Article: Dirac Live 2 Digital Room Correction Software Walkthrough

[mitchco]

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[The Computer Audiophile]

Thanks for the article Mitch. Top notch as always. 

[Archimago]

Wow. Nice work Mitch. Very detailed as usual! Gonna have to take some time to unpack this article... 🙂

[sem115]

Awesome Job!! Been searching for A/B article with Dirac and REW to compare results are legit.  Now trying to Figure out best way to implement Dirac with streaming Qobuz.  Roon? NAD C658,  or there a way with using $349 route using my laptop?

[mitchco]

Thanks @sem115 One will require an application to "host" the Dirac Live Processor (DLP) plugin. An oldy but goody is VSTHost on Windows. I just tried loading the DLP VST plugin and was successful. There are several VST host's available, some free, some $$'s, some standalone and some integrated with other music player software. The trick is routing the audio.

I ran out of time to try DLP in this configuration. But essentially, you will want to route Qobuz or Roon's output through the application hosting the DLP plugin and then out to the DAC and rest of the system. Perhaps other members here have tried this approach and can assist.

[flak]

4 hours ago, mitchco said:

Thanks @sem115 One will require an application to "host" the Dirac Live Processor (DLP) plugin. An oldy but goody is VSTHost on Windows. I just tried loading the DLP VST plugin and was successful. There are several VST host's available, some free, some $$'s, some standalone and some integrated with other music player software. The trick is routing the audio.

I ran out of time to try DLP in this configuration. But essentially, you will want to route Qobuz or Roon's output through the application hosting the DLP plugin and then out to the DAC and rest of the system. Perhaps other members here have tried this approach and can assist.

 

Excellent... thorough and knowledgeable review as expected from mitchco!

@sem115 one of the simple solutions for streaming Qobuz can be Audirvana that directly supports it (together wih other streaming services) and supports standard plugins as well

[digitaldufferme]

Complete noob here and was fascinated by your article! You have corrected your sound without the subs connected I believe. I have a 2.2 system (KEF LS50 & REL T9i) how would I do this as I believe the subs have a massive effect on the room sound? I use ROON ROCK on a NUK8i7.

[sem115]

8 hours ago, flak said:

 

Excellent... thorough and knowledgeable review as expected from mitchco!

@sem115 one of the simple solutions for streaming Qobuz can be Audirvana that directly supports it (together wih other streaming services) and supports standard plugins as well

Thanks guys for the info.  Great news since I already have Audirvana & Mic I use with REW. Excited to get Dirac next week and spend all weekend listening to music.  

[blue2]

Thanks for another great article! $349 sounds reasonable but what about a trial/evaluation to find out what it can do for my room+system? Do you know if that's available? I can't find anything on the Dirac web site.

[Flashman]

Seems like a preview of the NAD Masters M33, which will feature the first mass-market implementation of Purifi amplification and built-in DiracLive.

[audiobomber]

Finally, some evidence of why Dirac is better than REW. Looks like I need to upgrade. 5 stars!

 

I'm using REW with a miniDSP to integrate my subs. Anxiously looking forward to Part 2, Active Bass Management. 

 

PS As per my PM message, I'm hoping you can review the miniDSP SHD. The SHD Studio is also very interesting.

[monteverdi]

I wonder why the corrected step response shows much more ringing than the uncorrected. As far as I can see it is at around 20kHz. Is it an artifact of Umik with step transitions (I see similar ringing just measuring my Wideband drivers using Umik) or is it introduced by the DSP?

I understand digital speaker correction which is what basically Dirac is doing at higher frequencies but I can not understand how the interaction of bass frequencies with room modes can be corrected by just altering the woofer output (past a single point in space). So I am looking forward to learn more about active bass management!

[mitchco]

18 hours ago, digitaldufferme said:

Complete noob here and was fascinated by your article! You have corrected your sound without the subs connected I believe. I have a 2.2 system (KEF LS50 & REL T9i) how would I do this as I believe the subs have a massive effect on the room sound? I use ROON ROCK on a NUK8i7.

 

Yes, I did not have the subs connected, but the the little Purifi's have solid output below 30 Hz. But my Rythmik dual F18's go down to 6 Hz in my room. How is your 2.2 system connected? Is it Y cabling or ?

[mitchco]

10 hours ago, blue2 said:

Thanks for another great article! $349 sounds reasonable but what about a trial/evaluation to find out what it can do for my room+system? Do you know if that's available? I can't find anything on the Dirac web site.

Thanks! From: https://www.dirac.com/faq-general it looks the free trial is 14 days. Perhaps @flak can confirm...

[flak]

4 minutes ago, mitchco said:

Thanks! From: https://www.dirac.com/faq-general it looks the free trial is 14 days. Perhaps @flak can confirm...

 

Yes, I confirm but the trial versions aren't ready yet,

they will be available soon but I can't say when

[mitchco]

3 hours ago, monteverdi said:

I wonder why the corrected step response shows much more ringing than the uncorrected. As far as I can see it is at around 20kHz. Is it an artifact of Umik with step transitions (I see similar ringing just measuring my Wideband drivers using Umik) or is it introduced by the DSP?

I understand digital speaker correction which is what basically Dirac is doing at higher frequencies but I can not understand how the interaction of bass frequencies with room modes can be corrected by just altering the woofer output (past a single point in space). So I am looking forward to learn more about active bass management!

 

I did not use a UMIK-1 for this particular article, even though I do have one and have not come across any ringing artefacts with it yet. But I am going to test it out extensively in an upcoming article. As the speakers are also gone, I can't retest easily to confirm what the issue was. I could have goofed on my loopback test and resampled somewhere in the chain like 48 kHz signal through a 44.1 kHz filter. When I get a chance, I will confirm using another speaker/test, but given the amount of time I have spent on trying to identify (pre)ringing artefacts previously, it certainly inaudible to these ears. The main point I was trying to get across was the time alignment.

 

Understanding room correction is complicated A separate article is required to get though it all and I am contemplating writing one. In a nutshell, good room correction software will take an acoustic measurement and extract the minimum phase response and since speakers are minimum phase devices, correcting the frequency response will also correct the phase response. However, that is only half the picture as there is the room to deal with, which is what Dirac calls mixed phase or others call it excess phase, which includes room resonances and reflections.

 

And in the time domain, we know what the ideal speaker target is by looking at the timing (i.e. step) response of an "ideal" minimum phase speaker. So... the room correction software corrects the time domain to follow the ideal minimum phase target. You can see that if you have my book or some of the articles here at AS show that as well. But the trick is that this is wavelength dependant, so at low frequencies, the correction time window is long (like 600ms for example) and as frequency increases the correction time window becomes shorter so above the rooms transition frequency we are looking at more of the direct sound plus baffle of the speaker. Often called frequency dependant windowing. In other words, at low frequencies, the room correction software has a large time window that corrects both the direct sound and reflected sound (i.e. room resonance) towards a target response. At high frequencies, it is mostly the direct sound because if we tried to also correct for mid-range and high frequency comb filtering room reflections, the high frequency response of the loudspeaker sounds like a dentists drill. This is how one can hear "over correction" in the high frequencies.

 

Hope that helps somewhat. Like I say, requires a separate article to fully explain.

[monteverdi]

6 hours ago, mitchco said:

 

I did not use a UMIK-1 for this particular article, even though I do have one and have not come across any ringing artefacts with it yet. But I am going to test it out extensively in an upcoming article. As the speakers are also gone, I can't retest easily to confirm what the issue was. I could have goofed on my loopback test and resampled somewhere in the chain like 48 kHz signal through a 44.1 kHz filter. When I get a chance, I will confirm using another speaker/test, but given the amount of time I have spent on trying to identify (pre)ringing artefacts previously, it certainly inaudible to these ears. The main point I was trying to get across was the time alignment.

 

Understanding room correction is complicated A separate article is required to get though it all and I am contemplating writing one. In a nutshell, good room correction software will take an acoustic measurement and extract the minimum phase response and since speakers are minimum phase devices, correcting the frequency response will also correct the phase response. However, that is only half the picture as there is the room to deal with, which is what Dirac calls mixed phase or others call it excess phase, which includes room resonances and reflections.

 

And in the time domain, we know what the ideal speaker target is by looking at the timing (i.e. step) response of an "ideal" minimum phase speaker. So... the room correction software corrects the time domain to follow the ideal minimum phase target. You can see that if you have my book or some of the articles here at AS show that as well. But the trick is that this is wavelength dependant, so at low frequencies, the correction time window is long (like 600ms for example) and as frequency increases the correction time window becomes shorter so above the rooms transition frequency we are looking at more of the direct sound plus baffle of the speaker. Often called frequency dependant windowing. In other words, at low frequencies, the room correction software has a large time window that corrects both the direct sound and reflected sound (i.e. room resonance) towards a target response. At high frequencies, it is mostly the direct sound because if we tried to also correct for mid-range and high frequency comb filtering room reflections, the high frequency response of the loudspeaker sounds like a dentists drill. This is how one can hear "over correction" in the high frequencies.

 

Hope that helps somewhat. Like I say, requires a separate article to fully explain.

Thanks for your response, Toole and also in a similar version Geddes are proposing to use multiple subwoofers spaced over the room to allow wider zones of bass correction (with specific phase corrections). I wonder if that is something Dirac can do and if that leads to a significant improvement compared to standard 2 woofers/subwoofers? Of course that adds a lot of complexity to the setup both computational and room design wise. REW room simulator shows some benefits but I wonder how real these simulations are?

[digitaldufferme]

10 hours ago, mitchco said:

 

Yes, I did not have the subs connected, but the the little Purifi's have solid output below 30 Hz. But my Rythmik dual F18's go down to 6 Hz in my room. How is your 2.2 system connected? Is it Y cabling or ?

Following the advice of REL, I connect the left speaker and the left sub to one RCA output on the amp and the same for the right channel so that the REL T9i get a full range signal.

[Zapuan]

Thanks mitchco, always very useful your articles and reviews. I have been using Dirac 1.x since 2013 and lately I have been studying Audiolense and Acourate to try to have a (perhaps) better room correction by linearizing the speakers first, and after the room in the sweet spot..
Do you think that a better result can be achieved than Dirac 2.0?

[audiobomber]

Hey @mitchco, for Part Two, can you please discuss integrating subs using ported vs. sealed speakers? 2nd-order vs. 4th-order monitor roll-off is a complicating factor.

[SteveS1]

Great article, thank you.

[mitchco]

16 hours ago, monteverdi said:

Thanks for your response, Toole and also in a similar version Geddes are proposing to use multiple subwoofers spaced over the room to allow wider zones of bass correction (with specific phase corrections). I wonder if that is something Dirac can do and if that leads to a significant improvement compared to standard 2 woofers/subwoofers? Of course that adds a lot of complexity to the setup both computational and room design wise. REW room simulator shows some benefits but I wonder how real these simulations are?

 

Yes, I have seen both Toole's, plus Todd Welti's presentation on multiple subs, and Earl's paper, plus Duke LeJeune's swarm system. All show positive benefit's but one still needs room correction to obtain the smoothest bass response based on experiments I have run with multiple subs and locations.

 

Even if your sub(s) are part of your two channel system (i.e. not using digital XO), room correction is still a major benefit, which is what Dirac does. However, the new Dirac Bass Management will provide further control, but also requires more than 2 DAC channels.

 

REW Room Simulator works very well and is quite accurate! Room mode calculators are mostly based on the physical dimensions of one's room. Room construction and rooms treatments (to a certain degree as most do little below 100 Hz) have an impact, but below the room's transition frequency, it is all about the room ratio. The reality is that no matter where the speakers/subs are placed in the room relative to the listening positions, there is no escaping room modes. All that happens is that the dips and peaks move in frequency based on these (super)positions. One can get lucky and minimize, so it is worth the effort. However, in the end, still need room eq...

[mitchco]

7 hours ago, Zapuan said:

Thanks mitchco, always very useful your articles and reviews. I have been using Dirac 1.x since 2013 and lately I have been studying Audiolense and Acourate to try to have a (perhaps) better room correction by linearizing the speakers first, and after the room in the sweet spot..
Do you think that a better result can be achieved than Dirac 2.0?

Cheers @Zapuan As mentioned in the review, I did not get a chance to try Dirac 1.x, but according to the manufacturer, there are several improvements upgrading to D2. As I understand it, you are entitled to a free upgrade and given the simplified measurement process, it is worth a shot to try first 🙂

[mitchco]

14 hours ago, digitaldufferme said:

Following the advice of REL, I connect the left speaker and the left sub to one RCA output on the amp and the same for the right channel so that the REL T9i get a full range signal.

 

There is no reason why this would not work with Dirac. When the free trial is available, you might want to give it a try. The only issue is that Roon does not support VST plugin's at this time. So you would need to temporally try it in a different music player that supports VST plugins. Then at least you could ascertain the sonic benefit, which I think would be significant in your setup.

[Zapuan]

46 minutes ago, mitchco said:

Saluti @Zapuan  Come menzionato nella recensione, non ho avuto la possibilità di provare Dirac 1.x, ma secondo il produttore, ci sono diversi miglioramenti che aggiornano a D2. A quanto ho capito, hai diritto a un aggiornamento gratuito e dato il processo di misurazione semplificato, vale la pena provare prima 🙂

my question is whether in your opinion with Acourate or Audiolense you can achieve a better result than that obtainable with Dirac 2