Aurea | The proportion that comes first
"Though changed, I rise again identical to myself."
The golden ratio is not invented. It precedes. We find it in shells, in galaxies, in the veins of leaves. Bernoulli called it the Spira Mirabilis — the marvellous spiral — because it remains identical to itself through any transformation.
Aurea applies this same idea to acoustics: Italian drivers with Fibonacci cones, a cabinet built to measure, a crossover that forces nothing. The mathematics does the work. We listen.
The Project
Two passive floorstanding loudspeakers, two-way. Two 8" woofers in parallel for the low end, a dome tweeter for the highs. MDF cabinet, 40 litres net, reflex tuning.
The two circular reflex ports on the lower front baffle are fitted with 3D-printed honeycomb diffusers — a solution that reduces turbulence at the port mouth and controls airflow without restricting it.
Fibonacci Technology
The cone of the RS Speakers W 220.50 woofer is built according to the Fibonacci sequence: the rib distribution follows the progression 1, 1, 2, 3, 5, 8, 13… spreading cone resonances across frequencies that are not harmonically related. The result is a cone with no single dominant break-up mode — it breaks up at many different points rather than at one.
A solution that comes from the mathematics of nature, not from the engineering of compromise.
The Structure
The rear panel carries the K4Revenge binding post panel with dual terminals — biwiring and biamping are genuine, not nominal. The two crossover networks are physically separate: no shared connection between woofer section and tweeter section.
Steel spike feet isolate the cabinet from the floor and allow precise levelling on any surface.
The Sequence
Each number is the sum of the two before it. The ratio between consecutive terms converges toward φ = 1.618… — the golden ratio. A proportion nature has always used, now embedded in the Fibonacci cone.
The logarithmic spiral repeats identically at every scale — like music across its octaves.
The Crossover
Second-order electrical on both ways. Crossover point at 1700 Hz. A deliberately simple topology to keep colouration on the signal to a minimum. The two networks are physically separate: biwiring and biamping are real.
Woofers ×2 — LP
2nd order electrical
Tweeter — HP
2nd order electrical
Crossover point
~1700 Hz
acoustic, measured
An Aesthetic Note
It is rare to find components crafted to this level of care. The cone ribbing is visually magnificent — each rib follows a rhythm the eye recognises before the mind explains it. The outer flange is domed, with a finish that is anything but ordinary. The tweeter is equally striking: the machining on its flange recalls the texture of a vinyl record. Details that speak to a 360-degree attention to quality, well beyond acoustics. Italian elegance, in the most precise sense of the term.
The Drivers
The Suspension
Linear simulation on the W 220.50 T/S parameters predicts 8.8 mm excursion at 68 Hz with 200W AES — beyond the rated ±6 mm Xmax. At 100W it drops to 6.1 mm, still at the limit. In listening and in measurement, the driver handles it better than these numbers suggest.
The working hypothesis is that the asymmetric double-roll NBR surround develops a progressively stiffening compliance as excursion increases — a natural braking mechanism that linear T/S parameters do not model. The driver tightens up where it needs to, without this being declared in the datasheet.
Measurements
Measurements taken in a real-world environment, with the tools used every day. Calibrated instrumentation, declared method.
| Cabinet Specifications | |
|---|---|
| Net volume | 40 litres |
| Type | Reflex |
| Tuning frequency | ~40 Hz |
| Reflex ports | 2× 74 mm — lower front |
| Port diffusers | Honeycomb — 3D printed |
| Material | MDF |
| Biwiring | Yes — physically separate networks |
| Acoustic & Electrical Specifications | |
|---|---|
| Sensitivity | 94 dB (1W/1m) |
| Minimum impedance | 3.8 Ohm @ 130 Hz |
| AES power handling | 400 W |
| Dimensions (H×W×D) | 90 × 26 × 30 cm |
| Measurement Equipment | |
|---|---|
| SPL | REW + UMIK |
| Impedance | DATS LA — Dayton Audio |
| Environment | Untreated room |
Aurea — Turn Key Pair
Complete system: designed, built, measured, tested.
* Price per pair of finished loudspeakers, VAT included
Also available as a DIY Kit with or without CNC machining.
Get in touch to discuss your project.
RS Speakers W 220.50 Fibonacci — Technical Data
8" woofer with Fibonacci cone ribbing. RS Speakers, spin-off of SICA Altoparlanti — Italian production.
RS Speakers TW 104.28 N/Ag — Technical Data
28mm dome tweeter with silver voice coil. Neodymium magnet. Italian production.
