How to finish my printed horn

Warning and Disclaimer

Drying your painted speakers or horns at excessively high temperatures or/and use of incompatible products can irreversibly damage them.

Unlike car bodies, which are typically made of separate, non-glued parts that can expand or move under high temperatures and are often painted with 2K paints designed to cure chemically and withstand such heat,
speakers and horns are complex, glued, hermetic assemblies made of various materials, including different types of wood, printed parts, and adhesives. These components expand and contract differently when exposed to heat.

Rapid artificial drying can cause:

Professional painters who specialize in audio equipment use controlled drying processes tailored to the specific materials and thickness of each component. Over-drying is a common mistake with severe consequences.

We strongly advise against using high temperatures to speed up the drying process, including direct sun. Proper drying conditions are essential for the longevity and performance of your speakers or horns.

Traditional 1K painting are design to dry at temperatures around 20/25°C, 30°C maximum, while some car parts are dried at much higher temperatures (60-70°C), often with 2K paint design for.

Professional audio painters typically use short, controlled drying times based on the paint or/and varnish thickness and chemical properties.

If you are unsure about the correct drying process, please consult a professional painter with experience in audio equipment or follow our guidelines.

Protect your investment by following recommended drying procedures. AudioHorn cannot be held responsible for damage caused by improper drying methods.

For applications requiring extreme conditions, please contact us to discuss alternative materials.

1. Protect

Primer

Don’t forget to protect the hole screw with a false screw in PLA or screw that you will not use, otherwise you will not be able to use the screw’s hole at the end of the entire process.

You can ask us to provide it.

Protect yourself also with real mask like the AirGearPro M-500 or others, even when sanding raw PLA if possible.

2. Spray Putty/ Sealing primer

We start by sanding with P150 or P220 grit before applying 2 or 3 thin layers of Motip Spray Putty at a distance of 30/35 cm (to avoid depositing excess solvent on the surface), waiting approximately 2 to 3 minutes between each layer. This duration is long enough for the layers to properly fuse without causing runs or sags, but short enough to prevent the previous layer from drying out too much.

The required thickness should be achieved progressively through 2 to 3 thin, consecutive coats rather than by applying a single heavy coat, which can trap solvents and lead to severe defects.

Once the putty is fully dry, sand the surface and wait a few hours to ensure any trapped solvents or air within the newly exposed underlying layer have fully flash-off and stabilized.

Repeat the process as necessary until the surface is perfectly smooth, waiting 10 to 24 hours before applying a new coat for each iteration.

Important: Spray Putty must be reapplied either wet-on-wet (2 to 3 minutes after the previous coat) or after 10 to 24 hours, once the underlying layer is fully cured. Never apply a new coat during the intermediate drying window.

During this intermediate phase, the previous layer is too dry to fuse correctly with the fresh spray, yet it is still actively releasing trapped solvents and gases. Because the new coat forms a quick surface film, these escaping gases will burst through, causing immediate bubbling and pinhole craters.

Sprayed coats applied from too close a distance will produce the exact same defect due to excess solvent saturation.

Note on High Temperatures (24°C+): High ambient temperatures accelerate surface drying, causing a skin to form rapidly over the coat. Counterintuitively, you must wait slightly longer (3 to 4 minutes), until the surface turns completely matte, to ensure all trapped solvents underneath have fully escaped before applying the next coat.

Don’t forget to remove as much dust as possible.

spray-putty

In the US, you can find 4-in-1 products, by order of preference:

Providing adhesion, sealing, and light corrosion resistance, while remaining a 1K product and not a true 2K high-build primer.

The final sanding can be done with P180 and then up to P600.

You can sand with these sanding sponges, without water:

sponge

They can be cleaned with water and liquid soap.

At this stage, the state of the surface must be perfect.

3. Base Coat Paint

Primer

Use paint according to the brand’s instructions, ideally the same brand as the primer to avoid chemical reactions 6–12 months later, which can cause cracks or peeling if incompatible.

Apply thin layers with a regular aerosol paint. Two or three fine layers are usually enough.

You can sand the last layer up to P800 to provide enough adhesion for the clear coat.

4. Clear Coat / Varnish Protection

Still using the same brand, apply 2 or 3 layers of aerosol varnish to protect your paint once it’s dry.

Dry

In every step, let product dry itself to official time and condition given by the brand, do NOT try to speed up it artificially in any manear.

Professional speed-up dryng in audio is done in a very controled and different way than car body parts, according to material, products used, thickness… See disclaimer section for more informations about it.

Warning about drying outside in direct sunlight: 1K paints are designed to dry at 25–30 °C. In direct sun, a black horn can reach 80–90 °C. Beyond the risk of dust contamination, such heat can cause 1K paints to crack or lose adhesion. While PLA offers the best torsional strength for indoor use (cf. PRUSA test), prolonged outdoor exposure to very high temperatures in direct sunlight is not recommended. If outdoor use is required, other filament types can be used.

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