Constrained Layer Damping

ATC’s programme of research and development has generated many loudspeaker technologies – from small details to major innovations. Constrained Layer Damping (CLD) is a driver cone technology from ATC that represents another advance in driver performance – one that transfers directly to system performance and the reproduction of music.

A fundamental trade-off in the properties of a driver cone is mechanical stiffness versus mechanical damping. High stiffness tends to produce a cone with extended axial frequency response but with poor off-axis response and multiple high Q resonances. High mechanical damping however, while improving a cone’s resonant behaviour, tends to increase moving mass reducing efficiency. CLD is a new approach to cone damping that brings the advantages of high damping with a smaller mass increase.

Conventional cone damping techniques involve the application of damping compounds directly to one or both side of a semi-rigid cone. With CLD, two lightweight cones sandwich a constrained damping layer. Constrained layer damping is effective because, as the cone flexes, the damping material is forced into a shape that shears adjacent material sections. The alternating shear strain dissipates the vibration energy as low grade frictional heat.

The enhanced damping performance of CLD can bring significant improvements to bass/mid drivers incorporating the technique. Three areas of driver performance benefit:

•Harmonic Distortion: The harmonic distortion is typically reduced between 300Hz and 3kHz compared to a conventionally constructed cone.

•Axial Frequency Response: The resonance free frequency response can extend a further octave higher so easing constraints on cross-over filter frequencies and slopes.

•Off-axis Response: Thanks to its effective damping the dispersion performance of a CLD cone approximates to that of a smaller driver as its effective radiating area gradually reduces with frequency.

Loudspeaker Technology Ltd, Gypsy Lane, Aston Down, Stroud, Gloucestershire, GL6 8HR.
Tel: +44 (0)1285 760561 Fax: +44 (0)1285760683 Email:

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