A car subwoofer is an important element in complex speaker systems. In this case, it is important not only to select and connect the sub correctly, but also to configure it.
In practice, only after tincture does the subwoofer begin to produce the desired sound. Next, we will look at how the subwoofer settings are made, what parameters you need to pay attention to, and also how to configure the amplifier for the subwoofer.
What should be the correct setting for a subwoofer in a car?
Setting up the subwoofer should be done at the stage of designing the speaker box. During this, many different parameters are taken into account: the music that the owner will listen to most often, the amplifier that will work with the speaker and the car in which the subwoofer housing will be installed.
When designing a box, an important role is played by the parameters of the speaker, which determine in what acoustic design it can work. For example, if a speaker is capable of playing well in a bass reflex enclosure, its port can be adjusted either higher or lower, depending on the music you prefer.
Of course, if you get a subwoofer in a factory case, its customization options are limited. But with the right approach, achieving acceptable sound is quite possible. Where to start setting up a subwoofer?
Parameters by which you can determine whether the settings are correct
Whether the tuning was done correctly or incorrectly, everyone will have to determine for themselves, since our tastes in music are completely different, and cars with sound insulation are also different. In addition, the design of the subwoofers is different, which is also important. Despite the fact that the feeling of music is a completely subjective matter, filters still need to be well debugged and you can be absolutely sure that the bass sounds, if not ideal, then of quite high quality. The main indicator can be considered the fact that from the driver's seat you hear all the music as a whole piece, sounding from the front speakers and you can hear each instrument separately.
For installation and to control the correctness of the settings, it is advisable to use music in which live instruments sound as clearly as possible, and not electronic ones. This is due to the fact that we all know how such instruments sound live and will strive to get that sound in our car. With electronic music, everything will be much more complicated.
Setting up the LPF (low pass filter) filter
Naturally, the speaker must be correctly connected to the amplifier. First, you need to turn on a filter on the subwoofer amplifier or head unit, which is usually designated as LPF (low pass filter). That is, this filter allows low frequencies to reach the speaker while cutting off high frequencies. For example, a popular cutoff frequency for subwoofers is 50 to 63 Hz.
The first stage of tuning is to set the filter to approximately this frequency. Then this value will need to be slightly adjusted. Moreover, if it is possible to use LPF on the head unit, you should enable it there. Otherwise, you can adjust the cut using the “twist” on the amplifier. There is no need to turn on the filter on the GU and the amplifier at the same time.
How do you know if you have configured your subwoofer correctly?
If the subwoofer is connected correctly, then people in the car simply cannot hear it, since it should not interfere with the main signal. If you listen to music at low volumes, it may seem that there are not enough bass frequencies. The absence of bass at low volumes is a sure sign that the subwoofer was connected correctly. Of course, there should be no noise, distortion or delay in the audio signal, and it makes no difference what type of design is used. The percentage of bass in each track must be different, that is, the playback must completely match the original track recorded by the producer.
The next article we recommend reading is called “How does a subwoofer box affect the sound?”
Setting up "Sabsonic"
Afterwards you need to use a filter called “sabsonic”. In essence, this is a high-pass filter operating in the sub-bass region. Simply put, it cuts off infra-low frequencies from the signal and passes everything higher. Subsonic is not available on all amplifiers. But if your speaker operates in the acoustic design of FI or HF, then you need to choose an amplifier that has such a filter.
Why does he need a “sabsonic”? The fact is that the subwoofer speaker will also try to reproduce frequencies that lie outside the audible range, for example 20-25 Hz and below. At such frequencies, the diffuser stroke increases, which can lead to the coil leaving the gap and damaging it. Sabsonic cuts off all the “infra” and does not allow the speaker to exceed the stroke. In addition, the quality of reproduction of the desired bass range only improves, and the volume increases.
The “Sabsonic” should be tuned approximately 5 Hz below the tuning frequency of the bass reflex port. For example, if its tuning frequency is 35 Hz, then the subsonic should be tuned to 30 Hz. To do this, you need to turn on the switch and rotate the “twist” to the required numbers.
Selecting a subwoofer section
I think there is no point in dwelling in detail on the choice of a specific subwoofer concept; for a person familiar with home appliances, many things are obvious. But in some ways, automotive specifics still differ from home ones.
For home appliances, the volume of the housing, although it plays a certain role, is not as significant as in a car. Here it is desirable to fit the entire structure into as small a volume as possible. This task is very controversial, and its solution is a complete compromise. As soon as you squeeze the speaker into a tight volume, the lower limit frequency immediately increases and the subwoofer simply turns into a woofer. To restore the status quo, manufacturers have to make the moving system heavier, which entails a decrease in sensitivity and therefore requires a more powerful amplifier. Therefore, you should not be surprised at car bass monoblocks with a power of hundreds of watts - they usually have to pull quite tight drivers.
So, when choosing a speaker, you have to set priorities - either give preference to “lightweights” with soft suspensions and low moving weight, with a good impulse response and not exorbitant amplifier requirements, but which will require large cases, or “heavyweights” that fit in compact housings, but require high-power amplifiers.
A subwoofer does not have to be large and take up half of the trunk. It can also be a small, neat design that does not eat up useful space in the trunk
Now a little about the sizes of the speakers. The fact that large loudspeakers, all other things being equal, require large enclosures, I think, is already obvious. But there is also another factor. The size of the subwoofer also directly determines how well it can be combined with speaker systems. For example, if the bass potential of the latter is completely bad, then choosing some heavy 15-inch sub is at least stupid - it is unlikely to work normally above 50-60 Hz. But, for example, “tens”, all other things being equal, can easily reach the acoustics from below and dock well with it.
Perhaps these are the two main points that you should pay attention to when building a low-frequency link for a car audio system. Everything else is a matter of specific speaker implementations. There can be both lightweight, large-sized subwoofers and small “slow-moving” subwoofers. Each of them, naturally, requires its own approach to choosing acoustic design. But this is a separate topic and there is no need to go deeper into it now.
By the way, as for the design, I think it is necessary to mention the subwoofer speakers for free-air installation. They usually stand a little apart. These do not require separate housings. Or rather, the housing for them will be the volume of the trunk - they are placed in the rear parcel shelf or partition between the trunk and the passenger compartment. Despite their apparent simplicity, it is quite difficult to provide them with proper design, if only because the seats for the speakers have to be radically strengthened to stone hardness, and this is due to the high labor intensity of such work. Throwing the body into the trunk is much easier, so there are very few “free air” subs on the market. Although, in my opinion, these are still one of the best subwoofers, which provide the most accurate sound in the low-frequency range.
What you need to know about filters
Another thing to remember about filters is that none of them cut the signal sharply, like a knife. That is, it does not happen that the LPF is set to 63 Hz, and there is no sound at 64 Hz. All frequencies higher will be attenuated, with a smooth decline. And the smoothness of this decline will depend on the so-called filter order.
A 4th order filter will give a flatter rolloff, while a 1st order filter will give a steeper rolloff. Some head units allow you to select the filter order. This is important for setting the “junction” of the subwoofer and midbass operating areas.
Midbass and subwoofer adjustments
As practice shows, the subwoofer setting should be done so that the woofer fits well with the front speakers, there are no frequency dips, etc. In other words, it is not enough to adjust the subwoofer, since the midbass speakers will also require adjustment.
As an example, if the subwoofer is configured to have a 63 Hz top cut, but the midbass is cut 100 Hz at the bottom, then a dip may occur. A different cutoff frequency causes certain frequencies to “stick out” while others are less audible.
For proper tuning, you will need to make the frequency response section smooth by slightly changing the cutoff frequencies LPF and HPF. This is done both by ear and with the help of an RTA analyzer. The main thing is to achieve dense and spacious sound so that there is no “dropout” in frequencies.
Adjusting the subwoofer input sensitivity “GAIN” or “LEVEL”
Another important step in setting up a subwoofer is adjusting the subwoofer's input sensitivity level. It is located on the subwoofer amplifier and is designated by the word “GAIN” or “LEVEL”.
It looks like a “twist” with numbers, for example, from 0.3 to 5 V. This is not a volume level, as some people mistakenly think, although when set to maximum values, the volume does increase. This function is needed to match the level of the head unit and amplifier.
“GAIN” is adjusted using different methods. But their essence is something like this: a music signal in the form of sines with a certain frequency is supplied to the subwoofer. The level of input sensitivity is minimal.
Gradually increase the volume on the head unit until audible distortion appears. After this, the volume knob is turned back so that the sound becomes clear again. Then the “GAIN” is adjusted in the same way, turning the “knob” until signal distortion appears. Then they return it a little back. Setting up the subwoofer in the car will be more accurate if you use an oscilloscope in the process.
Preparing equipment for adjustment
First, you need to pay attention to the process of installing equipment in a car. A suitable location is selected depending on whether the subwoofer is used - active or passive.
How to adjust an active subbuffer
The active version of the acoustics consists of two housings. One contains the amplifier, the other contains the main device. Installing such equipment is relatively simple. The main component is most often placed under the driver's seat, since this place is located close to the battery - you don't have to bother with wires. However, this will somewhat muffle the sound of the bass, and not everyone likes the vibration that occurs at some points.
An active subwoofer is easy to install, but requires careful configuration
You can also place the component in the back seat or on a special shelf. This will make it possible to better distribute sound throughout the cabin, but you will need to use several wires. Take two wires: narrow and wide. Connect them to the terminals of the acoustic equipment. The wide wire must be attached to the “+” terminal on the battery, and the narrow wire to the radio.
Most models of active equipment are equipped with a relatively weak bass amplifier. You can achieve normal sound only when listening at low volume. Its increase leads to the appearance of wheezing and other distortions. To avoid this, pay special attention to the settings.
How to set up passive acoustics
Passive subwoofers do not have a built-in amplifier, but it can be connected separately. Just make sure that the power of the main component is less than the power of the amplifier, otherwise it will overheat!
A passive subwoofer is popular with most audiophile drivers
Adjusting the subwoofer's acoustic phase
Setting the acoustic phase of the subwoofer is also important. Without going into the nuances of terminology, it should be said that correct phasing allows you to ensure the sound of the “sub” in the front, along with the front speakers. If the subwoofer can be heard from behind, from the trunk, then something was done wrong.
Many amplifiers have a phase shifter “twist” that allows you to smoothly rotate the phase. Therefore, it is advisable to purchase just such amplifiers. If this is not possible, you can rotate the phase on the PG, if it has such a function. Or you can simply swap the positive and negative wires on the speaker.
How to avoid common mistakes
Many car owners believe that if the diffuser is actively moving and almost “jumps” out of the speaker, then this indicates that the bass is correctly adjusted. In fact, everything is completely different. This means that you are having problems setting up the low pass filter. If you adjust it, the sound will become much clearer and more elastic, and the buzz will disappear.
Another mistake is the location of the oval speakers and subwoofer at the rear of the car. It is important not to overdo it in this matter. Oval speakers themselves produce rather low sounds, so if you place them next to a subwoofer, you will greatly lose the richness of the bass.
Do not configure the subwoofer in such a way that listening to music in the car will be harmful to your health.
It is difficult to give universal instructions for adjusting a car's sound system - everything depends too much on personal preferences. However, by following the above rules, you will achieve good sound and only then you will be able to adjust the acoustics with your own hands to individual requirements.
A subwoofer is a good addition to a car's sound system. But it’s worth considering that buying an expensive subwoofer does not guarantee high-quality sound, since this device needs to be properly configured. To connect and configure a subwoofer properly, you must not only have good hearing, but also a deep knowledge of car audio theory.
Setting delays
The next step in setting up a subwoofer in a car is setting the delays. But this is only possible on a processor head unit or with an external processor. Some acoustic designs, such as FI, do not always have good impulse response, so the bass may be a little late. This is not always pleasant to hear.
For example, the front speakers played a note, and a split second later the sub played. To prevent this, the delays are adjusted, which allows the front speakers and subwoofer to play simultaneously.
Why do you need to set up a subwoofer in your car?
High-quality audio systems include subwoofers that can independently adapt to the radio in the car. But there are so-called “passive” subs that require individual tuning.
The need for proper tuning can be felt when you find yourself in a car with a low-frequency speaker that is not working correctly - you will clearly feel too large a range of musical frequencies in the car, which leads to resonance of the trim and rattling of all plastic parts of the interior. A trip with loud music on will not be enjoyable, but will only cause discomfort. To avoid this situation, the subwoofer must be configured individually.
Configuring the receiver:
1) The receiver's subwoofer channel is turned off.
2) All receiver channels are adjustable by levels and delays.
3) The receiver's subwoofer channel turns on.
4) Receivers have a built-in subwoofer low-pass filter. You need to either turn it off or set the cutoff frequency to the maximum.
5) On all other speakers, frequency filtering must also be turned off, and the receiver/amplifier’s equalizer must be turned off.
WARNING: Please be aware of safety precautions. Do not put your ear close to the speakers, as Low-frequency signals that are hard to hear, however, completely rock the eardrum of the human ear, which can lead to permanent hearing damage.
It is recommended to carry out the adjustment within a period of time NO MORE THAN 30-40 minutes, because, due to hearing fatigue, the result of the adjustment can only worsen. It’s better to take a break for 1-2 hours, and then continue further.
Closed box
This type of design is the simplest. A closed box for a subwoofer is easy to calculate and assemble. Its design is a box of several walls, most often 6.
Advantages of ZY:
- Simple calculation;
- Easy assembly;
- Small displacement of the finished box, and therefore compact;
- Good impulsive characteristics;
- Fast and clear bass. Plays club tracks well.
A closed box has only one drawback, but sometimes it is decisive. This type of design has a very low level of efficiency compared to other boxes. A closed box is not suitable for those who want high sound pressure.
However, it is suitable for fans of rock, club music, jazz and the like. If a person wants bass, but needs space in the trunk, then a closed box is an ideal option. A closed box will not play well if the wrong volume is selected. What volume of box is needed for this type of design was long ago decided by experienced people in car audio through calculations and experiments. The choice of volume will depend on the size of the subwoofer speaker.
The most common speaker sizes are: 6, 8, 10, 12, 15, 18 inches. But you can also find speakers of other sizes; as a rule, they are used very rarely in installations. Subwoofers with a diameter of 6 inches are produced by several companies and are also rarely found in installations. Mostly people choose speakers with a diameter of 8-18 inches. Some people indicate the diameter of the subwoofer speaker in centimeters, which is not entirely correct. In professional car audio, it is customary to express dimensions in inches.
Recommended volume for a closed box subwoofer:
- an 8-inch subwoofer (20 cm) requires 8-12 liters of net volume,
- for 10-inch (25 cm) 13-23 liters of net volume,
- for 12-inch (30 cm) 24-37 liters of net volume,
- for 15-inch (38 cm) 38-57 liters net volume
- and for 18 inches (46 cm) you will need 58-80 liters.
The volume is given approximately, since for each speaker you need to select a certain volume based on its characteristics. The setting of a closed box will depend on its volume. The larger the volume of the box, the lower the tuning frequency of the box will be, the bass will be softer. The smaller the volume of the box, the higher the frequency of the box, and the bass will be clearer and faster. You should not increase or decrease the volume too much, as this is fraught with consequences. When calculating the box, adhere to the volume that was indicated above. If there is too much volume, the bass will turn out vague and indistinct. If the volume is not enough, then the bass will be very fast and “pound” the ears in the worst sense of the word.
A lot depends on how the box is configured, but an equally important point is “Setting up the radio.”
THERE IS ANOTHER FREQUENCY
A speaker in a “closed box” design, which also includes the case of an acoustic screen, is like an infinitely large closed box, has a strictly defined lower frequency limit of effective radiation. This is the fundamental resonance frequency of the speaker in the box. Below this frequency, with the input power still constant, the sound pressure drops at a rate of 12 dB/oct. And the amplitude of the diffuser oscillations stops growing. Below the resonant frequency it remains constant. In home acoustics, this is what is considered the lower frequency limit; below that, the speaker produces very little sound. And this is exactly what the inventor of the closed box, Edgar Vilchur (last issue of V.V.), had in mind when he spoke of the “optimal resonant frequency.” Optimal is when the amplitude does not go beyond linearity. A 6-inch speaker with a resonant frequency (in a box) of 20 Hz at lower frequencies will choke due to the excessive movement of the cone. And if the resonant frequency is not 20, but 60 Hz, the increase in amplitude at this frequency will stop (being 9 times less than it would be at 20 Hz at the same sound pressure) and the distortion will remain normal.
But this is at home, there is space, but in our cabin there is cramped space and a transfer function. With the steepness of the slope, let me tell you, the same 12 dB/oct. This means that at home it turns out like this: as soon as the resonant frequency is passed, the amplitude of the diffuser’s oscillations stops growing, therefore, as the signal frequency decreases, the sound pressure will fall in inverse proportion to the square of the frequency (this is exactly 12 dB/oct.). And in our salon, if the amplitude of the diffuser oscillations remains constant where the compression zone has already begun, this means: an “acoustic pump” operates with a constant piston stroke and creates a constant sound pressure independent of frequency, that is, a horizontal frequency response. Or, if you prefer, in a different way. Sound pressure drops at a rate of 12 dB/oct., and the transfer function grows at the same pace. And so it turns out that way. But where it will start to fall and where it will grow is a separate question.
A slightly more realistic, but still suboptimal case. With the best intentions, a subwoofer with a resonant frequency of 20 Hz was designed for the car. A home audiophile's dream. What happened: up to 20 Hz, the frequency response in the cabin grows under the influence of the transfer function, and only there it turns into a horizontal line (which a home audiophile cannot even dream of). Neither ordinary people, nor even more famous champions want such an frequency response, as can be seen from our statistics. Including because the diffuser stroke at ultra-low frequencies that are not very necessary for sound is still very large.
In real life, this happens when, out of foolishness or mischief, a subwoofer head with a low resonant frequency, intended for installation in a box, is mounted in the rear shelf and it operates in infinite screen mode (free air)
