FAQ on making a Stealth type subwoofer

Subwoofer with my own hands

A subwoofer is an integral part of any sound system. Lush and rich bass makes the speakers for the music center, computer or car interior sound different. You can buy a bass speaker in a specialized store or make one yourself. All types of speakers are passive and active. The passive speaker is a box in which the low-frequency speaker is installed. On one of the walls of the structure are terminals for connecting an external sound source.

Typically, a passive design requires a low-frequency amplifier, since most audio devices do not provide enough signal level for a powerful loudspeaker to work properly. Any loudspeaker system can be made by yourself, but an amplifier will be required to make an active speaker. To make a subwoofer with your own hands, you must first purchase a low-frequency speaker, as the cabinet calculations are performed by the electrodynamic head.

Passive subwoofer with your own hands

How to make a simple passive subwoofer.Such a design is a case in which the low-frequency speaker is installed. The volume of the enclosure is usually measured in liters and depends on the diameter of the dynamic head and the design of the enclosure. There are no adjustments on the cabinet of the passive speaker, and on the back or side wall there is a terminal block for connecting the sound source.The box for a subwoofer can be made according to one of three schemes:

Closed design.
Acoustic phaso inverter
Bandpass

The closed box design is the simplest solution. The volume of the enclosure is easy to calculate, and the assembly of the construction is not difficult even for the novice craftsman. To make a homemade sub will require a small number of parts of a simple shape. The top, bottom and two side walls can be cut to the same size. In the front wall, a hole is cut out to install the speaker, and in the rear wall is cut into the block with contacts.The internal volume of the closed box depends on the type of loudspeaker. The dimensions of the enclosure of a bass speaker can be determined from the following table:

20 cm speaker – 8-12 liters
25 cm speaker – 13-14 liters
30 cm speaker – 25-38 liters
38 cm speaker – 39-58 liters

In addition to the simple design, the closed box produces a clear, fast bass and has a relatively flat amplitude-frequency response.

How to make a subwoofer with your own hands schematic. The picture shows the acoustic low-frequency system, designed for a speaker 15 inches or 38 sanitmeter. The enclosure is made of 20 mm thick material. It is recommended to make the front wall double thickness. A socket with pins for connecting the cable from the sound source can be installed on the back wall of the device. To increase the acoustic volume of the speaker, its interior is filled with a damper. For this purpose, you can use ordinary absorbent cotton, which is stuffed into a gauze bag, or sintepon. On the bottom wall you need to screw rubber feet with self-tapping screws. How to make a closed-type subwoofer. Once the choice of speaker head is made, you need to prepare the material.

For low-frequency loudspeakers usually used multi-layered well-glued plywood or a finely divided fraction (MDF). For a home speaker, particleboard can also be used. It is better not to use this material for car speakers, since from the constant shaking and vibration and high humidity the fasteners will turn out spontaneously, and the speaker may collapse. For the assembly of a powerful speaker system plywood, even multilayer, is not recommended. With strong vibration of the structure, the plywood box will resonate, which will create unpleasant sound overtones when listening to music.

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How to make a powerful subwoofer with your own hands

To assemble a powerful subwoofer with your own hands, you can use the design of the speaker with an acoustic phasoinverter. The principle of the acoustic subwoofer explains the following example. When a sine wave signal of sound frequency is applied to the speaker, the positive half-wave moves the cone forward and the negative half-wave moves the cone backward. Therefore, the waves to be emitted are out of phase. The acoustic inverter, due to its design, “reverses” the negative half-wave and reflects it back to the listener. Thus, a person perceives two phased half-waves. The volume of the loudspeaker system increases as well.

Compared to a closed box, the volume level of a phase-inverter design will be 1.5-2 times higher due to its high efficiency. It is very difficult to achieve a perfect match in the design of the two half-waves. Therefore, when listening to music on a speaker system with a phase inverter, the bass will not be as clear as from a closed box, but a little “smeared”. The design with an acoustic bass inverter can be made by yourself.

Making a subwoofer with your own hands. The internal volume of the speaker with a phase-inverter, for one type of loudspeaker, is about twice as large as for a closed box. For a speaker 8 inches in diameter (20 cm) the volume of the speaker with a phase-inverter will be from 20 to 35 liters, and for a speaker 12 inches (30 cm) – 45-80 liters. And this is a “pure” volume, excluding the space occupied by the dynamic head. The acoustic inverter (FI) may be in the form of a slot. In this case, its inner part is formed by additional planes that form reflective surfaces. The tuning of an acoustic FI is determined by the resonant frequency of the loudspeaker head, so it is useless to start making an enclosure without having a loudspeaker with a known resonant frequency. The resonance frequency of the FI should be 1/3 lower than the resonance frequency of the loudspeaker.

There are special formulas for calculating the dimensions of the planes. The slotted phase inverter does not allow for fine tuning or frequency tuning. Therefore, when making a low-frequency speaker according to the drawing, it is necessary to strictly observe all the specified dimensions. To replicate the design, a speaker with a cylindrical phase inverter is better suited. This is two pieces of plastic pipe, one of which can move inside the other. This design allows you to make adjustments to the inverter by moving the moving section, thereby changing its area. Using a version of the speaker with a cylindrical port you can make a subwoofer for the cinema with your own hands. Cylindrical phase inverters of different sizes can be purchased at the radio market or in specialized stores.

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What you can make a subwoofer from

To assemble a proper subwoofer with your own hands it is necessary not to make a mistake in the choice of material. The following product can be used to make a speaker system:

Multilayer (shiplap) plywood
Fine particle board (MDF)
Particle board (chipboard)

For the construction of a high-power acoustic cabinet a material with a thickness of at least 18mm would do. It is hard to find plywood of this thickness, so it is better to use MDF. Chipboard can be used, but it will not be the best option. This material is more loose, so over time, all the fasteners will be loose. In addition, particleboard is not good moisture resistance. It absorbs atmospheric moisture, which is why it quickly deteriorates.

MDF panels are available in different thicknesses, they do not absorb moisture and reliably hold fasteners. You can purchase MDF panels coated with expensive wood species. Many firms selling lumber perform free cutting of panels according to drawings or specified dimensions. The front panel, where the dynamic head is installed should be made double. This will give the structure more rigidity. The two parts of the front wall should be glued together and fixed with self-tapping screws. When assembling a low-frequency loudspeaker you can not economize on fasteners, so self-tapping screws should be screwed in every 3-5 cm. To assemble the cabinet you must use special furniture screws. First, at the mounting points you drill holes with a diameter smaller than the screws, then pour glue and screw in the fasteners. If the speaker is equipped with a very powerful speaker, all the inner corners of the box are additionally reinforced with bars of a triangular shape. If the cabinet will be laminated with cloth or finished in any other way, the wooden surfaces must be treated with varnish. This will increase the resistance of the construction to moisture.

How to Make a Small Subwoofer

A simple compact subwoofer with their own hands is easiest to make in the form of a closed box, as the size of such a construction will be minimal. When making a bass speaker, the diameter of the loudspeaker is taken into account. This parameter is decisive in choosing the size of the speaker. To make a mini subwoofer with your own hands you need to use speakers with a small diameter. For a homemade low-frequency speaker, heads of 5 or 6 inches will do. Such small radiators are not capable of giving a full and rich bass, so compact devices are used as an addition to personal computers or laptops.

You can make a small subwoofer with your own hands from any material, since the power of small speakers is usually small and it is not necessary to use thick MDF panels or multi-layer plywood. To increase the acoustic volume, the interior space of the cabinet is filled with fiber material. You can even make a small sub with your own hands from polycarbonate.

Diagram of an active subwoofer with your own hands

The design of the active loudspeaker, in addition to the loudspeaker, includes a low-frequency amplifier. This allows you to feed a weak signal to the device from the line output of any signal source. How to assemble an active subwoofer. The design of the speaker can be any, but when calculating the volume of the cabinet will need to take into account not only the space occupied by the speaker, but also the size of the amplifier.

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Homemade active subwoofer can be used both at home and in the vehicle. The element base of integral design allows assembling low frequency amplifiers without deep knowledge of radio engineering. The devices have a simple circuit diagram, do not require adjustments and after proper installation start working immediately. A small subwoofer with your own hands can be assembled on a chip TDA1519A. It contains two low frequency amplifiers. In this circuit, the speaker is bridge-connected, which provides 15 watts at the output when powered by a car battery. The signals from the left and right channels are summed and fed to the level control. A passive LC-filter is used to cut the high frequencies. You can make a low-frequency speaker yourself, or you can make a subwoofer active, using a speaker with a dynamic head. For this purpose, it is enough to install a low-frequency amplifier in the cabinet.

Good day dear fans of fiberglass and quality music. Today, on the example of Mitsubishi Lancer X will be considered the construction of “Stealth” type subwoofer in the left wing.

Since there are a lot of people who want to build but don’t know the technology and/or how to use the materials properly, so this article claims to be a Step-by-Step instruction for beginners! (approved by community owner)

IMPORTANT: If anyone is too lazy to read, watch or anything else, just walk past and do not ask questions that will be disclosed here. All materials you can find in the market.

You wanted to build a Stealth type subwoofer.

Before you start work, you need to buy thoroughly, namely:

Polyester resin IPP – 3 kg. Polyester resin IPP – 3 kg (with reserve) Steklomat 300 gr./m2 – 3 packages (with reserve) Scotch masking – 2 pcs. Wide Brushes 2.5-3 cm. width – 5-7 pcs. (I’ll explain below why and why such a width of the brush) Fabric Lycra – 1m. Cloth Carpet – 1m. Glue 88 – 1 jar (900g. I think) Glue “Moment” – 2 tubes Rubber gloves – 3-5 pairs. This is your safety.

Now we have everything you need to start working.

STEP 1. Disassembly of the trunk and getting ready to start work.

Disassemble the trunk, take everything out! For added neatness we wrap paper, cloth, plastic film, etc. around the bumper and the elements that are in close proximity to the place of the body elements works. It is a very hard and thankless job to take the tar off afterwards.

Take masking adhesive tape. Glue the place for lamination. We are trying to make hard-to-reach places such as the area of rear lights, the upper part, would not be a problem to pull out the workpiece from the trunk.

IMPORTANT: Do not allow any layers of tape to fit loosely together! If you make such a mistake, then later on the resin will flow into these gaps and then it will be very difficult to remove the scotch from the workpiece.

STEP #2. Getting started

We have coped with the first stage. All the most interesting things lie ahead.

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The fiberglass mat. We bought the glass mat with a density of 300gr/m2. We open the package. Unwrap the roll. We cut it into small squares. Approximately 10×10 cm. Steklomat has a tendency to delaminate. Take 5-7 such pieces and split them into 3 parts. Take a piece in your hands and you will immediately understand how to do it.

So we have different densities of glass mats. 300 and 100 grams. Dilute the resin. Divide first 100-150gr. This will be quite enough. How to properly prepare the resin will not tell. On the bank there are instructions.

And now we are all ready!

You are going to take a brush. We are going to smear a small area about 15×15 cm. What is it for? It’s like an adhesive layer, so you can properly place the mat. We put on this area with 100g of fiberglass mat and soak it in. Repeat the procedure over the entire area.

By the way, do not smear too much. Resin we will need more. About the brush. If we had used wide brushes it would have been a big waste of resin. I checked! And overconsumption means wasted money. We don’t need it.

And while you were reading all this, this layer has already dried. If you want to dry faster, you can use a construction hair dryer or other devices. The main thing is not to put too close a stream of air!

PART #3. Processing of the workpiece.

If you did everything correctly and the first layer dried, then you can safely take your workpiece out of the trunk. It should be noted that the body of the workpiece is not yet very strong. And you should not use brute male force. It is better to gently pull it out.

Did you get it out? That’s good. Now we need to build up the thickness. It’s much easier and quicker to do it outside the trunk.

First, we separate all the tape from the workpiece. We take glass mat with 300 density (later we will do everything only with this density) and gain the thickness. 2-3 layers is quite enough. GATHER THE THICKNESS FROM THE INSIDE ONLY! Otherwise it will not fit in the trunk.

Leave to dry. It needs to dry thoroughly.

Now we have to put our billet in the trunk. I hope you have realized that with the trunk already had to peel off all the tape and everything else. Let’s see, everything was fine. Somewhere that something somewhere clings or does not fit. This is normal. We put it in the fender. We take a marker and outline the line on which we will cut our workpiece.

WARNING: This operation is very bad for your health.

We pull out the workpiece. We take the grinder and cut the excess on the line, which you have outlined. This operation should be carried out outdoors. with a respirator and clothing. The dust that will fly is very harmful. Take care of your health.

PART #4. There is no limit to the individuality or imagination.

After processing, we still need a few times to figure out our billet. Yes, it is still a billet for now. For it to be called a hull we need to go through this stage.

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Making the front wall allows you to show your imagination and different skills. It can be made as flat (from plywood and/or chipboard), or smooth, shaped, whatever you want to call it.

First you need to decide on the size of the speaker. I think how to choose the speaker you do not need to tell. I will only say that to measure the volume, just pour water into the blank. And then the choice is up to you.

I chose 12″ speaker JBL GTO-1214.

We need to cut the ring. For the speaker. We cut it out.

What would fix the ring, we need stops.

Also made out of chipboard. You can do from the rails for drywall, various fasteners for suspended ceilings etc. Show your imagination!

Subsequently they will remain inside and will not be removed. They will serve as dop.reinforcing. We expose the ring to the desired slope, pitch, etc.

We try to put it in the trunk. Do not forget that you will still have things in the trunk. so be guided by this as well.

I fastened everything with glue “moment”. The picture shows gel. That’s where I made a mistake. I shouldn’t have taken it.

Well, fix the ring and stops in the desired position.

Well, now the responsible thing.

We take the fabric “Lycra” and stretch it on a plane. Around the perimeter fix the fabric with the same glue.

Soak the fabric in resin. And wait until it dries.

The second layer. Till we get a “peeling” state.

Put the mat on top and thoroughly impregnate with resin. Note that on the sides you need to strengthen the design. To do this, when the box dries, cut a few strips of mat and put it at the joint with the inner side of the box.

Well and then build up 2 or 3 layers.

PART 5. The last battle is the hardest

So our box is thoroughly dry. Yes. Now it is a full box. Now we need to cut holes for the terminal and (if it has a phase-inverter).

We estimate all these things and you can wrap it up! It all depends on your money, tastes and desires. The easiest variant is carpets. Glue it can be 88, Titan, spets.sprays for carpets.

You can trim kozhvinilom, Leather, Alcantara, paint, etc. This is up to your discretion and taste. Inside you need to lay 100% of the area box vibroizlyatsiyami. Vprinpipa 3 mm. quite suitable. I also glued the noise.

I chose 3M carpets in color “ash”.