Something that just popped into my head and I haven’t really thought it through yet... what if you measured a driver's Thiele and Small parameters using very high impedance current drive instead of the usual low impedance voltage drive? For one thing, the Qes would measure a great deal higher. Given that the measured parameters would be different, you then go about constructing a bass reflex box according to these new parameters and feed the driver with a current source amplifier. I wonder what sort of results you would get? For one thing, the cone displacement would likely shrink right down at the box/port resonant frequency, more than usual.
This question is not simply about the usual ins and outs of feeding a driver with a current source signal. That has been done to death. This is about feeding a driver with a current source signal while it is in a bass reflex box that has been calculated from a driver that has had its parameters measured using a current source signal.
Edit-> I just realised that the resistor you put in series with the speaker to do the measurements in the normal fashion turns the signal into more or less a current drive anyway. Told you I hadn’t thought it through...
This question is not simply about the usual ins and outs of feeding a driver with a current source signal. That has been done to death. This is about feeding a driver with a current source signal while it is in a bass reflex box that has been calculated from a driver that has had its parameters measured using a current source signal.
Edit-> I just realised that the resistor you put in series with the speaker to do the measurements in the normal fashion turns the signal into more or less a current drive anyway. Told you I hadn’t thought it through...
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Nice thought experiment.
Qes however is a property of the woofer itself, not of the woofer + amplifier + box. The same holds true for other T&S parameters. The measurement process of T&S parameters typically is based on measuring the woofer impedance (including phase and at different frequencies), by making a voltage divider comprising the woofer and a known resistor. Then the their voltage drops (and phases) are compared, which tells us the impedance of the woofer. As it is a voltage divider, it does not matter whether it is being driven by a current source or a voltage source. Another way to view it, is that it would be strange if the impedance of some component (like a woofer) would depend on the impedance of what is driving it (like an amplifier).
The above ignores non-linearities (which are not captured in the T&S parameters anyway). Of course additional steps are required to find all parameters, like weighting the cone, putting the woofer in a known box, measuring moving mass, measuring cone diameter etc.
One step back, your thoughts can still be simulated. If you set Qes of a specific woofer to infinite (current drive offers no electrical damping) and then design a box for it, it would be designed for current drive. The frequency response will not be flat, because Qts becomes equal to Qms, which usually is larger than 0.7. Then plug in the real parameters to see what happens with voltage drive.
Qes however is a property of the woofer itself, not of the woofer + amplifier + box. The same holds true for other T&S parameters. The measurement process of T&S parameters typically is based on measuring the woofer impedance (including phase and at different frequencies), by making a voltage divider comprising the woofer and a known resistor. Then the their voltage drops (and phases) are compared, which tells us the impedance of the woofer. As it is a voltage divider, it does not matter whether it is being driven by a current source or a voltage source. Another way to view it, is that it would be strange if the impedance of some component (like a woofer) would depend on the impedance of what is driving it (like an amplifier).
The above ignores non-linearities (which are not captured in the T&S parameters anyway). Of course additional steps are required to find all parameters, like weighting the cone, putting the woofer in a known box, measuring moving mass, measuring cone diameter etc.
One step back, your thoughts can still be simulated. If you set Qes of a specific woofer to infinite (current drive offers no electrical damping) and then design a box for it, it would be designed for current drive. The frequency response will not be flat, because Qts becomes equal to Qms, which usually is larger than 0.7. Then plug in the real parameters to see what happens with voltage drive.
Not necessarily, measuring T&S parameters with a resistor of 0.1 ohms is perfectly acceptable. It is done this way because it makes poor use of the dynamic range of the sound cards analog to digital convertors.
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