5.5″ woofers

Our 1961 series utilize 5.5″ woofers that are built around the same core fundamentals as their bigger brothers from the 1723 series. The cone body is the same, using long fibre pulp paper with our proprietary coating that ensures covering a wide frequency range from the deepest bass to well above 1500Hz without any hint of cone resonance. The cone material also makes it inherently self-damped which results in a natural sound without coloration throughout the frequency band.The entire surround of the driver is designed to follow the same curvature as our waveguide, so the entire baffle of the speaker has a sleek appearance. No screws or cheap plastic to hide them. The looks are just like on our 1961 Subwoofers and 1723 Subwoofers, except here it is a single integrated piece in the woofer design.

Modelling

While many brands may advertise FEA design and modelling, usually this only refers to the basic magnetic circuit. Arendal Sound has taken the science of transducer modelling to another level. The motor topology is designed first to meet flux density and excursion requirements. Fine-tuning the materials and geometry to minimize flux modulation and stabilize the inductance vs both position and current comes next. Lastly, the voice coil stroke or BL(x) shape is optimized for zero-point centring and symmetry which are the final points for maximizing motor control over excursion and minimizing distortions.

Extensive analysis

To analyse the compliance of both the spider and surround to achieve excursion requirements and optimize Cms(x) to compliment the motor we use non-linear FEA modelling which works on a much deeper level compared to linear FEA modelling analysis. This translates to increased excursion and lower distortions which equals maximum sound quality.We utilize Klippel Laser based diagnostics. It’s a tool often misunderstood, but when used properly in conjunction with component design, a woofer’s design can be dialled in. Klippel testing basically serves to confirm the initial FEA modelling and accuracy of part tooling and offers the diagnostic abilities to allow our engineers to refine the initial designs until final goals for excursion, linearity, stability and distortion are met.

Materials selection and design

Distortion is closely related to how far the cone and motor have to move at a given volume level. Size presents its own engineering challenges, so the motor, suspension and diaphragm all must be delicately balanced to be able to cover the critical midrange frequencies without coloration.We utilize low carbon steel specifically chosen for its ability to carry more flux in the magnetic circuit.

Vented motor structure

The vented T-yoke is CNC milled to final dimensions to ensure tight tolerances, correct fit and to prevent flux robbing losses often found in typical motor assemblies. Vents in the aluminium bobbin as well as the T-yoke, vents in the basket under the spider and in the cone body all together reduce physical and thermal compression, maintaining a hugely dynamic response. This continuous exchange of air mitigates thermal compression and increases the woofer’s overall power handling capability. Second, the airflow relieves asymmetric compliancy and noises (i.e., distortion) due to non-linear compression and rarefaction of air typically trapped under the dust cap and spider. Typical vented pole designs will be limited in effectiveness due to the lack of airflow volume. Meaning, at the highest power and excursion where the airflow is needed most, the pole vent alone will not be sufficient.Aluminium voice coil wire is chosen for its weight and conductivity properties and its lower sensitivity to temperature changes compared to copper. This results in higher efficiency and lower thermal compression. The driver also has a large linear excursion of 13mm peak to peak and a very low inductance design to maximize sound quality, bass response and extension.We use copper shorting rings to reduce inductance, increase frequency bandwidth and lower distortion.Symmetrical suspension consists of critical components such as the NBR surround, polycotton spider material with progressive roll geometry, and integrated tinsel leads. All combined to create very high excursion capabilities with exceptionally linear suspension. Again, this contributes to high output and low distortion at all operating frequencies.