Understanding the State of the Art of Digital Room Correction

[antcollinet]

My pet peeve in presentations...

@mitchco - sorry that was rude. I hadn't spotted you were linking your own video, otherwise I'd have phrased it as constructive feedback instead. I'm deleting my original post as lacking excellence.

If we're ever in the same bar, I owe you a beer.

 

[dougi]

Nope it is not, at least at the speaker level as discussed in the last few posts. It really depend on the frequency range of the drivers and whether you have a cross-over in the critical ITD frequency range. There is a reason why there is no preference advantage for so called time aligned speakers overall. We are not talking totally unaligned, but close enough.

OK. So are you saying there are no general preferences for time aligned speakers, but there are good reasons to do so for other design reasons?

 

[PierreV]

@mitchco - sorry that was rude. I hadn't spotted you were linking your own video, otherwise I'd have phrased it as constructive feedback instead. I'm deleting my original post as lacking excellence.

If we're ever in the same bar, I owe you a beer.

And the good news is: there is a document that you can read yourself.

Accurate Sound Reproduction Using DSP , Barnett, Mitch - Amazon.com

Accurate Sound Reproduction Using DSP - Kindle edition by Barnett, Mitch. Download it once and read it on your Kindle device, PC, phones or tablets. Use features like bookmarks, note taking and highlighting while reading Accurate Sound Reproduction Using DSP.

www.amazon.com

 

[audio2design]

OK. So are you saying there are no general preferences for time aligned speakers, but there are good reasons to do so for other design reasons?

No I am saying somewhat close alignment is good enough. Perfect alignment, so called time aligned speakers have shown no advantage in preference selection w.r.t. people choosing preferred speakers. I am also saying that outside the ITD frequency discrimination range, there is no mechanism, that I am aware of, that would make a time aligned speaker sound "better".

 

[mitchco]

@mitchco - sorry that was rude. I hadn't spotted you were linking your own video, otherwise I'd have phrased it as constructive feedback instead. I'm deleting my original post as lacking excellence.

If we're ever in the same bar, I owe you a beer.

Haha, no worries Tony, I can assure you I wasn't reading slides during the Acourate and Audiolense demos I hate giving presentations as I am more of a sit at the bar and chat kind of guy. I will take you up on your offer ;-) As far as the presentation, I had not anticipated a feature length film here. There are too many technical bits for my old slow brain to remember, so I had to write some of it down.

 

[Newman]

???

I think he is saying that misaligned speakers cause a frequency response error and a phase response error, and we know the frequency response error is audible, but the jury is out on whether the phase response error is audible as a separate thing itself. Controlled tests, on the audibility of an all-pass filter (a change in phase response with no change in frequency response) on music coming from speakers, seem to suggest we can’t hear it, unless the phase change is ridiculously high and not representative of anything that occurs in speakers and hifi electronics.

 

[dougi]

No I am saying somewhat close alignment is good enough. Perfect alignment, so called time aligned speakers have shown no advantage in preference selection w.r.t. people choosing preferred speakers. I am also saying that outside the ITD frequency discrimination range, there is no mechanism, that I am aware of, that would make a time aligned speaker sound "better".

Thankyou for clarifying.

 

[Daverz]

I've been using the free DRC-FIR for several years with good results. I'm wondering whether these commercial solutions would make a worthwhile improvement. It looks like I'd also need a Windows 10 laptop to run the measurements? Or can I use my macbook?

 

[mitchco]

Re: time alignment. As Rod Elliott said some time ago, "For what it's worth, I originally started this article not to praise, but to debunk the theory that time alignment is the only way a speaker should ever be designed. Having done the research, run tests, and written the article, I confess that I must agree with many (perhaps even most) of the points made by the time alignment proponents."

Many would agree. And building a "proper" time aligned speaker is not an easy task to begin with.

But that is not my point. I am talking about using excess phase correction to correct for non-minimum phase behaviour in the room, not only at low frequencies but ensuring both channels are as close together over time as possible. In a proper AB or even ABX test, it is pretty easy to hear the difference in bass clarity and depth of field in the music...

 

[mitchco]

I've been using the free DRC-FIR for several years with good results. I'm wondering whether these commercial solutions would make a worthwhile improvement. It looks like I'd also need a Windows 10 laptop to run the measurements? Or can I use my macbook?

Dave, if you check out the video you will see that DRC-FIR makes the list for SOTA DRC If you decide to go digital XO's one day, then yah you would need to go with one of the commercial versions, which indeed are Windows programs.

 

[ernestcarl]

I have a room-induced (likely mild) excess phase issue around 80Hz in my desk setup coming from the sub only. I don't correct for it due to the computational requirement causing delay, but once corrected for, it does sound much better. I can do an ABX test within foobar2000 and would easily pass the test. Since it is only occuring in the sub, I listen to the sub solo... and by switching back and forth playback between a bassy audio track (bass guitar etc.) that has been convolved vs one without, one can then determine for himself/herself whichever sounds "best".

 

[JWAmerica]

PC Master Race REW user checking in. What's this all about?

 

[dlaloum]

Does DIRAC qualify here? I thought Dirac also did Impules / Time alignment?

 

[McFly]

I'm way underqualified to speak on room correction and digital EQ's and am yet to watch the video (I will tonight) so forgive me if its covered, but seems to me the target market would be Home Theatre - and the problem with low frequency room corrections is it can result in rather large audio delays and subsequent audio/video lip sync issues. Until we have video processors than can deliberately add delay to the video signal to allow the audio DSP to catch up, its not much good to the HT guys.

Like when you go to your tv settings to adjust lip sync, its always 0-200ms audio delay. Like why not -200 to +200ms, and the minus is adding a delay to the video only? Most times the audio is lagging the video, why would I wanna add more audio delay?

Yes I know we are mostly audio guys here but the money is in HT.

 

[Χ Ξ Σ]

Does DIRAC qualify here? I thought Dirac also did Impules / Time alignment?

Dirac only does phase correction above a certain frequency. The exact cutoff frequency is unknown, although I have verified that Dirac will perform phase correction between the tweeter and the midrange/midwoofer but not so much between the midrange and the woofer on my then Neumann KH310 and KH120.

 

[dlaloum]

I thought basic Dirac Live versions were limited to below 500Hz, rather than above a certain frequency?

 

[jhaider]

This speaks for itself!

View attachment 161562

How so? Does it really tell you anything except that the software can auto-EQ a (single? if so even less useful) point in space? Given that we generally hear the speaker above the transition region and not what-a-mike-sees-at-one-point-in-the-room, I'm far from convinced that auto-EQ gyrations based on listening position measurements do anything except for soothe the eyes of people who like orderly-looking graphs.

 

[maverickronin]

I'm way underqualified to speak on room correction and digital EQ's and am yet to watch the video (I will tonight) so forgive me if its covered, but seems to me the target market would be Home Theatre - and the problem with low frequency room corrections is it can result in rather large audio delays and subsequent audio/video lip sync issues. Until we have video processors than can deliberately add delay to the video signal to allow the audio DSP to catch up, its not much good to the HT guys.

Like when you go to your tv settings to adjust lip sync, its always 0-200ms audio delay. Like why not -200 to +200ms, and the minus is adding a delay to the video only? Most times the audio is lagging the video, why would I wanna add more audio delay?

Yes I know we are mostly audio guys here but the money is in HT.

His solution was to rip your BD's to an HTPC and use a good video player like J River which can add all the delay you want in any direction...but then you'll loose out on Atmos et al. since there are no PC based decoders because of the movie cartel so it not great either way...

 

[mitchco]

How so? Does it really tell you anything except that the software can auto-EQ a (single? if so even less useful) point in space? Given that we generally hear the speaker above the transition region and not what-a-mike-sees-at-one-point-in-the-room, I'm far from convinced that auto-EQ gyrations based on listening position measurements do anything except for soothe the eyes of people who like orderly-looking graphs.

Whoosh!

 

[amirm]

I thought basic Dirac Live versions were limited to below 500Hz, rather than above a certain frequency?

No but I think there is a light version of Dirac with such a limit.