The era of cassette car radios and the “tinny” sound pouring into the ears of passengers and car drivers from homemade sound systems or speakers is becoming a thing of history. Very quickly, car enthusiasts appreciated the benefits of digital sound and the advantages of high-quality audio equipment, in particular subwoofers. These devices complemented the standard acoustics with powerful bass, which made it possible to enjoy rich sound that caused a friendly run of “goosebumps” on the skin. In our rating of the best active and passive subwoofers for cars, we tried to cover the most interesting (according to reviews from car enthusiasts and experts) models in different price categories.
A subwoofer that doesn't need an enclosure - Free Air
Free Air is a low-frequency speaker that does not need a closed volume - that is, a housing.
Free - free, air - air.
This subwoofer has fast, accurate and articulate bass with minimal time delays.
In this material we will consider the pros, cons and distinctive features of these speakers. free air suitable for and how to properly install such a subwoofer in a car.
Specifications
When a motorist thinks about which subwoofer is best for him to put in his car, after studying the varieties and design features, he should move directly to the technical characteristics of the car subwoofer.
In terms of parameters, we recommend paying special attention to the following indicators:
- Frequency range. This is the frequency range. For most modern subwoofers it ranges from 30 to 150 Hz. In rare cases, there are models with the ability to reproduce 20 Hz. Anything below 20 Hz is a sound that most people are unable to hear. There are 3 conditional ranges. These are deep, medium and high. Typically, the more expensive the subwoofer, the narrower its range. This situation is due to the fact that good speakers can reproduce high-pitched sounds without a subwoofer.
- Amplifier power. This is a recommended parameter that is relevant for passive models of car subwoofers. In the case of active devices, the power characteristic or low-frequency amplification power is used.
- Crossover (cutoff) frequency. Is the frequency threshold above which the frequency distribution device (crossover) will begin to suppress the signal. When the cutoff frequency is 120 Hz, then the car subwoofer will reproduce sounds below the 120 Hz mark.
- Sensitivity indicators. This parameter displays the efficiency of turning or converting power into sounds. At high sensitivity, even not the most powerful amplifiers provide increased sound pressure, that is, output volume.
- Dimensions and weight. There is a fair argument that more speaker weight produces more power. This is logical, since more powerful equipment requires the use of heavy magnets. There is also a rule that a larger speaker produces better sound. This is fully consistent with the characteristics of subwoofers. But the use of bass reflexes in modern solutions makes it possible to reduce the size, but without compromising the low-frequency range. You should pay attention to the dimensions, since not every model can be installed in limited space in the car interior or luggage compartment.
- Gain. Low-frequency speakers are required to amplify the low-frequency signal. Subs can be active, that is, equipped with a built-in amplifier, or without it. Then you have to connect a separate amplifier. It is important that a corresponding separate low-frequency output be provided on the subwoofer.
Having decided on all the key characteristics, you can also turn your attention to the design solutions and external features of the model.
Since it is now possible to order a subwoofer based on an individual project, not only technical characteristics are provided, but also appearance, problems with selecting a subwoofer for the interior of the vehicle should not arise.
Prology Wow Box 1000
Features of Free Air subwoofer
A freeair subwoofer can have advantages in euphony even over a closed box. He doesn't need a body, as such. And it can also be one of the best solutions for a sedan with the ability to install in a shelf.
Due to the absence of compressed air on the back side, such a subwoofer produces accurate, fast, but pleasant bass over a wide sound range.
It is well suited for instrumental genres, rock and similar genres. At the same time, it will cope well with popular music and various hip-hop, RnB and similar compositions, and in general it can be quite universal.
But, oddly enough, recently the popularity of its use has been declining, and manufacturers are not paying much attention to it.
Let's look at why such a good and simple, at first glance, option is not widely used.
But first things first.
How Free Air works
As a rule, speaker manufacturers design them in such a way that the Thiel-Small parameters, which affect the sound when the speakers are placed in a certain volume, reach optimal values.
The fact is that when a speaker is placed in a closed volume, its resonant frequency and quality factor rise. If the volume is too low, the subwoofer will not play low enough and will produce boomy and unpleasant bass. And if the volume is too large, then the bass will be smeared and inaudible, and the speaker may reach maximum speed too early, not realizing its power.
The main influence on the character of the bass in this case is the final quality factor (also called Qtc), which the speaker will have in its housing. The quality factor shows how quickly the speaker stops after the signal is stopped. The faster he does this, the lower this quality factor is and, accordingly, vice versa.
When designing a closed box, they usually strive for a final quality factor ( Qtc ) of 0.7 or 0.707 to be precise. With this value, low frequencies have the smoothest decline in frequency response , which is beneficial to the ear. Or 0.57 - in this case, the sound is characterized by minimal time delays .
You need to understand that it will not always be possible to obtain any required quality factor in an adequate volume. It will depend on the initial parameters of the speaker itself.
And how low the subwoofer can play is determined by the final resonant frequency of the speaker in the housing ( Fc ), you can also focus on F3 , this is the frequency at which the volume drop will be 3 decibels. And the lower it is, the lower the subwoofer will play.
When installing a speaker in a certain closed volume, the natural resonant frequency (FS) and total quality factor (Qts) rise and the smaller the volume, the higher these values will be.
Therefore, a speaker that is intended to be used in a closed box must have such values that when placed in the housing they will fall into the desired ranges.
Now we return to free air. Since there will be no volume behind the speaker.
Theoretically, the volume of air ceases to affect the behavior of the speaker if it exceeds the equivalent volume of the speaker (Vas) by 3 times.
And if there is no influence of air, then, accordingly, the quality factor and resonant frequency will not rise, but will remain unchanged.
That is why, if a speaker for a closed box is placed in a free-air design, then these parameters will be too low, and we have already noted above how this affects the sound.
Installing a subwoofer in a hatchback
- Setting up a passive subwoofer in speakers with a processor
Types of acoustic design of subwoofers
A car with a hatchback body is better than others for installing a subwoofer in the trunk, since the luggage compartment of the car and the interior have a direct connection, and nothing prevents the subwoofer from freely distributing bass throughout the cabin. Among the existing types of acoustic design for woofers, cabinet-mounted subwoofers are suitable for hatchbacks, with the exception of “free air”. This is a type of acoustic design in which the trunk of a car acts as a volume for the subwoofer.
The most popular among motorists are subwoofers with the following housing types: closed box and bass reflex. Participants in car audio competitions use subwoofers with a band pass (BP) housing.
- A closed box (CL) is a type of subwoofer for a woofer that has a sealed housing. For such a sound box, you will need a box of fairly compact dimensions, compared to other types of acoustic design. When configuring subwoofers, we take into account that the SZ has a gentle decline at the lower limit of the frequency response (amplitude-frequency characteristic) and has a slope of 12 dB/octave. This circumstance does not provide bass depth in comparison with a bass reflex and band pass, but at the same time provides clean and collected lows with a high rate of fire.
- A box with a bass reflex (PI) is a housing with a built-in pipe (bass reflex) or an acoustic slot. The bass reflex is adjusted to a certain frequency and when playing music, deep and strong bass is obtained. The lows in a subwoofer of this design sound louder. For the same speaker, the box with the FI must be larger than the SF.
- Subwoofers with a band pass enclosure type (they are also called a strip enclosure) are a device consisting of several chambers, in one of which a woofer speaker is mounted. The bass from the device comes out through the bass reflex. Unlike a closed box and a bass reflex, in a power supply unit the frequency response decline along the lower and upper boundaries is carried out at the same (12 dB/octave) slope. This allows you to more accurately tune the sub and get excellent bass, although all the advantages of the power supply are offset by the huge subwoofer housing, which will hardly fit in the trunk of an ordinary car.
We have extensive experience in installing and configuring subwoofers in various acoustic designs for cars with a hatchback body type, we will take into account your musical interests and configure the subwoofer for optimal low-end radiation.
Active and passive subwoofer
When buying a ready-made subwoofer according to your own understanding, pay attention to whether it is active or passive.
An active sub has a built-in low-frequency amplifier, which is installed by the manufacturer during assembly. The amplifier and woofer are matched in basic parameters, and a high-quality active subwoofer will provide good bass in the car. It will only need to be connected and configured correctly.
The passive sub does not have a built-in amplifier, so its hardware will require the purchase of an additional amplifier. It is preferable to install a single-channel amplifier (monoblock) in pair with the subwoofer, which will exceed the power of the subwoofer's low-frequency head. Installing and configuring a passive subwoofer will require additional time, since there will be work to connect and configure the amplifier.
Place for a subwoofer in a hatchback body
The place for a subwoofer in the trunk of a hatchback is theoretically and practically determined - this is the position near the walls of the rear seats with the speaker facing the car number. This position will give a reflected low-end signal and direct it deeper into the cabin. In order to save space in the trunk of a hatchback, it is possible to install a stealth-type subwoofer in the spare tire or in the side niche of one of the rear wings.
Installing, connecting and configuring an active subwoofer in a car with a hatchback body type
An active subwoofer has a built-in amplifier “on board” and its installation; connection comes down to choosing a place in the trunk, routing power wires, signal wires, and control from the head unit. At the final stage, we configure the active subwoofer to work correctly in the speaker system along with other components: midbass and tweeters.
Installing and connecting an active subwoofer
We install and connect the active subwoofer in the hatchback in the following sequence.
- We determine a place for the subwoofer in the hatchback trunk (usually at the back of the rear seats in the center).
- We install the subwoofer box in the trunk. The box, shaped like a beveled pyramid, has a tilt angle of 28 degrees, which makes it possible to install it close to the back of the rear seats.
- We secure the subwoofer to the walls of the seats with special belts so that the sub does not move around the trunk while the car is moving.
The final fixation of the active subwoofer is carried out after connecting it to the mains power and setting it to play bass.
The subwoofer kit usually comes with a set of connecting wires. We check the wires, make sure of their quality and sufficient cross-section, and if necessary, replace them with wires of a larger cross-section. This applies to power cables.
We start connecting the active device by pulling the positive power cable from the engine compartment into the trunk of the car. At the same time, we find (or install) a rubber plug in the body, through which we pull the cable from the passenger compartment to the engine compartment. There we bring it to the battery and insert a fuse at a distance of 30 cm from the “+” terminal.
Pulling along the left side
In the car interior, on the left driver's side, we dismantle the plastic trim on the threshold and place the positive cable in the resulting niche, having first put a corrugated protective sleeve on it. Protection is needed so that the wire insulation does not rub against metal parts of the body during operation, which will eliminate a possible short circuit. We put the positive cable into the trunk and connect it to the contact on the subwoofer amplifier, which is designated “PWR”, or in other versions “+12 V”. We connect one end of the negative wire to the terminal of the subwoofer amplifier, which is labeled “GND”, and the other end to the ground of the car. We find a place for connecting the ground on the car body as close as possible to the subwoofer. The connection is made securely and with tight contact.
Pulling on the right side
The next step is to stretch the wiring along the car that will connect the car radio to the subwoofer amplifier. We are talking about three wires: two of them are equipped with “tulip” type connecting terminals and the audio signal is picked up from them, and the third wire performs the functions of controlling the power of the amplifier. We lay the wires on the right side of the car in the niche between the threshold protection and the threshold. Just like on the power cable, we put a corrugation on it to protect against short circuits. We route the wires on different sides of the car to prevent interference, which will lead to distortion of the sound in the woofer.
Connection to head unit
We remove the head unit from the seat and connect the tulips to the sockets that have the inscription “SUB OUT”, while maintaining the accuracy of the connection and focusing on the colored markers on the contacts. We connect the control wire on the main unit (head unit), which has the inscription “RMT”, with the third cable (usually blue). On the amplifier we find places to connect the wires. We connect the linear input wires to the amplifier, observing the polarity. We connect the control cable at the point marked “RMT”. After all the manipulations, we put the positive terminal on the battery, and then connect the negative terminal, making sure that all car systems are connected to the electrical network and there are no disturbances in their operation.
Checking connections
Once again we check all connections of wires and cables to the amplifier, head unit and on-board network of the car. We turn on the power and the car radio and make sure that the GU plays musical compositions, and the subwoofer works and responds to adjustments both on the head unit and on the subwoofer itself. Next we move on to setting up speakers with a subwoofer, which consists of creating a musical scene with accentuated, high-quality bass.
Setting up an active subwoofer, pre-setting midbass
Correctly installing and connecting an active subwoofer in a hatchback is half the battle; the comprehensive setup of the entire system is no less important. You can get accentuated and high-quality bass in a car only when it sounds together with other speaker components in unison. We achieve the organic sound of car acoustics by ideally tuning its components.
When installing a subwoofer into the system, we reconfigure it taking into account the bass that appears. Essentially, bass sounding by itself does not bring pleasure to the listener. It will be possible to enjoy music only when the acoustic system produces the main sound “impact” from the midbass, and the subwoofer gives weight to the lows.
When setting up, we coordinate the work of the subwoofer with the midbass and achieve the sound of tones and overtones belonging to the same note as one whole. Before adjusting the subwoofer, we adjust the frequency cutoff for midbass using high-pass filters (high-pass filter) at a level not lower than the resonance frequency of the speaker itself (Fs). The filter removes excessively low frequencies from the signal that enter the midbass and thereby makes the music reproduced by them light and fast-paced.
Setting up an active subwoofer in a speaker system that is not equipped with a processor
On the body of the active subwoofer there is a block of regulators, with the help of which we make the final settings. The car radio may also have adjustment functions for the subwoofer. We use the capabilities of the head and amplifier to obtain the best results. To make adjustments, we resort to the settings of the low-pass filter (LPF), the Subsonic filter and the phase shifter.
As a musical sample for making adjustments, we take a high-quality recording of acoustic instruments that contain a double bass.
- On the active subwoofer amplifier we set the low-pass filter cutoff frequency to approximately 80 Hz.
- We turn on the test recording and balance the volume of the subwoofer with the work of the midbass.
- Using a phase shifter, we change the polarity (direct, reverse) several times and set the one at which the woofer will acquire clarity and pressure in the sound.
- Using the Subsonic regulator, we cut off the low-frequency signal at the upper limit (infrasound), to do this we stop the arrow at 30 Hz.
- More precisely, we configure the work of the subwoofer at the junction with the midbass. By adjusting the signal level (volume) of the subwoofer and the low-pass filter, we achieve a seamless sound of bass and midbass at the maximum level.
This setting is very important, as it makes it possible to get music that you can listen to for hours. Too much bass on the sub amplifier will result in the mid-bass hits being hard to hear. In turn, if the low-pass filter excessively cuts off the high frequencies, a gap will form between the frequencies of the bass and midbass. This will lead to localization of the LF head. We will get low-quality music in the cabin if we allow excessive frequency overlap in the bass and midbass.
When making the last adjustment, we repeatedly change the positions of the level and cutoff frequency controls according to the principle: higher the low-pass filter cutoff frequency - lower the bass level and vice versa, higher the bass level - lower the cutoff frequency.
A number of head units have a function for adjusting the low-pass filter slope. We enable it and set it when tuning in the range from 12 to 24 dB/octave, select the appropriate value.
Thus, after all the manipulations with the settings, we find a balance in the sound of different components of the speaker system and flawlessly adjust it to your musical preferences.
Installation, connection and configuration of a passive subwoofer in a hatchback
If you purchased a passive subwoofer or ordered its production in a car audio studio, then you will additionally need a power amplifier to install it in the car, connect and configure it. The best choice for a subwoofer is a monoblock - a single-channel amplifier. You can also connect a sub to a multi-channel amplifier.
Installing a passive low-frequency radiator in a car with a hatchback body type is not much different from installing an active counterpart, except that you will need to install an amplifier and mount it in a suitable place. We usually mount the amplifier in the trunk on the wall of the rear seats, next to the subwoofer. The wires for connecting the amplifier are the same as when connecting an active subwoofer: power cables “+” and “–”, interconnect wires connecting the output from the head unit, and the power control wire for the amplifier.
We stretch cables and wires according to the same principle as described above. In the version with a passive subwoofer and an additional amplifier, you will also need speaker wires to connect the subwoofer to the amplifier output. Having stretched the wires and cables, connecting the amplifier and woofer, we begin setting up the speaker system.
Setting up a passive subwoofer in speakers with a processor
The processor in the car's speaker system allows you to tune the music channel by channel, using time delays for each channel. In addition, such a system has a number of other settings, with the correct selection of which you can get the perfect music in the car. Let's consider the option of setting up speakers with a passive subwoofer and a processor-based monoblock, provided that the car already has two-way or three-way acoustics installed.
Setup steps.
- We set frequency cuts between the subwoofer and midbass at 60–80 Hz, between midbass and midrange speakers at 200–1000 Hz, between midrange speakers and tweeters at approximately 3000–6000 Hz.
- For all filters we set the same slope of 12 dB per octave.
- We measure the distance from each speaker to the tip of the driver’s nose, who is leaning back in his seat.
- We enter the obtained values into the processor (some processors cannot calculate the time delay themselves, depending on the distance of the column to the driver, therefore, using tables, we enter delay indicators manually).
At the next stage, we make the initial adjustment of the front acoustics: midbass, mid-frequency speakers (in a three-way speaker system), tweeters to create a musical stage, which becomes in the center of the windshield.
The next step is to turn on the subwoofer and configure its channel with filters. At the same time, we adhere to the rule: first of all, we establish the best indicators of the steepness of the decline, and then the frequency cutoff.
To set up filters, we take an instrumental recording in which the double bass is the soloist.
- We leave only the bass speaker on, all others are turned off.
- Turn off the low-pass filter and use the subsonic filter to set the low-frequency cutoff at 20 Hz.
- We turn on the recording of the double bass and listen to its sound at frequencies of 80–00 Hz, change the steepness of the subsonic decline, find a position where the bass will sound clear and accentuated.
- We connect the low-pass filter and cut off the frequencies at the upper value within the range of 80–100 Hz. We select the steepness of the frequency decline so that the sub sounds with good bass.
- We return to the subsonic settings and cut the frequencies to the optimal lows.
- Once again we select the cutoff frequency with the low-pass filter.
Depending on the design of the subwoofer and the acoustic properties of the car interior, we adjust the cutoff frequency of the subsonic in the range from 20 to 32 Hz. Subwoofers with a bass reflex require special precision in filter settings. And using a low-pass filter, we achieve perfect coordination of the woofer and midbass at the intersection of frequencies. As a rule, in all subwoofer settings we set the value of the cutoff filters in the range from 12 dB/octave to 24 dB/octave.
We always have excellent results with subwoofer installations in cars with various body types.
How to choose a Free Air subwoofer
From all this it follows that the speaker must have ready-made parameters. This is the key difference between Freeair type subwoofer speakers and others.
And if you see a speaker whose resonant frequency and quality factor are unusually higher than others, most likely it will be FREEAIR.
So, for example, the Challenger SD-200 with the FA has a quality factor of 0.55 and a frequency of 50.5 - which indicates that it is free-air.
Additionally, taking into account that there will be no air cushion created by a closed volume behind the speaker, it becomes logical that the subwoofer suspension should be rigid enough so that it does not reach its maximum stroke too early.
Freeair can be placed not only on a shelf
As a rule, manufacturers indicate if the speaker is designed for free-air installation. Usually this is the letter F/F or FA/FA, as in the example above, or something similar in the name. But with an understanding of the principle, you can independently navigate the choice.
How to properly install a Free Air subwoofer
Correct installation is the most important point!
Despite the fact that at first glance the installation of such a subwoofer may seem very simple, in fact, for a good result it will require close attention and work .
Firstly, it is necessary to strengthen the shelf in which the speaker will be installed as much as possible to eliminate vibrations (which conceal efficiency and have a detrimental effect on bass quality). Here vibration isolation and an additional base made of the same plywood, for example, are used.
The next one is one of the main aspects! In order to get the best possible sound from free air, you need to completely isolate the outside of the diffuser from the inside . In order not to lose sound efficiency. And in a normal installation, say in a sedan, separating the shelf with metal will not be enough.
The point is that you need to completely separate the sides of the diffuser from each other. And here it is important not to leave any opportunity for air to move from the trunk to the cabin and vice versa.
The fact is that if the subwoofer operates in an open space, then you will not hear the usual bass sound, because the required pressure is not created in front of the speaker. It flows into the area of vacuum that the diffuser itself created with its movement. And if these two spaces are separated, then this effect will disappear and sound waves will begin to form.
But even a small leak on the back side will deteriorate the sound efficiency , since some of the air will flow from an area of high pressure to an area of low pressure, causing the sound wave to be smeared.
For separation directly in cars, in particular in sedans, wooden partitions can be used to block trunk openings, and they must be sealed around the perimeter of the seal. And since all these surfaces are not smooth, you can imagine how much effort such processing can cost. Do not forget about possible holes in the shelf itself.
Yes, of course, you can get by with processing only the shelf, but as you can understand, you won’t get much in terms of quality and even volume.
Taking these details into account, it becomes clear that installation can be more difficult hatchbacks and the like . You can, of course, make a separate shelf for such a subwoofer, but then you will have to reliably seal it around the perimeter, including where it contacts the glass.
Well, the most important point that can repel most car owners. The main installation location for the freeair is the rear shelf, and as you understand, it’s not often that these places have standard holes for installing a subwoofer speaker. Therefore, most often you will have to cut metal , and not everyone is ready to do this.
So, as you can see, there can be quite a lot of work and in most cases it is easier to assemble a closed box.
Theoretical information
Let's look at what types of acoustics are generally used in a car. Four types of systems are popular - the so-called infinite acoustic screen, closed-type acoustics, strip-type acoustics and a case with a bass reflex. I would immediately like to note that the use of complex acoustics for the low-frequency head makes it possible to install lower-power amplifiers. At the same time, the volume and sound quality remain at the same level. Considering that the cost of an amplifier largely depends on its power, this aspect is very important.
When purchasing a subwoofer, you need to ask how many voice coil windings are in the device. Today, “low-frequency drivers” with 1, 2 or 4 windings are on sale. In principle, increasing the number of windings is some trick of manufacturers, who enable customers to use several devices of lower power instead of one powerful amplifier.
The so-called active cabinet subwoofers, which are sold in conjunction with an amplifier, are very popular. In this case, the car enthusiast’s task is simplified, because the time for choosing devices is significantly reduced. And the sound quality always remains at its best. The advantage of active subwoofers is simplicity and high speed of setup. In addition, they are easy to install and are equipped with all necessary inputs. But there is a drawback - there are no inputs from the built-in amplifier. This means that if it burns out during operation, the speaker itself will no longer be usable.
Results
Pros of a free air subwoofer
- No need for calculations;
- Lack of housing;
- One of the best impulse characteristics - fast and high-quality bass with the lowest possible delays;
- Successful possibility of use in a sedan;
- Space saving
Cons of a free air subwoofer
- Labor-intensive installation;
- Possible need to cut structures;
- Not the largest selection of speakers.
Since not a very large number of people are ready to properly install a freeair subwoofer, manufacturers do not place much emphasis on the development of this segment. Therefore, the choice of free air is not as wide as other speakers.
