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Does step/impulse response matter?

bachatero

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I'm wondering if there is an audible effect of the step/impulse response of a speaker based on what kind of damping it has and how long the response lasts. I would assume the perfect impulse response is the dirac function (H(0) = 1, H(t) = 0 otherwise) and the step response is a perfect stair step, but no speaker I've seen comes even close to that. It looks like most speakers have an underdamped response with a couple specific ones being critically damped and none overdamped. Why is this?
 
To get a perfect step response would require bass extension to DC. Short of that, you end up with sort of a right triangle shape. The best step response I have seen is the Kii Three. (Stereophile's measurements here: https://www.stereophile.com/content/kii-audio-three-loudspeaker-measurements). Speakers are generally not designed with overdamped bass because that results in a drooping low end response, and frequency response is the most audible parameter, i.e., the relative lack of bass will be more objectionable (to most) than the increased ringing of a critically damped (maximally flat) alignment.
 
From that article, it looks like the "perfect" step response comes with an absurdly high latency, while the underdamped one has low latency. Is this the reason why other speakers like studio monitors with low latency always look underdamped?
 
Tweeter from the RS Minimus 77:
m77.png


Morel MDT30s:
mdt30s.png



Morel MDT39:
mdt39.png


The Morels are ferro-fluid damped and the RS is not.
 
All frequencies!

He is referring to @sam_adams post showing the step response of the tweeters. So those are tweeter frequencies.

Anyway, to answer the OP's question: does step response matter? Depends on whom you ask. If you ask Amir, he does not see much value in it. He has said on a few occasions that he only posts step response for the ASR people who want it.

If you ask anybody who DSP's, then yes it matters. It is very good for spotting pre and post ringing. The second peak should not be higher than the first peak, and the rise time of the step response should be as short as possible. The length of the step response is a good indicator of post-ringing.
 
Anyway, to answer the OP's question: does step response matter? Depends on whom you ask. If you ask Amir, he does not see much value in it. He has said on a few occasions that he only posts step response for the ASR people who want it.
Since step response and frequency response are tautological, they must surely both matter equally. My understanding is that Amir prefers frequency response to present his formal standardized measurements. I completely agree with him. Otoh, I think questions like the OPs are valuable in teaching us about or reminding us to bear in mind the relationships between time and frequency domain response. The well-known mechanical engineering concept of damping is relevant in loudspeaker design and made an appearance in this thread thanks to step response, usefully related to bass performance by @Another Bob .
 
Is this the reason why other speakers like studio monitors with low latency always look underdamped?
Yes, one is the corollary of the other.
 
Yes, one is the corollary of the other.
I beg to differ. Although in the case of the Kii, the processing is both causing the latency and modifying the low end response/damping, one might have processing in the system that creates latency with no effect on damping whatsoever. Conversely, one could build a highly damped, passive speaker that would have essentially no latency. Here are the Stereophile measurements of the Thiel CS2.4 that shows a pretty good step response: https://www.stereophile.com/content/thiel-cs24-loudspeaker-measurements Since it is a passive design, there is no latency.

It should be noted that there are multiple causes of wiggles in the step response. The wild swings one sees near the leading edge are usually due primarily to the lack of time alignment between the drivers. This is what you see in the Kii Three "Minimum" setting. There are plenty of debates over whether time alignment is audible. Lack of driver damping generally appears later, and in fact woofer ringing will be most visible beyond the narrow time window provided in the Stereophile measurements.
 
Some woofers to compare against the tweeters. Measurements done on a baffle unless otherwise noted.

Silver Flute W17RC38:

W17RC38.png


GRS 6PR-8:

GRS 6PR-8.png


Heppner 4846-SD:

Heppner 4846-SD.png


Faital Pro 5FE120-8:

Faital Pro 5FE120-8-P.png


Faital Pro 5FE120-8 (Same driver as the above but in an enclosure with lots of poly-ether foam damping.):

Faital Pro 5FE120-8-B.png
 
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