Direct Impulse Response measurements

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soongsc

soongsc

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Joined 2005
Different signals may be processed using different windowing automatically, I guess you have to figure it out as nobody seems to have experience with this device. Why don't you move it into more open area if you want better results? Why not use devices specifically for speaker measurement?
 
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jzagaja

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Joined 2004
instagram.com/stettinerhorn/
Windowing is the same in this three examples. The only difference is aliasing filter on green curve (Digigram VX440). I probably overloaded my amplifier because you can see blue curve (8Hz) is distorted and resulting FFT is highly nonlinear. I've used an old 9V battery for Vcc of my generator (it has fixed output from external supply). Stabilized power supply doesn't work :confused:
 
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jzagaja

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Joined 2004
instagram.com/stettinerhorn/
Stabilized PSU now works but on low unbalanced output (+5V) there's a ultrasonic ringing (16us), 16% of max. amplitude. It can be due to PSU (switching regulators) or IG's (impulse generator) opto-isolator.

External amplifier can be omitted but then square wave looses low frequencies (why)?

Schoeps has sent me Manger MSW step record (Microtech Gefell MK301 ref. microphone). Interestingly overall rise time is much slower than advertised 13us. Amplifier is -3dB@70kHz. Overall response is resonant free however well known impedance mismatches occurs. Maximum speed of JXR6 is 36us as advertised. I cannot upload any more images.
 
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jzagaja

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Well Schoeps says ~30us - see appended picture. Jordan is down sampled from 1MHz to 192kHz sample rate. What is new? Please see MSW response from Schoeps MK2. You see no pre ringing and nice differentiation. Normally differentiation leads to "noisy" result seen on my measurements. Please don't confuse this pre ringing with aliasing filters and indirect methods of impulse response calculation. This is a RAW data.
 

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soongsc

soongsc

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Joined 2005
jzagaja said:
Well Schoeps says ~30us - see appended picture. Jordan is down sampled from 1MHz to 192kHz sample rate. What is new? Please see MSW response from Schoeps MK2. You see no pre ringing and nice differentiation. Normally differentiation leads to "noisy" result seen on my measurements. Please don't confuse this pre ringing with aliasing filters and indirect methods of impulse response calculation. This is a RAW data.
Click to expand...


jzagaja said:
And resulting FFT in comparison to 40us pulse without amplifier on JXR6.

Do you think we have a Doppler effect on JXR6 when heaviside pulse is used? HF resonances are shifted upwards and membrane excursion was strong and visible.

It looks like microphone noise has big influence on differentiation.
Click to expand...
I do have a few comments:
1. Measurements using different mics will have different results due to difference in mic performance and bandwidth.

2. Measurements in comparison need to be in the same location with the same type of mounting. This means if you measure in a different room and/or use a different baffle it's hard to make comparisons.
 
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phase_accurate

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Joined 2002
No I mean there must be a series output cap at the mic's output which forms a highpass togehter with the input that it drives. The lower the input impedance - the higher the cutoff.

A cap between the output and ground will definitely form a lowpass - what you absolutely don't want for this type of measurements..

Regards

Charles
 
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