is an energy, the fading of it is converted into heat. Although the amount of this heat is very small, it still has an impact on the acoustic characteristics of the system.
Among the advantages of this type of construction, it’s possible to mention the simplicity of frame and virtually no sound “leaks” from the emitting surface. They have the lowest signal delay and the flat frequency response. Closed subs have a deep and rich bass. However, due to design features, a diffuser of the LF driver in the sealed box is loaded with sound pressure arising in the case. Due to this, the diffuser mobility decreases, and the output also becomes smaller. Therefore, to obtain high-quality and powerful bass closed woofers require a fairly significant volume of the housing and they are often very bulky and heavy. When reducing the volume to less than a certain limit, there is an abrupt loss of low-frequency component. Therein lies the main drawback of the given type of models. Of course, we should clarify that there are very powerful (700W or more) subwoofers in a sealed (closed) box, which are of a relatively small size, but in most cases, this significant advantage is sharply limited by not very cheap price.
Vented Box Subwoofer
Bass reflex system, which is also known as a vented box, is the next most common type of acoustic enclosure. It consists of a box with a speaker inside and an opening on the back or any other part. The diffuser stroke increases, so the best woofer in a vented box can produce much lower bass than in the closed one. Through the use of the bass from the back side of low frequency driver, the produced sound is stronger and louder. In addition to a higher coefficient of efficiency, bass reflex has another important advantage: cone excursion is significantly reduced close to the frequency tuning. But vented subwoofers are much more picky to the calculation of the working volume because it is a rather complicated oscillating system, which must take into account a large number of interrelated factors. Thus the choice is subject to at least three parameters: the volume of a box, cross-section, and the length of a tunnel. Among other shortcomings, bass reflex requires fine tuning and very often can become the main cause of non-linear distortion.
While sealed box and bass reflex are acoustic high-pass filters, the bandpass, as the name implies, combines filters of high and low frequencies. The main advantage is that among the traditional designs, bandpass type is the efficiency champ. The housing consists of two volumes, one of which is a closed box, and the second is a bass reflex. This achieves a higher sound pressure level, but the frequency range becomes narrower. By changing the volume of the cells of bandpass subwoofer, it’s possible to influence the sensitivity or frequency range, but it is also a very complex procedure, which requires a skilled approach. Therefore, advantages can be assessed only by experienced people who know how to manually fine-tune multi-channel sound system. And despite the best quality of the bass, the same factor will be a drawback for non-professionals.
So, choosing the best sub enclosure is quite difficult. Each has its pros and cons, and the final choice depends on the specific requirements and conditions. For example, vented subs have good output and large loudness, and closed subs are more often used to produce the high-quality, deep bass.
Apart from the classification of enclosure design, woofers are divided into powered (or active) and passive types. To begin with, let’s consider the structural differences between passive and powered sub woofers.
– Passive Subwoofer consists of subwoofer enclosure + speaker
Passive woofer differs by the simplicity of design and has two possible types of connection. The first type is the least preferred because of the presence of sound distortion and lower transmission quality – in this case, a signal of the stereo amplifier is fed not only to the subwoofer but also to the other speakers. Connect with electronic crossover is much more reasonable because it separates the quality bass and the signal going to the other speakers. Connection with electronic separation filter is much more reasonable because it qualitatively separates the bass and the signal going to the other speakers.
– Powered Subwoofer consists of woofer enclosure + speaker + amp
That is, a powered subwoofer is a passive subwoofer but with a power amplifier, which is located inside or outside the housing. And if in the case of a powered subwoofer the manufacturers have already taken care of us, then for a passive subwoofer you have to buy the amplifier separately.
Usually, if we compare the cost of the powered subwoofer is slightly higher than the passive, which is due to a built-in amplifier. But due to the fact that for a passive subwoofer you must purchase a separate amplifier or AV receiver, the cost of equipment in total can be much higher. Powered subwoofer with its default settings is better suited for heavy or dance and rhythmic music since it better conveys the bass frequencies and has more flexible settings and adjustments. However, a system with a passive subwoofer is quite possible to set up so that it will sound much better than a system with an active subs, but it is very tedious and delicate process. In this regard, a powered type is much more convenient, because it is much faster and easier to set up, but a lot of good sound experts prefer to invest time and effort to configure passive systems.
Key Parameters (Characteristics) of Subwoofer
But that’s not all the characteristics and differences among the subs. Let’s now turn to the dynamic characteristics and some aspects. So, what are the key parameters to consider when choosing the best home woofer.
- The frequency range, which is measured in Hertz (Hz), is the limit range of reproducible subwoofer frequencies. It can be divided into a low bass range of 20-40 Hz, the middle range of 40-80 Hz, and a high range of 80-160 Hz. The vast majority of subwoofers sound in the range of 40-200 Hz, that is, basically – mid and high bass. With the rare exception, some brands can reach the upper limit of 250 Hz. Of course, the subwoofers with a lower frequency limit transmit the sound more accurately, so the ideal frequency range for the best subwoofer is 30-60 Hz.
- Crossover frequency is the indicator at which the separation of frequencies takes place. Thus, at a certain value, in the signal supplied to the subwoofer all components with frequencies above this value are weakened.
- The maximum sound pressure level is the ultimate volume of the subwoofer. If you need just the right and quality bass, this parameter can be ignored.
- As for sensitivity, which is measured in decibels, it is recommended to select the speaker system with a sensitivity of 90 dB and above. With a good indicator of the sensitivity, the less powered amplifier can be used. The greater is the sensitivity of the speaker, the less will be the load on the amp and thereby the overall volume of the system will increase.
- The diameter of the LF driver is indicated in millimeters or inches. Its optimal size is 10-12 inches.