Aluminium and the cut
Braeburn ran its own machining centres in Newbury Park, California, and cut each body from a single block. For an acoustic part that choice has consequences beyond appearance.
Unibody means no seams in the horn
The archive is specific about construction: “all aluminium CNC unibody”. A unibody horn has no glued joint, no snap fit and no parting line running along the duct.
Seams matter acoustically. A joint inside a horn is a small discontinuity in the wall and, if the halves flex independently, a source of buzz at particular frequencies. An assembled plastic horn must be designed around its parting line; a milled one has none to design around. The geometry can therefore follow the acoustics rather than the tooling.
Mass and stiffness, not resonance
Thin walls radiate. A horn wall that flexes under internal pressure re-radiates part of that energy a few milliseconds late, smearing what the mouth delivers. A solid aluminium body is both stiff and heavy for its size, so the wall contributes very little of its own.
The same mass keeps the cradle still on a desk. A light horn in contact with a hard surface couples into that surface and the desk becomes an unplanned soundboard. Weight here is a specification, not an accident of material choice.
What machining costs and what it buys
Cutting from billet wastes most of the block and takes machine time per unit, where injection moulding spreads one tooling cost across thousands. For a small production run the economics can favour machining; at volume they do not.
What it buys is tolerance and freedom. Internal radii, wall thicknesses and the throat opening can be held closely and revised between runs without new tooling — which matters when the aperture position changes with every device generation. A firm that owns its machines can iterate a horn in an afternoon.
| Item | Value |
|---|---|
| Construction | Unibody, machined from solid |
| Material | Aluminium |
| Process | CNC milling, in-house machining centres |
| Location | Newbury Park, California |
| Acoustic benefit | No internal seam; high wall stiffness |
| Secondary benefit | Mass decouples the body from the desk |
Reading the marks the machine leaves
Tool paths are visible on the inside of a horn
A milled duct carries the record of how it was cut: the scallop pattern left by a ball-nose cutter stepping along the flare, finer where the step-over was small. On an acoustic surface these ridges are far shorter than the wavelengths involved and cost nothing, which is why an as-machined interior is acceptable where a moulded one would be polished.
Why the outside gets more attention than the inside
The exterior is finished to a standard the eye demands: consistent satin grain, clean edge breaks, no witness marks. The interior is finished to a standard the ear demands, which is a much lower bar. Production time concentrates where it is visible, and acoustically that is the right allocation.
The fixture is half the job
A unibody part with an internal cavity has to be held while material is removed from several directions without the workpiece moving. Designing that fixture is often harder than programming the cut, and it is the reason a small change to the throat can mean remaking a jig rather than editing a file.