Usually I see quite similar positive and negative spikes in impulse response graphs. I am modeling a driver in Hornresp and I get a very different looking asymmetrical impulse response (+9 -3). What does this mean? Is this good or bad?
I always assumed an impulse response is measured with a full wave. So it is actually a half wave impulse and everything going negative is overshoot?The response of a natural system is asymmetric and there's nothing bad about it. The same applies to the step response. A symmetry on impulse / step responses indicates a constant group delay which is rarely seen in naturally occuring systems. Nothing to worry about.
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Deleted member 375592
How could an impulse response start with a slow dip down, then slope up, and then a peak? Shouldn't it begin with a spike of the direct path?
You're measuring a band limiting system.
An example of step response from system with BW2 HP@20Hz and BW2 LP@22kHz response.
An example of step response from system with BW2 HP@20Hz and BW2 LP@22kHz response.
Hmmm, it is still going over my head. I need layman's terms. I just modeled another woofer in similar enclosure and this one has equal spikes positive and negative.
Is this better or worse than the previous woofer with asymmetrical peak and trough?
Is this better or worse than the previous woofer with asymmetrical peak and trough?
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Deleted member 375592
Symmetric positive and negative spikes indicate that you have a first-order high-pass filter, with +6dB/octave, aka differentiator. The real problem is that your modeled IR is neither bad nor good, but wrong.
No, an impulse response corresponds to the output of a system to an impulse input (below). Here, the impulse is centered at zero time, but it could be anywhere.
The 'best' impulse response is the one that is closest to the impulse itself.
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The real problem is that even after reading articles about impulse response I still don't understand. What does impulse response have to do with high pass filters and how are both graphs wrong?
Explanations quickly go into Fourrier transfer functions and then I am totally lost. Can someone explain impulse response as if they are talking to a 14 year old.....that is probably my level of understanding physics.
My current understanding goes as far as knowing short spike duration with minimal squiggles afterwards is best. But that isn't really understanding much....
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Deleted member 375592
You need the classic: Richard Hamming's "Digital Filters". It is been translated into all languages of the world and can be found in any university library.
How do I know the assumed input in the Hornresp IR graph? Which of the graphs is closest to the input?
That's a fairly standard thing in control theory and signal processing. To know more, you might actually have to visit that university library mentioned above. Or maybe Mr. @David McBean could help you with using Hornresp.
Example of the test signal vs a different kind of full-range speaker:
https://www.stereophile.com/content/quad-esl-63-loudspeaker-measurements
https://www.stereophile.com/content/measuring-loudspeakers-part-two-page-2
"An impulse response is extremely hard to interpret, not least because, with a loudspeaker, it is visually dominated by the tweeter's output. Its shape doesn't really tell you much in itself about woofer and midrange-unit behavior."
. . .
"What I have found more useful as a diagnostic tool is the speaker's step response. Instead of driving the loudspeaker with a single rectangular pulse, you feed it a voltage which instantaneously rises from zero to a positive value and stays there (fig.10). This has practical certain problems, so I use the MLSSA software to calculate a loudspeaker's step response from its impulse response. A plot of the step response appears to give more-or-less equal visual weighting to the outputs of all of a speaker's drive-units. You can now glean a lot more information about the lower-frequency drivers, as well as getting a good idea of how time-coherent the speaker is."
https://www.stereophile.com/content/quad-esl-63-loudspeaker-measurements
https://www.stereophile.com/content/measuring-loudspeakers-part-two-page-2
"An impulse response is extremely hard to interpret, not least because, with a loudspeaker, it is visually dominated by the tweeter's output. Its shape doesn't really tell you much in itself about woofer and midrange-unit behavior."
. . .
"What I have found more useful as a diagnostic tool is the speaker's step response. Instead of driving the loudspeaker with a single rectangular pulse, you feed it a voltage which instantaneously rises from zero to a positive value and stays there (fig.10). This has practical certain problems, so I use the MLSSA software to calculate a loudspeaker's step response from its impulse response. A plot of the step response appears to give more-or-less equal visual weighting to the outputs of all of a speaker's drive-units. You can now glean a lot more information about the lower-frequency drivers, as well as getting a good idea of how time-coherent the speaker is."
I just discovered the impulse spectrogram in Hornresp and that seems more informative/intuitive.
Impuls response is calculated from frequency response and phase. Its useful to see polarity of driver, also to estimate flight time of sound and maybe blending of multiway speaker at design axis. I dont know other useful meaning of impulse response.