Only correct under Schroeder freq?

k_kovacs
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Joined: 15 Jul 2021 17:11

Only correct under Schroeder freq?

Post by k_kovacs » 16 Sep 2021 04:04

Helo I want to correct only under Schroeder freq. Nothing at all above. How do I do this?

Cheers
Mitch Barnett
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Joined: 19 Oct 2019 18:05

Re: Only correct under Schroeder freq?

Post by Mitch Barnett » 17 Sep 2021 01:13

Check out Arch's blog for the procedure: http://archimago.blogspot.com/2021/03/h ... ction.html

Note that the transition or Schroeder frequency is not an instant "switch" from waves to rays: https://www.audiosciencereview.com/foru ... ost-902606

For example, if your rooms transition frequency is 150 Hz, the rule of thumb is 4 x transition frequency through the diffusion zone. So you may want take the partial correction out to about 600 Hz.

Have fun experimenting!
k_kovacs
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Joined: 15 Jul 2021 17:11

Re: Only correct under Schroeder freq?

Post by k_kovacs » 18 Sep 2021 02:11

Thx for your answer Mitch!

I will mail you when im done with the tweaking. So you can do some more tweaking :mrgreen:
rschloemer
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Joined: 25 Sep 2020 15:17

Re: Only correct under Schroeder freq?

Post by rschloemer » 23 Feb 2022 12:11

Hi all,

I may be missing something, but wouldn't it be enough to identify a frequency where L/target and R/target intersect, and then set the L/R HF limits in Macro 3 to these values? Ideally, you'd find a frequency where all three intersect, of course.
Archimago's solution is more generic as it lets you define any frequency range you want (and not just 0 Hz - X Hz), but for combating the room this usually is not necessary.

(If you read this as 'Have I been doing it wrong all the time?', you are correct :lol: )

Regards,

Rolf
Ecwl
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Joined: 19 Feb 2021 01:05

Re: Only correct under Schroeder freq?

Post by Ecwl » 24 Feb 2022 04:47

I think if you don't use Archimago/CutNWindow technique, and only rely on Macro 3, then your target below cutoff frequency would need to match the measured frequency response above the cutoff frequency. Otherwise, the volume level of the below cutoff frequency and above cutoff frequency can then be off. Based on my room measurements, I've lately experimented with various cutoff frequencies just using Macro 3 and I ended up enjoying the sound with partial correction only up to 1300Hz.
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UliBru
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Re: Only correct under Schroeder freq?

Post by UliBru » 24 Feb 2022 10:26

I clearly recommend to use the SplitNJoin (not CutNWindow) approach as described by Archimago.
Stay well tuned
Uli

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Acourate system: JRiver/Roon -> AcourateConvolver -> miniDSP U-DIO8 -> TacT M/S2150 amps -> DIY horn speakers
Ecwl
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Joined: 19 Feb 2021 01:05

Re: Only correct under Schroeder freq?

Post by Ecwl » 24 Feb 2022 13:32

Thanks. I see now if we don't use SplitNJoin and just use Macro 3, in addition to the gain issue, the phase correction between Macro 3 and the 1:1 filter would also be different.
Or does Macro 4 only look at the amplitude and not the phase of the Inverse filter so the use of SplitNJoin would only address the gain between frequencies above and below cutoff frequency?
rschloemer
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Joined: 25 Sep 2020 15:17

Re: Only correct under Schroeder freq?

Post by rschloemer » 24 Feb 2022 14:45

Thanks Uli!
So...if that's not it, what is the purpose of the HF Limits in Macro 3? They have to be good for something ;)

Regards,

Rolf
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UliBru
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Re: Only correct under Schroeder freq?

Post by UliBru » 24 Feb 2022 15:28

rschloemer wrote:
24 Feb 2022 14:45
So...if that's not it, what is the purpose of the HF Limits in Macro 3? They have to be good for something ;)
HF Limit means a high frequency limitation. Usually at higher frequencies the frequency response shows a falling slope. This behaviour is quite natural for far-field listening setups. Furthermore a brickwall filter in ADC and DAC also causes a falling response at the top end.
Now after macro3 you can quite often see a boost of the high frequency correction. But it does not really make sense to boost a tweeter too much.
And for this cases the HF Limit function creates a horizontal correction and thus avoids the boost.
Stay well tuned
Uli

Moderator
Acourate system: JRiver/Roon -> AcourateConvolver -> miniDSP U-DIO8 -> TacT M/S2150 amps -> DIY horn speakers
Ecwl
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Joined: 19 Feb 2021 01:05

Re: Only correct under Schroeder freq?

Post by Ecwl » 05 Mar 2022 19:24

In the past month, I have gone back to a convolution filter that only uses partial correction. The reason was that while I appreciate the coherence of sound from a full frequency correction, I have found that a partial correction (following a similar target curve) often has better transient responses in my system (e.g. more precise guitar plucks, hand clapping, piano strikes).

But because I miss the coherence of sound from the left & right speakers with a full correction, I started increasing the cutoff frequency of the correction beyond Schroeder frequency and then beyond the transition frequency and I was able to get great correction with coherence and transient accuracy up to say 1300Hz as a cutoff.

While I have been enjoying this filter, I still miss the coherence in the upper frequencies. But after reading this thread and thinking about it some more, I started wondering if the loss of transient accuracy in my system was perhaps due to the over-aggressive correction above 1300Hz during a full frequency correction.

Hence, I decided to create a new inverse target by generating a full frequency correction first and then smoothing the inverse at 1/3 octave. And then I split and join the standard inverse from 10-1300Hz with the 1/3-octave smoothed inverse from 1300Hz-24000Hz. The “1300Hz” was determined by where the 1/3-octave smoothed and original inverses intersect approximately around that frequency range. I created a convolution filter using this new inverse filter. I was quite worried at first since the maximum IACC I was able to achieve was significantly worse than full or partial correction. But once I started running the new convolution filter, I felt like I’ve finally achieved the best of both worlds: optimal coherence in sound from both channels, while preserving transient accuracy as much as possible.

Perhaps this is a unique problem to my system or to my method of generating convolution filters. But I thought that if some of you out there really like partial correction for the same reasons that I did, perhaps you would be interested in trying this split and join method and see if you like the sound too.
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