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Old 15th November 2013, 07:18 AM   #1
Juhazi is offline Juhazi  Finland
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Default Step response ringing

I posted these in my AINOgradient thread but so far discussion is minimal,

What is the importance of ringing in impulse/step response of a transducer?

I measured two dynamic coil drivers and planar/ribbon B&G Neo8-PDR in dipole minimal baffle. Responses, distortion and decay are naturally different but not much,

Here are ETC, impulse and step responses (ne-95 different polarity)

ETC is fastest for Neo8, but it has ringing Step response - Wikipedia, the free encyclopedia
The phenomena of oscillation about final value is called ringing. The overshoot is the maximum swing above final value, and clearly increases with μ. Likewise, the undershoot is the minimum swing below final value, again increasing with μ. The settling time is the time for departures from final value to sink below some specified level, say 10% of final value.

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Last edited by Juhazi; 15th November 2013 at 07:34 AM.
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Old 15th November 2013, 11:54 AM   #2
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I wouldn't ascribe too much to the ringing of a step or impulse response.

Remember that an impulse is similar to a white noise source. Half of its energy is in the top Octave so it higlights tweeter ringing that may be at a supersonic frequency. Lots of metal domes ring out of band and have poor looking impulses because of it. Unless you have "bat hearing" it probably won't be audible.

If you have a good eye and practice you can see some details in a multiway steo, such as relative driver polarity and delay. Still, I wouldn't say those matter, just that they might be revealed.

Step response is similar, but integrated, so bass end is a little more visible.

Best thing to do with an impulse is FFT it so that you can see frequency response.

David
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Old 15th November 2013, 02:17 PM   #3
Juhazi is offline Juhazi  Finland
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These graphs ar from REW measurements, it does a sine sweep (here 100Hz -20kHz). Single drivers without any xo or eq.

This is amplitude response from those.from a sweep Below is a new attachment from a sweep just 500-10000Hz
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File Type: png neo8 sweep step 500-10000hz.png (79.0 KB, 173 views)
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Old 15th November 2013, 04:16 PM   #4
gedlee is offline gedlee  United States
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Impulse responses can be a decent diagnostic tool, but as Dave says, you have to be careful about how you look at them. The HFs will always appear the most obvious. Look for ringing that occurs somewhere out away from the initial decay, such as the ETC peak at 7 ms in the red curve. Except that I suspect that 7 ms peak is from your room. But a peak like that would be an issue for me and I might investigate further if I knew that it was not from the room - say at 2 ms. I often look at the frequency response over a limited range of the impulse response to see if something shows up (say 1-3 ms if there is a peak at 2 ms). Of course doing this makes the resolution very poor, but it can sometimes tell you the frequency range of a potential problem. Then go and look at the frequency response in that frequency range, or better yet the polar response and see if something is apparent.

If, for example, there is an aberration in the polar map then you can use the impulse response timing (2 ms in the example) and the speed of sound to see if you can trace down something, although this doesn't always work since it could be structural and the speed of sound is different.

Never use the impulse response alone as it is only useful in the context of its frequency response.

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Old 15th November 2013, 07:20 PM   #5
Juhazi is offline Juhazi  Finland
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Ok, if one cannot hear driver's impulse ringing.

If that kind or response would show up in an amplifier, no one would use it!

http://cc.ee.nchu.edu.tw/~aiclab/tea...AIC/lect10.pdf
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File Type: png step ringing amp.png (50.8 KB, 154 views)
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Old 15th November 2013, 08:24 PM   #6
gedlee is offline gedlee  United States
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NO, no one said that. You certainly can hear impulse response ringing, just not what you see on the very early part of the impulse response. That's too high in frequency. You need to look later and with a wider wavelength.

Ringing like you show in an amplifier implies instability. As a passive device a speaker cannot be unstable so that very HF ringing is not the same issue as it is in an amp. But is an amp had a 3 dB peak at 25 kHz it would not be audible, yet would show up as a serious ringing in the impulse response. A peak at 3 dB 100 Hz would be barely visible because of its long period and yet would be quite audible.
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Old 16th November 2013, 08:45 AM   #7
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Ok, so we don't care about what happens during first 0,3ms but focus on what happens during first 5ms period.

In this perspective ribbon Neo8 is superior to Vifa NE95 and Audax HM100. We can see the first room reflection coming at 7ms. The Audax is considered one of all-time fastest 4" cone drivers, and it really is superior to the modern neo-motor Vifa NE.

This impulse/step response graphics is the same thing that we see in CSD graphs, then we have also frequency icluded.
Attached Images
File Type: png etc step combi text.png (176.8 KB, 42 views)
File Type: png neo8 raw 0¤ csd 1ms rise.png (147.5 KB, 38 views)
File Type: png hm100z csd 1msrise.png (148.7 KB, 30 views)
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Old 16th November 2013, 10:26 AM   #8
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Quote:
Originally Posted by Juhazi View Post
Ok, so we don't care about what happens during first 0,3ms but focus on what happens during first 5ms period.
I wouldn't say that, more that each time span relates to a particular frequency range.

Your red curve is quite distinctive with some clear ringing. It looks to me like there are 5 cycles in 400 usec. Thats 5 cycles in 0.4 msec or 12.5 cycles in 1 msec.... 12.5 kHz. In the frequency response curve there is a strong peak at that frequency so we know that the peak and the ringing are one and the same.

At the same time the response dip at 7kHz should be clearly audible but I'm not seeing it in the time response. I'm sure it is there somewhere but it isn't obvious.

If we look at the blue frequency response there is a pretty strong prominance at 2kHz. That would correspond with a period of 500 uSec. I do see an inflection a 600 uSec that might correspond with it. Hard to say if that is truly periodic without seeing a longer trace.

I think that is the point. Some strong aberrations in the upper frequency range can be picked out of a step or impulse response, but the frequency response is much easier for us to get meaning from.

David
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Old 16th November 2013, 12:11 PM   #9
Juhazi is offline Juhazi  Finland
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This is kind of funny - I slipped and fell on my b*tt this morning when getting the papers from the mailbox, so I can't go out and enjoy the nice weather today...

I made some new measurements of Neo8 and Audax. Raw drivers handheld at 10cm from microphone. REW sweeps of limited frequency.

ETC and Step response 500-600Hz, 4000-4500Hz and 10000-10500Hz

I am planning to use Neo8 with LR4 xo at 800Hz and 4500Hz, the most comfortable dipole range it has.
Attached Images
File Type: png etc step audax neo8 500-vert.png (134.1 KB, 39 views)
File Type: png etc audax neo8 4000-vert.png (133.6 KB, 33 views)
File Type: png etc step audax neo8 10000-vert.png (156.8 KB, 28 views)
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Old 16th November 2013, 04:41 PM   #10
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handheld measurements are useless.
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