Marc, I'm afraid that is a resistance plot of a complete 3.6 speaker (including its passive XO). Not just the ribbon itself (with no other drivers and no passive XO components connected).
Andy
Fabrice,
there is a strong possiblity that your measurement method is giving you incorrect results.
Use the scope to show you have a good unclipped signal that is substantially free from noise and interference, don't use it for measurements.
Attach an accurate attenuator to the input of the power amplifier. Switch the attenuation to match the amplifier gain.
Now apply a test signal to the attenuator input.
The input signal should be the same as the output signal.
say you input 1.9Vac @1kHz to the attenuator and it reduces it's output to ~66mVac
That ~66mvac input drives the amplifier to 1.9Vac @ 1kHz.
Now use any DMM to measure the input signal and to measure the output signal since both are 1.9Vac @ 1kHz any inaccuracies in the DMM will result in the SAME reading. You have made a comparison voltage and eliminated the DMM inaccuracies from the measurement.
Now change to 2kHz and repeat. compare input to output. If necessary adjust the attenuator slightly to ensure the input and output voltages are identical.
I use a switched attenuator that has steps of 0.05dB from 0dB to -60dB.
It only uses 12off 2pole 2way manual switches to cover that whole range without any gaps in the steps. But it does need accurate resistors to fit to the T attenuator wrapped around each switch.
there is a strong possiblity that your measurement method is giving you incorrect results.
Use the scope to show you have a good unclipped signal that is substantially free from noise and interference, don't use it for measurements.
Attach an accurate attenuator to the input of the power amplifier. Switch the attenuation to match the amplifier gain.
Now apply a test signal to the attenuator input.
The input signal should be the same as the output signal.
say you input 1.9Vac @1kHz to the attenuator and it reduces it's output to ~66mVac
That ~66mvac input drives the amplifier to 1.9Vac @ 1kHz.
Now use any DMM to measure the input signal and to measure the output signal since both are 1.9Vac @ 1kHz any inaccuracies in the DMM will result in the SAME reading. You have made a comparison voltage and eliminated the DMM inaccuracies from the measurement.
Now change to 2kHz and repeat. compare input to output. If necessary adjust the attenuator slightly to ensure the input and output voltages are identical.
I use a switched attenuator that has steps of 0.05dB from 0dB to -60dB.
It only uses 12off 2pole 2way manual switches to cover that whole range without any gaps in the steps. But it does need accurate resistors to fit to the T attenuator wrapped around each switch.
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