How to calculate the volume of a box for a subwoofer online. How does a subwoofer box affect the sound?

The subwoofer is an important part of any complete speaker system. In some cases, a low-frequency speaker can be assembled by hand. In this case, you need to take into account a number of important characteristics of the subwoofer in order for the speaker to sound the way it should.

One of the main parameters of a low-frequency speaker is the size of the cabinet. It is very easy to decide on the material from which the box will be made - you should use a dense and hard material that absorbs sound well - for example, pressed medium-density wood. Size is not so easy. To calculate the correct linear parameters of the box, special programs are used that you need to learn how to use.

Before proceeding with the calculation of the hull, you should decide on the type of duct. He can be:

• open - with a phase inverter - a cylindrical hole in one of the walls, which allows the sound to be better focused;
• closed - with full-bodied walls and a sealed body.

Obviously, the quality of the low-frequency speaker directly depends on the diameter of the dynamic radiator - the larger it is, the better. Therefore, the column, by definition, cannot be small if you want to achieve the highest quality sound. In addition, the shape of the body must be strictly defined - cubic or rectangular. Having mastered these basic principles, you can begin to calculate the size.

Calculation of a closed subwoofer enclosure

If the right speaker has already been selected and it remains only to place it in a suitable enclosure, the task becomes quite simple. Calculating a box for a low-frequency speaker using a special program is a simple matter if you understand its interface. We can say that it will be much more difficult to decorate this box beautifully. As a result of the calculation, a box should be obtained with such a volume that the sound from the speaker built into it has the most straightforward amplitude-frequency characteristic in a particular room or inside the car.

To calculate the hull, you will have to use one of the programs designed for this; there are a huge number of them, and, in principle, any will do. A good option is JBL SpeakerShop, it is free and has a simple interface that even an inexperienced user can easily understand. The only problem is that the program is completely in English, which can be an obstacle for some people. However, some special knowledge will not be needed - the main thing is to press the right buttons.

In order to correctly configure the program to calculate the required box, you need to find the instructions or data sheet that came with the woofer. In it you need to find the Thiel-Small parameters:

• Fs is the resonant frequency of the emitter, measured in hertz;
• Vas - effective body volume, calculated in liters;
• Qts is the quality factor of the speaker, which is a set of physical forces that arise near the radiator during its operation and are associated with its mobility.

You can find other parameters in the data sheet of the speaker - if they are known, you can enter them into the program, but this is not at all necessary. For a fairly accurate calculation of the box, the three above indicators are sufficient.

Calculation process

The calculation is made as follows:

• Net volume - the volume of the body, not occupied by anything. It does not include the space occupied by the bass-reflex port and the emitter housing, as well as the sound-absorbing material that upholsters the walls of the box from the inside.
• Port setting - selecting the size of the phase inverter in such a way that at a certain frequency (in the case of a subwoofer - low), the sound is amplified and receives a linear frequency response.

Net Hull Volume Calculation

You have to act in exactly the same way as in the case of a closed box. We open the program for calculation, enter the indicators Fs, Vas and Qts in the appropriate fields. We build the calculated frequency response, which we then change by adjusting the calculated volume of the subwoofer case.

A few liters should be added to the resulting volume to account for the volume that will be occupied by the speaker cabinet and the phase inverter port. Everything is clear with the speaker, but how do you know how much space the phase inverter will take?

Bass reflex port calculation

The phase inverter port will also be calculated using a special program - BassPort. This program is designed specifically for a subwoofer, since a phase inverter with certain parameters is required for low frequencies.

Using the program is easy:

• enter the frequency of the phase inverter;
• indicate the net volume of the box;
• the effective area of ​​the emitter membrane, for the calculation of which you need to know the diameter of the speaker;
• peak amplitude of the diffuser oscillation, it can be found in the instructions for the speaker;
• at the bottom of the main window, select the shape of the tube;
• indicate the dimensions of the phase inverter;
• after clicking on the “calculate” button, the program will display the missing port parameters: its length, volume to be added to the net volume of the box, wind speed in the tube, etc.

Subwoofer box calculation: video

Most car owners pay a lot of attention to the audio stuffing of their car, install multifunctional head units that are in no way inferior in performance to modern computers, connect powerful sound amplifiers, and make special audio podiums to improve the sound quality of the speakers. An important role in the sound equipment of the car is occupied by a subwoofer - a special low-frequency speaker that reproduces the bass components of a musical composition.

Ordinary car speakers can be installed in regular car sockets, but the subwoofer needs a special box in which it will be installed. You can make such a case yourself, and if you take into account the size and shape of the trunk when designing and manufacturing, the subwoofer will fit perfectly into the luggage compartment and will not take up much space.

Calculation of the required volume, type of body

Making a cabinet for a woofer begins with determining the type of cabinet we need. Boxes are:

• with an open body;
• with a closed case;
• with a phase inverter;
• bandpass body.

The type and volume of the case is quite simple to determine. To do this, you need to know three characteristics of the speaker (the optimal speaker size for a 12-inch car subwoofer), they are indicated on the box from the subwoofer or in the instructions, you can also find these characteristics on the manufacturer's website:

• Fs is the natural resonance frequency;
• Qts - full quality factor of the speaker;
• Vas is the speaker's equivalent volume.

The enclosure type is determined by dividing the resonance frequency Fs by the quality factor of the speaker Qts:

• Fs/Qts>30 – open case;
• Fs/Qts>50 – closed case;
• Fs/Qts>85 - phase inverter;
• Fs/Qts>105 – bandpass.

So, having decided on the type of case, how to calculate the required dimensions based on the given volume Vas? It is best to calculate the subwoofer enclosure using special programs such as Perfect Box 4.5, Blaubox, VASCalc. With the help of such programs, it is possible to calculate boxes of any geometric complexity. These programs are shareware, so no problems with the law. In order for the subwoofer to fit well in the trunk and at the same time not take up useful space, approach the measurement process with all seriousness, the future box should fit where you intended.

Housing materials

Subwoofer enclosures are made mainly of chipboard with a thickness of at least 16 mm, or plywood, preferably birch or marine. If the thickness of the material is not enough, you can fold 2 sheets together, fastening with glue or self-tapping screws. Also in the manufacturing process you will need silicone sealant or wood glue, contacts for connecting the audio wire to the subwoofer and a round phase inverter if the appropriate enclosure is selected.

A phase inverter can be bought in specialized stores or made independently from a piece of plastic pipe. To protect wood from moisture and condensate, the body must be painted inside and out with nitro enamel. Outside, the body is sheathed with carpet in the color of the trunk lining.

body stealth

Well, if you don’t want to lose space in the trunk and bother with body calculations, you can make a stealth box. This box is discreetly installed in one of the trunk niches, for example, from the side of the wing. This subwoofer enclosure is good for speakers sized 12 inches and below. The principle of making this case with your own hands is quite simple.

The niche for the subwoofer is released and completely pasted over with masking tape, preferably in a couple of layers. Cover with film or newspaper those parts of the skin and body that can accidentally get epoxy, otherwise it will be very difficult to remove it later. A thin layer of epoxy resin is applied on top of the masking tape, after drying, the base of the stealth body is pasted over with epoxy resin in pieces (10 * 10 cm) of fiberglass over the entire surface. After applying the first layer of fiberglass and completely dry, the workpiece can be carefully removed from the trunk.

Fiberglass is pasted over in 2-3 layers for strength and a set of the desired thickness. After drying, we try on the future case in the trunk niche and mark the edge trim line with a marker. We cut off the excess with a grinder, and we are left with an almost finished case for the subwoofer. We make a washer from chipboard or plywood into which the speaker will be attached. Please note that if the speaker is 12 inches, then the seat for it should be appropriate, try it on right away. We fix the landing ring at the desired height inside the future body using epoxy resin and stop rails.

We cover the top of the body with lycra and coat it with epoxy, then glue the upper part of the body with fiberglass in 2-3 layers, without sealing the hole for the speaker. Particular attention should be paid to the junction of the upper and lower parts of the body, it is best to glue them inside and out. After drying, holes are cut out for the phase inverter (if necessary) and for the subwoofer terminals. The body is glued with carpet, connected and installed in the trunk niche.

Advantages of a hand-made case:

• The case will ideally fit into the trunk, because all dimensions were taken into account individually during the design.
• The efficiency of a homemade cabinet will be on par, if not higher, than the standard models sold in the store, because your cabinet is designed for a specific speaker, and not just for the size of the seat.
• The stealth case will not take up space in the trunk and will give high-quality sound.
• You choose the color of the upholstery yourself, and you can choose materials that blend perfectly with the interior.

The body of the bandapas is much more difficult to make. The design provides for several cameras and phase inverters, but the sound quality with the correct calculations of such a box will be at the level of professional technology. Although, if you try hard, even the most complex subwoofer enclosure can be made by hand.

BassPort Program, created specifically for calculating the parameters phase inverter. Capable of performing calculation various types of ports: hourglass, funnel, round, round with flanges, slotted, etc. The BassPort program also includes a calculator that allows you to pre-set the port already in the actual subwoofer box.

The program is an invaluable tool when calculating and creating a phase inverter housing. Knowing the required volume for a certain speaker, and entering the necessary indicators, BassPort will calculate: how long the bass reflex port should have, indicate the air speed in the subwoofer, as well as the volume of air that it displaces.

Description of Bass Port

The program is equipped with a simple and intuitive interface, all the necessary fields for data entry are clearly indicated. Consider the interface of this program.

The first thing that catches your eye is the value of the speed of sound, which by default has a value of 344 meters per second. This field is editable. The next step in PHI calculation is to write incoming data to the following windows:

• Bass reflex tuning frequency, indicated in Hz;
• The volume of the subwoofer box, in liters;
• Speaker cone diameter, (measured at the center of the cone corrugation);
• The number of low-frequency speakers;
• Diffuser stroke (indicator in the speaker passport);
• Number of ports in the case;
• Port section (circle or rectangle).

After entering all the necessary data, click recalculate. Then he presses the next button below, and we get a drawing of the future subwoofer.

To make a good subwoofer, you need a special jbl speakershop program, only the manufacturer's recommendations are not enough. Because they don't take into account where the box will be installed and what kind of music it will play. Of course, you can make a box according to the scheme that comes with the subwoofer. He will play well if you follow all the recommendations and do the job well. But, you can achieve maximum return only if you calculate the “sub” for yourself, your music and your car. Therefore, it is very desirable to calculate your own box for each specific speaker.

In order to do this, there are many specialized programs. The oldest and one of the most famous is SpeakerShop from JBL. Even though jbl speakershop is quite old, most subwoofer makers still use it. And they get excellent results in the form of smartly playing “subs”.

For a beginner to understand the program jbl speakershop it can be a bit difficult, because although it is small, it contains a lot of fields, graphs and indicators in which, out of habit, it is easy to get confused.

Installing jbl speakershop

Let's start with the installation. SpeakerShop runs under Windows. And only with older versions, not newer than XP. In order to install SpeakerShop on 7, 8 or 10, you need virtual machines on which Windows will be installed. And already it will be possible to put jbl speakershop on it. From virtual machines it is possible to recommend Oracle Virtual Box. It is free and easy to install and configure.

Getting Started with JBL SpeakerShop

After installing JBL SpeakerShop, you get two modules: one for calculating , the second for calculating crossovers. Having launched the SpeakerShop Enclosure Module, we can start the calculation. You can simulate the frequency response in the "speakershop" for a bass-reflex case, a closed box, a bandpass and a passive radiator. In the vast majority of cases, the first two are calculated.

Although the program jbl speakershop offers to enter many parameters, we need to enter only three main ones:

• Fs (resonant frequency),
• Qts (full quality factor),
• Vas (equivalent volume).

Entering the required parameters

If you, in the manual for the speaker, have many other characteristics, and you enter them into the program fields, it will not be worse. But only the first three and main ones are required, which are called the Thiel-Small parameters. You can enter them by selecting the Loudspeaker → Parameters minimum menu item, or by simply pressing Ctrl+Z. After confirming your data with the Accept button, you can start modeling the frequency response.

Calculation of the phase inverter housing

Bass reflex box

We will do this using the example of calculating a phase inverter housing. To do this, click the Custom button from the Vented Box section. The program already offers a ready-made calculation under the Optimum button. But often it turns out not to be what we need, so we click Custom and enter the approximate volume of the box (denoted as Vb), and the setting (Fb).

It is worth saying that the setting must be chosen for the music that you most often listen to. A lower setting, at 30-35Hz, is selected when you listen to genres with an abundance of low frequencies: rap, dubb, etc. Higher, 40 and more - when you prefer live music, rock, trance, club music. And if you listen to a little of everything, choose something in between.

The volume of the box is selected depending on the size of the speaker. For a 12-inch speaker in a bass-reflex box, you need approximately 40 to 80 liters of "clean" volume. Enter different numbers, press Assept, and then Plot - and you will see a graphical representation of the frequency response of your speaker in a specific box. By changing the tuning frequency and volume numbers, you can observe how the graphic curve changes. A good graph can be considered a frequency response in the form gentle hill, rising to about 6 dB, without sharp peaks and valleys, the upper part of which is in the area of ​​\u200b\u200bthe tuning frequency you have chosen (35-40 Hz, for example).

Subwoofer calculation using jbl speakershop

Yes, don't forget to include the cabin transfer function if you're looking for a car subwoofer! It takes into account the rise in low frequencies that occurs due to the interior of the car. The function is displayed as a "flag" in the right part of the program window, next to the small car icon.

When you have achieved the desired type of frequency response, it remains to calculate the port. To do this, go to the menu item Box → Vent, or simply press Ctrl + V. We also enter the numbers in the Custom section. If you need a round port, select Diameter, if slotted, then Area.

Eg you want a slotted port. How to choose the area? You need to multiply the volume of the box by a number from 3 to 3.5, approximately. If you have a “clean” box volume of 60 liters, then 60 liters must be multiplied by 3. It turns out 180 cm². We enter this figure in the field, and the program automatically calculates the length of the port. Let's say it turned out 60 cm.

Everything, the calculation is ready! But remember that you only have the "net" volume of the box and the volume of the port. To know what the “dirty”, that is, the total volume, will be, it is necessary to add the port volume, the volume of the port wall and the volume displaced by the speaker to the “clean” volume. It can easily turn out another 20 liters.

Calculation of the housing type “closed box”

closed box

It is even easier to calculate the case of the "closed box" type. To do this, on the right side of the jbl speakershop program, in the Closed Box section, you also need to click the Custom button. Enter the desired volume in the Vc field. For a closed box, it will be less than for a bass-reflex case.

For example, for a 12-inch speaker, the optimal volume is from 20 to 30 liters, approx. By varying the input numbers and starting the drawing with the Plot button, you can see how the frequency response graph changes. For WL, a frequency response with a slight rise in the low-frequency region, without peaks and, moreover, dips, can be considered good.

Now it remains to draw a drawing on a piece of paper, or in a 3D modeling program, adding wall thickness, detailing, sawing plywood and assembling a box! It is worth saying that it is recommended to do all the calculations before buying a subwoofer speaker in order to understand whether it can play the music that you like and do it the way you want.

A subwoofer is an element of a speaker system that reproduces the sound of audio tracks at the lowest frequencies. Having a good subwoofer is a music lover's dream, because everyone loves the high-quality sound of music in the car. However, such a device is not cheap. However, most car owners can calculate the box for the subwoofer and make it with their own hands in order to avoid unnecessary spending on the factory model.

How to choose speakers for your subwoofer

Subwoofers are used in cars to improve the sound of music at low frequencies. For normal listening to melodies or radio broadcasts, a standard audio system in a car is quite enough, but connoisseurs of loud and clear sound at low frequencies prefer to place a subwoofer in the cabin.

During the selection of speakers for a future product, the car owner learns that they can be round or oval in shape and size. Usually (based on the dimensions of the car interior), round speakers with a diameter of 10, 13 or 16 cm are selected, as well as oval ones with a length of 15x23 cm. Accordingly, the larger the speaker diameter, the better the sound will be reproduced at low frequencies.

How to know which car speakers are right for you

Before self-manufacturing a subwoofer in a car, you need to clarify a few basic theses:

• the shape of the speakers does not affect the sound quality of music in the car;
• only the size of the speaker affects the depth and richness of the sound;
• it is necessary to think carefully about exactly what shape and size the speakers are needed so that the subwoofer looks appropriate in the cabin.

Design is not of paramount importance, therefore, when choosing a speaker, its technical characteristics are priority

Designing a homemade subwoofer

Car subwoofers are installed in the luggage compartment or on the rear shelf, so this system is called the rear.

The most serious moment in manufacturing is the determination of its size and device. Depending on the tasks set, the design can have a variety of variations.

Types of subwoofers

There are two main types of subwoofers. If we talk about the attitude to the sound power amplifier, then conditionally they are divided into:

• active. They have already built-in amplifier and crossover, which provide high quality sound and remove high frequencies from the sound. The active subwoofer receives signals from any source with which it has a connection;
• passive. The device is not equipped with additional amplifying elements, therefore it is connected to the main audio system of the passenger compartment. The only disadvantage of a passive subwoofer is that it seriously loads all the channels of the system, and therefore the sound quality also decreases.

Active subwoofers do not load the standard interior audio system, so they have better sound quality

Where to install: in the trunk or under the seat

If an active subwoofer can be placed almost anywhere, then the purity and power of its sound at low frequencies will directly depend on the location of the passive device. Depending on the preferences of the car owner and the availability of free spaces in different types of car, several places are offered for installation:

• in the center in front - the optimal position for communication with the front speakers, which will provide almost perfect sounding of tracks in the cabin. However, in most vehicles there is no space in the front to accommodate any large devices, so the central position in front is more suitable for minibuses;
• in the trunk, with the speaker directed forward - one of the most popular ways for drivers to place a subwoofer. Suitable for all kinds of vehicles;
• in the trunk, with the speaker directed backwards - more suitable for a hatchback car, since the sound wave does not encounter obstacles in its path. The location in the trunk back is unacceptable for sedan or coupe cars, as the sound will be strongly deformed due to the specific design of the luggage compartment;
• on the floor under the seat - another option, which, however, is not very popular with drivers. Due to the fact that the subwoofer is located flush with the floor, in addition, the cabinet is located under the seat, the sound encounters many obstacles in its path;
• on the rear shelf is one of the best subwoofer placement options in all types of vehicles. The main condition is that the shelf must be wide and strong enough to withstand low-frequency bass.

Photo gallery: the main places to place the device in the car

The program algorithm will take into account all the wishes and make the calculation of the volume and other parameters of the case quickly and correctly

What to make a box from

A subwoofer box is not just a box that contains a speaker. The box must comply with many of the dynamic laws of acoustics in order for the sound to be truly rich and clear. For the manufacture of different types of boxes, different materials will be required, and the manufacturing methods will in many ways be different from each other.

How to build a bass reflex subwoofer box

The standard version of a homemade subwoofer is a phase inverter. This is the simplest type of subwoofer, besides, its box is good because a special phase inverter tube allows you to reproduce low frequencies that are practically not perceived by the human ear. And the design of the box is quite simple, which makes its manufacture accessible to almost everyone.

Required tools:

• soundproofing;
• wood screws 50 mm long;
• drill;
• screwdriver;
• electric jigsaw;
• liquid Nails;
• sealant;
• PVA glue;
• carpet.

The case for placing a bass-reflex subwoofer must be as durable as possible and not transmit sound waves. For these purposes, multilayer plywood or high quality chipboard is perfect. The best option is to take a plywood sheet 30 mm thick.

For the manufacture of the case, you need to follow this plan:

1. Prepare parts of the body: front, back, two side, bottom and top according to your calculations or the parameters displayed by the programs.
2. Under the size of the speaker (for example, diameter 160 mm), cut a hole in the front of the case blank.
3. Above the hole for the speaker, you will also need to cut a slot for the bass reflex tube and screw the bass reflex compartment to it.
4. After two holes are made on the front panel, it is necessary to glue all the side parts of the box together, and then screw them together with self-tapping screws.
5. In this case, it is especially important to tighten each self-tapping screw all the way, as the empty spaces between the panels will seriously distort the sound of the speaker.
6. Next, on the back of the case, you will need to cut a small hole for the wires.
7. Before connecting all parts of the case, we insert the speaker.
8. Next, it is necessary to carry out the interior decoration of the case: for this, all joints and cracks must be smeared with resin or sealant to increase sealing, after which soundproofing fabric is glued to all side panels.
9. After completing the interior decoration, you need to go to the outside: the body is covered with a Karapet fabric, and the fabric should also cover the slot for the phase inverter. Karapet can be stretched with a regular epoxy or a furniture stapler.

As soon as the speaker is fixed, wires are pulled from it through the hole and connected to the car's speaker system.

Photo gallery: how to assemble a compact box with a phase inverter

The subwoofer can be connected independently, based on the parameters of this circuit

Before starting work, make sure that the vehicle battery is disconnected. This is a safety measure that will not only avoid damage to the speaker system, but can also save the health and performance of parts of the human body.

Video: connecting and setting up a subwoofer

Independent design, manufacture and connection of subwoofers in a car is available to almost every driver. The key to the success of the case will be both a competent calculation of the dimensions and volume of the product, and accurate assembly of the case. At the same time, the motorist can independently choose the desired size of the speakers in order to create the bass sound in the cabin that suits him most.