How about using some of that air pumping functionality to cool the coil?
Add a sub chamber and and a mechanical diode (one way valve for the air) and project it along the coil or better inside it.
Now only do this at the exteme travel points and add damping and only pump cooling air when at max power when you need it.
That's not something you can rely on either.
For example, suspension compliance will change significantly with temperature, changing both the resonant frequency and impedance peak. Moving mass, on the other hand, should remain constant. :-)
Good point. But the *rise* in impedance should be linear with temperature. so, if you take a 25C measurement across the spectrum, you should get a nice linear increase across the full spectrum as temperature increases.
Author has briefed an important topic and triggered my thoughts. Always there is research going on improving the quality of the sound produce by the loud speakers. This is because the loud speaker efficiency is around 5% maximum. When it comes to fidelity again a quite a lot of limitations. This is because the speaker has to reproduce about more than a 1000 different types musical instruments sounds from a big drum to a smallest string instrument.So naturally it is difficult to design a single transducer to reproduce these sounds.And micro loudspeakers really tough to satisfy.Researchers can think of any other new type of transducer.
While what the author is stating is true it is much more important to provide a means of acoustic control over the diaphragm. The low frequencies need not be limited by back EMF nor the highs by inductance if a means to provide constant pressure behind the driver is provided. Typically the driver will have a more shallow roll off and not experience as much breakup under these conditions. Pat.7207413 B2 and others pending to allow for dynamic volume modification of the enclosed volume behind the driver. Impedance variations are also not as aggressive and critically damped resonance peaks enhance bass response. These conditions are established pre-electronics allowing for less aggressive DSP requirements to fix the speaker.
It is not strictly correct to state that loudspeaker impedance rises linearly with temperature. Only the resistive part of impedance due to the voice coil behaves this way.
Over most of the frequency range of a typical moving coil loudspeaker, the impedance is dominated by either the motional impedance caused by back-emf at low frequencies, or voice coil inductance at high frequencies. It is only essentially resistive in a narrow frequency range between these two, where it is largely determined by the voice coil resistance.
Any attempt to infer temperature by measuring current, must therefore take this into account (presumably by bandpass filtering the current sense signal).