>But the magnetic structure does play a major part in
>distortion, and poor drivers typcially having really
>loose suspensions (high Qms) will simply "ring all
>day long" once you hit them with a few short bursts
>at resonance, no matter what cabinet we put them in
>in attempt to damp the driver.
I think once an amplifier is connected to that system, (or the voice coil is shorted out) its response will be primarily determined by Qes, not Qms. This can be readily verified: take any speaker, disconnect the amplifier from the terminals, then tap on the cone. You may hear a boingy sound, and the speaker's cone will visibly ring -the higher the Qms, the more boingy the sound and the longer the ring. That's because Qms dominates when there are no connections to the speaker's terminals. Now, short the terminals with a piece of cable and tap on the cone again. The boingy sound should disappear immediately and the speaker will cease to ring (unless its Qes is also high, of course). Qes now dominates. The conclusion that can be drawn here is that the effect of Qms on the system's frequency response can typically be ignored once its several orders of magnitude greater than Qes.
>Data published by JBL and others attributes this to a
>concern primarily from the magnetic structure, and
>not the suspension or diaphram.
Perhaps, but if JBL is referring to a weak magnetic structure that's not exerting sufficient control over the cone, this suggests that it is Qes is the issue, not Qms - the weaker the motor, the higher the Qes of the driver. Obviously though, the higher the Qms, the greater the problem as Qes itself increases (Qts will approach Qms).
>But just look at the distortion graphs of any woofer,
>and you'll notice that from about a half octave above
>resonance, distortion rises dramatically
I'm not surprised - excursion rises dramatically as frequency decreases. The rate of increase will depend on the driver's Qts (the higher the Qts, the greater the increase).
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