Post ringing

PhilActiveAudio
Posts: 55
Joined: 21 Jan 2021 21:51

Post ringing

Post by PhilActiveAudio » 07 Sep 2021 22:51

Hi Uli,

While I am testing the various functions of Acourate to improve my understanding, I am probably doing some mistakes when performing logsweep measurements, pulse processing or playing with room macros. So far, I am using several logsweeps performed at 1,2m that were intended to measure drivers delay. It is thus not a room measurement but it is enough to learn how to create a 3 voices crossover and then generate filters that are being used with Roon. The resulting filter is not that good but good enough to listen to music :D.

However, I found that if I was able to get rid off (or almost) pre-ringing, I am having post-ringing that I can not remove. Reducing or enlarging FDW in macro 1 and/or 4 does not remove post-ringing...
Post ringing.JPG
Post ringing.JPG (47.63 KiB) Viewed 2001 times

In general, what could be the cause of post-ringing in the step response?
What should I do to limit or remove post-ringing?

For your information, my room is large (5,5m x 8m) but not treated (it is my leaving room). And there are many sources of reflection (concrete walls, wooden floor, lot of windows)
exaSound e68 DAC ==> class D / Accuphase / class D ==> Jensen Supravox / Arai Radian / Fostex
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UliBru
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Re: Post ringing

Post by UliBru » 08 Sep 2021 09:19

Do you mean the oscillations between time 0.062 and 0.064?
With high chance these oscillations are connected to to a rapidly falling frequency response at high frequencies.
Sometimes users do not run the logsweep to fs/2 = 24 kHz (q 48 kHz samplerate) but just to e.g. 20 kHz
This is equivalent to running a sweep to fs/2 but with a brickwall lowpass 20 kHz. The steep slope causes ringing. It cannot be removed by any filter setting.
So a picture of the corrected frequency response will tell more.
Stay well tuned
Uli

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Acourate system: JRiver/Roon -> AcourateConvolver -> miniDSP U-DIO8 -> TacT M/S2150 amps -> DIY horn speakers
PhilActiveAudio
Posts: 55
Joined: 21 Jan 2021 21:51

Re: Post ringing

Post by PhilActiveAudio » 08 Sep 2021 19:01

Yes, I mean these oscillations. I understand from your post that it is not post ringing.
I did the recording at 96 kHz but the sweep was limited at 30 kHz as the mic and the tweeter may not go beyond. Should I go at 48 kHz?

Here is the left pulse:
LPulse.JPG
LPulse.JPG (251.06 KiB) Viewed 1973 times
One comment: the High Frequency Treatment in Room macro 1 was set to 25 000 Hz. May that be the root cause?
exaSound e68 DAC ==> class D / Accuphase / class D ==> Jensen Supravox / Arai Radian / Fostex
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UliBru
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Re: Post ringing

Post by UliBru » 08 Sep 2021 22:26

The 30 kHz limitation causes the ringing.
But: if you measure up 48 kHz this does not necessarily help. Because the the tweeter and the mic also has to go up to 48 kHz.
Otherwise you see the ringing of the tweeter/mic lmitiation.
Stay well tuned
Uli

Moderator
Acourate system: JRiver/Roon -> AcourateConvolver -> miniDSP U-DIO8 -> TacT M/S2150 amps -> DIY horn speakers
PhilActiveAudio
Posts: 55
Joined: 21 Jan 2021 21:51

Re: Post ringing

Post by PhilActiveAudio » 09 Sep 2021 13:14

If I understand well, should I now perform logsweep measurement at 48 kHz with a measurement limited at 24 kHz ?
Can I convert 96 kHz measurement to 48 kHz with Acourate ?
exaSound e68 DAC ==> class D / Accuphase / class D ==> Jensen Supravox / Arai Radian / Fostex
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UliBru
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Re: Post ringing

Post by UliBru » 09 Sep 2021 13:37

Hi Phil,

I would recommend to record again with 48 kHz samplerate and sweep end frequency 24 kHz.
This is what I always recommend.
A samplerate conversion is possible but it introduces an additional necessary brickwall filter. Which will also show up ringing.

Anyway it should be clear that you cannot correct what you cannot measure, e.g. high frequency limitation by tweeter, microphone or sweep end parameter.
Stay well tuned
Uli

Moderator
Acourate system: JRiver/Roon -> AcourateConvolver -> miniDSP U-DIO8 -> TacT M/S2150 amps -> DIY horn speakers
PhilActiveAudio
Posts: 55
Joined: 21 Jan 2021 21:51

Re: Post ringing

Post by PhilActiveAudio » 09 Sep 2021 21:24

Thanks Uli, I will do so.
exaSound e68 DAC ==> class D / Accuphase / class D ==> Jensen Supravox / Arai Radian / Fostex
PhilActiveAudio
Posts: 55
Joined: 21 Jan 2021 21:51

Re: Post ringing

Post by PhilActiveAudio » 13 Sep 2021 17:52

I made some new measurements at 48 kHz / 24 kHz and then proceeded with Room macros. I still have the same issue with oscillations as you can see below:
Pulse 48.jpg
Pulse 48.jpg (154.18 KiB) Viewed 1925 times
Any idea of what the problem is as the 48 kHz did not correct the issue?
I can't tell if I can hear it or not... but it is quite weird.

I look back to Mitch book or Archimago article. They sometimes measured at 96 kHz with a sweep end set at 30 kHz but did not seem to face any problem later on. I am a bit lost...
exaSound e68 DAC ==> class D / Accuphase / class D ==> Jensen Supravox / Arai Radian / Fostex
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UliBru
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Re: Post ringing

Post by UliBru » 13 Sep 2021 19:55

Please also post the according frequency response of the test convolution
Stay well tuned
Uli

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Acourate system: JRiver/Roon -> AcourateConvolver -> miniDSP U-DIO8 -> TacT M/S2150 amps -> DIY horn speakers
PhilActiveAudio
Posts: 55
Joined: 21 Jan 2021 21:51

Re: Post ringing

Post by PhilActiveAudio » 13 Sep 2021 21:28

Recording was made at 48 kHz, 1,5m distance and 1m height (to prepare XO), from 10 Hz to 24 kHz, with standard values for fade in and fade out.

Pulse left:
Pulsu48L.JPG
Pulsu48L.JPG (278.88 KiB) Viewed 1921 times
Pulse right:
Pulsu48R.JPG
Pulsu48R.JPG (282.55 KiB) Viewed 1921 times
exaSound e68 DAC ==> class D / Accuphase / class D ==> Jensen Supravox / Arai Radian / Fostex
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