How to calculate a box for a subwoofer ⋆ doctor bass

How the device works

Any bass reflex type speaker has a hole - a bass reflex.
This is often called an acoustic tunnel or port. Its operating principle is to change the phase of the sound vibration caused by the rear side of the diffuser by one hundred and eighty degrees. When resonance occurs in the box, the vibration amplitude of the diffuser reaches a minimum value. The volume of air and the resonance frequency to which the channel is tuned depend on the size and type of the bass reflex port. The volume of air in the channel begins to resonate and enhance frequency reproduction when the moment comes when the diffuser emits the frequency for which the bass reflex is designed.

The classic tunnel is circular in shape. But to increase the useful internal area, it is often given a slotted appearance. Refusal of the cylindrical shape of the tunnel makes it possible to reduce its length and reduce the noise that occurs when air is released.

If there are errors in the calculation of a slotted bass reflex, it is much more difficult to configure it than the classic type, since it is manufactured together with the speaker. The calculation itself is more complicated than for closed-type systems: in addition to the volume of the box, the adjustable resonance frequency is taken into account. The optimal dimensions are selected taking into account the amplitude-frequency characteristics of the speaker, namely its uniformity.

How to work with JBL SpeakerShop?

The entire functionality of the program is divided into two large modules. Using the first one, you can calculate the volume of the subwoofer box. Using the second, the crossover is calculated. In order to start calculating, you should open the SpeakerShop Enclosure Module. It has the ability to simulate the frequency response for closed boxes, bass reflex enclosures, bandpasses, as well as passive radiators. In practice, the first two options are most often used. The multitude of input fields can be confusing. However, don't despair.

In order to calculate the displacement, it is enough to use only three parameters:

resonant frequency (Fs);
equivalent volume (Vas);
total quality factor (Qts).

To increase the accuracy of the calculation, it is permissible to use other characteristics. These can be found in your speaker manuals or online. Still, as mentioned above, you can completely get by with these three characteristics, called Thiel-Smol parameters. You can enter these parameters in the form that appears after pressing Ctrl+Z. In addition, you can go to the form after selecting the Loudspeaker – Parametersminimum menu item. After entering the data, the program will ask you to confirm it. At the next stage, it is necessary to simulate the amplitude-frequency response, then the frequency response.

QW Box Calculator

You've probably at least heard something about quarter-wave resonators. This type of enclosure is not so widely used in the construction of subwoofers and low-frequency sections of acoustic systems compared to, say, a bass reflex and a closed box. But why? After all, a quarter-wave oven provides undoubted fat advantages:

gain in efficiency,
excellent bass performance,
low level of group delays.

In a word, “both loudly and efficiently.”

Perhaps because there are disadvantages:

relatively large box volume,
CV does not tolerate overloads,
quite picky when choosing a speaker.

However, the last point also applies to the bass reflex.

Perhaps the widespread use of CV is also limited by the somewhat laborious nature of its calculations. Although the calculation itself is not that complicated, usually while you are designing a box, you have to go through several options, recalculating everything again each time. This is both tedious and time-consuming. And when you do something for a long time, you start making mistakes, and they are completely unacceptable when calculating the frequency factor.

There are two approaches to designing CV boxes:

“maximalist”: we study theoretical issues for a long time using foreign sources (ours simply do not exist), we use the Hornresp program by David J. McBean, and then, using graph paper and a calculator, we painfully develop the details of the box;
“minimalist”: we set the tuning frequency, and using the Quarter Wave Box Calculator program (let’s call it briefly: QW Box Calculator) we easily and quickly design a frequency wave box, completely forgetting about the evenings spent with a calculator, pencil and ruler. Now you only need a few minutes to design the CV housing!

The QW Box Calculator program is completely Russian-language. This is what the QW Box Calculator 2.4 window looks like:

As a result of the calculation, you receive a complete list of all parts and their dimensions. The overall dimensions of the box and its approximate weight are also displayed for reference.

This version supports three types of corner designs:

without decoration (simple corners)

gusset (45 degree inserts are glued into the corners from the inside)

radius (the corners from the inside are rounded with a radius equal to the width of the channel).

You select the desired corner design method, and the length of the channel is calculated taking into account the properties of this design. If calculated manually, this would be an additional headache.

QWB ox Calculator version 2 supports the following six types of housings:

Besides:

a correction for the acoustic resistance of the outlet is automatically taken into account, not everyone knows about this effect, and almost no one takes it into account when manually calculating, but in vain;
there is a Help System;
saving/loading projects;
printing;
the number of screws for assembly is calculated;
the minimum possible channel width is calculated.

And the calculated box can be drawn in three-dimensional form using the Google SketchUp program. We simply transfer the data to this program, and the box is automatically drawn, something like this:

The QW Box Calculator program is very easy to use, does not require resources, and pays off its price many times over.

To purchase the QW Box Calculato, click the "Proceed to Checkout" button directly below this line.

Box for 12 subwoofers with bass reflex

To build the box we will need:

Dense multi-layer plywood or chipboard
Self-tapping screws
Screwdriver or screwdriver
PVA glue
Carpet
Sound insulation materials
Wires and terminal block

Cover the inside of the box with sound insulation. Before screwing in the screws, use a thin drill to mark holes so that the plywood does not burst. Assemble the structure, cut out the carpet with a margin to bend along the edges. Apply glue, let dry, and staple.

There are many options for acoustic boxes in car audio. Many beginners do not know what is the best choice. The best types of subwoofer boxes are a closed box and a bass reflex box.

We obtain the dimensions of the body based on the known displacement

So, we come to the final stage of events. Now we need to calculate what geometric dimensions the bass reflex housing will have if its total displacement is known - 60.3 liters. We take measurements of the trunk, determining acceptable dimensions. For example, a structure 60 cm long and 40 cm high suits us. It remains to find out the width. Let’s decide that we will make the walls of the box from plywood 1.8 cm thick. Now we need to subtract the wall thickness from the length and height of the structure (1, 8x2) and get the following values: length – 56.4; height – 36.4 cm. Next we carry out the following calculations: 60.3x1000:36.4:56.4=29.4. This will be the width of the case, however, without taking into account the thickness of the walls. Let's add it and get 33 cm. This is an approximate calculation of a subwoofer housing with a bass reflex for a specific speaker. Please note that this article is only a general guide; it does not take into account many of the subtleties and nuances that arise during the work process.

How to calculate a box for a 15-inch subwoofer

If the size of the luggage compartment of the car allows, then you can implement a box with a bass reflex. The biggest advantage of such a system is a noticeable increase in efficiency. In order to get the most out of a speaker in a closed box, you have to deliver maximum power from the amplifier. In bass reflex designs, the output power, and therefore the efficiency, increases due to the use of forward and reverse stroke of the speaker cone. In closed systems, sound is emitted only by the front plane of the loudspeaker, and the return radiation is damped inside the box. Calculations for a 15-inch subwoofer box include the area of the bass reflex port. These are complex calculations, so when making a bass reflex box yourself, it is best to use ready-made diagrams and drawings. You can also use the JBL Speaker shop, Bass Port or Box Plot computer program.

We obtain the dimensions of the body based on the known displacement

Calculating the bass reflex enclosure

To begin with, we will show an example of calculating a bass reflex enclosure. In the Vented Box section, select Custom. Clicking the Optimum button allows you to automatically fill in all fields. But in this case the calculation will be quite far from ideal. For more precise settings, it is better to enter data manually. In the Vb field you need to indicate the approximate volume of the box, and in Fb - the setting.

Box volume and settings

It should be understood that the setting is selected according to the genre of the music that will be played most often. For music with dense low frequencies, this parameter is selected within the range of 30-35 Hz. It is suitable for listening to hip-hop, R'n'B, etc. For fans of rock, trance and other relatively high-frequency music, it is worth setting this parameter to 40 or higher. For music lovers who listen to various genres, the best option would be to select average frequency values.

When choosing the volume size, you must proceed from the size of the speaker. Thus, a 12-inch speaker requires a bass reflex box with a “net” volume of about 47-78 liters. (see article about boxes). The program allows you to repeatedly enter different combinations of values, then click Accept, and then Plot. After these actions, graphs of the frequency response of the speaker installed in various boxes will appear.

By selecting the volume values and settings, you can arrive at the required combination. The best option is the frequency response curve, which resembles a gentle hill. At the same time, it should rise to a level of 6 dB. There should be no ups and downs. The top of the imaginary hill should be located in the area of the value that was indicated in the Fb field (35-40 Hz, above 40 Hz, etc.).

Do not forget that when calculating a subwoofer for a car, it is necessary to include the interior transfer function.

In this case, one should take into account the rise of the “bottoms” that occurs due to the volume of the cabin. You can enable this function by checking the box next to the small car icon located above the upper right corner of the graph.

Port volume calculation

After modeling the frequency response curve, all that remains is to calculate the port. This can be done via the Box-Vent menu item. Also, the window can open after pressing Ctrl+V. To enter data, you must select Custom. For a round port, select Diameter, and for a slot port, select Area. Let's say you need to calculate the area for a slot port.

In this case, you need to multiply the volume of the box by 3-3.5 (approximately). With a “net” volume of the box of 55 liters, the result is 165 cm2 (55*3=165). This number must be entered into the appropriate field, after which the port length will be automatically calculated.

At this point the calculations are considered complete! However, it is worth remembering that the program calculates only the “net” volume. The total volume can be determined by adding the volumes of the port and its wall to the “net” value. In addition, you need to add the volume that is required to accommodate the speaker. After determining the required values, you can begin preparing the drawing. It can be depicted even on a simple piece of paper, or using 3D modeling programs. When designing, it is worth considering the thickness of the walls of the box. Experienced people advise making such calculations even before purchasing a speaker. This will allow us to produce exactly the subwoofer that can satisfy all requests.

Perhaps your box is in our database of ready-made drawings.

Option No. 2

First of all, guided by Fig. 1 and the table, it is necessary to make a “standard volume” - a sealed plywood box, all joints of which are carefully adjusted, glued and coated with plasticine to avoid air leaks.

rice. 1

Speaker diffuser diameter, mm	Dimensions, mm
A	IN	WITH
200	255	220	170
250	360	220	220
300	360	220	270
375	510	220	335

Next, the natural resonance frequency of the loudspeaker located in free space is measured. To do this, it is suspended in the air away from large objects (furniture, walls, ceiling). The measurement diagram is shown in Fig. 2.

rice. 2

Here ZG is a calibrated sound generator, V is an alternating current tube voltmeter and R is a resistor with a resistance of 100–1000 ohms (at higher resistance values the measurement is more accurate).

By rotating the frequency adjustment knob of the sound generator in the range from 15-20 to 200-250 Hz, achieve the maximum deflection of the voltmeter needle. The frequency at which the deviation is maximum is the resonant frequency of the loudspeaker in free space Fв.

The next stage is to determine the resonant frequency of the loudspeaker Fв when it is operating at a “standard volume”. To do this, the loudspeaker is placed with a diffuser on the hole of a “standard volume” and pressed lightly to avoid air leaks at the junction of the surfaces. The method for determining the resonance frequency is the same, but in this case it will be 2–4 times higher.

rice. 3 fig. 4

Knowing these two frequencies, the dimensions of the bass reflex are found using nomograms. Depending on the diameter of the loudspeaker diffuser, select the nomogram shown in Fig. 3 (for diameter .200 mm), in Fig. 4 (for diameters 250 and 300 mm) or in Fig. 5 (for diameter 375 mm). Using the selected nomogram, the volume of the bass reflex is determined by connecting the points corresponding to the found frequencies on the “Resonant frequency” axes with a straight line.

How to make an impressive result in your system?

Body (salon)

What is done in the back of the Civic is not unique. Can be repeated in almost any body. And in bodies with a reduced main resonance, it’s even easier to repeat. That is, anyone who has the desire can do it, but with any body it is necessary to do a lot of work!

At these frequencies and at this pressure, the body experiences enormous loads. Vibration isolation must be approached very, very thoroughly. The hardest material that adheres very firmly to metal - we completely vibrate all the iron.

Shvi is “invisible” work. And many people think that if it’s not visible, then it doesn’t exist. Everything in the Honda with vibration isolation is very good, all that remains is to eliminate the overtones.

Unobstructed air access is another point that must be ensured.

Power

To achieve such a long-term result, it is necessary to get maximum useful energy from the speaker. This is possible provided that the speaker receives all of its RMS from the amplifier. Of course, we are talking about power without a hint of a clip, because if the speaker sees even a minimal percentage of distortion, operating on the edge, then overheating will occur quite quickly.

The first task is to improve heat dissipation as much as possible. As with the Honda, installing an upward-firing speaker with the magnet facing outwards is a great move. But it’s good when there is at least 15-20cm between the bottom flange of the magnetic system and the opposite wall.

An even more significant factor for heat dissipation is the correct load, but more on that later, in the part about the box.

Next, the task is to get pure RMS + a little more. The stronger the magnetic system, the more efficient the subwoofer, but the higher the impedance rise and the sharper the impedance drop from peak to edge. Once again we see that positivity does not happen without negativity, miracles do not happen.

An increase in impedance is a frankly negative factor, which both worsens linearity at neighboring frequencies and seriously increases the budget. Various technologies and solutions (such as Faraday rings) help to some extent combat the increase in impedance.

To obtain RMS with a small margin for DD Z, you will need an amplifier 3-4 times more powerful than the subwoofer rating. That's why Honda prescribed the DD M4a with a subwoofer RMS of about 2-3 kW. For PowerTuned SC subwoofers - 2-3 times. For PowerTuned, HiDef and HDC - 2-2.5+ times. For Redline and HDS - 1.5-2 times.

We can connect the subwoofer to a resistance lower than 1 Ohm, but this is a risk! The speaker exceeded its stroke and the coil left the gap - the amplifier died. A frequency has risen that is far from the peak of the impedance growth - the amplifier has stopped working... Connecting at 0.5 Ohm - the risk is quite small and allows you to significantly save on the amplifier, but connecting below - only highly tuned SPL systems operating within + -3-5 Hz from the combat one.

We picked up the amplifier, now we need to feed it. We ALWAYS focus on the fact that the amplifier will at some point give the maximum and consume the maximum. That is, if there is a request for pure RMS of 1000W, and you are watching without taking your eyes off that there is no clip, then you must give the amplifier the opportunity to receive a current of 100A. Accordingly, if the generator does not produce as much, then the life of the system is limited by the capacity of the battery, and if the battery does not produce either, then the system is not viable at all.

In Honda, apparently not everything is so smooth with power supply - in all videos the system works for 1-5 minutes, and everyday listening takes place at a significantly lower volume. With the right approach and budget, you can do better.

Now a banal thought will be heard once again, but extremely important. The more efficient the speaker, the higher the pressure as a result, but the more expensive the entire system is (and the speaker itself is more expensive, and all other elements of the system too). Comparing the cost of the system on the HDC315 and the Z315, we get a significant difference.

Speaker and housing

Performance, and therefore the proportions of the cabinet, directly depends on the performance of the speaker, which in turn directly depends on the power supplied to it.

The Honda is in perfect order with the performance of all elements - the subwoofer is perhaps the most efficient in the world, the amplifier gives it the clean power it needs, and the body reveals its full capabilities. You should have such balanced systems, because they all really surprise with the results - I have demonstrated this in many of my projects, and I’m far from alone.

As already stated, the more powerful a speaker is, the more powerful the enclosure it should be powered by. I researched this point in great detail for many (almost all) of our subwoofers and this is what I came to...

First, about the most important thing, about the port.

The port shape is round with flanges. Why round? - a round port allows you to use a larger air mass earlier (at lower power) than a slotted one. It is easy to improve the aerodynamics and thereby increase the port throughput at increased flow rates by making flanges. The length of the round port is required to ensure the proper load, which means that the total volume can be saved quite well. The round port is easy to change, easy to explore different port areas and lengths.

However, if you build a slotted port NOT along the wall of the housing, then in terms of characteristics and capabilities, if it is inferior in any way to a round one, it is not much. If the slot port is located along one of the walls of the housing, then, firstly, a significantly larger length is required to ensure a similar nature of the acoustic load, and there is also a much more pronounced virtual elongation of the port, which affects the tuning. In other words, a port along the wall is a successful solution in cases where something is missing to obtain the required stroke value.

How can I make a round port work the same as a slot port located along the walls? It’s very simple - you need to install a round port flush in one of the walls of the box... With this position of the port, getting overstroke at powers above RMS is also very simple, just like with a slotted port along the walls.

Flanges are another important factor that helps win efficiency. To be honest, I’m not good at aerodynamics, but I’m persistent - I tried 20-30 different profiles to achieve maximum port efficiency, all other things being equal. I am attaching the drawing once again.

IMPORTANT!

Everything written below applies exclusively to our speakers installed in enclosures with my flange design. For other forms of ports, for other speakers, all this is unlikely to work.

Now about the connection between the speaker and the port. In the course of several thousand experiments, I established some connections for myself...

Firstly, the port area. In order to get maximum output efficiency without overloading the subwoofer, I obtained the following diameters:

Z15″ - port diameter 21cm.

HDC15″, DD PowerTuned SC 15″ – 20cm.

DD PowerTuned, DD Hidef - 19cm.

Redline, HDS - 18-18.5 cm.

Net internal diameter shown. As you can see, there are no standard pipe diameters here. Take a larger diameter pipe and make it smaller. There are a lot of different options for making the required diameter using improvised means.

The length of the port in all cases was in the region of 27-35 cm, depending on the frontal load. A larger interior means a longer port, a smaller interior means a shorter one. With such a port length, the system operates in the range of 7-10Hz at powers of about RMS and in the range of 3-5Hz at powers of about 2*RMS.

If you increase the port length beyond the specified values, the operating range becomes wider. As the length of the port increases, the load increases, which requires a reduction in the port area and/or volume to compensate (depending on the situation and goals) - without doing this, the speaker will be overloaded and will overheat. By reducing the port area or volume, we lose pressure accordingly. Thus, the width of the range is directly related to efficiency, there are no options.

Case volume. The volume is convenient for obtaining the necessary configuration of the case. In essence, changing the volume setting is generally the only way I know of to obtain an actual change in the operating range relative to the frequency of the main resonance of the port. And this is quite understandable, since no one has canceled the work of the FI as a ground cell at many frequencies.

For low settings (20-30Hz) volume is required. For medium (30-50Hz) - average volumes, for high (50-60Hz) - minimum. The volume is directly related to the port area, which allows us to make some forecasts based on empirical data. So, for tuning around 30Hz, a port area to volume ratio of 2:1 is suitable, for medium settings - 3:1, for high settings - 4:1.

For example, for a DD Z, the area of the specified port will be 346 sq. cm. Accordingly, for a low setting it is worth trying a box with a volume between 346/2 and 346/3, or 173-115 l.

Because The volume of the body represents only part of the load, when the other part is the interior, then the final volume will differ slightly from body to body. It is impossible to give exact data here, only approximate ones. Accurate data is provided by measurements of each individual system.

So, the volume of the body in a Honda, as the author himself writes, is 6 cu.ft. or 170 liters. And this is actually pure volume, since the speaker and port are almost completely located outside.

Reliable fastening of the body to the body is a very, very important point. Without securing, you always lose a serious part of the energy that could be converted into sound waves!

Settings, filters

In all boxes, the range of operation of which lies within relatively narrow boundaries, precise work with filters of the highest possible orders is required!

As you can see, the Civic owner calmly opens the trunk without fear of overtravel. This peace of mind is precisely what precise filtering gives when the speaker operates in the range where the port holds, and does not work where the port is no longer effective.

We will sum up the results with the answer to the following question: “what pressure can you expect using something less expensive rather than DD Z?”

Using HDC or PowerTuned SC instead of Z, you will lose about 0.6-0.8 dB in pressure, all other things being equal. In the case of PowerTuned or HiDef - 0.8-1.2 dB. With Redline or HDS - 1.2-2 dB.

In all these examples we are talking about losses with equal power, but Z is also more powerful, that is, in fact there will be more losses. A pair of 12″ in terms of long-term power turns out to be a much more advantageous option.

The DD Z is, to put it mildly, not the most common speaker. But if there is a task to uncover any one DD\SQ spot, then today’s post should definitely contribute to this!

In the memo in the figure, I have collected the key values in a convenient table - use it. There is no point in making drawings here, since such designs are not something that will work the same in many systems - they need to be adjusted in each case in order for the end result to turn out cool.

Save money and get the same result? On the one hand, the question seems simple, but the answer is not simple at all. In a nutshell, it’s possible, but the system will work differently.

Think for yourself, for example, if we replace one 15″ with two less powerful 12″ - the total area is 15 vs 2*12, the total moving weight, the total power, stroke... All these points will not be the same, which means the system will not work the same. But if you install a pair of 12″ ones in the same box instead - yes, it turns out quite well, the result will please you!

I wish you all successful buildings and good results with DD\SQ!

Flanges for other pipe diameters are directly proportional. The pipe is twice as large - all the dimensions of the forming ellipse are also twice as large... The larger the diameter of the pipe, the smaller the relative diameter of the flanges can be made.

Vas indicator

This parameter for speakers can be measured using two methods:

additional mass;
additional volume.

In the first case, measurements are made using some weights (10 grams for every inch of diffuser diameter). These could be, for example, weights from pharmacy scales or old coins whose denomination corresponds to their weight. The diffuser is loaded with such objects and its frequency is measured. Next, the necessary calculations are made using the formulas.

When using the additional volume method, the sound emitter is hermetically sealed in a special measuring box with the magnet facing outward. Next, the resonant frequency is measured and the electrical and mechanical quality factors of the speaker, as well as the total, are calculated. Then, taking into account the obtained data, Vas is determined using the formula.

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It is believed that the lower Vas, other things being equal, the more compact design can be used for the speaker. Typically, small values of this parameter at the same resonant frequency are the result of a combination of a heavy moving system and a rigid suspension.

Product Features

In our online store we sell subwoofer enclosures for any car body. After studying the catalog, customers will be able to order products for:

pickups;
sedans;
hatchbacks;
minivans;
station wagons, etc.

Installation of housings for speakers is possible in both passenger cars and utility vehicles. This is due to the variety of products available, which differ in both design and size. From us you can buy small enclosures for subwoofers of 22–29 liters, which are ideal for small cars.

Standard models with a capacity of 35 liters are also sold. For owners of large vehicles, our specialists can offer products from 45 to 120 liters.

How the device works

The volume of air and the resonance frequency to which the channel is tuned depend on the size and type of the bass reflex port. The volume of air in the channel begins to resonate and enhance frequency reproduction when the moment comes when the diffuser emits the frequency for which the bass reflex is designed.

Drawings for a 15 subwoofer on a pipe

A low-frequency speaker with a bass reflex in the form of a piece of hollow pipe is easier to manufacture than a sound system with a slot bass reflex. The drawing of a 15-inch subwoofer does not contain complex details. All body elements are cut from thick plywood or MDF with a thickness of 18-25 mm. A hole is cut in the front wall for the loudspeaker. The second hole for the cylindrical port can be made in the front or top wall, depending on the design features of the column. You can buy a ready-made industrial speaker, but practice shows that a home-made device often has better characteristics than a branded sample. Polypropylene sewer pipes are used as a pipe for a homemade acoustic system. They are dark gray in color and come in several sizes. The port size is calculated based on the type of speaker. Adjusting the bass reflex port involves changing the length of the pipe. The shorter the cylinder, the higher the frequency.

To perform calculations and configure the port, it is convenient to use the “Bass Port” program. The tuning frequency of a cylindrical bass reflex depends on the requirements for the speaker and musical tastes. If you choose a frequency of 25-30 Hz, this will give deep and rich bass. The most common band is 30-35 Hz. It is suitable for high-quality reproduction of music of any genre. For “black” music and electropop style, a setting of 35-42 Hz is used. Higher, the low-frequency system, as a rule, is not tuned. To check the quality of playback, low-frequency tracks in the range from 25 to 60 Hz are used. They can be downloaded from the Internet, fed to the input of a car amplifier and broadcast through a speaker.

Making your own port

The bass reflex, just like the speaker, is involved in sound reproduction. To avoid the interference effect, the channel is placed closer to the low-frequency emitter at a distance not exceeding its wavelength. Rigid structures are used as FI, for example, plastic sewer pipes are used in homemade products.

But when trying to calculate a bass reflex for a subwoofer, consumers are faced with the fact that the diameter of such pipes does not coincide with the calculated values, so the pipe is made from a dense material at hand - whatman paper. In order to make a channel yourself, you will need:

newsprint;
whatman;
glue.

A strip cut from whatman paper, the width of which coincides with the length of the tube, is wound in several turns on the surface of newsprint. In this case, epoxy glue is applied before each turn. It is obtained by mixing resin and hardener according to the instructions. After all the turns have been completed, the product is wrapped in a circle with thread to impart rigidity and placed to dry.

After a day, the base is removed. If difficulties arise, it can be broken from the inside and taken out in parts. A manufactured channel of this type has good strength and is easily subject to additional processing. Next, the resulting tube is installed in the hole of the speaker, but not all the way, and listening to the sound begins. In the factory, a special device is used. Such a device operates on the basis of a multivibrator, which is tuned to the resonant frequency of the dynamic head. After connecting the speaker, the generator starts and the length of the pipe is adjusted to the maximum fluctuation of air in it.

You can do the same setup yourself. To do this, a low frequency signal is supplied to the input. The tube is moved forward or immersed inside the box, and then the volume of escaping air is assessed. Having established the position of its maximum outlet, the excess pipe is removed from the outside, and the port itself is sealed. If desired, to give the structure a finished look, open the pipes, but you can do without it.

Subwoofer box drawings 15

The volume of the box for a car's low-frequency acoustic system is calculated based on the diameter of the diffuser and the type of design chosen. The easiest sound system to make is a closed box. Its volume in liters for a 15-inch speaker will be 45-60 liters.

This is a “pure” volume, that is, the volume occupied by the loudspeaker must be excluded from the internal volume of the box. You can make a simple closed box from panels of the same size. They are all 42 centimeters. The only thing that will be difficult to do is cut a round hole in the front wall for the speaker. Its diameter is 34.9 cm.

The internal volume of the speaker system is equal to 47 liters, which is quite normal for a 15-inch speaker to operate in a closed volume. It is best to use a finely divided MDF board, 18-20 mm thick, as the material. The assembly of the structure is carried out using self-tapping screws, which must be positioned as often as possible for the strength of the system. During the process of assembling the box, all internal cracks at the connection points of the plates must be treated with silicone sealant. According to some data, MDF is very weak, but it allows air to pass through, so experts recommend that plates made of this material intended for an acoustic system be impregnated with drying oil or other pore-filling compound.

The internal volume can be filled with damping material such as padding polyester or other fibrous material. This procedure allows you to get rich and deep bass from a closed box of small volume. Filling a box with material virtually increases its internal space by an average of 40%. It is believed that the best composition for filling the internal volume of speakers is a fibrous material such as polyester wool. A 50-liter low-frequency speaker filled with material will work as a 70-liter structure. This will increase the transparency and purity of bass notes, and the lowest frequencies will be reproduced strongly and clearly.

Bass reflex differences

Every speaker has a resonant frequency. When working above this indicator, you get good sound, and below this, the pressure level drops by 12 dB per octave (frequencies are reduced by 2 times). The lower level of reproducibility is considered to be 6 dB. By installing the speaker in a box, the resonant purity increases due to the additional elasticity of the air. Increasing the resonant frequency pulls up and the lower limit. The less air in the box, the better the elasticity and the higher the performance.

You can make a “big box” without increasing its size. For this purpose, a material with damping properties

(cotton wool). The more of it there is in the box, the lower the frequency of the speaker. But when there is too much filler, it has the opposite effect. For inexperienced people, the quality of the box and its size are not important. In most cases, the column size is optimal.

A bass reflex is a pipe, not necessarily round, of a certain length, which has resonance. Thanks to the “second resonance”, the sound output of the speaker increases. The vibration frequency of the speaker in the box should be lower than in the normal state. Thus, the decline is compensated and the sound expands. These indicators for a bass reflex will be 24 dB higher than for a buried box. It extends the low end frequencies of the speaker.

To avoid barrel sound

, resonance indicators should not be higher than that of a closed box. And if the frequency is too low, the speaker's performance drops. This is the essence of adjusting the bass reflex in order to get a positive effect and not spoil the sound. And at home you can achieve good sound with an error of 5%.

[Q] Where can I read about open design?

[A] Open drawers and screens are the simplest type of design. Advantages: ease of calculation, no increase in resonant frequency (only the type of frequency response depends on the size of the screen), almost constant quality factor. Disadvantages: large size of the front panel.

Quite competent and simple calculations for this type of design can be found in V.K. Ioffe, M.V. Lizunkov. Household acoustic systems, M., Radio and communications. 1984. And in old Radios there are probably primitive amateur radio calculations.

What does the quality factor of a speaker affect?

Q in acoustic systems primarily affects the frequency response and impulse characteristics of the speakers. That is, this indicator largely determines the sound characteristics of the speakers. With a quality factor of 0.5, for example, the best impulse response can be achieved. With an indicator of 0.707, an even frequency response is obtained. Also when:

Q factor 0.5-0.6 speakers produce audiophile bass;
indices of 0.85-0.9, the bass becomes elastic and prominent;
quality factor of 1.0, a “hump” with an amplitude of 1.5 dB appears in the cut, perceived by the human ear as a biting sound.

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With a further increase in the Q indicator, the “hump” in the sound grows and characteristic buzzing noises begin to emanate from the speakers.

[Q] I now have speaker parameters, what should I do with them?

[A] When designing each speaker, it is tailored to a specific type of acoustic design. To find out what exactly it is for, let's look at the quality factor.

Qts > 1.2 are heads for open boxes, optimally 2.4
Qts < 0.8-1.0 - heads for closed boxes, optimally 0.7
Qts<0.6 - for bass reflexes, optimum - 0.39
Qts<0.4 - for horns

It would be more correct to sort heads not by quality factor, but by Fs/Qts value. I’ll quote from memory, I don’t feel like calculating the formulas.

Fs/Qts > 30 (?) screen and open case
Fs/Qts > 50 closed housing
Fs/Qts > 85 bass reflexes
Fs/Qts >105 Bandpasses (bandpass resonators)

Elasticity, meatiness, dryness and other similar characteristics of the sound produced by a bass speaker are largely determined by the transient response of the system formed by the speaker, the woofer design and the environment.

In order for this system to avoid overshoot in the impulse response, its quality factor must be less than 0.7 for systems with radiation from one side of the speaker (closed and bass reflex) and 1.93 for two-way systems (screen and open box design)

Determine the total volume of the body

By calculating the bass reflex with the JBLSpeakerShop program, we determined the required net volume for our specific subwoofer and the frequency to which the port needs to be tuned. BassPort "told" us the length of the port, as well as the volume that it will occupy. Now we carry out the following arithmetic operations: we add up the volumes - port, pure and displaced by the speaker. The resulting value will be the total internal displacement of our future body. It should be noted that if roundings, stiffeners are used in the body, or it is slotted, then we will have to take into account all these nuances. Approximate calculation of a slotted bass reflex: 1. The net volume is 45 liters.2. Slot port – area 140 cm3, 36 Hz – 8.5 l. Let's add 3.8 liters to the port walls (made of 18 mm plywood).3. Displaced by speaker - 3 l.4. We add these values and get 60.3 liters - the total displacement of the hull.

[Q] What type of approximation should I choose for the bass reflex?

[A] So, before building a simple bass reflex, you need to know the volume of the box and the tuning frequency of the bass reflex (pipe, hole, passive radiator). If you choose the smoothest frequency response as a criterion (and this is not the only possible criterion), you will get the following plate

A) Qts < 0.3 - the quasi-third order curve will be the smoothest. The bass reflex is adjusted to 40-80% higher than the resonance frequency.

B) Qts = 0.4—better described by Butterworth curves. The bass reflex is tuned to the resonance frequency.

B) Qts> 0.5 - you will have to allow waves on the frequency response, according to Chebyshev. The bass reflex is tuned below the resonance frequency.

In addition, in these cases there will be a different volume of the case. In order to find the exact tuning frequencies, you need to take the original formulas, which are cumbersome enough to present them here. Therefore, I refer those interested to the Audio Store for 1999, after this educational program it will be possible to figure it out there, or to Aldoshina’s books. And even Ephrussi’s articles in Radio for ’69 will do.

Option #3. Calculation of the bass reflex size according to the nomogram

rice.
9. Nomogram In the low frequency range, the operation of a loudspeaker does not depend on the shape of the box or the type of bass reflex, but is determined only by two acoustic design parameters - the volume of the bass reflex box V and its tuning frequency Fb. The calculation of acoustic design basically comes down to finding these quantities. In order to understand the methodology for calculating loudspeakers using a nomogram, let's consider several examples.

Example 1. Calculate the optimal acoustic design for a known low-frequency driver. Let's assume that using measurements the head parameters are determined: Qa=3.2, Qe=0.33, Vas=0.120m3, fs=40 Hz. When operating from an amplifier with zero output resistance (Rg=0), the Qt of the head will be 0.3. Let's mark the point Qt=0.3 on the abscissa axis, draw a straight line perpendicular to the axis through it and find the ordinates of the points of intersection of the straight line with the curves in the upper and lower parts of the nomogram: Vas/V=3, fb/fs=1.25, f3/fs= 1.47. Substituting the measured values of the head parameters Vas=0.120m3, fs=40 Hz into the resulting ratios, we find: V=0.04 m3, fb=50 Hz, f3=59 Hz. Thus, if you do not take measures to additionally regulate Qt, to obtain a smooth frequency response of the loudspeaker, it is enough to place a given head in a bass reflex box with a volume of 0.04 m3 and tune it to a frequency of 50 Hz. The cutoff frequency of the loudspeaker will be equal to 59 Hz.

Example 2. For the same original head with Qa = 3.2, Qe = 0.33, Vas = 0.120 m3, fs = 40 Hz, it is necessary to calculate the parameters of the bass reflex box so that the cutoff frequency of the loudspeaker is equal to 35 Hz. At a specified cutoff frequency, the calculation begins by determining f3/fs. In the case under consideration, f3/fs=0.875. Next, a straight line is drawn through the point with ordinate 0.875 on the f3/fs curve, perpendicular to the abscissa axis, and the coordinates of its intersection points with the Vas/V and fb/fs curves are determined, i.e. Qt=0.415, Vas/V=1.05, fb/ fs =0.93. Substituting the head parameter values Vas=0.12m3, fs=40 Hz into the resulting ratios, we find V=0.114 m3, fb=37 Hz. Therefore, in order to obtain a smooth frequency response of a loudspeaker with a cutoff frequency of f3 = 35 Hz, the volume of the bass reflex box should be 0.114 m3, and the tuning frequency should be 37 Hz. In addition, since the required value of the total Q of the head differs from the measured one (when operating from an amplifier with zero output impedance Qt = 0.3), additional adjustment of this parameter will be required to achieve the desired shape of the frequency response.

Example 3. A low-frequency head is given (Qa=3.2, Qe=0.33, Vas=0.12m3, fs=40 Hz) and the volume of acoustic design is set to 19 V=0.06 m3. It is required to design a loudspeaker with a smooth frequency response. Let's define the ratio Vas/V =2. Through the point with ordinate 2 on the Vas/V curve we draw a straight line perpendicular to the abscissa axis and find the coordinates of its intersection points with the fb/fs and f3/fs curves: Qt=0.345; fb/fs=1,1; f3/fs=1,2. Substituting the values of the head parameters into the last ratios, we find fb=44 Hz, f3=48 Hz. Thus, in order to obtain a smooth frequency response of the loudspeaker with a given head and in a box of the specified dimensions, you will need to adjust the bass reflex box to a frequency of fb = 44 Hz and, using control means, bring the total Q of the head to a value of 0.345.

10-inch business class subwoofers

The very first test of subwoofers in this magazine, I looked at, was dedicated to heads of this caliber.

Rainbow SL-S10-231395 || DLS RW10i || Massive Audio NEO10 || KickerCWRT 102 || CDT Audio HD-1000CF || Polk Audio MM1040UM || AlpineSWR-10D2 || Phoenix Gold Ti210D2 || MTX FPR10-04 || Audison AV 10

Summer 1998, by the way. The article was called “Chervonetsy”. Today such a headline cannot be given; the generation that knows what a chervonets is has melted away or moved away, as luck would have it. Modern readers of the magazine are convinced that “fifty dollars” is a fifty-ruble bill. Hence the phrase attributed to Pyotr Arkadyevich Stolypin, which has become incomprehensible to many: “I am not a chervonets to please everyone.” Not to mention possible problems with the soft sign in the last word.

Unlike the prime minister and like the chervonets, ten-inch subwoofers can be considered to be liked by everyone. To us, especially, as we have admitted more than once. The same applies to the champions of autosound sports, which they have proven more than once. The love here is down to earth, even with interest, this is how the maps of electroacoustic parameters are formed, so that ten-inch heads in optimal acoustic design are able to provide the most even and smooth frequency response in the cabin, and the design volumes that turned out to be optimal are, as a rule, not frightening, often small, in some cases - scanty. Well, how can you not fall in love?

The convenience of design and the results achieved with its help are especially pronounced when it comes to closed boxes, and “tens” are most often placed in them; FI is used much less frequently, and this has a completely understandable basis. In home acoustics, FI has become, as far as I can tell, practically the only type of acoustic design used for heads with a caliber of 100 mm and above. There, FI is done in order to obtain the lowest possible cutoff frequency of the loudspeaker. We don’t have such a problem; taking into account the effect of the transfer function of the cabin, the cutoff frequency of 60 - 70 Hz (in open space) theoretically turns into zero hertz. Practically, of course, not to zero, but reaching 20 Hz is never a problem. Why do they put FI in a car? This is a step in the other direction, this is a pursuit of the sound pressure level, which FI can provide significantly more, at least in a certain frequency range. But those for whom the main thing is sound pressure usually pass by a display case with “tens” without raising their eyes; for them, an acceptable caliber starts from 12 inches.

“Tens” for the most part can also work in FI, and when this is the case, we present this design option, even if the manufacturers forgot about it or did not recommend it for their own reasons. Let us note in this regard: in practice, many such bass reflexes are not implemented without difficulty. The optimal volume of the FI case is small (which is good, of course), but the FI tunnel has different habits: the smaller the box, the longer the port is required to tune to the same frequency. Sometimes it turns out that the required tunnel cannot simply be stuffed into the resulting box; it is necessary to resort to tricks: bending it, making slot structures or reducing the diameter, which simultaneously reduces the efficiency of the FI and increases the likelihood of jet noise in the tunnel.

All of the above applies, in principle, to all “tens” regardless (or almost regardless) of their price. What then is better about relatively expensive 10-inch heads than about relatively inexpensive ones?

First, of course, the design. Cast baskets, advanced diffuser materials, sophisticated voice coil ventilation systems, reinforced terminals, all these are components of reliability and durability. But not only. In some of the subwoofers in this test, we found non-trivial cone suspension designs that gave a clearly visible effect of increasing linearity. For one, there was nothing unusual in the suspension even with the slightly armed eye, but the effect was also obvious. In short: tens of “business class” are more linear, that is (even more briefly) they play cleaner. It used to be that more expensive heads required much smaller volumes of design; now we are noticing a softening (not disappearing, but just softening) of this trend. It seems that manufacturers have stopped being carried away by super-rigid drivers capable of working in a few liters, sacrificing sensitivity and transient characteristics at the same time, and it was still not always possible to realize fantastically small volumes: the speaker has its own volume and dimensions, and they began to determine the possible outlines box. But the commendably compact specimens turned out to be compact in the sense of design, and not in their own dimensions. But the dimensions too, in the group of tested there were representatives of a variety of flat and rather flat, as if flattened, heads, one of these turned out to be simply unique: a flat subwoofer head, suitable for installation in an acoustic screen, that is, in a flat design of zero volume. This is a rare installation opportunity, we appreciated it. In general, business class is a pleasure to deal with.

TO WHOM - WHAT

One of the determining factors when choosing a subwoofer is the volume of required acoustic design, and the smaller the better. From this position there is a wide choice. Only two participants require a fairly significant volume, and, interestingly, the same for ZY and FI. So we advise fans of non-trivial solutions and owners of convertibles to pay attention: with a slight movement of the hand, the subwoofer can turn from FI to ZY and back.

The remaining participants can also work both in ZY and in FI - but in a significantly different volume. Rainbow produces a very compact SG (only 15 liters) with an attractive frequency response. Solid, as if to justify the brand, Massive Audio NEO10 feels great in free air, one might say, this is its purpose. If the dimensions of the rear parcel shelf allow, it is an excellent choice for sedans and a “Recommendation” for the participant.

The rich-looking CDT Audio HD-1000CF has decent linearity, but requires either volume of design, or amplifier power, or both.

The modest-looking DLS RW10i does not allow liberties; its impedance is 2 Ohms, which immediately implies an increase in the amplifier power by 30 - 50% or more - if you are lucky with the amplifier. The required amount of design is considerable, but its type (ZY or FI) can be changed literally on the fly. And all this for very reasonable money.

The thoroughly made Polk Audio MM1040UM, thanks to its shallow installation depth and “marine” design, will be of interest not only to yachtsmen and motorcyclists. There are few distortions, their spectrum is favorable.

The creators of the Kicker CWRT 102 managed to make not only an extremely flat (installation depth of 87 mm), but also a very linear subwoofer. Distortion is represented only by the "musical" second harmonic, combined with a flashy appearance it is an excellent choice. The original impedance formula “3 + 3” gives flexibility when connecting, we can wholeheartedly recommend it. Another “flat” participant can work in free air - a rare combination. The MTX FPR10-04's distortion levels aren't the lowest, but the design is admirable. Audience Award and our “Recommendation”.

The universal impedance formula “2 + 2” was found in two participants - Alpine SWR-10D2 and Phoenix Gold Ti210D2. They are distinguished by a very compact (and Phoenix Gold - extremely compact) design and, despite the completely different designs of suspensions and magnetic systems, by the highest linearity. Our verdict is “Favorites”. The undisputed “Leader” is Audison AV 10. The highest linearity is combined with excellent impulse characteristics and excellent frequency response. Plus the possibility of transforming ZY into FI.

Tags: Group test

Bass reflex differences

You can make a “big box” without increasing its size. For this purpose, a material with damping properties

To avoid barrel sound

[Q] How to calculate a closed box?

[A] Closed box design comes in two types, infinity screen and compression gimbal. Getting into one category or another depends on the ratio of the flexibility of the speaker suspension and the air in the box, denoted alpha (by the way, the first can be measured, and the second can be calculated and changed using filling).

For an infinite screen the flexibility ratio is less than 3, for a compression suspension it is more than 3–4. As a first approximation, we can assume that the heads are sharpened with a higher quality factor for an infinite screen, and with a lower quality factor, for a compression suspension.

For a pre-installed speaker, a closed enclosure like an infinity screen has a larger volume than a compression box. (Generally speaking, when there is a speaker, the optimal enclosure for it has a uniquely defined volume. Errors that arise during parameter measurements and calculations can be corrected within small limits by filling).

Closed box speakers have powerful magnets and soft surrounds, unlike open box speakers. Formula for the resonant frequency of a speaker in volume V design

Fс=Fs*SQRT(1+Vas/V)

, and an approximate formula connecting the resonant frequencies and quality factors of the head in the housing (index “c”) and in open space (index “s”) Fc/Qtc=Fs/Qts

In other words, it is possible to realize the required quality factor of the acoustic system in the only way, namely by choosing the volume of a closed box. Which quality factor should I choose? People who have not heard the sound of natural musical instruments usually choose speakers with a quality factor of more than 1.0.

Speakers with such a quality factor (=1.0) have the least uneven frequency response in the low-frequency region (what does sound have to do with it?), achieved at the cost of a small overshoot in the transient response. The smoothest frequency response is obtained at Q=0.7, and a completely aperiodic impulse response at Q=0.5. Nomograms for calculations can be taken from the above book.

More details and a calculator can be found in the article “Calculation of a closed box.”

Calculation of the FI box using JBL SpeakerShop and BassPort programs. — DRIVE2

Before you begin calculating the bass reflex enclosure for a specific subwoofer speaker, you need to find out what Thiel-Small parameters the speaker has and understand what they are: For an adequate calculation, three parameters are enough. Fs is the resonant frequency of the speaker, indicated in Hz (hertz). Vas is the equivalent volume indicated in liters.

Qts – total quality factor of the speaker.

1. Calculation of the net volume and tuning frequency of the bass reflex. To do this, you need a program for calculating subwoofer enclosures, there are quite a lot of them, both paid and free, the most popular and easy to use is the JBL SpeakerShop program. In the program, you need to specify the Thiel-Small parameters, selecting the volume of the box and setting the bass reflex port, to obtain the required frequency response graph.

2. Calculation of the bass reflex port. Very quickly and conveniently, and most importantly with great accuracy, you can calculate the port at the desired frequency in the BassPort program.

We enter in the program: The required frequency of tuning the FI port The previously obtained net volume of the box The effective area of the speaker diffuser (measured, the length along the center of the speaker from one middle of the suspension to the opposite middle of the suspension) The maximum stroke of the diffuser in one direction (indicated in the instructions or on the manufacturer’s website as Xmax , can be indicated either in one direction or in both directions at once) Select the port cross-section Enter the dimensions of the port Press the calculate button and get the required port length “L”, as well as other equally important data, in particular - the displacement of the port, which will be added to the volume of the subwoofer enclosure.

3. We calculate the total volume of the FI case. In the JBL SpeakerShop program, we learned what pure volume is needed for a particular subwoofer, as well as what frequency is best to set the FI port. At Bassport, we calculated how long the FI port should be based on its area, and found out how much volume the port would occupy.

Now we add up: net volume + port volume + 3 – 4 liters (volume displaced by the speaker) and we get the total internal volume of the future FI case. If roundings, stiffening ribs are used in the housing, if the housing is slotted, etc., this must also be taken into account in the total volume. Example: *Net volume - 45 liters.

*Slotted port, area 140 cubic cm. at 36 Hz - 8.5 l., plus 3.8 l. on the port wall of 18 mm. plywood. *Displacement by speaker - 3 liters. *Total - 60.3 liters. the total volume of the hull FI. Now, it would seem the most incomprehensible thing is how to obtain the dimensions of the hull based on the known displacement? We have a volume of 60.3 liters.

Advice

We measure the trunk, see what dimensions suit us, for example: height - 40 cm, length - 60 cm, we just need to find out the width. We subtract the thickness of the walls from the height and length (let it be 18 mm plywood) and we get: height - 36.4 cm, length 56.4 cm.

Now we calculate: 60.3 * 1000 / 36.4 / 56.4 = 29.4 - the width of the body, without walls, with walls 33 cm.

This is what the calculation of a bass reflex enclosure for a specific subwoofer speaker looks like. I ask you not to take this article as a clear guide to making a FI subwoofer, there are a lot of points and subtleties that are not taken into account.

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8" subwoofers

Measurements: Yuriy EVTUSHENKO

The third dimension is what turns area into volume. Participants in today's test sometimes had almost no measurement of this.

The diameter is obvious, even eight, but still inches, not centimeters, this is already size. The installation depth for some also turned out to be rather large. And the volume, if we understand it as the volume of acoustic design, is more than modest for everyone. There is both a general, enduring pattern and a trend that depends on time.

Precision Power A.8SQ | Kicker CVR 82 | ESX SX 840 | Cadence S2W8-S2 | Audio System HX 08 sq

With invariable regularity, in the preface to the tests of eight-inch subwoofers, we open the eyes of everyone and strive not to offend the little ones. I think our regular readers have already learned: in practice, the advantages of the “eights”, without a doubt, outweigh their disadvantages. I even admit that some of these materials have reached subwoofer manufacturers (albeit with the loss of the charm of the original language). But what can specialists do against the marketing department? If demand is low, then supply will be curtailed, and at an accelerated pace. The situation with eight-inch subwoofers is exactly the same; they are not present in the model range of all manufacturers, or at least not in all lines. Retail, as I understand it, signals to dealers, who signal to importers, and they already give their weighty word to manufacturers: if they sell poorly, we won’t take them. Or maybe retail just doesn’t know how to sell them?

The main disadvantage of “eights”, from the seller’s point of view, is not their low recoil - the espiel heads have even lower ones, but this does not bother anyone. And it’s not that they have slightly increased nonlinearities - I don’t think that sellers operate with such categories at all. The main problem is their lack of prowess. The main caliber is “dvenashka”, “ten” is like a “dvenashka” for a medium-sized car... To purchase an “eight”, as it seems, there can only be two reasons: either you have very little space in the car, or you are struggling want to save money. What kind of show-off is there?

But the main advantage of the “small” ones is the absence of a third dimension in them, or rather in their design. Later you will see that today’s participants, as if by agreement, agree to climb into a 10-liter ZY or a 15-liter FI. Some people agree to less, and this is already comparable to their own volume, the volume of ferrite, steel and cellulose. And this is not the only advantage of the “eights”, it is simply the most noticeable.

How would I sell subwoofers of this caliber myself? I would not declare that it is the eights that are capable of demolishing the tower for you and your passengers with the greatest efficiency - buyers will not believe it, and the subwoofers will not be demolished. But they are the ones who are able to reproduce the bass structure with audiophile precision - that’s how they are designed. There is a corollary from this fact: due to the flat shape of the frequency response, typical “eights” can be paired with fronts at any reasonable frequency - be it 60 Hz, if your fronts are bassy, or at least 120 Hz, if not. Moreover, if the fronts have obvious problems with bass, then they should not be treated with a “two” (this is like treating osteochondrosis with weightlifting), but rather with a “eight”.

After such an argument, some potential clients will not even want to look at the “twelve”, but will sign up with you for the “eight”. Only the most persistent ones will remain: I need to get my guts moving, and in general, so that the boys can see that I have a specific sub. Then - here we convert the title from last year's test - take two! In terms of sound pressure, two “eights” will not be inferior to the average “two”, and the boys will definitely appreciate that two subwoofers are cooler than one. Now only those who from the very beginning expected to take a pair of 12-inch heads will leave me without the “eight”. Okay, don’t be greedy, give them a couple of “twins”.

The audiophile inclinations of the “eights” are dictated by the peculiarities of their design - a slightly increased resonance frequency, which results in an increased value of the EBP factor. The growth of this indicator, as we should have already learned, reflects two trends: a) leveling of the frequency response throughout the bass range and b) a decrease in acoustic gain. It is the absence of a rise in the direction of low bass that allows you to easily connect an eight-inch subwoofer to the front at a relatively high frequency. And the low (or negative) acoustic gain, coupled with low reference sensitivity, means that the “eights” really have quite low returns.

What about the third dimension? Or rather, its absence? If we accept (rounded, for estimation) that the equivalent volume of heads doubles with the transition to each next caliber, and assume in the zero approximation that their total quality factor does not change, then we can conclude: for the “eight” you will need half the volume required “ten”, and a quarter - necessary for “two”. In the next approximation, it turns out that the electrical and total quality factor tends to decrease as the caliber decreases (the “magnetic ratio” per unit mass of the moving system increases), which further reduces the volume of optimal acoustic design. And finally, there is a not very pronounced, but noticeable trend: manufacturers are responding to the increase in typical amplifier powers by strengthening (and making heavier) the moving head system, in order to keep the resonant frequency where it belongs, the suspension is made more rigid, and... the required volumes are reduced .

It should be noted: those manufacturers who still have G8s in their lineup, as a rule, take the issue seriously. It cannot be otherwise - if “tens” are most often made “based on” twelve-inch heads, then “eights” (like “tags”, by the way) require a special approach - they have their own coils and different magnetic systems. (Perhaps this is precisely the reason why other manufacturers are abandoning this caliber - the increase in sales is disproportionate to development costs.) So most modern eight-inch heads look serious, without any allowance for the “frivolousness” of the sizes. True, the values of the Thiel-Small parameters specified by the manufacturer often have less in common with reality than we would like. Of course, I am aware that it is becoming increasingly difficult to maintain the mechanical parameters of parts in our electronic age, but should we at least try? Previously, the typical deviation was plus or minus 10, well, 15 percent, and then there were manufacturers who set more stringent limits for themselves. However, I will not exaggerate the minor tones: most of the participants made the most favorable impression on us, regardless of how much the real parameters diverged from the declared ones.

And now, as always, we will list the design features of the heads participating in the test, which we will omit in the description of the design and take for granted. The suspension is rubber, the central cap is plastic and convex. The speaker cable is fixed with spring-type clamps, this has become our standard. The height of the magnet is 20 mm, if it is said about it that it is “double height”, it means 40, this is what it turns out to be if the calculator doesn’t lie. Inside, the washer of the magnetic system has an annular groove that prevents damage to the coil during the maximum stroke of the diffuser. We assume the diameter of the voice coil to be 50 mm (actually 2 inches, it’s a little more, but that’s not the point). The diffuser holder (popularly called a basket) is stamped. The centering washer is flat with a regular sectional shape of the corrugations. In a word, everything is as always. And the third dimension has disappeared somewhere...

PARADE OF PARAMETERS
Highest sensitivity	ESX	85.2 dB/W
Lowest Resonance	Precision Power	30.3 Hz
Lowest distortion	ESX	2,10 %
Most compact design	Cadence	FI 6 l

ESX collected the largest amount of points. Actually, from the very beginning there was a feeling that the head was promising; after all, our eye had already been targeted. Next comes Kicker. In comparison with the winner, he loses only in terms of distortion. Of the remaining three, the one that most deserves a “Recommendation” is Precision Power, which in its behavior approaches the two winners, being inferior to them in sensitivity. Not in the order of a formal distribution of awards, but to attract attention, let us mention the Cadence, the head is very unusual, and the magnitude of the required volumes of design is especially unusual.

Tags: Group test

Subwoofer housing: how to make it yourself

Taking into account the fact that the bandpass is the most difficult to manufacture, this enclosure is difficult to design and calculate the subwoofer box without special skills, knowledge and experience.

On the one hand, you can use the WinlSD program to calculate the subwoofer. This software allows you to select the size, calculate the volume of the subwoofer, and even create a three-dimensional model.

However, on the other hand, such a task is usually beyond the capabilities of an ordinary car owner without special knowledge (you need to know the characteristics of the speaker, take into account a number of additional features, etc.).

In fact, to make a sub with your own hands, it is better to choose a closed box or bass reflex

In this case, it is recommended to pay attention to the second option as a homemade subwoofer. This solution (subject to proper design) will be more than enough

The bass reflex makes it possible to qualitatively play the lowest frequencies, provides increased efficiency, etc.

This solution (subject to proper design) will be more than enough. The bass reflex makes it possible to play back the lowest frequencies with high quality, provides increased efficiency, etc.

So, first we select the material for making the subwoofer. Typically, multilayer plywood is used for these purposes. You can also take chipboard. These materials are affordable, easy to work with, and provide good sound insulation.

As an example, consider a subwoofer made of multilayer plywood (3 cm thick). In order to make a box for a subwoofer, you need to prepare, on average, about 100 wood screws 50-55 mm.

You also need to purchase sound insulation, have a drill, a screwdriver or screwdriver, a jigsaw, liquid nails, sealant and PVA glue, about 3 meters of carpet and a terminal block. The next step is the drawings of the subwoofer box.

The calculation of the subwoofer box is individual; the parameters depend on the size of the speaker, etc. Using an example, consider a sub with one 12-inch speaker. The volume of a box for a subwoofer with one such speaker, according to the recommendations of experts, is 45-50 liters.

To calculate the box for the subwoofer, below is an introductory diagram with the dimensions of the panels. If you do not have the skills to do this kind of work, it is recommended that you separately study the materials on how to make a drawing for a subwoofer yourself.

During design, you need to separately ensure that the minimum distance from the walls of the case to the speaker, as well as the volume of the box itself, is calculated exclusively on the inner surface, and not on the outer one.

Let's move on. After preparing all the elements, you can proceed to assembling the subwoofer box. First of all, use a jigsaw to cut out a hole for the speaker. For example, 30 cm speaker

Please note that the shortest distance from the center of the diffuser to the wall of the subwoofer is, conditionally, 200 mm. You can measure 230 mm, since 3 cm is the width of the plywood itself

Then a hole is cut for the bass reflex slot. You can also use a tube instead of a slit. Then you can assemble the bass reflex slot, and then attach it to the front panel of the subwoofer. The joints are glued with liquid nails, then screws are tightened. The screws must be tightened as tightly as possible to avoid resonant vibrations.

Now you can assemble the side walls of the case, coating them in the same way with liquid nails and tightening them with self-tapping screws. You also need to cut a hole for the terminal block on the back cover of the case for the subwoofer. Next, all parts of the subwoofer need to be connected, checking the correct dimensions of the structural elements themselves and the quality of fastening.

At this stage, you can insert the speaker without screwing it in, check its fit and then move on to finishing the box. At the initial stage, it is necessary to glue the joints, cracks and gaps with epoxy glue. You can also use sealants. Then, using PVA glue, the entire upper surface is glued with sound insulation.

The outer surface is covered with carpet (including the bass reflex slot). The carpet is attached with epoxy glue and/or a furniture stapler. The speaker can now be reinserted and screwed in place. The final stage is drawing the wires from the speaker to the terminal block. After the entire structure has “settled” and dried, the sub can be connected to the amplifier. To do this, you need to know how to connect a subwoofer in a car correctly.

How many liters to measure in meters or displacement of acoustic systems

It would seem that what is the connection between acoustic systems and liters?
In fact, the connection is direct, the volume of speaker systems is measured in liters. Look at your speakers - why are they the size specified? The volume of speaker systems is calculated based on the parameters of the speaker used. Let’s say you can read that some speaker systems have a volume of 60 liters. Do you think these columns are large or small, how to determine what a liter is equal to. Of course, 1 liter is equal to 1000 milliliters, but how many centimeters is 1 liter equal to? Agree - an unusual question. Let's start with a simple example and a simple question - show with your hands, like avid fishermen - how much is a liter in volume? I'll simplify your task. Imagine a cube whose sides are 10 cm and whose height is also 10 cm. Rub measuring 10 x 10 x 10 cm is a liter. From this it is easy to determine that 1 liter = 10*10*10 = 1000 cm or 10 cubic centimeters. Let's return to the first question - is an acoustic system with a volume of 60 liters a large acoustic system or not? Let's try to count. We need to multiply the width, depth and height together and get the displacement. It turns out something like this formula: 60l = Width * Depth * Height Let's arbitrarily set the height and width, let the width be 35 cm and the height 50 cm. For a correct calculation, let's convert liters to centimeters: 60 liters = 60*1000 = 60000 cm Let's substitute into the formula: 60000 = 35* Г *50 Г= 60000/(35*50) = 34.3 cm Let’s check, to get the displacement, you need to multiply the width, depth and height between each other and you should get the required number in centimeters. Width = 35 Depth = 34.3 cm Height = 50 cm 35* 34.3* 50 = 60025 cm Divide by 1000 to get liters. 60025 / 1000 = 60.025 liters Conclusion, acoustics with a displacement of 60 liters is a box of approximately the following size - 50 cm in height, 35 cm in width and 34 cm in depth. In general, they are not small speakers, but not large either. It’s true that these are big shelf-sitters. There is also such a thing as the golden ratio of an acoustic system. To put it as simply as possible, you need to correlate all dimensions with a ratio of 1.6. Those. let one side be equal to 1 meter, then the second side is 1 * 1.6 = 1.6 m, and the remaining 1/1.6 = 0.6 meters This is of course a large size. Let's take more mundane dimensions, for example 0.5 m. 0.5 * 1.6 = 0.8 0.5/1.6 = 0.3 As a result, we have an AC with a front width of 50 cm, a depth of 30 cm, and a height of 80 cm. In the old days, we came to the golden ratio with experience by obtaining that this aspect ratio minimizes resonances. Let's consolidate the acquired knowledge in practice. The popular Technics SB-6 acoustic systems are given in the following sizes: Width 35 cm Height 60.6 cm Depth 31.8 cm

Question: what is the displacement of these speakers? We count: 35 * 60.6 * 31.8 = 67448 cm Which is equal to 67448/1000 = 67.4 liters. The correct answer is the displacement of the Technics SB-6 is 67.4 liters? Not certainly in that way. We are counting the empty volume of the case, but in reality it will be occupied to some extent by the speakers - figure it out yourself, if a liter is a cube of 10 by 10 by 10 cm, then approximately how much the speakers will occupy in the case. I can assume that they take up 5-7 liters, so the actual displacement of these speakers is about 60 liters. On the other hand, if you decide to create a speaker yourself, for example on a wideband speaker - if this is your first attempt, then let it be something very cheap, for example this:

On Aliexpress, such speakers cost about 3.5 thousand rubles per pair. Traditionally 8 Ohm speakers sound more delicate. Copy-paste from the lot of the same name: 4-inch full-range speaker Aiyima or similar. Impedance: 4ohm/8Ω Shape: Round/Octagonal Power Rating: 15W Power Range: 15-30W (Max Power 30W) Voice Coil Diameter: 25mm Frequency Response Range: 50Hz-20kHz Sensitivity: 88±3dB DCT : 0.77 Volume: 5.6L

Here we see an equivalent speaker volume of 5.6 liters, and a DCT of 0.77. I can assume that DCT is translated from Chinese as quality factor. If the quality factor is 0.77, then what does this mean? The quality factor varies, it can be 0.2 or 1 or more, but it is important for you to understand only one point. If the quality factor is 1, then after the sound has stopped, the speaker will make another 1 move by inertia. Accordingly, it will give more after-sounds, of course it will lie, but the bass will definitely be deeper, but also more, how to say, loose or amorphous. If the speaker has a quality factor of 0.2, then the speaker stands rooted to the spot almost immediately after the sound signal has disappeared, and this means that, again, there will be less of those after-sounds, there will be less bass, but such a speaker will be more accurate. Based on this, it is clear that the golden mean is good, for example 0.5. Having a quality factor of 0.7, we can assume that the speaker will give a “thicker”, “longer” sound over time. Of course, you shouldn’t expect deep bass from a broadband speaker, especially with such a graph (see below). But it will be deeper than expected for this size - 4 inches is about 10-11 cm.

What do we see in this graph? Of course, we can say that the speaker starts at 20 Hz, but although formally yes, but in reality no. And here's why: if the volume of a low frequency sound is 5-6 dB lower, then you won't hear it; it will be covered by the sound of a higher frequency. The specs say the speaker operates at 50Hz, which is pretty cool for a speaker like this, is that correct? Let's see. On the graph we see that at a frequency of 50 Hz the volume is 79 dB, and the approximately flat overall volume line of all frequencies, including the nearest slightly higher ones, is greater.

We see that we can’t hear 50 Hz; they will be interrupted by the sound at 76 Hz, which is louder by as much as 11 dB. Based on this, we can say that real performance can be expected from this speaker at a frequency of approximately 80 Hz. This frequency can be artificially lowered, but this is done by choosing a design - a shield, an open box, a sound box, a bass reflex, etc. In my opinion, the parameters are a pretty good speaker on which you can start experimenting. In addition, I know that many have already experimented with it with good results, according to amateur developers. I see the main disadvantage of this speaker in two ways: low sensitivity - 88 dB. It seems to be a broadband speaker, but it won’t fit into a tube amplifier, its path is transistors. And the second point is the rubber suspension, which will most likely eat up some of the delicacy of the sound. You can try more advanced speakers, for example Visaton B200 or the much cheaper Visaton BG20, but our review was not about that, but about how many liters are measured in meters. If you don’t agree with the review, if something is said incorrectly, if you want to correct it, if you have additional information, write in the comments.

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Box for 12 subwoofers with bass reflex

We obtain the dimensions of the body based on the known displacement

How to calculate a box for a 15-inch subwoofer

We obtain the dimensions of the body based on the known displacement

Calculating the bass reflex enclosure

Box volume and settings

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Drawings for a 15 subwoofer on a pipe

Making your own port

Subwoofer box drawings 15

Bass reflex differences

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[Q] I now have speaker parameters, what should I do with them?

Determine the total volume of the body

[Q] What type of approximation should I choose for the bass reflex?

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