Floor Loudspeaker Reviews

Editor: In his measurements accompanying Art Dudley's revie, John Atkinson found a cabinet resonance at 273Hz. I measured the acceleration of the cabinet with a foam gasket on the woofer (shown in blue in the attached graph), and the acceleration of the cabinet with Mortite and foam on the woofer (shown in red). The 273Hz resonance shown in John's waterfall plot has been removed with this simple modification. This indicates that the 273Hz resonance was caused by the coupling of the woofer frame to the cabinet. The addition of the Mortite decouples the woofer from the frame, and the 273Hz resonance is now gone. In addition, some of the higher-frequency spikes are significantly reduced by the decoupling.

Fig.1 Sonist Concerto 3, acceleration of cabinet sidewall, 100Hzñ1kHz, with woofer directly mounted on the front baffle (red trace) and with the woofer decoupled with Mortite and foam (blue trace).

This change will not require any structural modifications to the production cabinet. I will field-upgrade all Concerto 3s already purchased, and will use the Mortite in all future production of the Concerto 3.—Randy Bankert, Sonist Loudspeakers