• WANTED: Happy members who like to discuss audio and other topics related to our interest. Desire to learn and share knowledge of science required. There are many reviews of audio hardware and expert members to help answer your questions. Click here to have your audio equipment measured for free!

State-of-the-art digital room correction

Status
Not open for further replies.

markus

Addicted to Fun and Learning
Joined
Sep 8, 2019
Messages
646
Likes
653
These days nearly every manufacturer offers some sort of "digital room correction", claiming "state-of-the-art" while keeping details at a minimum, unfortunately. In order to shed some light onto what can be done by "distorting the direct signal" (alternative definition of DRC) here's a good scientific review available for free at https://www.mdpi.com/2076-3417/8/1/16
 

andyc56

Active Member
Joined
May 14, 2016
Messages
119
Likes
166
That's about the best summary of "room correction" articles I've seen yet. A while back, I went searching through AES to try to grab as many articles on the subject as I could. This summary lists and describes all of what I found and more.
 

Χ Ξ Σ

Senior Member
Forum Donor
Joined
Jul 16, 2020
Messages
457
Likes
1,969
Location
UTC-8
Wow, that's a lot to digest.
Table 1.png
 

Attachments

  • Table 1.png
    Table 1.png
    1.3 MB · Views: 97

Flak

Senior Member
Industry Insider
Joined
Nov 18, 2018
Messages
385
Likes
593
New approaches to speaker optimization in audioXpress December 2021 including an article about Spatial Room Correction technology :
 
Last edited:

mitchco

Addicted to Fun and Learning
Audio Company
Joined
May 24, 2016
Messages
640
Likes
2,397
Hey, isn't this my thread title from two weeks ago? ;-)


Re: https://www.mdpi.com/2076-3417/8/1/16 Is a 4 years old. While it recognises the importance of excess phase of the room transfer function:

"The human ear is sensitive to the excess-phase of the RTF"

And gets the definition of excess phase mostly technically correct:

"... an impulse response that is the time-reversal of the impulse response of the excess-phase system"

There isn't any discussion or graphs of excess phase of the room transfer function at all, even though it is deemed to be important.

How can this be called "state of the art" when 1/2 of the room transfer function (i.e. excess phase, including low frequencies), is missing from this "scientific review?"
 
OP
markus

markus

Addicted to Fun and Learning
Joined
Sep 8, 2019
Messages
646
Likes
653
Hey, isn't this my thread title from two weeks ago? ;-)


That thread got locked as you were just pushing your agenda instead of actually discussing the topic. Please stop doing the same here.

Re: https://www.mdpi.com/2076-3417/8/1/16 Is a 4 years old. While it recognises the importance of excess phase of the room transfer function:

"The human ear is sensitive to the excess-phase of the RTF"

And gets the definition of excess phase mostly technically correct:

"... an impulse response that is the time-reversal of the impulse response of the excess-phase system"

There isn't any discussion or graphs of excess phase of the room transfer function at all, even though it is deemed to be important.

How can this be called "state of the art" when 1/2 of the room transfer function (i.e. excess phase, including low frequencies), is missing from this "scientific review?"

Did you actually read the whole thing?
 

restorer-john

Grand Contributor
Joined
Mar 1, 2018
Messages
12,588
Likes
38,291
Location
Gold Coast, Queensland, Australia
That thread got locked as you were just pushing your agenda instead of actually discussing the topic. Please stop doing the same here.

Self interests unfortunately always get in the way, where money is involved.
 
OP
markus

markus

Addicted to Fun and Learning
Joined
Sep 8, 2019
Messages
646
Likes
653
Self interests unfortunately always get in the way, where money is involved.
<rant>Unfortunately it's common for businesses to misuse forums or social media in general as just another marketing instrument. Even for very small businesses – paint yourself as an expert, cite some authorities that (seem to) agree with your position, slip into people's preconceptions, write a book, fire some logical fallacies at people that endanger your agenda, etc.pp. In my mind a (science) forum should be a place for open, truthful and educational discussion and that just isn't possible if you're a manufacturer and can't talk openly about certain aspects of your product/service. Two examples just right above.</rant>
 
Last edited:

ernestcarl

Major Contributor
Joined
Sep 4, 2019
Messages
3,106
Likes
2,313
Location
Canada
How can this be called "state of the art" when 1/2 of the room transfer function (i.e. excess phase, including low frequencies), is missing from this "scientific review?"

There are nearly 300 cross-linked references in that one academic summary paper. It's heavy in the technical jargon and there seems to be so much overlap in the things covered so it took me a while... I have previously only skimmed it before, and finally re-read the review to completion now, as well as looked at one or two of the reference links which were available open access thus far, though much of the math is still beyond me. I know one could spend many months, maybe even years just going through these all. BUT, I think it is rather laid out clearly that it is up to the reader to go out and learn about all the room response correction related topics out there that is of most interest to them. The fact that it is completely platform agnostic is rather a good thing, IMO.
 

mitchco

Addicted to Fun and Learning
Audio Company
Joined
May 24, 2016
Messages
640
Likes
2,397
That thread got locked as you were just pushing your agenda instead of actually discussing the topic. Please stop doing the same here.
It was the other way around... Technical explanations by myself and others like @j_j were repeatedly dismissed by you.

Are you not markus767 on https://www.avsforum.com/threads/the-official-dirac-live-thread.3137722/ promoting everything Dirac?

The main paper referenced does not address the non-minimum behaviour at low frequencies that exists in virtually ever room. This requires excess phase correction. Please show me where this is addressed. Otherwise, how can it be called state of the art?
 

j_j

Major Contributor
Audio Luminary
Technical Expert
Joined
Oct 10, 2017
Messages
2,267
Likes
4,759
Location
My kitchen or my listening room.
These days nearly every manufacturer offers some sort of "digital room correction", claiming "state-of-the-art" while keeping details at a minimum, unfortunately. In order to shed some light onto what can be done by "distorting the direct signal" (alternative definition of DRC) here's a good scientific review available for free at https://www.mdpi.com/2076-3417/8/1/16

Well, since distortion, i.e. nonlinearity, is not involved, we're off to the races already.
 

j_j

Major Contributor
Audio Luminary
Technical Expert
Joined
Oct 10, 2017
Messages
2,267
Likes
4,759
Location
My kitchen or my listening room.
That thread got locked as you were just pushing your agenda instead of actually discussing the topic. Please stop doing the same here.



Did you actually read the whole thing?

Yeah, I did, including the part where my stuff is cited.

It's a review of many methods. It does not lead one to a specific conclusion.

And as a review of the review paper, it's a bit off in its summary of hearing research. Mel scale is not related to partial loudnesses, and isn't terribly germane. The Bark Scale is a standardized view of the cochlear filter widths, but it is frankly obsolete. The ERB scale, on the other hand, is a scale in which hearing response is much more uniform across "bands" (remembering that there are a huge number of such bands, that heavily overlap). In the ERB scale, with some modifications for time-domain interference with the measurement of ERB's at low frequencies, is the proper bandwidth to consider. Also mostly omitted is the variation in time sensitivity (both monaural and binaural) across frequency, which matters greatly in realizing which part of the signal (corrected or not) actually matters at a given frequency.

Finally, no mention of coherence length or spatial relationship to perception is noted. It's not a bad article, it's written by a very good author, that's fine, but it is quite old in technical terms, and is missing quite a bit of newer work. (As it must, being old.) It's also missing coherence length vs. wavelength discussions.

The discussion on echo cancellation seems mostly orthogonal to me, as well.
 

j_j

Major Contributor
Audio Luminary
Technical Expert
Joined
Oct 10, 2017
Messages
2,267
Likes
4,759
Location
My kitchen or my listening room.
There are nearly 300 cross-linked references in that one academic summary paper. It's heavy in the technical jargon and there seems to be so much overlap in the things covered so it took me a while... I have previously only skimmed it before, and finally re-read the review to completion now, as well as looked at one or two of the reference links which were available open access thus far, though much of the math is still beyond me. I know one could spend many months, maybe even years just going through these all. BUT, I think it is rather laid out clearly that it is up to the reader to go out and learn about all the room response correction related topics out there that is of most interest to them. The fact that it is completely platform agnostic is rather a good thing, IMO.

Indeed, but Markus cites it as vindication, and it's nothing of the sort. I do know the math. I do know the field. I'm cited in the early references. Yeah, it's an elderly, but good summary. It makes no particular point of Markus's, nor does it refute anything that Mitch has to say.
 

tvrgeek

Major Contributor
Joined
Aug 8, 2020
Messages
1,017
Likes
566
Location
North Carolinia
The conclusion this only alludes to is, what can we buy for our home system, be it stereo or HT? Dirac Live? And what applies to professional sound reinforcement epically for live terrible venues like small bars or coffee shops where local talent is to be found, but listenable sound is not.
 
Status
Not open for further replies.
Top Bottom