Test & measurement
Within a speaker cabinet, using foams and damping materials can drastically alter/improve its acoustic performance. These materials can be divided into two categories: those that selectively absorb energy over a narrow range and those that can shift or move energy elsewhere. All vibrating bodies produce sound pressure waves. These can cause airborne interference, which degrades the overall listening experience. Therefore, an acoustically dead speaker cabinet is required for the optimum cabinet acoustics, and numerous designs exist to match these criteria with varying performance degrees.
Generally speaking, one can split speaker damping into two types of loudspeaker damping – mechanical and electrical. The loudspeaker's suspension and the air load on the diaphragm determine the amount of mechanical damping. Electrical damping is directly related to the resistance load on the speaker, which is the amount of the speaker's cable resistance and the amplifier output impedance.
Here at SoundImports, you can buy mechanical speaker damping material, among others, out of polyester, moulded foam and muhwolle from our premium brands Monacor, Sonic Barrier and Visaton. Acry-Tech also offer a liquid solution – damping coating that gets applied inside the speaker cabinet!
The critical impact of damping in a speaker is to lower the SPL emitted by the diaphragm moving due to inertia after the signal has stopped. The resonant frequency of the moving device would be the frequency of the sound it generates with this movement. The damping material in closed boxes can absorb the back wave of the speaker completely. Since the speaker is almost transparent to sonic waves (a back wave that returns after a reflection on the back wall), some of it will come out of the speaker with a slight pause, resulting in a less-than-clean echo. Vibrations from the inside should not be sent to the outside. Therefore, radiation should only arise from the speaker. As a result, the perfect damping material will dampen the cabinet while still absorbing direct radiation.