Here's what Harbeth has to say (From their website)....
14. What is the importance of the cabinet construction, and what is a 'thin wall cabinet'?
Everything in the universe resonates, and that definitely includes loudspeaker cabinets! Some resonances are rather useful - such as the fundamental resonance of the air mass inside the cabinet which acts as a spring against the bass/mid diaphragm (cone) and when correctly proportioned, permits a good system bass response. Other resonances are not so useful or desirable, but result from Newton's Second Law of motion: 'every action has an opposite and equal reaction'. For example, as the cone moves inward, the cabinet must, by definition, push back against it, and this sets up peaky resonances inside the cabinet structure which are measurable outside the cabinet with suitable equipment.
At the design stage of a speaker system we need to be aware of the contribution of the cabinet walls to the overall sound perceived by the listener, even if not in the system's frequency response curves. At certain frequencies, untreated wood will be so acoustically transparent that sound waves will pass through it from inside the cabinet as if it is almost invisible; at some (and hopefully different) frequencies the combination of the panel's stiffness and mass will encourage it to sympathetically resonate with notes in the music. Taming these panel resonances is extremely time consuming at the design stage, and demands great attention to the smallest details of the cabinet construction, measuring equipment much trial-and-error. Whatever solution one arrives at, the best one can achieve is to suppress a panel's output and/or to steer it into a frequency band where it is either inaudible or benign: this implies at the bottom end of the audio spectrum.
It is self evident that if the 'raw' untreated panel is thin, that damping that applied damping will have a proportionately greater beneficial effect than if the panel is thick, where no amount of conventional surface damping can adequately suppress latent peaky resonances. The superiority (although at very high cost) of the 'thin wall' panel philosophy was invented and used by the BBC from the 1960's, backed up by measurements and Research, and is, to our mind, the best overall solution for an acoustically quiet mid band, where the ear is extremely sensitive to buried resonances.
14. What is the importance of the cabinet construction, and what is a 'thin wall cabinet'?
Everything in the universe resonates, and that definitely includes loudspeaker cabinets! Some resonances are rather useful - such as the fundamental resonance of the air mass inside the cabinet which acts as a spring against the bass/mid diaphragm (cone) and when correctly proportioned, permits a good system bass response. Other resonances are not so useful or desirable, but result from Newton's Second Law of motion: 'every action has an opposite and equal reaction'. For example, as the cone moves inward, the cabinet must, by definition, push back against it, and this sets up peaky resonances inside the cabinet structure which are measurable outside the cabinet with suitable equipment.
At the design stage of a speaker system we need to be aware of the contribution of the cabinet walls to the overall sound perceived by the listener, even if not in the system's frequency response curves. At certain frequencies, untreated wood will be so acoustically transparent that sound waves will pass through it from inside the cabinet as if it is almost invisible; at some (and hopefully different) frequencies the combination of the panel's stiffness and mass will encourage it to sympathetically resonate with notes in the music. Taming these panel resonances is extremely time consuming at the design stage, and demands great attention to the smallest details of the cabinet construction, measuring equipment much trial-and-error. Whatever solution one arrives at, the best one can achieve is to suppress a panel's output and/or to steer it into a frequency band where it is either inaudible or benign: this implies at the bottom end of the audio spectrum.
It is self evident that if the 'raw' untreated panel is thin, that damping that applied damping will have a proportionately greater beneficial effect than if the panel is thick, where no amount of conventional surface damping can adequately suppress latent peaky resonances. The superiority (although at very high cost) of the 'thin wall' panel philosophy was invented and used by the BBC from the 1960's, backed up by measurements and Research, and is, to our mind, the best overall solution for an acoustically quiet mid band, where the ear is extremely sensitive to buried resonances.