How is a Polypropylene cone made for subwoofers?

Cones are among the lightweight parts of subwoofers and speakers made using various types of materials including Polypropylene.

Cones are important components as they move to create pressure waves using the surrounding air which results in a bassy sound.

Polypropylene is a form of plastic (a synthetic material) that is resistant to moisture and humidity which makes it an ideal choice for high-end audio and auto-sound systems.

In this article, you will learn the process involved in making polypropylene cones for subwoofers.

What is a Polypropylene cone in a Subwoofer?

Polypropylene is a form of plastic crafted from thermoplastic polypropylene polymer which is used to make several components in sound systems including cones.

Moreover, additives such as talc, glass fiber, carbon black, mica, etc., are added to the solution to make a perfect blend ideal for subwoofer and speaker cones.

Unlike paper cones, most manufacturers and designers of subwoofers and speakers prefer polypropylene to make cones. This is due to the low production cost, excellent damping properties, rigidity, and durability of polypropylene as a synthetic material.

How is a Polypropylene cone made?

Polypropylene cones for subs and speakers are typically made using two methods Thermoforming and Injection Molding.


It generally refers to the process of transforming a plastic sheet into a multi-dimensional shape with the help of heat, vacuum, and pressure.

In simple words, thermoforming is manufacturing plastic items including cones for different sound systems such as speakers and subwoofers.

When it comes to making propylene subwoofer cones, plastic sheets are heated and melted at higher temperatures until they become soft.

The required additives are included in the process to make a perfect blend for cones.

They are then formed into cone shapes using vacuum pressure techniques. In simple words, the melted solution is transferred to molds that are designed to shape cones.

They are then set to cool for hours or a specific period of time. Upon cooling, the cones are ejected from the molds to be trimmed by the edges to offer finishing touches.

Finally, several applications and coatings are applied to result in the finished product.

Using the process of thermoforming gives a lot of benefits to cone manufacturers than other types of molding techniques.

  • The ability to create several finished cones of different sizes from the same material.
  • It allows for the detection of different-sized cones to design and fitting issues before it is too late.
  • The thermoforming process not only saves time but also the making costs.

Additionally, the cones made using the thermoforming process offer many benefits to both the manufacturer and the end user as follows.

  • The finished products using the process turn out to be more efficient.
  • The manufacturing and selling costs are comparatively lower.
  • Quick manufacturing allows the manufacturers to supply the demands in a short time.

Injection molding

The thin wall injection molding process is typically used to make thin and lightweight plastic items without compromising their structural properties.

This particular process is another time-saving method of constructing polypropylene cones.

It helps the manufacturers and designers to produce subwoofer cones in bulk quantities in a short span of time.

The structure of a speaker and subwoofer cone should meet mechanical and dimensional requirements and hence injection molding is used to accomplish the needs.

Steps involved in making polypropylene cones for subwoofers

Step 1: Building Molds

At first, the designers built molds of different shapes and sizes as per the requirements.

The cost of making molds is relatively higher and the process is complex.

Note: The molds typically have two main parts, the cavity and the core. The blend of plastic and other additives is injected into the cavity and the core fits it to form the cone’s shape.

Step 2: Melting the blended materials

The blend of raw materials is added to the injection molding machines that are typically powered by hydraulics or electricity.

The raw pallets of plastic are added to a large barrel through a hopper where high temperatures are used to melt the blend.

Step 3: Injecting the molds

Usually, an electric injection molding technique is used to inject the molten materials into molds of different sizes and shapes.

It is injected with high pressures followed by fitting the core of the mold fitting its cavity.

The cavity and the core of the mold are held with very high pressure which is also known as clamp pressure.

Step 4: Determining the cooling time

The mold is held closed for a set amount of time depending on the complexity of the product and the type of blend used. However, the typical holding time can range from milliseconds to minutes.

Next, the pressure is released off the mold considering the holding time has been followed.

Finally, the molded cones are left inside the molds for a few minutes for cooling.

Step 5: The finishing touches

After the the cooling time ends the cones are ejected from the molds to offer finishing touches.

The finishing touch may include coating, polishing, trimming, etc., that are performed by other operators or different pieces of machinery.

Once the finished products (Cones) are ready they are then forwarded for distribution or assembling purposes.

Let us also look into a few benefits to the manufacturers of using the injection molding method to make subwoofer cones.

What are the benefits of injection-molded Polypropylene cones?

There are a few benefits, especially from the manufacturing prospectus with the injection molding process over traditional molding. Let us look into a few below.

  • Mass production: The injection molding process offers a boost in productivity to the cone manufacturers. Thousands of cones can be manufactured in a quick time at a consistent quality.
  • Cost-Effective production: When it comes to injection molding, the cost of building different mold designs is higher. However, once the mold is ready, the cost of making per piece is fairly low, especially when produced in good quantities.
  • Liberty of choice: It gives the liberty of choice to the designers and manufacturers to pick a specific mold design for the subwoofer and speaker cones. Additionally, the manufacturers can choose the type of thermoplastic and additives to use in cone making process for different applications.
  • Quality products: Even complex designs with high detailing, and strong or tensile cones of different shapes and sizes can be designed without compromising their quality.

Other benefits include reduced carbon emissions and minimized waste in the making.

Difference between thermoforming and injection molding methods to produce cones:

The main difference between the two processes is that thermoforming is usually employed for short production runs and large-scale designs.

On the other hand, the injection molding process is ideal for small, delicate products and runs on large-scale manufacturing.

In simple words, the thermoforming method is ideal for producing large (sized) cones in low quantities. And, injection molding process is ideal for producing average to small-sized cones in large numbers.

Final Thoughts

Polypropylene being a kind of synthetic material is quite popular in various sound systems including subwoofers and speakers.

To enhance the rigidity and complexity of the cones there are various additives used to prepare a perfect blend in their making.

The production of Polypropylene cones for subwoofers and speakers is typically done using thermoforming or injection molding methods.

Both methods have their own benefits and drawbacks to the manufacturers and designers, hence the choice of methods completely depends on them.

Frequently Asked Questions

Are plastic cones better for subwoofers?

Polypropylene cones are typically rigid and hold significant damping properties that have control over vibrations resulting in less distortion in sound and a smoother high-end roll-off. The choice of using plastic or paper cones typically depends on the technicality, mechanism, types, and sizes of subwoofers.

Do all subwoofers have plastic cones?

It is not necessary that all subwoofers will include plastic cones, you will also find subs with cones made using paper, metal, and other aramid materials.

What are the benefits of plastic subwoofer cones?

Subwoofer cones made of Plastic or Polypropylene are highly damped, do not absorb moisture, and have low distortion in sound.

Are propylene cones expensive?

Comparatively, due to low production costs plastic cones are reasonably inexpensive than their counterparts.

Armed with a Diploma in electrical engineering and a remarkable 12 years of expertise, he excels in rejuvenating music systems, washing machines, dryers, and laundry-related appliances. Manish's profound insights and practical know-how establish him as a credible authority in appliance and music system repairs. Contact: manish.singh (at) He's always ready to lend a helping hand!