Article: Dirac Live 2 Digital Room Correction Software Walkthrough

[Tonygeno]

A while back you reviewed the Dynaudio Focus 600XD and raved about this speaker. Additionally you discussed its step response and its importance. Would Dirac benefit this type of active speaker and in doing so, would the step response be compromised?

[mitchco]

@ZapuanSorry for misunderstanding. If you know what you are doing, yes, because of additional features and/or exposing functionality for the user to control:

- create multi-way digital crossovers of varying types, slopes, you have complete control.

- linearize individual drivers.

- time align individual drivers.

- user control over frequency dependent windowing. Both low and high frequency window widths can be independently adjusted for both magnitude and excess phase correction.

- the amount of correction applied.

[mitchco]

1 hour ago, Tonygeno said:

A while back you reviewed the Dynaudio Focus 600XD and raved about this speaker. Additionally you discussed its step response and its importance. Would Dirac benefit this type of active speaker and in doing so, would the step response be compromised?

 

Nice speaker, a little bright sounding to my ears if I recall... Yes, they are time aligned. No, Dirac would not compromise the time alignment, if anything optimise further if possible. Yes, Dirac would be a benefit as we still have room modes to deal with. The boundary controls on the speaker are helpful, but rudimentary compared to what Dirac can do. 

 

Here is the 600 XD frequency response in my room. Dirac would indeed smooth out the response below 600 Hz:

 

 

 

 

 

[Tonygeno]

Thanks for the comment Mitch. I have a DDRC-22D that I have had in and out of my system using Dynaudio 60XDs (the successor to the 600). It definitely fixes the bass, which in my room becomes too wooly uncorrected. I also have run Dirac full range which also works well as the 22D has four presets that allow different curves or cutoff. I was just wondering if it messed up the time alignment but it looks like your review actually speaks about that.

[ted_b]

Mitch, great review!  As I contemplate, for the first time in my long audio life, the idea of putting my signal through the twists and turns of DSP in order to correct for room interactions (and I'm building said room as I type this) I have two issues, one long-term that is too OT for this thread (is DSP worth not being able to do DSD512, etc) and one very short term:

* why, if you are working hard to alleviate interactions caused by walls and ceilings, first reflections, etc...why change the room before you start (removing coffee table, sofa, etc) and then change it back? 

Thx

Ted

[baconbrain]

Excellent content!

[mitchco]

13 hours ago, ted_b said:

Mitch, great review!  As I contemplate, for the first time in my long audio life, the idea of putting my signal through the twists and turns of DSP in order to correct for room interactions (and I'm building said room as I type this) I have two issues, one long-term that is too OT for this thread (is DSP worth not being able to do DSD512, etc) and one very short term:

* why, if you are working hard to alleviate interactions caused by walls and ceilings, first reflections, etc...why change the room before you start (removing coffee table, sofa, etc) and then change it back? 

Thx

Ted

 

Thanks Ted, appreciate it. That's awesome about your room build! Would love to hear more about that or perhaps it is an article? Wrt objects between the speakers and/or chair/couch in the way... If using a full range correction, we are correcting mainly for room interactions below 600 Hz and the loudspeakers direct sound (and some near reflections like the speaker baffle, stand), so we want to move any objects that are in the direct sound path. Not move them out of the room, but off to the side temporarily during measurements and then replace when finished. So the DSP is correcting for room and loudspeaker, not room/loudspeaker and coffee table, for example.

 

Using this approach yields the best sounding correction as one is dealing with the room and the speaker, with it's natural dispersion pattern, not broken up by objects in the way, or reflections from the couch getting in the microphone if using UMIK-1's little stand to sit on the top of the couch. Myself and others have tried corrections with objects in the way of the direct sound field and/or chair couch inches from the measuring mic and then with the objects moved to the side. The consensus is that with the objects temporarily out of the way for measurement and then returned after, sounds better than the correction with objects in the path and/or mic sitting on the chair or couch. 

 

I have tried this many times, in many rooms, and in every case, the correction sounds better with an unobstructed path to the measurement mic and placing the objects back for listening. Leaving objects in the direct sound path and/or having reflections from the couch back getting into the mic produces an inferior sounding correction. Not so much at low frequencies, but at frequencies above the rooms transition frequency, i.e. 600 Hz and above. It can alter the tone and sound like comb filtering or just unnatural sounding and then folks blame the DSP 🙂 Of course, folks are free to do whatever they want, but myself and others have found this measurement approach works more effectively for achieving the best sounding correction.

 

Best of luck with your room!

Mitch

[monteverdi]

That avoiding early reflection from furnitures  for measurements  but not for listening is an interesting observation. Our brain can use these early reflection to have an acoustical map of the space around us but on the other hand direct sound from the loudspeaker and secondary sound generated by (edge) diffraction or early reflections will be merged if sufficiently short (5-10msec, I was reading slightly different numbers). So I am wondering also how much the direction of these reflection plays a role in its discrimination of direct and reflected sound. I was reading that coffee tables in front of the listener that have an audible influence and my limited experience it may be true (I have my table on the side).

[mitchco]

It is not so much the direction and cues, which is indeed affected to a certain degree, it is more of the “comb filtering” that colours the frequency response is the main issue. I can’t show it because of copyright issues, but if you happen to have a copy of Bob Katz’s excellent book on Mastering, there are a couple of charts that show the frequency response comb filtering issues when, in his case, a mastering desk is placed between him and the speakers. Bob also adjusted the angle of the desk to minimize the comb filter to almost be the same as without the desk there.

 

When I “critically listen” I move my coffee table out of the way. Aside from the comb filtering colourations, I want to hear the full radiation pattern off the speakers for the best possible imaging. When I place the coffee table back, I can hear the comb filter coloration and the image height is reduced (i.e. the bottom half), by a bit, but since our ears/brains quickly adapt, it is soon forgotten and I am back to background music listening. I also have a “half back” couch as when I had a full back couch, it drove me nuts as I moved further back into the couch, I could easily hear the comb filtering from both channels reflecting off the couch and into my ears, aside from cutting off the ambient sound from behind me.

 

But the most important aspect is that if one corrects for the “comb filtering” off the coffee table for example, then that correction is now embedded in the frequency response of the loudspeaker including it's off axis response. We know from Sean Olive’s and Floyd Toole’s extensive work that a smooth off axis frequency response is just as important as smooth on axis response (think spinorama). So if we correct for the comb filter off the coffee table, we have just coloured the off axis response of the loudspeaker. So now the combination of the direct sound and early reflections in the listening window sounds “coloured” even sitting in the sweet spot and worsens when one moves around the room. This is one of the reasons why folks mistaken that it is the DSP that has coloured the sound when what they have done is coloured the off axis response, so the later reflections after the coffee table are coloured and to our ears does not sound right (and never will!).

 

There are no hard and fast rules, and I encourage folks to experiment. Having been using DSP extensively for a decade, these are some of my experiences.

[ted_b]

1 hour ago, mitchco said:

When I “critically listen” I move my coffee table out of the way.

Ahh, makes even more sense now...plus the comb filtering explanations.  Thx

[mwhitak]

On 2/27/2020 at 1:08 PM, Zapuan said:

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

Or Sonarworks, another option.

[One and a half]

On 2/26/2020 at 4:45 AM, 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.

Thanks @mitchco for an eye opener of a program, it takes a great walkthrough like this to realise, hey, I could do this

 

Roon doesn't support any VST plugins, let alone cataloging Box sets correctly, I don't envisage Roon having that vision any time soon. The VST host is one way, yes. Thinking out load, my server PC is 25m from a Lumin, which uses the RAAT networking protocol over CAT5e. I can see VST working on a local basis with USB out for example, any ideas on how a DLNA server can come in between VST host?

 

DSD files are sent as is over the network, already converted by Roon to PCM.

 

Roon -> VST host (with Dirac VST) -> DLNA Server -> Cat 5e -> Lumin ?

[One and a half]

15 hours ago, One and a half said:

 

 

Roon -> VST host (with Dirac VST) -> DLNA Server -> Cat 5e -> Lumin ?

Follow up, VST host looks for ASIO or sound cards as inputs and outputs rather than an application. It could not see Roon. Roon can output to system audio which might be a way around, but Server 2016 has the audio service disabled. 

Is there a hardware device that performs room EQ as a passthrough like this one from Accuphase?

 

 

[mitchco]

@One and a half you need digital loopback capability to route the output of Roon to the VST and then to the DAC. On the PC something like https://www.vb-audio.com/Cable/ or https://vac.muzychenko.net/en/ should work.

 

I see this person got it to work in a basic setup:

https://community.roonlabs.com/t/roon-vst-plugins-hifiberry-digi-pro-possible/73928

There is also a Dirac doc on how to do it as well:

http://diracdocs.com/Windows-Using_Dirac_plugins_with_players_not_supporting_plugins.pdf

 

But, I have no idea about DLNA...

 

Unfortunately, most hardware devices are limited by the processing power required for low frequency control. The lower the frequency, the more "filter taps" required. So most hardware is limited to 8,000 FIR filter taps, whereas on the PC we can easily do 65,536 or even 131,072 taps. https://www.deqx.com/ is about the only hardware solution I would consider, but it is considerably more expensive than Dirac...

[mitchco]

19 hours ago, mwhitak said:

Or Sonarworks, another option.

While Sonarworks is indeed another option, it is not in the same category as Dirac, Acourate or Audiolense, it is amplitude correction only. It does not have any timing correction capabilities.

[One and a half]

11 hours ago, mitchco said:

@One and a half you need digital loopback capability to route the output of Roon to the VST and then to the DAC. On the PC something like https://www.vb-audio.com/Cable/ or https://vac.muzychenko.net/en/ should work.

 

I see this person got it to work in a basic setup:

https://community.roonlabs.com/t/roon-vst-plugins-hifiberry-digi-pro-possible/73928

There is also a Dirac doc on how to do it as well:

http://diracdocs.com/Windows-Using_Dirac_plugins_with_players_not_supporting_plugins.pdf

 

But, I have no idea about DLNA...

 

Unfortunately, most hardware devices are limited by the processing power required for low frequency control. The lower the frequency, the more "filter taps" required. So most hardware is limited to 8,000 FIR filter taps, whereas on the PC we can easily do 65,536 or even 131,072 taps. https://www.deqx.com/ is about the only hardware solution I would consider, but it is considerably more expensive than Dirac...

Thanks here for the tips, can see how to route Roon's output to the virtual cable and then to Dirac. If the PC has an attached spdif. USB DAC, there's no problem.

 

For Ethernet routing, the Dirac output can be 'wired' to Jriver, as Jriver is a sound card in itself and can operate as a service. Jriver can send Ethernet packets to the Lumin via DLNA. 

 

You may well ask why not use Jriver in the first place to select what to play and avoid the run around, I don't use Jriver for primary listening, although I have purchased a licence. Roon has the controls on android, ioS well established, Jriver bought the best remote and left it to rot.

 

Also thought about Roon's integration with HQPlayer,  but  NAA and Lumin don't work together. 

 

I take it Dirac setup once commisionined is a set and forget excercise, if regualr changes are required, I would need to bring my server to the living room for the microphone calibrations every time, or use a spare dedicated Cat5 cabling for the microphone, also possible.

[mitchco]

Hi @One and a half yes, once you take the measurements, and happy with them, you are good to go, and can put the measurement mic away. Of course if you change speakers, speaker placement, listening position, etc., then you will need to measure again. Now that you have the measurements, you can play with the target response and try a partial correction from 600 Hz on down, or full range correction, different target curves, etc., and easily A/B them in Dirac Live Processor while listening to music. Once you have settled on what sounds best to your ears, it is set and forget and enjoy the music!

[Le Concombre Masqué]

On 2/26/2020 at 3:30 PM, audiobomber said:

 

[GSWaul]

My desktop running JRiver is in a different part of my house from my audio system.  Question- is there a way to load Dirac Live 2 on a laptop and connect to the desktop running JRiver and the DLP VST?  

[mitchco]

Hi @GSWaul Sorry for the delay. Not sure about your details, I presume the laptop and desktop on the same network? If so, it should be able to see it. You might have to make a few adjustments as described here: https://forum.avast.com/index.php?topic=221321.0 

[Axial]

Excellent review and analysis, thank you sir mitchco.

[JR4321]

Why do so many audiophiles dislike/distrust and avoid room correction software products?  I see this on multiple forums and in conversations with many.

[mitchco]

@JR4321 

Great question!! I can offer one perspective with some thoughts:

 

1) Room correction is a technically complicated subject area as there are several aspects to it. As alluded to in the article, some aspects are; audio digital signal processing, loudspeaker directivity, Schroeder frequency, standing waves, room resonances, early reflections, late reflections, the ears amplitude and frequency response non-linearity’s to sound, what to correct, what not to correct, etc., is what makes it a technically complicated subject area. I have yet to find a well written “layman’s” article on how room correction works and what the results are supposed to be. I go into gory detail in my book, but it isn’t a summary article. There is such a thing as an ideal loudspeaker in an ideal room that can be modelled and emulated. Unfortunately, most explanations are either too technical or are (wildly) incorrect, which leads me to a 2^nd reason.

 

2) Because of the technical complexity, most folks don’t have the technical skills to understand what they are seeing on a chart and how it correlates to what we hear. So it makes it difficult to know what the end result should be or sound like, and most importantly, how to obtain it. There have been several scientific studies that correlates what makes for a good sounding loudspeaker in a room with objective measurements. Floyd Toole and most notably, Sean Olive have undertaken several scientific studies in this area correlating peoples listening preferences with objective measurements with loudspeakers in rooms and room correction systems. I have linked to a few studies in this article, plus other room correction articles I have written. In fact, there are literally dozens of repeatable scientific studies in this area, but again requires some level of technical acumen to spend the time reading and understanding.

 

3) This ain’t your granddaddies 31 band eq 🙂 Modern Digital Signal Processing (DSP) software is very sophisticated and coupled with powerful computers one can alter the frequency and timing response of a loudspeaker in a room to just about anything you want. Put another way, not all DSP room correction systems/techniques are the same and some are orders of magnitude better than others. Some work in the time domain, others do not. Some offer tailoring of every possible parameter, others do not. The list goes on. But perhaps the most important point is that most folks don't know how powerful software room correction has become.

 

4) And the elephant in the room, double pun, is that loudspeaker manufacturers (mostly) do not want folks to use room eq with their loudspeakers for a whole pile of reasons (e.g. don’t mess with my voicing, mics aren’t ears, yet those are used in the design of the loudspeaker in the first place, and a laundry list of other myths built up over the years - some justified with very poor eq systems from yesteryear). The biggest reason being that if one were to use state of the art DSP room correction system on Speaker A and then use the same target frequency response for a similar Speaker B and then A/B them (which is difficult to do) one may be hard pressed to tell the two speakers apart. Kudos to some speaker manufacturers, who have the confidence in their products to actually make a statement like that. For example, Martin Mensink, designer of the Dutch and Dutch 8c, “I've had the Kii's and the 8c's side by side in my living room for a while. The Kii's too are remarkably good speakers. With just some subtle EQ the two could be made to sound very similar on most program material - to the extent that I might not be able to distinguish them in a proper blind test. I'm still amazed sometimes by the extent to which differences in sound can be explained by frequency response.” Having performed the same experiment above myself with the speakers mentioned and others, there is considerable truth to this.

 

The irony is that for around $500, which includes the calibrated measurement microphone and state of the art room correction software, will make the biggest sonic optimization/improvement that one can make to your existing sound system that is both audible and measurable for the $’s spent. The caveat is one must know what one is doing to achieve a successful result. Companies like Dirac are making it easier to obtain a good result by limiting the amount of variables the user can play with. But as I mentioned in the article, that in itself is also a trade-off.

 

At this stage in the progression of software based room correction adoption, most folks that have experienced good room correction, even just for levelling out the bass frequencies, would not go without it. The audible difference in smooth sounding bass versus uneven bass response, virtually everyone can hear the difference as the difference is considerable. We are talking going from +20 dB peak to peak ripple response in the low end to +- 3 dB envelope. Everybody that has a pair of ears can hear the difference 😉 Again, part of this is the education to know that below the room’s transition frequency into standing waves/room modes, is to know that the room is in control of the bass response, not the loudspeaker. It takes a bit of understanding/time to wrap ones head around that.

 

Hope some of that is useful. I have considered writing a layman’s article on the subject area to help folks understand what is being measured, what is being corrected and why. Maybe it is time...

 

Have a great weekend!

Mitch

[JR4321]

Thanks for the thoughts.  Agree!  Your point #4 reminded me of that story about Carver making his amp sound like any other they want and getting reviewers to try to tell them apart.  

[cpdk]

Hi @mitchco

 

Great article!

For reference, have you done a 3-way comparison: Dirac vs. Acourate vs. Audiolense?