Step response of a loudspeaker is a unique, measurable parameter. However, the SW systems I use (Holmimpulse and omnimic) each show impulse response, but offer no display of step reaponse.
What SW out there on the WWW, either commercial or free has the capability to resolve and display step response?
What SW out there on the WWW, either commercial or free has the capability to resolve and display step response?
ideally the step response is just the integral of the impulse response
the step response can make lower frequency effects more human eye visible but for a linear time invariant system contains no new information
speakers do have some nonlinearity and time variable parameters such as voice coil heating, viscoelastic effects in suspension/surround which violate the linear time invariant assumptions built in to most simple impulse/frequency response analysis software
the step response can make lower frequency effects more human eye visible but for a linear time invariant system contains no new information
speakers do have some nonlinearity and time variable parameters such as voice coil heating, viscoelastic effects in suspension/surround which violate the linear time invariant assumptions built in to most simple impulse/frequency response analysis software
Speakerdoctor,
I've seen this as a question in a few places, seems like none of the free measuring softwares can do step response. I can certainly understand it's value especially given D’Appolito's articles detailing the information you can get from it.
I've been thinking, wouldn't it be possible to tell the software to measure impulse, then use the impulse signal to trigger a simple digital circuit (like a 555 timer in a-stable configuration, or microcontroller- you want a long square wave so you don't overheat the speaker with DC). The output of the digital circuit would be a square wave, and the software would record and display the response as an "impulse" but the recorded data would be a step response. Do you think that would work?
I've seen this as a question in a few places, seems like none of the free measuring softwares can do step response. I can certainly understand it's value especially given D’Appolito's articles detailing the information you can get from it.
I've been thinking, wouldn't it be possible to tell the software to measure impulse, then use the impulse signal to trigger a simple digital circuit (like a 555 timer in a-stable configuration, or microcontroller- you want a long square wave so you don't overheat the speaker with DC). The output of the digital circuit would be a square wave, and the software would record and display the response as an "impulse" but the recorded data would be a step response. Do you think that would work?
just plot a running sum of the impulse response data - should look like the step response
may have to remove offset to avoid ramping
may have to remove offset to avoid ramping
Muddtester, you lost me with your last paragraph. Way above my head.
jcx, where do I find impulse response data? FRD file? if that, which column is it?
jcx, where do I find impulse response data? FRD file? if that, which column is it?
jcx,
As you indicated, that does assume a LTI system, which speakers are not. Of course, no real system is LTI, it's just a matter of degree, right? I would imagine that, for speakers, in some cases that's more relevant than in others, but I wouldn't want to risk that without data to back it up.
How would one go about the post processing you're proposing? Is it as simple as exporting the data to a spreadsheet and calculating the running sum? Seems like the amount of data should be manageable that way (at 48KHz sample rate 10ms of data is only 480 points).
As you indicated, that does assume a LTI system, which speakers are not. Of course, no real system is LTI, it's just a matter of degree, right? I would imagine that, for speakers, in some cases that's more relevant than in others, but I wouldn't want to risk that without data to back it up.
How would one go about the post processing you're proposing? Is it as simple as exporting the data to a spreadsheet and calculating the running sum? Seems like the amount of data should be manageable that way (at 48KHz sample rate 10ms of data is only 480 points).
speakerdoctor,
I was suggesting a hack. It would take the impulse that comes from the audio out of the computer that's supposed to go to the amplifier, feed that into a digital circuit that can use the impulse as a trigger (to get the timing right) to generate a square wave that then goes to the amplifier. That way the amplifier gets a square wave instead of an impulse. Electrically speaking, it should be pretty simple to do.
I was suggesting a hack. It would take the impulse that comes from the audio out of the computer that's supposed to go to the amplifier, feed that into a digital circuit that can use the impulse as a trigger (to get the timing right) to generate a square wave that then goes to the amplifier. That way the amplifier gets a square wave instead of an impulse. Electrically speaking, it should be pretty simple to do.
pretty sure the sum is good enough integration approximation for the things that you see more easily in step response
REW - Room EQ Wizard Room Acoustics Software can display step response. JohnM's freeware is excellent.
Impulse Graph - scroll down to see step response.
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