I'm in a bit of a dilemma, I'm not sure whether or not loudspeaker diaphragms are acoustically transparent or the degree to which it effects their motion.
A few ideas,
Below the fundamental mode of the enclosure, the air behaves with a single phase. The acoustic forces (and their effects on diaphragm motion) within the enclosure could be described accurately by the air compliance.
Within the modal region of the enclosure, the air has a multi-dimensional phase property, however Ray acoustics still do not apply. The acoustic forces (and their effects on diaphragm motion) within the enclosure could be described accurately by analyzing the modal surface encompassing the diaphragm.
Above the Schroeder frequency of the enclosure, we'll assume Ray acoustics apply. In this region, acoustic waves should be propagating through the enclosure space (ie reflections will be present due to the impedance mismatch between the air and enclosure walls/diaphragm). It is over this bandwidth that the effects of the acoustic transparency of the diaphragm have me curious.
At the interface between two dissimilar masses, an impedance mismatch is found. This is the reason we observe reflections.
Above the Schroeder frequency, reflections are believed to occur. If we assume a reflection occurs, we must also assume the presence of an impedance mismatch.
Let's assume we have two masses (Mass A = air, Mass B = loudspeaker diaphragm). We assume a propagating wave (Mass A --> Mass B) contacts the interface between the two masses. At the interface we observe a reflection (wave is reflected back to Mass A), however some of the energy is absorbed by Mass B.
Wouldn't this dictate that propagating waves have an influence on diaphragm motion due to the impedance match (ie 100% reflections are not observed) and we must thus consider their influence if we wish to accurately simulate a loudspeaker system?
Over what bandwidths should the impedance match be considered?
If any of my assumptions are inaccurate or incomplete, I would much appreciate some feedback.
Thanks,
Thadman
A few ideas,
Below the fundamental mode of the enclosure, the air behaves with a single phase. The acoustic forces (and their effects on diaphragm motion) within the enclosure could be described accurately by the air compliance.
Within the modal region of the enclosure, the air has a multi-dimensional phase property, however Ray acoustics still do not apply. The acoustic forces (and their effects on diaphragm motion) within the enclosure could be described accurately by analyzing the modal surface encompassing the diaphragm.
Above the Schroeder frequency of the enclosure, we'll assume Ray acoustics apply. In this region, acoustic waves should be propagating through the enclosure space (ie reflections will be present due to the impedance mismatch between the air and enclosure walls/diaphragm). It is over this bandwidth that the effects of the acoustic transparency of the diaphragm have me curious.
At the interface between two dissimilar masses, an impedance mismatch is found. This is the reason we observe reflections.
Above the Schroeder frequency, reflections are believed to occur. If we assume a reflection occurs, we must also assume the presence of an impedance mismatch.
Let's assume we have two masses (Mass A = air, Mass B = loudspeaker diaphragm). We assume a propagating wave (Mass A --> Mass B) contacts the interface between the two masses. At the interface we observe a reflection (wave is reflected back to Mass A), however some of the energy is absorbed by Mass B.
Wouldn't this dictate that propagating waves have an influence on diaphragm motion due to the impedance match (ie 100% reflections are not observed) and we must thus consider their influence if we wish to accurately simulate a loudspeaker system?
Over what bandwidths should the impedance match be considered?
If any of my assumptions are inaccurate or incomplete, I would much appreciate some feedback.
Thanks,
Thadman
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