Dirac validation

dallasjustice

Member Sponsor
Apr 12, 2011
2,067
7
0
Dallas, Texas
I have been an avid DIRAC Live user for a while now. DIRAC has two parts. The first part is the measurement and filter creation tool. It is called the Dirac Live Calibration Tool (DLCT). The second part is the filter itself. The filter is stored inside of the Dirac Audio Processor (DAP). DIRAC is very different from any of the other full frequency target based DSP tools in two important ways. First, the mixed phase filter is unique in that it's not a fully FIR filter nor IIR filter. It's designed to be low enough latency so that one can turn it on and off on the fly to clearly hear what the filter is doing in real time and sound super transparent.

Second and more importantly, DIRAC uses a measurement protocol which requires a total of 9 measurement positions for both the right and left speakers. That's a total of 18 measurements. Why is this so important? First of all AES member JJ Johnston ("In the rain" on this forum) opened my mind to the limitations related to condenser mics (measurement mics). It's my understanding that DIRAC doesn't simply average the 9 points, but rather, it combines the measurements in a way that helps create filters that can correct what needs to be corrected and not correct what doesn't need to be corrected. In my experience, the measurement is THE most important part of DSP: Garbage in---->Garbage out. It's that simple. Here is an image of the measurement points in 3D:
chair measurement dirac.jpg

When the user has completed their DLCT session and created an optimized filter, DLCT creates a "predicted" frequency response and "predicted" impulse response. These graphs are intended to represent the before and after responses as they are combined inside DIRAC as derived from the 18 measurements taken. Here is an example from my system:
Screen Shot 2014-07-07 at 10.55.30 PM.jpg Screen Shot 2014-07-07 at 10.54.53 PM.jpg

Now, I must say that I've wondered what the "real world" measurements would be if I were to combine the same 18 measurements that DIRAC takes and do a before and after DIRAC filter to determine whether the DIRAC filter actually comes close to the "predicted response." So the problem is: How can I validate the DIRAC filter to see if it's really working?

To do this, one needs to be able to take a log sweep measurement through the DAP with the desired filter on and then take the same measurement through DAP with the desired filter off. So, instead of taking 18 measurements in 9 positions, this experiment requires a total of 36 measurements in 9 positions. Ughh!

I first tried REW on my windows server. I couldn't get a valid measurement through the DAP filter. I think the problem has something to do with the REW interface with DAP. I really have no idea why it won't work. But trust me: it won't work. I tried everything and it's impossible.

At this point, I almost gave up. But then I remembered that I have a mac book pro. I haven't turned it on on more than a year. I'm not a mac person. I turned it on and downloaded a program called fuzzmeasure. I am sure you mac folks know this wonderful measurement tool very well. Anyway, it was a breath of fresh air. I am used to using REW. When I fired up fuzzmeasure, I was taking good measurements through the DAP with my desired filter in five minutes. Rejoice!! I like using it so much and found it so intuitive, I bought it. If you've ever felt that REW was too complicated or intimidating (like me), you should try out fuzzmeausure if you have a mac. It's a wonderful thing.

So my setup for measurement is a calibrated Earthworks m23 with the calibration file installed in fuzzmeausure. I use an ADC/mic pre called the USBpre2. The USB pre2 is an awesome high end calibration device. It's very simple to use, very powerful and super accurate. There's no need for a loopback FR correction. I ran all measurement through my DEQX HDP-4 which acts as a crossover and some small speaker correction. So all measurements go through the exact same system with which I listen. The measurement protocol is was exactly the same used in the DLCT; 9 points of individual right and left impulse response sweeps.

This is a 1/24 per octave average of all 18 measurements with NO DIRAC FILTER:
24 filter off cube average.jpg

And now this is the exact same 1/24 per octave average of all 18 measurements with DIRAC FILTER ON:
24 octave average filter ON DIRAC cube.jpg
 
Last edited:

dallasjustice

Member Sponsor
Apr 12, 2011
2,067
7
0
Dallas, Texas
Impulse Response

Frequency response is only one half the coin. What about impulse response? Does DIRAC live really work in the time domain as well? I tried to average normalized impulse responses for all 18 measurements, but it didn't work well. Instead I posted below the combined right/left impulse reponses at center seated position. The green line is NO DIRAC FILTER and the yellow line is the impulse response measured through the DIRAC filter.
average impulse R L Center comparison.jpg

Anyone interested in better understanding this measurement should read flavio here.
 
Last edited:

dallasjustice

Member Sponsor
Apr 12, 2011
2,067
7
0
Dallas, Texas
Very interesting. Hope there's more parts coming up?
What would you like to see? I thought about posting waterfalls but it can't figure out how to do waterfall overlays in fuzzmeasure. I know they can be done in REW. I thought it would be a little annoying to post 36 individual waterfalls. :)

I am open to criticism or help. If someone else knows of better or more relevant measurements, please let me know. However, I think the FR and impulse response are the best representations.
 

Dre_J

Industry Expert
Mar 6, 2012
478
1
0
Do you really have a 20 dB hump in your low bass without signal processing? Is this because the subs are turned up really high and uncorrected? If so what does it (the low bass FR) look like when adjusted without your signal processing and these subwoofer amplitude offsets you have added for the processing software to work?
 

Dre_J

Industry Expert
Mar 6, 2012
478
1
0
It's my understanding that DIRAC doesn't simply average the 9 points, but rather, it combines the measurements in a way that helps create filters that can correct what needs to be corrected and not correct what doesn't need to be corrected.

Can you expand on this? How does this combining work? How does it determine what to alter and what not to alter?
 

Dre_J

Industry Expert
Mar 6, 2012
478
1
0
I ran all measurement through my DEQX HDP-4 which acts as a crossover and some small speaker correction.

What is the DEQX HDP-4 doing that the software can't do?

In your situation, is this hardware required to accomplish your specific situation or can you do everything you are currently doing without it?

What is "small speaker correction" in the DEQX that can't be done in the DIRAC processing SW you are describing?
 

dallasjustice

Member Sponsor
Apr 12, 2011
2,067
7
0
Dallas, Texas
Do you really have a 20 dB hump in your low bass without signal processing? Is this because the subs are turned up really high and uncorrected? If so what does it (the low bass FR) look like when adjusted without your signal processing and these subwoofer amplitude offsets you have added for the processing software to work?

At 23.5hz my length mode rings like a bell. My room is 24' long. Therefore the half length of the primary length mode is 23.5hz. I have 6 Modex plate and other LF control. None of them touch this frequency. DSP is the only answer for pretty much everything below 75hz.
 

Dre_J

Industry Expert
Mar 6, 2012
478
1
0
At 23.5hz my length mode rings like a bell. My room is 24' long. Therefore the half length of the primary length mode is 23.5hz. I have 6 Modex plate and other LF control. None of them touch this frequency. DSP is the only answer for pretty much everything below 75hz.
That is all understood but looking at the 1/24th octave smoothed/averaged chart it looks like there is a user created broad band amplitude peak for the purpose of processing. If this isn't the case, is the bass in that room really that unbearable?
 

dallasjustice

Member Sponsor
Apr 12, 2011
2,067
7
0
Dallas, Texas
That's a different topic. There are other ways to do a crossover and speaker correction. I find the DEQX to be an excellent and simple solution. I need to integrate my jl audio f113 mono subs on front and back walls. I may post before and after with and without the subs later on when I find the time. However, I can tell you they do eliminate the primary room mode at. 47.5hz. They also smooth out bass response, reduce speaker distortion at LF and give my system unheard of dynamics.

What is the DEQX HDP-4 doing that the software can't do?

In your situation, is this hardware required to accomplish your specific situation or can you do everything you are currently doing without it?

What is "small speaker correction" in the DEQX that can't be done in the DIRAC processing SW you are describing?
 

dallasjustice

Member Sponsor
Apr 12, 2011
2,067
7
0
Dallas, Texas
That is all understood but looking at the 1/24th octave smoothed/averaged chart it looks like there is a user created broad band amplitude peak for the purpose of processing. If this isn't the case, is the bass in that room really that unbearable?

You can draw the target curve in DIRAC how ever you wish. I've found the recommended target curve best.
 

Dre_J

Industry Expert
Mar 6, 2012
478
1
0
That's a different topic. There are other ways to do a crossover and speaker correction. I find the DEQX to be an excellent and simple solution. I need to integrate my jl audio f113 mono subs on front and back walls. I may post before and after with and without the subs later on when I find the time. However, I can tell you they do eliminate the primary room mode at. 47.5hz. They also smooth out bass response, reduce speaker distortion at LF and give my system unheard of dynamics.

Again, what you say is understood. It may be thought of as a different topic but it is relevant, at least to me, to the before and after FR plots posted for proper perspective. To me, this is similar to my question about that huge bass hump since I'm looking for context since my reading of the FR chart at that level (1/24th octave) of measuring tells me something else is going on regardless of whether the software is on or off especially in the bass. Based on the post quote above, my suspicions appear to be valid.
 
Last edited:

Dre_J

Industry Expert
Mar 6, 2012
478
1
0
You can draw the target curve in DIRAC how ever you wish. I've found the recommended target curve best.

Understood, again.

However, I'm talking about the huge broadband hump in the bass of the before DIRAC plot. Doing some deciphering of your posts so far, it leads me to believe you have the bass amplitude set pretty high and that accounts for the huge bass hump more than the room induced peak comment. Again, this is with DIRAC turned off.

Is this so you can "correct" it with the DIRAC software enabled to reach your target curve? If so, this explains the anomalies of the before and after curves. and some of the purpose of the DEQX.
 

audioguy

WBF Founding Member
Apr 21, 2010
2,778
61
445
Near Atlanta, GA but not too near!
I use OmniMic. I place the signal generating files provided by OmniMic on my server so running with and without Dirac running is very simple. I must say, your "without Dirac" FR (excluding the ginormous bass hump) is very good.

I too have found the recommended Dirac target curve the best. I have tried a number of other options and each that I have tried, while they do have some upside, have more downside.

Love Dirac and am waiting to get an SSP with it!
 

dallasjustice

Member Sponsor
Apr 12, 2011
2,067
7
0
Dallas, Texas
As I previously said, subwoofer integration is a different topic. Before you start claiming my sub integration is right, you need a lot more information; crossover points, slopes, room dimensions, sub positions time and phase measurements. I've done the work to integrate my subs. Nyal and I have worked on integration and I know they are optimally integrated. I am not going to get into that here.

The purpose for this thread is to demonstrate that DIRAC LIVE does exactly what it sets out to do. It greatly improves frequency and time behavior. The end results is MUCH better music.


Understood, again.

However, I'm talking about the huge broadband hump in the bass of the before DIRAC plot. Doing some deciphering of your posts so far, it leads me to believe you have the bass amplitude set pretty high and that accounts for the huge bass hump more than the room induced peak comment. Again, this is with DIRAC turned off.

Is this so you can "correct" it with the DIRAC software enabled to reach your target curve? If so, this explains the anomalies of the before and after curves. and some of the purpose of the DEQX.
 

Dre_J

Industry Expert
Mar 6, 2012
478
1
0
As I previously said, subwoofer integration is a different topic. Before you start claiming my sub integration is right, you need a lot more information; crossover points, slopes, room dimensions, sub positions time and phase measurements. I've done the work to integrate my subs. Nyal and I have worked on integration and I know they are optimally integrated. I am not going to get into that here.

The purpose for this thread is to demonstrate that DIRAC LIVE does exactly what it sets out to do. It greatly improves frequency and time behavior. The end results is MUCH better music.

No need to put up a defensive shield. I simply wanted to know what is going on in the before DIRAC plot and what accounted for the huge broadband bass hump. If it's something required for your particular integration approach/situation/setup, that's fine. Getting a clear answer felt like pulling teeth to me.

Don't worry, I'm not asking for anything more than what I deciphered. Which is you are using other methods for bass integration and that accounts for the huge broadband bass hump when DIRAC is off. At least that's my understanding based on the posts so far.
 

dallasjustice

Member Sponsor
Apr 12, 2011
2,067
7
0
Dallas, Texas
The FR plot I am showing here is not designed to show how I've integrated my subs. I can start a new thread on that. And I might do so later. Btw,if you read both FR graphs I've posted without using DIRAC, you will notice the "hump" is only between 20-30hz.

Before you start with scary adjectives like "unbearable", you need to understand that the measurements I've taken here are from a 3D 9 point average of 1/24th per octave FR. If I showed the higher resolution single point shots Nyal and I did in REW used to integrate the subs, things would look different than they do here.

Graphs don't totally explain how a system sounds. They are only tools to demonstrate and help to solve room acoustics problems and give broad acoustic trends. In this case, all I am trying to show is the differences in the before and after DIRAC filters. It just so happens to be a very effective demonstration on what DIRAC is doing to improve sonics in my room.

No need to put up a defensive shield. I simply wanted to know what is going on in the before DIRAC plot and what accounted for the huge broadband bass hump. If it's something required for your particular integration approach/situation/setup, that's fine. Getting a clear answer felt like pulling teeth to me.

Don't worry, I'm not asking for anything more than what I deciphered. Which is you are using other methods for bass integration and that accounts for the huge broadband bass hump when DIRAC is off. At least that's my understanding based on the posts so far.
 
Last edited:

Dre_J

Industry Expert
Mar 6, 2012
478
1
0
The FR plot I am showing here is not designed to show how I've integrated my subs.
Amazingly, that's why I asked the question. Do you think I'm the only one that noticed the plot and thought to ask about some of it? I'd like to think it was a reasonable question that would allow you to quickly explain so others would not ask the same.

Before you start with scary adjectives like "unbearable", you need to understand that the measurements I've taken here are from a 3D 9 point average of 1/24th per octave FR. If I showed the high resolution single point shots Nyal and I did in REW when we integrated the subs, things would look different than they do here.

Graphs don't totally explain how a system sounds. They are only tools to demonstrate and help to solve room acoustics problems and give broad acoustic trends. In this case, all I am trying to show is the differences in the before and after DIRAC filters. It just so happens to be a very effective demonstration on what DIRAC is doing to improve sonics in my room.

I have my answer already. You really don't need to go any further unless you want us to play this out until it's end. again.
 

Nyal Mellor

Industry Expert
Jul 14, 2010
590
4
330
SF Bay Area, CA, USA
Just thought I'd chime in. I did the sub integration work here.

There are many ways to integrate subwoofers. You can integrate them so they drive a room mode constructively, or destructively, for example.

The peak in the before measurements is really inconsequential to this discussion. It was a conscious choice we made because we knew Dirac (or parametric EQ for that matter) could take the bass peak out.

If I was integrating a sub and for whatever reason the client did not want to use EQ then we would have integrated them differently, to reduce the level of that bass peak. For example we could have used the ELF control on the JL subs (low frequency shelving) to shelve down the low frequencies or we could have delayed the rear sub differently so that it drove the room mode destructively.
 

Brucemck2

Member Sponsor
May 10, 2010
354
55
373
Houston area
I use an ADC/mic pre called the USBpre2. The USB pre2 is an awesome high end calibration device. It's very simple to use, very powerful and super accurate. There's no need for a loopback FR correction.

Great before and after posts on Dirac! I've seen similar impressive before and after results in my system under Trinnov, as measured by both the frequency and impulse response plots generated by REW.

Do you get time/distance measures and also phase measures, like in REW, even without a loopback? (Perhaps the loopback is already hardwired into the device for one channel?) I thought the loopback was required to get a consistent timing reference.
 

About us

  • What’s Best Forum is THE forum for high end audio, product reviews, advice and sharing experiences on the best of everything else. This is THE place where audiophiles and audio companies discuss vintage, contemporary and new audio products, music servers, music streamers, computer audio, digital-to-analog converters, turntables, phono stages, cartridges, reel-to-reel tape machines, speakers, headphones and tube and solid-state amplification. Founded in 2010 What’s Best Forum invites intelligent and courteous people of all interests and backgrounds to describe and discuss the best of everything. From beginners to life-long hobbyists to industry professionals, we enjoy learning about new things and meeting new people, and participating in spirited debates.

Quick Navigation

User Menu

Steve Williams
Site Founder | Site Owner | Administrator
Ron Resnick
Site Co-Owner | Administrator
Julian (The Fixer)
Website Build | Marketing Managersing