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Registered Member #60240
Joined: Mon May 16 2016, 07:01PM
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Posts: 304
Using a condenser microphone and the FFT HP3561A analyzer, a 200 Hz square wave signal was fed into an ESL (Martin Logan Sequel II electrostatic loudspeaker):
This is the electrostatic speaker:
FT signal of the 200 Hz square wave of the function generator:
Registered Member #162
Joined: Mon Feb 13 2006, 10:25AM
Location: United Kingdom
Posts: 3141
At 200 Hz and its third,fifth,seventh and probably higher harmonics you are measuring the response of the cone bass/lower-mid speaker. What is the crossover frequency ?
Registered Member #60240
Joined: Mon May 16 2016, 07:01PM
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Posts: 304
The Martin Logan ESL with a 200 Hz square wave:
Signal of the square wave into the amplifier input at the top, 20 mV/cm, 40 mVpp. At the center of the screen the microphone signal 5 mV/cm, 27 mVpp, is shown. At the bottom of the screen the current signal 1 A/cm, 5 App is shown, (output current of the amplifier into the input of the Martin Logan ESL).
FT of the current signal 5 app, center frequency 1 kHz:
FT of the current signal 5 app, center frequency 5 kHz:
Registered Member #60240
Joined: Mon May 16 2016, 07:01PM
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The Martin Logan ESL with 200 Hz sine, the same experimental setup as the 200 Hz square wave:
Signal of the sine wave into the amplifier input at the top, 20 mV/cm, 40 mVpp Center: microphone signal 5 mV/cm, 17 mVpp At the bottom: current signal 200 mA/cm, 900 mApp (output current of the amplifier into the input of the Martin Logan ESL).
As you can see, in contrast to the square wave, there is full agreement of the waveforms of all three signals (amplifier input, amplifier output or loudspeaker input and microphone signal)
FT of the current signal 900 mApp, center frequency 1 kHz:
Spectrum-pure sine of 200 Hz of the current signal 900 mApp.
Registered Member #60240
Joined: Mon May 16 2016, 07:01PM
Location:
Posts: 304
The Martin Logan ESL with 5 kHz sine, the same experimental setup as the 200 Hz square wave:
Signal of the sine wave in the amplifier input at the top, 20 mV/cm, 40 mVpp Mid microphone signal 5 mV/cm, 6 mVpp Down current signal 500 mA/cm, 1.25 app (output current of the amplifier into the input of the Martin Logan ESL).
As you can see, in contrast to the rectangle, there is full agreement of the waveforms of all three signals (amplifier input, amplifier output or loudspeaker input and microphone signal)
FT linear of the current signal 1.25 app, center frequency 25 kHz:
FT log of the current signal 1.25 app, center frequency 25 kHz:
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200 Hz square wave into an ESL analyzed by a HP3561A
