Anodising and powdercoat
The product line offered satin aluminium alongside six powdercoat colours. On an acoustic part a coating is not purely cosmetic.
What was offered
The archive records a satin aluminium finish and six powdercoats: glossy black, ocean blue, army green, pearlescent white, robin egg blue, and a red listed as Haas Automation red — named after the machine tool manufacturer, which is a workshop's choice of reference rather than a paint company's.
Satin aluminium and powdercoat are different processes with different consequences. A satin surface is the metal itself, textured and left bare or lightly anodised. Powdercoat is an applied polymer layer, cured onto the part, measurably thicker.
Thickness inside a duct is a dimensional change
A powder layer is typically a few tens of micrometres. On an outside face that is irrelevant. Inside a throat only millimetres across it is a real reduction in area, applied unevenly — powder builds up on edges and thins in corners.
A throat is the most sensitive dimension in the whole geometry, which is why coated horns are usually masked internally, or the throat is cut after coating. Where neither is done, two units of the same model in different colours can measure slightly differently.
Surface hardness and what it does to the inside wall
Horn walls should reflect, not absorb. Both bare aluminium and cured powdercoat are hard and smooth enough to reflect well across the audible range, so neither choice costs output in any meaningful way.
Texture is a different matter. A heavily textured or matte powder finish begins to scatter at the shortest wavelengths — a few millimetres at the top of the audible band. The effect is small, but it is the one case where choosing a finish is choosing an acoustic property.
The seven options
| Item | Value |
|---|---|
| Bare option | Satin aluminium |
| Powdercoat colours | Glossy black, ocean blue, army green |
| Pearlescent white, robin egg blue, Haas Automation red | |
| Coating thickness | Tens of micrometres, unevenly distributed |
| Sensitive area | The throat, where area change matters most |
| Acoustic effect | Negligible if smooth; scattering if textured |
Choosing a finish for a part that has to work
Satin aluminium shows wear differently
A bare satin surface marks, but the marks blend into the grain and the part ages evenly. A glossy powdercoat resists marking better and then shows every chip against the colour beneath. For an object handled daily on a desk, the bare metal usually looks better after a year even though it looks worse after a week.
Light colours inside a horn are a practical choice
A pale interior shows dust, and dust in a throat is a real area reduction over time. On a dark interior the same accumulation is invisible until the output changes. Nothing acoustic favours one colour over another; maintenance does.
Masking is the detail that separates runs
Where a throat is masked before coating, every unit of every colour shares the same internal dimensions. Where it is not, colour and acoustics become coupled by accident. This is invisible in a catalogue photograph and is the first thing to check on two units that measure differently.