Article: Acourate Digital Room and Loudspeaker Correction Software Walkthrough

[mitchco]

View full article

[MikeJazz]

Fantastic article!

[ackcheng]

I cannot agree with you more! I have been using Acourate for over 7 years and cannot live without it! Once you have a chance, rip out the passive XO in your speaker and run Accourate enabled active XO, you will be surprised how much further improvement you can achieve!

[Guy La Rue]

So if I understand correctly (I am a novice) ..it modify the signal streaming from my server/laptop to the DAC ? the DAC play the modified file to compensate the negative room effect? Can in work with server like Aurender and so on?

 

thanks a lot!!

 

Guy;-)

[Supperconductor]

I was astounded at the difference I heard from the Dirac software demo at THE Show in Newport Beach, CA recently. It really piqued my interest in speaker/room correction software. Thanks for a great article.

[ted_b]

Mitch,

Great article! Incredible detail, yet well paced and understandable. You set a standard for us reviewers to have to strive for.

 

Question: although I have the luxury of having a professionally designed and built acoustic space, there is still room for improvement, especially in surround applications. As the computer audio world slowly but surely embraces higher than 24/192 PCM rates, and then also DSD64, DSD128, etc do you see this type of room correction becoming available for that segment?

Ted

[Guy La Rue]

Got my answer....went to their web site !! NAS solution !!!

[MarcB83]

Great and very useful article! Thanks!!

 

Any suggestions for an external ADC to use with a Windows laptop and Acourate?

 

Thanks.

 

Marc

[artaudio]

Mitch,

 

Thanks, for the detailed walk through. my question is do you know the latency of the FIR processing? not sure this would be compatible with video based sources. while most of our time is 2 channel audio only where latency is not an issue we often use digital TV where lip-sync would be an issue.

 

thanks,

 

Alan

[input username here]

I have used DRC (TacT) with mixed success in the past.... The problems with this technology include the difficulty in setup (which is touched on in this article) and the pervasive suspicion that one could always improve the results with just a bit more tweaking--leading to a lot of tweaking and correspondingly less listening to music. Although the Katz's suggestion that "[f]or the first time with any correction system, [he] felt no need to change or tweak any filters or add any filters to the circuit" is certainly welcome; I've spoken with Peter Lyngdorf at length too about his post-TacT DRC and he said that removing (most) user-tweak-able features from his products was intended to reduce the sense of anxiety from the user (though I cannot comment on the effectiveness of the Lyngdorf system in my own system/room).

 

DRC is not an issue for me now, as I use a headphone system (with a heavy dose of DSP of its own). But, if I ever went back to a speaker system, DRC would certainly be something I'd like to give another try and Acourate seems like a powerful and cost-effective approach. However, if I do go back to speakers, it will be with mbl omnis, my favorite speaker family. So I wonder, will DRC work with these types of speakers? Given that omnis create, as a matter of course, distortion that is filtered via the psychoacoustic "precedence effect." Would DRC try and correct away the "distortions" by which omni-directional speakers make their magic? Would Acourate (or Tact or Lyngdorf or Trinnov, etc.) try and get an mbl to preform like an ideal direct radiator or would it let it be the "flawed" omni that it was made to be? (The same concerns would impact fans of dipolar speakers, like Maggies, too, I expect).

 

Finally, I'd like to thank Computer Audiophile (and "guest" author mitchco) for continuing to report on, in depth, technologies of great interest to the audiophile and computer communities, great article!

[mitchco]

MikeJazz and ackcheng – thanks! ackcheng – active XO is my next step. I should have mentioned that Acourate has extensive capabilities around digital XO. Functions like Butterworth filters, Linkwitz-Riley filters, Neville-Thiele filters, Bessel filters and also Horbach-Keele filters are available. The speaker drivers can be linearized individually. Time delays between the drivers (caused by the different positions of the acoustic centers) can be detected and corrected easily. The crossover frequencies can also be verified and optimized by checking the harmonic distortions of the individual drivers.

 

Guy La Rue, you beat me to it! - AcourateNAS.

 

Thanks Ted! Wrt to your q, I would ask Uli on the Acourate forum.

 

Marc, there are many to choose from, but other than my Lynx Hilo, I do not have experience with these. I would post your q on Acourate forum to see what other folks are using.

 

Alan, JRiver MC18’s Convolution engine takes into account FIR filter latency, so the audio and video are perfectly in sync. Works great on my system. Others on the Acourate forum have it working with surround as well (joining the forum is required to see the message linked).

 

Input user name here – thanks for your feedback. Wrt to tweaking – I cannot begin to tell you the amount of time I spent tweaking with other DRC systems. However, with Acourate, after my 3^rd run, which I reported on here, I have not felt the need for any further tweaking – which for me is a first :-). Wrt your q about omni or dipole speaker designs, I would ask the Acourate forum (linked above) for first-hand experience.

[MikeJazz]

Would Acourate (or Tact or Lyngdorf or Trinnov, etc.) try and get an mbl to preform like an ideal direct radiator or would it let it be the "flawed" omni that it was made to be? (The same concerns would impact fans of dipolar speakers, like Maggies, too, I expect).

 

I can answer for my own experience with Quad esl, also a dipolar design...

Yes, the software can still work it's magic. It calculates it's filters with no problems, and I can easily perceive much better "focus" using the filters calculated for the listening positions I have.

Lyngdorf and Quad are working beautifully integrated!

 

I am always curious about "unboxy" designs, so I hope I can hear some MBL's in the future...

[wgscott]

Is it possible to use this on a Windows computer to generate the correction and then use the results with a plug-in on a suitable Mac OS X player (like Audirvana)?

[Ellsworth]

Great great article. Simple question that I should be able to figure out but am not sure of. Can this be used on a Mac running Audirvana Plus? It looks Windows based to me. Thanks in advance for any responses.

[bobkatz]

So if I understand correctly (I am a novice) ..it modify the signal streaming from my server/laptop to the DAC ? the DAC play the modified file to compensate the negative room effect? Can in work with server like Aurender and so on?

 

thanks a lot!!

 

Guy;-)

 

Normally you would run a convolver such as Acourate Convolver, or the Convolver in JRiver (using Acourate filter files), or the Convolver in Foobar. On the Mac side it is possible that Pure Music can run a convolver, check with them.

[bobkatz]

Is it possible to use this on a Windows computer to generate the correction and then use the results with a plug-in on a suitable Mac OS X player (like Audirvana)?

 

It should be possible to supply filter files to any player that has a built-in convolver. Acourate generates standardized filter files and with some work you can also create .cfg files in SourceForge's convolver format.

[bobkatz]

Regarding tweaking, what I found is that Acourate is the first DRC system I've tried where I was not tempted to further tweak the settings after they were made. (except for the Target, of course). Almost every other system I've tried overcorrects in some frequency range or another. Acourate does not overcorrect (or apparently, undercorrect, either). I've not had a suspicion of a bass note out of place since I got Acourate going. I am running extensive trapping in a well-designed room with a reflection-free zone, so your mileage may vary. The worse the room, the more likely you're going to find some resonant notes or missing notes, as you mustn't rely on DRC as your correction. DRC should be the icing on the cake in a well-treated room.

[bobkatz]

Mitch,

Great article! Incredible detail, yet well paced and understandable. You set a standard for us reviewers to have to strive for.

 

Question: although I have the luxury of having a professionally designed and built acoustic space, there is still room for improvement, especially in surround applications. As the computer audio world slowly but surely embraces higher than 24/192 PCM rates, and then also DSD64, DSD128, etc do you see this type of room correction becoming available for that segment?

Ted

 

I'm using Acourate at rates up to 192 right now, no problems. As for DSD, there is no hope for Acourate correction to work natively with DSD. All of these correction systems work in PCM and cannot play native DSD without converting to PCM first. So I lost the ability to play my SACDs when I installed Acourate. When I get the budget I'm going to try out the Oppo BDP-93 or possibly the 103 player with the Audiopraise Vanity converter. Since it effectively can "upsample" 64x DSD to a high rate PCM (176.4 kHz) with very low distortion, it is possible it can do that transparently or reasonably transparently. I hope to get that going in Surround to play my Surround SACDs in 176.4 kHz PCM with the Vanity mod. There will always be a sonic difference, but I've never considered 64x DSD to be the be-all-end-all. It's a bit "softer" sounding than a high rate PCM original. There's nothing magical about SACD, but it's a pleasant format and certainly better than 1644 CD!

[bobkatz]

Mitch,

 

Thanks, for the detailed walk through. my question is do you know the latency of the FIR processing? not sure this would be compatible with video based sources. while most of our time is 2 channel audio only where latency is not an issue we often use digital TV where lip-sync would be an issue.

 

thanks,

 

Alan

 

Yup: Acourate's 65K filter length has tremendous latency. More than a second at 44.1 kHz! This is not a problem for audio only listening. But as Mitch replied, if you convert Acourate's filters to .cfg format you can use them in JRiver's Convolution engine, and latency is completely taken care of. It's a wonderful pleasure to watch and listen BluRays with 5.1 surround fully corrected by Acourate. All sample rates from 44 through 192 (and possibly beyond but I've never tested) are transparently taken care of.

[Miska]

I'm using Acourate at rates up to 192 right now, no problems. As for DSD, there is no hope for Acourate correction to work natively with DSD.

 

I'm running digital room correction just fine for DSD at native rate...

[input username here]

I can answer for my own experience with Quad esl, also a dipolar design...

Yes, the software can still work it's magic. It calculates it's filters with no problems, and I can easily perceive much better "focus" using the filters calculated for the listening positions I have.

Lyngdorf and Quad are working beautifully integrated!

 

I am always curious about "unboxy" designs, so I hope I can hear some MBL's in the future...

 

Thanks for the answer Mike. I have to admit that this does not make intuitive sense to me--I don't see how the DRC can tell the baked-in "distortions" of these designs from room-induced distortions. But then again, I'm not a digital engineer! It's good to hear that you have DRC working with a non-monopole with success. It give me hope to clean up an omni without killing its unique character (if I do go back to speakers).

 

BTW Do try the mbl's if you get the chance. Although they are admittedly not everyone's cup of tea, (and notwithstanding that there are other omnis out there) I do not think that there is anything like them on the market. If they are your thing (as they are for me), there is just no substitute--I have heard many of the usual suspects out there (e.g. Magicos, Wilsons, Raidho, Avantgarde, etc. etc, etc.) and while many were mind-blowingly good (some more than others), I have never found a speaker I prefer to the mbl family.

[firedog]

I'm running digital room correction just fine for DSD at native rate...

 

Okay, but how are you doing it? If Acourate can't do it, some of us would be interested in what you are using as a substitute.

 

My (admittedly limited) knowledge of DRC programs is that they all work with PCM, and most will downsample 4X files to 24/96 in order to do the RC.

[UliBru]

Okay, but how are you doing it? If Acourate can't do it, some of us would be interested in what you are using as a substitute.

 

My (admittedly limited) knowledge of DRC programs is that they all work with PCM, and most will downsample 4X files to 24/96 in order to do the RC.

Acourate is the toolbox to measure the audio system and to calculate FIR filters. The filters have to be applied by a convolution software. The target is to simply get good filters (or very good or damn good).

 

Applying the filters is a second step.

There are different convolution programs on the market. Either as plugins (e.g. FooConvolver), stand-alone pograms (AcourateConvolver, Brutefir, JConvolver) or embedded in a player (JRiver Mediacenter, HQPlayer). You can get free programs or you have to purchase them.

 

A first test has shown that the Signalyst HQPlayer can apply Acourate filters also for DSD. It is anyway good to know that it works. I do not know if Signalyst will reveal details.

[Bob Stern]

Is it possible to use this on a Windows computer to generate the correction and then use the results with a plug-in on a suitable Mac OS X player (like Audirvana)?

 

It should be possible to supply filter files to any player that has a built-in convolver. Acourate generates standardized filter files...

 

Audirvana and Pure Music can host Mac OS X AU plugins.

 

Two convolvers in AU plugin format are:

 

Lernvall LAConvolver - free:

Lernvall Audio

 

Mellowmuse $50:

Mellowmuse IR1A - Zero Latency convolver RTAS, Audio Unit and VST plugin for OSX and Windows

 

One issue is that you need a different filter impulse response for each sample rate of music you will play. Lernvall performs SRC on the impulse response in real time to match the sample rate of the music. Alternatively, you can configure Audirvana or Pure Music to upsample the music to a fixed sample rate, such as 192 Kbs, and then use a 192 Kbs impulse response from Acourate.

 

Yet another approach is to avoid the need for real-time convolution by creating corrected copies of your music files before you play them (by convolving the music file with the Acourate impulse response). I believe this is what AcourateNAS does, but I'm not sure.

[Bob Stern]

Is it possible to use this on a Windows computer to generate the correction and then use the results with a plug-in on a suitable Mac OS X player (like Audirvana)?

 

It should be possible to supply filter files to any player that has a built-in convolver. Acourate generates standardized filter files...

 

Audirvana and Pure Music can host Mac OS X AU plugins.

 

Two convolvers in AU plugin format are:

 

Lernvall LAConvolver - free:

Lernvall Audio

 

Mellowmuse $50:

Mellowmuse IR1A - Zero Latency convolver RTAS, Audio Unit and VST plugin for OSX and Windows

 

One issue is that you need a different filter impulse response for each sample rate of music you will play. Lernvall performs SRC on the impulse response in real time to match the sample rate of the music. Alternatively, you can configure Audirvana or Pure Music to upsample the music to a fixed sample rate, such as 192 Kbs, and then use a 192 Kbs impulse response from Acourate.

 

Yet another approach is to avoid the need for real-time convolution by creating corrected copies of your music files before you play them (by convolving the music file with the Acourate impulse response). I believe this is what AcourateNAS does, but I'm not sure.