Choosing the Right Acoustic Filler

What goes inside the panel, what we have explored, and why we keep looking for better options.

Most people notice the fabric, the colour and the finish first. But inside every acoustic panel is the part doing most of the acoustic work: the filler.

Choosing that material is not simply a case of finding something soft and putting it in a frame. Different fillers behave differently, and the right choice depends on acoustic performance, density, thickness, practicality, consistency and, increasingly, environmental impact.

We have explored more than one route

Over time we have looked at a range of possible absorber materials, including mineral wool, recycled polyester and PET-based products, natural-fibre options such as wood fibre, hemp and sheep wool, and other lower-impact alternatives.

Each comes with advantages and compromises. Some are appealing from a sustainability point of view but are harder to source consistently. Some are pleasant to handle but do not offer the same acoustic performance at a given thickness. Others perform very well acoustically but have a greater embodied impact or are less straightforward to recycle.

That is why we try not to treat the choice as ideological. Our job is to balance acoustic performance, safety, durability, availability, cost and environmental considerations in a way that makes sense for the finished product.

Why mineral wool remains an important material

For us, mineral wool currently offers the strongest overall balance. Its acoustic performance is excellent and predictable, it is widely used across professional studios and listening rooms, and it is reliable to source and manufacture with consistently. Sustainability is part of that decision too: modern stone wool can contain recycled material, is highly durable and can be recycled. Taken together, it remains a very strong choice for the products we make.

The modern mineral wool products we use are designed for building and acoustic applications, are biosoluble, and are not classified as carcinogenic under current UK and European rules. As with any fibrous insulation material, we still handle and enclose it properly during manufacture.

Its big advantage is performance. At the right density and thickness, mineral wool gives us a reliable level of absorption across a broad frequency range, which is exactly what we need from a serious acoustic treatment product.

Eco-friendly does not always mean acoustically better

We are very interested in lower-impact materials, but sustainability is not just about what a product is made from. It also includes how efficiently it performs, how long it lasts, how far it travels, how consistently it can be supplied and how much material is required to achieve the same result.

A recycled or natural-fibre product can be an excellent solution. Equally, if it needs significantly more depth or material to reach the same acoustic target, the comparison becomes more complicated.

There is no single perfect filler, which is one reason we continue to test and compare different options rather than locking ourselves into one material forever.

Working with suppliers matters

Material consistency is a major part of acoustic manufacturing. Two products that look similar on paper can differ in density, stiffness, batch consistency and availability.

We work with suppliers to understand what is actually being supplied, how consistent it is from batch to batch, and whether it suits the dimensions and performance targets of our panels. Where possible, we look beyond the headline density and consider the way the material behaves in the finished absorber.

That relationship matters because a good acoustic panel should perform predictably whether it was made this week or six months from now.

We are willing to change

We do not see materials as fixed forever. If a new filler becomes available that gives us comparable or better acoustic performance, improved sustainability, reliable supply and sensible cost, we are interested.

That might mean a recycled synthetic fibre, a natural fibre, an improved mineral product, or something not yet common in small-scale acoustic manufacturing.

For us, the goal is simple: use the material that makes the most sense for the product, and keep questioning whether there is a better option.

Good acoustic treatment is not just about what you can see. Quite often, the most important decisions are hidden inside the frame.