How to make a subwoofer box correctly
To make a subwoofer enclosure yourself you will need:
Having the housing parameters for the subwoofer in hand (volume, area and length of the port), you can make a drawing yourself using special programs (in my opinion, SketchUp from Google is the most convenient for this). But if you make the box for yourself, then there is no point in wasting time learning the software and doing everything the old fashioned way - by hand.
If you do not know how to calculate the body, then read the material. You can also order a paid estimate on the Internet; as a rule, it is accompanied by a clear drawing for manufacturing.
An example of a drawing of a housing with a bass reflex (FI)
In order to make a box for a subwoofer, you need a material that should vibrate as little as possible. From experience, it is best to use MDF (not painted, not laminated, etc.)
MDF (MDF - Medium Density Fiberboard). In Russian - medium density fiberboard.
MDF is easy to process, has good density, due to its structure it has no resonances and does not delaminate - the bass in such a box is soft and dense. MDF is more expensive than plywood and is “afraid” of moisture.
Plywood is the most common option and costs less than MDF.
Do not use chipboard or old furniture to make subwoofer boxes. A plywood or MDF body will always sound better.
If the walls are thick enough, there is no need to cover the inside of the body with vibration insulation, etc.!
Do not use material thinner than 18 mm. and the larger the volume of your case, the thicker the walls should be.
Many large stores that sell sheet material offer a cutting service to your dimensions, where they will cut the perfect parts for you on a machine, all that remains is to assemble the body.
For fastening it is best to use yellow screws length at least 2 times the wall thickness. The heads of black ones often break off; they are thinner and not as strong. An advanced solution is furniture bolts, but if this is your first sub, then it will be easier with self-tapping screws.
Yellow screws, black screws, furniture bolts.
Cage nuts for attaching the subwoofer to the case - that's cool! The sub can also be secured with self-tapping screws, but with bolts in the mountings, the speaker is attracted as tightly as possible, and if necessary, it can be removed and installed as many times as necessary without damage. And the polished hex bolts look really cool.
Bolt with cage nut
If you are sawing the walls with a jigsaw or a hand-held circular saw, then the glue will additionally act as a sealant between the uneven edges; any liquid wood nails will do for this. If you unraveled the material on the machine and the edges of the body walls are perfect, then you do not need to use glue; it will be enough to coat the joints from the inside.
You can route the wires directly, but it is better to make a box for the subwoofer with a terminal block.
Terminal block for housing
Use threaded options - they are more reliable. For round seats, it is convenient to cut a hole using a nozzle.
You will need a piece of wire to connect the subwoofer coil to the output terminal block. Take any copper wire no thinner than 4 mm. in most cases this will be sufficient.
You will need:
So, you have decided on the shape for the sub box and you have a drawing.
Mark the sheet according to the parts and cut according to the marked dimensions. Use a disk with a large number of teeth; the smaller the tooth size of a circular saw blade, the fewer chips you will get, and their size will be insignificant.
If you use a manual circular saw and your hand is not full, better to use a guide, so as not to accidentally “fail” the cut.
It is better to do this work together, since it is quite inconvenient for one person to turn large sheets and hold them while working.
Below is a good video from Rockford Fosgate, although in English, but everything is clear here without translation - choosing the shape of the body, lining up the parts, cutting.
To properly make a box for a subwoofer, before screwing in a self-tapping screw, drill a hole for it with a thin drill, this will increase the strength of the fastening and protect the plywood from delamination. Distribute the number of screws evenly along the length of the side and make sure that they do not meet at the corners.
Almost always a template for cutting out the mounting hole comes with the sub; it can be part of the box or be a separate attachment. Cut out the template, transfer it to the front side of the box and cut it out with a jigsaw or router.
Template for mounting hole (cut from box)
If you don’t have such a template, you’ll have to arm yourself with a compass. When marking and cutting out the hole for the speaker, be very careful! The basket shelf is almost always narrow. If you cut less than required, the subwoofer basket will not fit into the hole; if you cut a little more or not exactly, the sub will not fit tightly or the mounting screws will hang in the air.
For heavy subwoofers, it is recommended to make the front wall of the housing double to eliminate vibrations during speaker operation.
Double front wall
With large dimensions of the case, double walls may not be enough and in some cases it will be useful to use spacers.
Options for struts and stiffeners
Please note that all wire entry channels, terminal blocks, etc. must be sealed, internal partitions (port walls) must not have any gaps.
It is convenient to cut a hole for a round terminal block using a nozzle; when installing it, do not forget to glue it around the perimeter.
When tightening the screws, do not overdo it so as not to tear it off and do not forget to pre-drill holes for them.
If you use cage nuts to mount the speaker, then first install it in the seat, accurately mark the drilling locations, remove the speaker and drill through the front wall according to the marks (make sure that the drill is always perpendicular to the plane). Select the thickness of the drill in accordance with the diameter of the embedded nuts. Install the nuts into the prepared holes from the inside of the body so that they do not fall out when the bolts are screwed into them.
Cage nuts on the inside of the front wall
When screwing the speaker, do not forget to connect it to the terminal block; for this, you can solder the wire to it or use special terminals.
Informative video of assembly and gluing using the example of Rockford's serial Subic.
If your case was correctly designed, it is sealed, strong and with sufficient wall thickness, then its sound will definitely please you.
In contact with
In car audio, there are many options for acoustic design of boxes. Therefore, many beginners do not know what is the best choice. The most popular types of subwoofer boxes are a closed box and a bass reflex box.
There are also designs such as bandpass, quarter-wave resonator, freeair and others, but when building systems they are used extremely rarely for various reasons. The speaker owner must decide which subwoofer box to choose based on sound requirements and experience.
This type of design is the simplest. A closed box for a subwoofer is easy to calculate and assemble. Its design is a box of several walls, most often 6.
A closed box has only one drawback, but sometimes it is decisive. This type of design has a very low level of efficiency compared to other boxes. A closed box is not suitable for those who want high sound pressure.
However, it is suitable for fans of rock, club music, jazz and the like. If a person wants bass, but needs space in the trunk, then a closed box is an ideal option. A closed box will not play well if the wrong volume is selected. What volume of box is needed for this type of design was long ago decided by experienced people in car audio through calculations and experiments. The choice of volume will depend on the size of the subwoofer speaker.
The most common speaker sizes are: 6, 8, 10, 12, 15, 18 inches. But you can also find speakers of other sizes; as a rule, they are used very rarely in installations. Subwoofers with a diameter of 6 inches are produced by several companies and are also rarely found in installations. Mostly people choose speakers with a diameter of 8-18 inches. Some people indicate the diameter of the subwoofer speaker in centimeters, which is not entirely correct. In professional car audio, it is customary to express dimensions in inches.
The volume is given approximately, since for each speaker you need to select a certain volume based on its characteristics. The setting of a closed box will depend on its volume. The larger the volume of the box, the lower the tuning frequency of the box will be, the bass will be softer. The smaller the volume of the box, the higher the frequency of the box, and the bass will be clearer and faster. You should not increase or decrease the volume too much, as this is fraught with consequences. When calculating the box, adhere to the volume that was indicated above. If there is too much volume, the bass will turn out vague and indistinct. If the volume is not enough, then the bass will be very fast and “pound” the ears in the worst sense of the word.
A lot depends on the settings of the box, but an equally important point is “”.
This type of design is quite more difficult to calculate and build. Its design is significantly different from a closed box. However, it has advantages, namely:
The bass reflex also has disadvantages, the number of which is greater than that of the ZYa. So, the cons:
Based on the advantages and disadvantages, you can understand where FI boxes are used. Most often they are used in installations where loud and pronounced bass is needed. The bass reflex is suitable for listeners of any rap, electronic and club music. It is also suitable for those who do not need free space in the trunk, since the box will occupy almost all the space.
The FI box will help you get more bass than from a small-diameter speaker. However, this will require much more space.
As with ZY, the numbers given here are imprecise. However, in a FI case you can “play” with the volume and take a value less than recommended, finding out at what volume the subwoofer plays better. But do not increase or decrease the volume too much, this can lead to loss of power and failure of the speaker. It is best to rely on the recommendations of the subwoofer manufacturer.
The larger the volume of the box, the lower the tuning frequency, the bass speed decreases. If you need a higher frequency, then the volume must be reduced. If your amplifier's rated power exceeds the speaker's rating, then it is recommended to make the volume smaller. This is necessary in order to distribute the load on the speaker and prevent it from exceeding the stroke. If the amplifier is weaker than the speaker, then we recommend making the volume of the box a little larger. This compensates for the volume due to the lack of power.
The port area should also depend on the volume. The average speaker port area values are as follows:
for an 8-inch subwoofer you will need 60-115 sq.cm,
for 10-inch – 100-160 sq.cm,
for 12-inch – 140-270 sq.cm,
for 15-inch – 240-420 sq.cm,
for 18-inch - 360-580 sq.cm.
The length of the port also affects the tuning frequency of the subwoofer box; the longer the port, the lower the box tuning; the shorter the port, the higher the tuning frequency. When calculating a box for a subwoofer, first of all, you need to familiarize yourself with the characteristics of the speaker and the recommended parameters of the housing. In some cases, the manufacturer recommends completely different box parameters than those given in the article. The speaker may have non-standard characteristics, causing it to require a specific box. Such subwoofers are most often found from manufacturing companies Kicker and DD. However, other manufacturers also have such speakers, but in much smaller quantities.
The volumes are approximate, from start to finish. It will differ depending on the speaker, but as a rule they will be in the same plug... For example, for a 12-inch subwoofer it is 47-78 liters and the port will be from 140 to 270 sq. cm, but how to calculate the volume in more detail, we will learn all this in subsequent articles. We hope that this article answered your question, if you have comments or suggestions, you can leave your comment below.
The information you learned is perfect for those.
The case must be strong, otherwise its vibration will generate frequencies that will give an undesirable color to the sound. We'll tell you what material is best to make a subwoofer box from and what types of enclosures there are.
Particle board. There are several types of slabs on sale, but chipboard of the highest density is recommended for cabinets. Although high-density varieties weigh more, they are easier to handle and sound better. High-density 16mm chipboard is perhaps the best choice for a high-power subwoofer, as it has the highest density and weakest resonant properties.
The disadvantage of chipboard is that it easily absorbs moisture and is difficult to cut with a saw. The box made from it should be painted to prevent swelling due to moisture.
Sealed (closed box). The most common form of subwoofer is a sealed enclosure. It is preferred due to the relative ease of development and construction. Sealed is a housing that completely isolates the internal air space of the subwoofer from the external one. The air inside the box supports the speaker membrane and acts as an additional suspension for it. This allows the speaker to handle more power.
The range of emitted frequencies of the subwoofer depends on the volume of the box. If the volume is less than optimal, the pressure inside the box will increase, which will cut some frequencies and enhance others. Instead of pure deep bass, the subwoofer will produce a booming, “failed” bass. By increasing the volume of the box, the bass improves, but to a certain level. The main design challenge is to determine the optimal volume for the speaker.
In practice, it happens that first a box is designed based on the limitations of free space in the trunk of a car, and then a speaker is selected to fit the internal volume of this box.
Phase inverted subwoofer enclosures They are widely used in home speaker systems and are widely used in car audio. This body shape is unique in that the bass reflex (ventilation duct) helps in reproducing the lowest frequencies in the audible range. The bass reflex actually becomes a sound source that contributes to the overall sound of the subwoofer. Phase inverted systems produce more bass with less power than sealed systems. A properly designed vent will produce increased output at the tuned frequency. The sound of phase-inverted subwoofers is cleaner, but the volume is larger than that of sealed subwoofers for the same speaker.
The disadvantage is the possibility of distortion when reproducing frequencies from a range below the calculated one. Calculations of the parameters of a ventilated enclosure are more complex, and even small errors may not justify the effort and time spent. Errors in the design and configuration of the bass reflex are the reason that the speaker system “mumbles” or the bass is “smeared”.
Isobaric design is a box in which two identical speakers are installed. This design is based on the idea of having constant air pressure between the membranes of the two speakers. As a result, two acoustically coupled speakers function as one speaker.
The advantage is volume savings. The disadvantage is that if there are two voice coils, only one membrane remains actually working. The overall output of an isobaric subwoofer is approximately 3 dB less than that of other subwoofers at the same input power. Structurally, a pair of speakers is located inside the housing on the same axis, membrane to membrane, magnet to magnet or magnet to membrane.
Bandpass enclosures consist of two chambers between which a speaker is mounted. One of the chambers is sealed, and the second chamber is phase inverted.
This design provides high-quality low bass compared to other subwoofers, which makes them popular. But their acoustic output is relatively low. When designing a bandpass, the relationship between the frequency response and the sound pressure developed by the enclosure should be taken into account. The lower and better the bass, the lower the acoustic output and power of the subwoofer. And vice versa, the more powerful the subwoofer, the higher and worse the bass it produces.
The disadvantage is the complexity of calculations and large dimensions compared to sealed or phase-inverted enclosures.
In this article we will look at how to make a subwoofer with your own hands, without delving into the depths of electroacoustics, without resorting to complex calculations and subtle measurements, although you will still have to do some things. “Without any special difficulties” does not mean “slap on a brick, drive away, grandma, mogarych.” These days, it is possible to simulate very complex acoustic systems (AS) on a home computer; See the end for a link to a description of this process. But working with a finished device on a whim gives something that you cannot get by any reading or viewing - an intuitive understanding of the essence of the process. In science and technology, discoveries at the tip of a pen are rarely made; Most often, a researcher, having gained experience, begins to “gut” understand what’s what, and only then looks for mathematics suitable for describing the phenomenon and deriving design engineering formulas. Many great people recalled their first unsuccessful experiences with humor and pleasure. Alexander Bell, for example, initially tried to wind the coils for his first telephone with bare wire: he, a musician by training, simply did not yet know that live wire needed to be insulated. But Bell still invented the telephone.
Do not think that JBL SpeakerShop or other acoustics calculation program will give you the only possible, most correct option. Computer programs are written using established, proven algorithms, but non-trivial solutions are impossible only in theology. “Everyone knows that you can’t do this. There is a fool who doesn't know this. He is the one who makes the invention."– Thomas Alva Edison.
SpeakerShop appeared not so long ago, this application was developed very thoroughly and the fact that it is used very actively is an absolute plus for both developers and amateurs. But in some ways the current situation with him is similar to the story with the first photoshops. Who else used Windows 3.11, remember? - back then they just went crazy with image processing. And then it turned out that in order to take a good picture, you still need to know how to take photographs.
A subwoofer (simply a sub) in its literal translation sounds funny: a burr. In reality, this is a bass (low-frequency, woofer) speaker that reproduces frequencies below approx. 150 Hz, in a special acoustic design, a box (box) of a rather complex device. Subwoofers are also used in everyday life, in high-quality floor-standing speakers and inexpensive desktop ones, built-in and in cars, see fig. If you manage to make a subwoofer that reproduces bass correctly, you can safely take on it, because LF reproduction is perhaps the fattest of the whales on which all electroacoustics stand.
It is much more difficult to make a compact low-frequency section of the speaker system than the mid-range and high-frequency (mid- and high-frequency) parts, firstly, due to an acoustic short circuit, when sound waves from the front and rear radiating surfaces of the speaker (loudspeaker head, GG) cancel each other out: lengths LF waves are meters, and without proper acoustic design of the GG, nothing prevents them from immediately converging in antiphase. Secondly, the spectrum of sound distortion in the low frequencies extends far into the best audible region of the midrange. In essence, any broadband speaker has a low-frequency section into which midrange and high-frequency emitters are built. But from the point of view of ergonomics, an additional requirement is imposed on the subwoofer: a subwoofer for the home should be as compact as possible.
Note: All types of acoustic design of LF GG can be divided into 2 large classes - some dampen the radiation from the rear of the speaker, the second reverse it in phase by 180 degrees (turn the phase) and re-radiate it from the front. A subwoofer, depending on the properties of the GG (see below) and the required type of its amplitude-frequency response (AFC), can be built according to a circuit of one class or another.
People can distinguish the direction of sounds below 150 Hz very poorly, so in an ordinary living room a sub can be placed basically anywhere. MF-HF speakers (satellites) of acoustics with a subwoofer are very compact; their location in the room can be selected optimally for the given room. Modern housing is, to put it mildly, no different in terms of excess space and good acoustics, and it is not always possible to “stuff” at least a couple of good broadband speakers into it correctly. Therefore, making a subwoofer yourself allows you not only to save a very significant amount of money, but also to still get a clear, true sound in this Khrushchev, Brezhnevka or modern new building. A subwoofer is especially effective in full surround sound systems, because... putting 5-7 columns on a full page each is too much even for the most sophisticated users.
Reproducing bass is not only technically difficult. The generally narrow low-frequency region of the entire spectrum of sound waves is heterogeneous in its psychophysiological effect and is divided into 3 regions. To choose the right bass speaker and make a subwoofer box with your own hands, you need to know their boundaries and meaning:
For midbass, the main task when creating a subwoofer is to ensure the highest GG output, a given shape of the frequency response and its maximum uniformity (smoothness) in the minimum volume of the box. The frequency response, which is close to rectangular towards lower frequencies, gives a powerful but harsh bass; Frequency response, uniformly falling - clean and transparent, but weaker. The choice of one or the other depends on the nature of what you are listening to: rockers need an “angrier” sound, while classical music needs a gentler sound. In both cases, large dips and spikes in the frequency response spoil the subjective perception with formally identical sound technical parameters.
The noise masking effect is especially necessary in a cramped and noisy car interior, so car subwoofers are optimized for sub-bass. Sometimes, for the sake of this, Hi-Fi lovers at high speed give the entire trunk to the subwoofer, placing 15”-18” monster speakers there with 150-250 W of peak power, see fig. However, a quite decent subwoofer can be made for a car without sacrificing useful volume in the body, see below.
Note: The peak power of a speaker is often equated with noise, which is incorrect. At peak power the sound is distorted, but still intelligible, i.e. distinguishable by meaning. Noise power is defined as that at which a speaker can operate for a certain period of time (usually 20 minutes) without burning out or suffering mechanical damage. The sound in this case is most often an incoherent wheezing, which is why such power is called noise. But in some types of acoustic design, the noise power of the speaker may be lower than the peak, see below.
A complete calculation of acoustic design is carried out according to the so-called. Thiel-Small parameters (TSP). Since we decided to spend time and labor on setting up the sub, we will only need the full quality factor of the head at its own resonant frequency Qts, because It is based on this that the optimal acoustic design option is selected. Depending on the Qts value, speakers are divided into 4 groups:
In the manufacturer's specifications for speakers, Qts may be designated as Qп or simply Q, but it is not always present there, and public databases like WinISD are full of errors. Therefore, we will most likely have to determine the Qts value at home.
First of all, we select and prepare a room for acoustic measurements. It should have as many curtains, curtains, carpets on the floor and walls, and upholstered furniture as possible. Hard horizontal surfaces (tables) need to be covered with something fluffy; It wouldn’t hurt to throw more pillows everywhere. Corners distort the sound field especially strongly, incl. hard furniture with walls, they need to be curtained with something, for example, clothes on hangers. Next, we connect long wires to the speaker and hang them in the geometric center of the ceiling (under the chandelier, if there is one) with the front side of the diffuser down at a height from the floor of 2/3 of the ceiling height.
Now you need to assemble a measurement diagram, as shown at the top in Fig. We will still need the lower circuit to measure the impedance (impedance) of speaker Z. This one differs from the measuring circuit without a transformer usually used by amateurs in quite professional accuracy: in conventional circuits, approx. 1.5 V even with an input resistance of the tester of 10 MOhm. The operation of this circuit is based on the fact that the impedance of the transformer and R2, on the one hand, is much greater than the impedance of the main generator; on the other hand, it is much less than the output impedance of an audio frequency power amplifier, and on the fact that the lousiest digital multitester at a limit of 200 mV has an input impedance of more than 1 MOhm. However, if the measurement signal is supplied from an audio frequency generator (AFG) with a standard 600-ohm output, this circuit is not suitable for measuring Z.
From a computer with a GZH emulation program, the measuring signal is supplied from the output of the sound card. You need to “drive” it within the range of 20-100 Hz at first with a discrete (step) of 10 Hz. If the GG resonance is not visible, it is unsuitable for a subwoofer. Or the seller shamelessly deceived you by selling you for 100 rubles. indifferent GG priced from $200.
When the boundaries of the resonant peak are determined, we “pass” it with a discrete of 1 Hz and build the frequency response. If the high- or medium-quality GG is closer to the upper limit of Qts, you will get a graph similar to the one in pos. I fig. In this case:
If the quality factor of the GG is closer to low or such, which is generally good, the resonance curve will be noticeably asymmetrical, and its peak will be flat, blurred, pos. III, or the test using formula (2) will not converge even with repeated measurements. In this case, from the graph we determine the points of greatest inclination of the tangents to the concave “wings” of the peak A1 and A2; mathematically, in them the second derivative of the function describing the resonance curve reaches a maximum. For Umax then we take, as before, its value at the top of the peak, and for Umin - calculated from the f-le at pos. III new value U(F1,F2).
Have you tried it on? Is the speaker suitable? Take your time to choose a design. First you need to choose a block diagram of the entire sound system, because its electronic part may account for as much of the cost as a good bass speaker. A sound system with a subwoofer can be built according to one of the following. diagrams, see fig.
Note: The equalizer and infra-low-pass filter FINCH (rumble filter) in all circuits are turned on before the inputs of stereo channels.
Pos. 1 – system with passive power filtering. Plus – you don’t need a separate bass amplifier; it connects to any UMZCH. Huge disadvantages, first, mutual electrical leakage of channels in the subwoofer along the midrange: for LC filters that reduce it to an acceptable value, you will need a decent case, which in order to purchase their components will first have to be filled by about a third with money (in 100 ruble bills). Secondly, the output resistances of the low-pass filters of the low-pass filter together with the input GG of the speaker form a tee, and each channel of the UMZCH will theoretically spend a quarter of the power on warming its neighbor with its low-pass filter. In reality – more, because on power and losses in filters are significant. However, the power-filtering system is applicable in low-power subwoofers with independent sound emitters, see below.
Pos. 2 – passive filtering to a separate bass UMZCH. There are no power losses, the mutual influence of channels is weaker, because The characteristic resistances of the filters are kilo-ohms and tens of kilo-ohms. Currently, it is practically not used, because Assembling an active filter on microcircuits turns out to be much simpler and cheaper than winding passive coils.
Pos. 3 – active analog filtering. The channel signals are added by a simple resistor adder, sent to an analog active low-pass filter, and from it to the bass UMZF. The interference of channels is negligible and unnoticeable under normal listening conditions, and the costs for components are low. The optimal circuit for a homemade subwoofer for a novice amateur.
Pos. 4 – full digital filtering. Channel signals are fed to a splitter P, which divides each of them into at least 2 equal to the original one. One signal from the pair is fed to the MF-HF UMZF (possibly directly, without a high-pass filter), and the rest are combined in adder C. The fact is that with resistor addition at the lower frequencies of the midbass and sub-bass, electrical interaction of signals in the low-pass filter is possible, several distorting the total bass. In the adder, the signals are added digitally or analoguely, eliminating their mutual influence.
From the adder, the common signal is fed to a digital low-pass filter with built-in analog-to-digital (ADC) and digital-to-analog (DAC) converters, and from it to the bass UMZCH. The sound quality and channel isolation are the highest possible today. The costs of microcircuits for this entire enterprise turn out to be feasible, but working with ICs requires some amateur radio experience, and even more if you do not buy a ready-made set (which is significantly more expensive), but select the system components yourself.
In Fig. The most common acoustic design schemes for home subwoofers are given. Labyrinths, horns, etc. do not meet the requirements of compactness. Schemes that are preferable for beginners are highlighted in green, schemes that are feasible for them are highlighted in yellow, and unsuitable ones are highlighted in red. Those with more experience may be surprised: is the 6th bandpass for dummies? No problem, this great bass tube speaker can be set up in a weekend. If you know how.
Designing a subwoofer in the form of an acoustic screen (shield, item 1) at home is feasible if the GGs are built into the wall cladding, because their sizes are comparable to the lengths of sub-bass waves. Hence the advantage - there are no problems with sub-bass, as long as the speakers can handle it. Another thing is that it is extremely compact; the sub does not take up any useful space at all. But there are also serious disadvantages. The first is a large amount of construction work. Secondly, the acoustic screen does not affect the frequency response of the GG in any way. “Humpbacked” will sing just like that, so you can only install expensive, low-quality and indifferent speakers on the shield. The downside, so to speak, is that their recoil is small and the shield is in no way capable of increasing it.
The biggest plus of a closed box (item 2) is deep damping of the GG; for inexpensive, high-output, high-quality speakers, this is the only acceptable type of acoustic design. But this plus also entails a minus: with deep damping, the noise power of the GG is often lower than the peak, especially for expensive powerful heads. The coil is already smoking, but no wheezing can be heard. An overload indicator is needed, but the simplest ones without a separate power supply distort the signal.
An equally big plus is the extremely smooth, smoothly falling frequency response and, as a result, the purest and most vibrant sound. For this reason, high-quality powerful high-quality generators are produced specifically for installation in closed boxes or 4th order bandpasses (see below).
Minus - of all speakers of equal volume, a closed box has the highest lowest reproducible frequency, because it increases the resonant frequency of the speaker and is not able to increase its output at frequencies below it. Those. In terms of compactness, a subwoofer in a closed box is a stretch. This drawback can be reduced to some extent by filling the box with synthetic padding: it perfectly absorbs the energy of sound waves. The thermodynamic process in the box then goes from adiabatic to isothermal, which is equivalent to an increase in its volume by 1.4 times.
Another significant disadvantage is that you can only make a passive subwoofer in a closed box, because The electronics in it get very hot even when placed in a fenced off compartment. If you come across old 10MAS-1M speakers, run them at half power for half an hour and touch the body with your hand - it will be warm.
Note: a passive radiator (PI) is equivalent in all respects - instead of a pipe with a port, a bass speaker is installed without a magnetic system and with a weight instead of a coil. There are no “tuning-free” methods for calculating PI, which is why PI is a rare exception in industrial production. If you have a burnt-out bass speaker lying around, you can experiment - the adjustment is made by changing the weight of the load. But keep in mind that it is better not to make an active PI for the same reason as a closed box.
Acoustics with deep slots (items 4, 6, 8-10) are sometimes identified with FI, sometimes with a labyrinth, but in fact this is an independent type of acoustic design. There are many advantages to a deep slit:
The deep slot has only one drawback, and only for beginners: it is not adjustable after assembly. As it is done, so it will sing.
BandPass means band pass, which is the name given to speakers without direct radiation of sound into space. This means that bandpass speakers do not emit midrange due to its internal acoustic filtering: the speaker is placed in a partition between resonating cavities that communicate with the atmosphere through pipe ports or deep slots. Bandpass is an acoustic design specific to subwoofers and is not used for completely separate speakers.
Bandpasses are divided by order of magnitude, and the order of a bandpass is equal to the number of its own resonant frequencies. High-quality GGs are placed in 4th-order bandpasses, where it is easy to organize acoustic damping (position 5); low- and medium-quality - in 6th order bandpasses. Contrary to popular belief, there is no noticeable difference in sound quality between the two: already at the 4th order the frequency response at low frequencies is smoothed to 2 dB or less. The difference between them for an amateur is mainly in the difficulty of setting: in order to accurately adjust the 4th bandpass (see below), you will have to move the partition. As for 8th order bandpasses, they obtain 2 more resonant frequencies due to the acoustic interaction of the same 2 resonators. Therefore, 8th bandpasses are sometimes called 6th order class B bandpasses.
Note: idealized frequency response at low frequencies for some types of acoustic design are shown in Fig. red. The green dotted line shows the ideal frequency response from the point of view of the psychophysiology of hearing. It can be seen that there is still enough work in electroacoustics.
Amplitude-frequency characteristics of the same loudspeaker head in different acoustic designs
Car subwoofers are usually placed either in the cargo compartment, or under the driver’s seat, or behind the back of the rear seat, pos. 1-3 in Fig. In the first case, the box takes up useful volume, in the second, the sub works in difficult conditions and can be damaged by feet, in the third, not every passenger will be able to tolerate powerful bass right next to their ears.
Recently, car subwoofers are increasingly being made of the stealth type, built into the rear fender niche, pos. 4 and 5. Sufficient sub-bass power is achieved by using special auto speakers with a diameter of 12” with a rigid diffuser, which is little susceptible to the membrane effect, pos. 5. How to make a subwoofer for a car by molding a wing niche, see next. video.
A very simple subwoofer that does not require a separate bass amplifier can be made using a circuit with independent sound emitters (IS), see fig. In fact, these are two channel LF GGs placed in a common long housing installed horizontally. If the length of the box is comparable to the distance between the satellites or the width of the TV screen, the “blurring” of the stereo is hardly noticeable. If listening is accompanied by viewing, it is completely unnoticeable due to involuntary visual correction of the localization of sound sources.
Using the scheme with independent FMs, you can make an excellent subwoofer for a computer: a box with speakers is placed in the far upper corner under the tabletop. The cavity underneath is a resonator tuned to a very low frequency, and an unexpectedly good sub-bass comes out from the small box.
FI for a subwoofer with independent FIs can be calculated in the speaker shop. In this case, the equivalent volume Vts is taken twice as large as measured, the resonant frequency Fs is 1.4 times lower, and the total quality factor Qts is 1.4 times higher. The material of the box, as elsewhere below, is MDF from 18 mm; for subwoofer power from 50 W – from 24 mm. But it is better to place the speakers in a closed box; in this case, it can be done without calculation: the length inside is taken at the installation site, ranging from 0.5 m (for a computer) to 1.5 m (for a large TV). The internal cross-section of the box is determined based on the diameter of the speaker cone:
In the worst case (an under-table computer sub with 6” speakers), the volume of the box will be 20 liters, and the equivalent with filling will be 33-34 liters. With a UMZCH power of up to 25-30 W per channel, this is enough to get decent midbass.
In this case, it is better to use LC filters of type K. They require more coils, but in amateur conditions this is not essential. K-filters have low attenuation in the stopband, 6 dB/oct per link or 3 dB/oct per half-link, but have an absolutely linear phase response. In addition, when operating from a voltage source (which, with great accuracy, is the UMZCH), the K-filter is little sensitive to changes in load impedance.
At pos. 1 pic. Diagrams of K-filter sections and calculation formulas for them are given. R for the low-frequency GG is taken equal to its impedance Z at the low-pass filter cutoff frequency of 150 Hz, and for the high-pass filter equal to the satellite impedance z at the high-pass filter cutoff frequency of 185 Hz (formula in position 6). Z and z are determined according to the diagram and formula in Fig. above (with measurement diagrams). Working diagrams of filters are given in pos. 2. If you prefer to buy additional capacitors rather than wind coils, exactly the same parameters can be made from P-links and half-links.
Data and circuits for making filters for a simple subwoofer with independent emitters
The attenuation of the low-pass filter in the stopband is 18 dB/oct, and the attenuation of the high-pass filter is 24 dB/oct. This frankly non-trivial ratio is justified by the fact that the satellites are unloaded from the low frequencies and give a cleaner sound, and the remainder of the low frequencies reflected from the high-pass filter is sent to the low-frequency speakers and makes the bass deeper.
Data for calculating filter coils are given at pos. 3. They need to be positioned mutually perpendicular because K-filters operate without magnetic coupling between the coils. When calculating, the dimensions of the coil are specified and the number of turns is determined using the inductance found in the order of calculating the filter. Then, using the laying coefficient, the diameter of the wire in the insulation is found; it should be at least 0.7 mm. It turns out less - increase the size of the coil and recalculate.
Setting up this subwoofer comes down to equalizing the volumes of the bass and satellite speakers, respectively. cutoff frequencies. To do this, first prepare the room for acoustic measurements, as described above, and a tester with a bridge and transformer. Next you will need a condenser microphone. For a computer one, you will have to make some kind of microphone amplifier (MCA) with bias applied to the capsule, because a regular sound card cannot simultaneously receive a signal and emulate a frequency generator, pos. 4. If you can find a condenser microphone with a built-in MUS, even an old MKE-101, great, its output is connected directly to the primary (smaller) winding of the transformer. The measurement procedure is simple:
Now you need to calculate the equalizing resistors. The volumes are equalized by muting the louder links in a series-parallel circuit (item 5), because it is necessary to keep the previously found values of Z and z unchanged modulo. Calculation formulas for resistors are given in pos. 6. Power Rg – not less than 0.03 of the power of the UMZCH; Rd – any from 0.5 W.
Another option for a simple, but real subwoofer is with a paired low-frequency generator. Pairing woofers is a very effective way to enhance their sound quality. The design of a subwoofer based on a pair of old 10GD-30 is shown in Fig. below.
The design is very perfect, 6th order bandpass. Bass amplifier - TDA1562. You can also use other high-quality GGs with a relatively small diffuser stroke, then you may have to make adjustments by selecting the length of the pipes. It is produced at control frequencies of 63 and 100 Hz. way (control frequencies are not resonant of the acoustic system!):
The tuning of the resonators is interdependent, so the pipes need to be moved according to: pulled out the short one, pushed the long one in by the same amount, in proportion to its original length. Otherwise, you can completely upset the system: the peak of the optimal setting at the 6th bandpass is very sharp.
After any of the adjustment procedures, the subwoofer is reconfigured. For its convenience, complete assembly with glue is not done at first: the partition is tightly smeared with plasticine, and one of the side walls is placed on double-sided tape. Make sure there are no gaps!
Ready-made elbow pipes for acoustics are sold in music and radio stores. You can make a telescopic acoustic pipe with your own hands from scraps of plastic or cardboard pipes. In both cases, across the inner mouth, you need to firmly glue 2 pieces of fishing line: one with tension, the other with a loop protruding outward, see fig. on right. If the pipe needs to be moved apart, press on the tight line with a pencil, etc. If you shorten it, pull the loop. Tuning a resonator with a pipe is thus speeded up many times.
Drawings of the 6th order bandpass for 12” GG are given in Fig. This is already a solid floor-standing design with a power of up to 100 W. It is configured like the previous one.
Drawings of a 6th order bandpass subwoofer for a 12″ speaker
Suddenly you have a 12” high-quality GG at your disposal; on it you can make a 4th order bandpass of the same quality, but more compact, see fig; dimensions in cm. However, setting it up will be much more difficult, because Instead of manipulating the pipe of a larger resonator, you will have to immediately move the partition.
6th order bandpass subwoofer for 12″ speaker
The bass UMZF for a subwoofer is subject to the same requirement as filters, the requirement of complete linearity of the phase response. It is satisfied by UMZCHs made using a bridge circuit, which also reduces the nonlinear distortions of integral UMZCHs with a non-complementary output by an order of magnitude. UMZCH for a subwoofer with a power of up to 30 W can be assembled according to the diagram in pos. 1 rice; 60-watt according to the circuit on pos. 2. It is convenient to make an active subwoofer on a single chip of a 4-channel UMZCH TDA7385: a couple of channels are sent to the satellites, and the other two are connected via a bridge circuit to the sub, or, if it has independent amplifiers, they are sent to the woofers. The TDA7385 is also convenient because all 4 channels have common inputs for the St-By and Mute functions.
According to the diagram at pos. 3 makes a good active filter for a subwoofer. The gain of its normalizing amplifier is regulated by a variable resistor of 100 kOhm over a wide range, so in most cases the rather tedious procedure of equalizing the volumes of the subwoofer and satellites is eliminated. Satellites in this version are switched on without a high-pass filter, and volume preset potentiometers with slots for a screwdriver are built into the mid-high frequency amplifiers.
You may want to design a slot sub from scratch rather than mess around with reconfiguring prototype subwoofers to fit your speaker. In this case, follow the link: //cxem.net/sound/dinamics/dinamic98.php. The author, we must give him his due, was able to explain at a “for dummies” level how to calculate and make a high-quality subwoofer using modern software. However, in a big deal there are some mistakes, so when studying the source, keep in mind:
Making a subwoofer yourself is a fascinating task, useful for the development of intelligence and skill, and besides, a good bass speaker costs one and a half times less than a pair of a lower class. However, during control auditions, both seasoned experts and casual listeners “from the street”, all other things being equal, clearly prefer sound systems with full channel separation. So first think about it: won’t you still have to deal with a couple of separate columns on your hands and your wallet?
What is the best way to make a subwoofer box?
What is the best way to make a subwoofer box with your own hands? Readers often ask. Let's try to figure it out.
This article was written precisely for this purpose. In addition, the reader will receive valuable instructions on how to make a cabinet for this speaker with their own hands. Having found out what would be the best material to make a subwoofer box from, you can safely proceed to the operation.
In principle, there are many materials from which a housing for such a speaker can be made. It can be plywood, MDF, chipboard and so on. Each of these materials has not only advantages, but also disadvantages.
Note. The best material for making a subwoofer enclosure, according to many experts, is shipboard laminated plywood.
Finding ship plywood is not as difficult as it seems at first glance. Construction sites and other manufacturing enterprises have such material.
Formwork is often made from this plywood. This material is always moisture resistant, very durable and tough. In a word, for a subwoofer body this is what you need.
Note. It will be useful to know that in the West, where the manufacture of homemade enclosures for subwoofers is highly encouraged, they prefer MDF. They don’t have any marine plywood at all, and many experts see this as the reason for their love for MDF.
Chipboard is also a good material, but it doesn’t like moisture at all. In addition, when processed, chipboard tends to crumble. On the other hand, if you take thicker material, the problem can be solved.
Some experts also recommend other materials, but they are, as a rule, not so popular - for example, glued laminated boards.
Let's get started:
Note. When choosing plywood, the main thing is to pay attention to its thickness. Try to select thick plywood, because the rigidity of the entire structure will depend on this, which will ultimately affect the sound.
Thus, the optimal thickness for a subwoofer box is considered to be 18 mm. This is quite reasonable: you won’t have to spend a lot of money (the thicker the plywood, the more expensive it is) and the quality will remain at the same level. On the other hand, everyone decides for themselves and sometimes the weight of a homemade box can reach more than 50 kilograms.
Note. Don’t forget to buy a piece of carpet, which we will use to cover the box at the last stage of production.
First of all, we start making the body of the box.
Started:
Note. You can do it differently. A hole of normal size is made in the first sheet, and a larger hole is made in the second sheet, which is on the outside. Thus, the subwoofer head will be recessed into the body, which has a positive effect not only on technical capabilities, but also on aesthetic components.
Let's continue:
Note. In other words, it is advisable to tighten the screws every 3-5 cm.
Note. Over time, furniture screws do not become loose, even from constant shaking and vibrations.
Let's get started:
Note. It is believed that a closed type of subwoofer box should not have any holes at all. And some experts even recommend checking the tightness of the box by pouring water inside. But this is already overkill and it is unlikely that this should be done.
How to make a box for a subwoofer
At this point, the process of making a subwoofer box with your own hands can be called complete. The instructions should not be ignored under any circumstances.
Video reviews and photos are of no small importance - materials that also need to be given attention (see). Thus, the price of the subwoofer housing will be the lowest, since you will only need to spend money on consumables.
