Article: Acourate Digital Room and Loudspeaker Correction Software Walkthrough

[JJJ]

Astonishingly little conversation about the design of the target curve... And SPL response is just one dimension to room acoustics...

[bobkatz]

Astonishingly little conversation about the design of the target curve... And SPL response is just one dimension to room acoustics...

 

Acourate actually addresses room acoustics problems multidimensionally. It's not a complete solution, but it pays attention to far more than just spl response (frequency response). Acourate's psychoacoustic response curve avoids overcorrection, which is the bane of simplified spl-based solutions (which are performed by many of Acourate's competitors). As explained to me by Uli, his psychoacoustic measurement makes thousands of calculations, calculating the room's transient response. It only deals with the peaks which it deems to be psychoacoustically important. To my ears, it works well.

 

The other thing which Acourate does is the variable FFT window, which is another form of psychoacoustic weighting. Some other systems (notably Audiolense) have a variable window, but Acourate's window appears to just work without user intervention. For more information on the advantages of a variable window, see the seminal papers by Jim Johnston et al, AES Preprints 7263, 8314 and 8379.

 

As for the target curve, I can speak for the ergonomics of Acourate's target curve, it allows you to make the frequency response you desire and the attenuation you desire very easily. As for the reasons for a target curve, I'm not an expert on it so all I can say is that a user-defined target seems to be necessary. As the measurement system cannot take into account the following: 1) taste 2) room acoustics interaction with the polar response of the loudspeaker. E.G. the narrower the polar response of the loudspeaker, the less influence the side walls have in the overall frequency response. Thus we need to have a custom target for the particular room/loudspeaker/user combination.

 

Hope this helps,

 

 

Bob

[JJJ]

My point was that determining the target curve is critical and not an easy topic.

 

And managing decay is another critical element to good acoustics.

[bobkatz]

My point was that determining the target curve is critical and not an easy topic.

 

And managing decay is another critical element to good acoustics.

 

 

Well, actually, working through the target curve is easy, it just takes time. I recommend you start with the philosophy that seems to agree with you. If you agree with my philosophy, that the target should be flat from DC to 1 kHz and then have a diagonal rolloff above that, then it's a pretty simple, but yes, time-consuming job. Since I started at 88.2 kHz for my measurements, and Acourate puts a dot in the target at Nyquist, then I use as my standard how many dB down at 44.1 kHz (the Nyquist freq) my target is set to. Then you can use a formula that will determine where to set the target for all other sample rates. FWIW, my target is -9.2 dB at 44.1 kHz, which ends up somewhere around -6 (if I recall correctly) at 20 kHz. You have to listen and change the target by 0.1 dB at a time until you are satisfied. Many people have been very happy using my target so if you like that idea, start with my target and you won't be more than a dB off, probably.

 

As for managing decay. Absolutely. Your room should be as well managed as possible preferably BEFORE you start playing with room correction. If you know how to measure and interpret Schroeder curves and interpret waterfall measurements, do it, and fix it BEFORE you play with room correction. If not, hire an acoustical consultant, FIRST. Or learn about it, first.

[esldude]

First hats off to another superb article by Mitcho. For the past decade have been using a Tact RCS system. Looking for possible software replacements, and well done reports like this one are invaluable for deciding what to take for a test spin in one's own system.

 

Even before owning a Tact I played around with speaker EQ. First with 1/3 and 1/5 octave warbles tones measured with a sound level meter and with more sophistication later on. I had read Peter Baxandall thought flat to 2khz with a roll-off was a good target. Quad designer Peter Walker was of the opinion response should slope downward 3 db per decade.

 

I think Bob Katz's suggestion of flat to 1 khz and 6 db down by 20 khz is pretty good. From there my own approach has shown that different people no surprise have slightly different preferences, and even with good EQ various rooms have some effect or perceived balance. My short and quick approach is flat to 2khz and -6 db at 20khz. Then move the inflection point downward in frequency and most people find a point they like best sometimes even down to 500 hz.

 

Beyond that many seem to like it a bit more if you go flat to 200 hz, from there slope to -3b at 2khz and -6 db at 20 khz. Then once again move only the 2 khz inflection point down in frequency to find your personal sweet spot. That can present plenty of choices, but does give some guidelines for personalizing your target response without it being overwhelming to do.

 

Once you listen to any of these you will experience a considerable benefit in terms of transparency and musical enjoyment. The fixed room/speaker response is addictive to your listening enjoyment.

 

Beyond that one can do more. 2 or 3 octave wide dips or bubbles on the curve of a fraction of a db are surprisingly obvious. With some care you can change apparent spatial depth, hall ambiance etc. etc. I would think your better mastering people would be able to do this with excellent results. This is highly recording specific however. I also think you can tweak yourself to madness with too much of this. So my suggestion is stop with just the basic suggested guidelines above for getting your personally preferred target curve.

 

Such DSP for the in room response is highly beneficial and I am glad to see it becoming more widely known and available.

 

And once again, I hope Mitcho has some idea how well he has done this article and how helpful it is. I may just give Acourate a try as it was on my short list of software based DSP to try next.

[PFaulds]

Hi all

I have some newbie questions to add to all the advanced discussions here.

I'm attempting to evaluate Acourate for my system. Using on-board Intel HD audio spdif.

Got a Dayton UMM-6 mic and downloaded the trial version of Acourate and the Logsweep Recorder. The mic does not appear as an input device in either Acourate product (I can choose HD audio mix 1 or 2) When I run the sweep, the input level does not register (no bar) but I produce apparently usable output files. What's going on here? The resulting response curves look very much like speaker response curves.

I have the mic set as the default input option and all other inputs disabled. I have "listen to this device" unchecked, because I don't want to produce feedback.

Anybody else use a similar configuration? Is there any way of being certain that I am in fact measuring the room/speaker response?

Thanks for any help and excuse my ignorance in this area

Phil

[UliBru]

Hello Phil,

 

Acourate expects an ASIO driver for a soundcard. In your case you run two different devices (Intel HD audio spdif output and USB input for mic). In such a case please use Asio4All as an Asio wrapper for Windows sound. In the Windows sound dialog you can select the USB mic as standard input and Intel HD spdif as standard output. It also makes sense to open the Asio4All control panel by the according button in the logsweep recorder, to click the tool button in the control panel and to inspect the selected input/outputs in the tree displayed at the left side of the control panel. Select a buffer size of 1024 samples.

Then the IO channel should also be listed correctly in the logsweep recorder and you can record the sweep as intended.

 

Cheers

Uli

[Bill M]

Hi Mitch,

 

Thanks so much for this excellent article. I purchased Acourate and implemented correction. My system has never sounded so good. Can't believe it took me so long to get into room correction.

[MarcB83]

Hi Mitch,

 

Thanks so much for this excellent article. I purchased Acourate and implemented correction. My system has never sounded so good. Can't believe it took me so long to get into room correction.

 

Hi Bill,

 

I am still on the fence about forging ahead due in part to the cost of the software. A few questions:

- Did you have an especially challenging room or setup where correction was almost a must?

- Is your gear very high-end?

- Would you the say the benefits are pretty much universal, i.e. regardless of music genre, volume level, etc.?

- In very few words, can you please describe the main benefits you've gain.

 

Thanks,

Marc

[mitchco]

Hi Mitch,

 

Thanks so much for this excellent article. I purchased Acourate and implemented correction. My system has never sounded so good. Can't believe it took me so long to get into room correction.

 

Hi Bill, I am glad you found the article useful. Enjoy your new sound! Cheers, Mitch

[Bill M]

Hi Bill,

 

I am still on the fence about forging ahead due in part to the cost of the software. A few questions:

- Did you have an especially challenging room or setup where correction was almost a must?

- Is your gear very high-end?

- Would you the say the benefits are pretty much universal, i.e. regardless of music genre, volume level, etc.?

- In very few words, can you please describe the main benefits you've gain.

 

Thanks,

Marc

 

 

Hi Marc,

 

I do have a very challenging room as I have a large bay window, a double French door (both on one wall), a very wide room, sitting against a rear wall, and the need to have a very large distance between speakers - 13.5feet. On the upside, it is dedicated to hifi and has solid concrete floors and no neighbours It is also fairly big 24 feet by 17 feet.

 

I would probably call my gear high-end although it is relative. I have Focal Maestro Utopia speakers and a Devialet d premier. I also have a vinyl front end in the form of. Vpi classic (although not relevant here I have power conditioning also.

 

I also have undertaken room treatment with GIK traps - 2 monster bass traps and 3 242s.

 

Benefits are most definitely universal - it is absolutely night and day better. My target curve is different to Mitch - I seem to prefer a slightly softer and fuller sound as I used a version of the B&K curve although mine varies by 13db from 20 to 20.

 

Benefits:

 

Much larger and deeper soundstage

much greater focused central image

Much more realistic timbre to instruments - I am very familiar with how acoustic instruments sound (particularly piano and orchestral)

Bass is solid and fast sounding with no overhang

[dallasjustice]

I have 2 questions:

 

How does one convert multipe .wav files into a .cfg format? IOW, how does one convert the convolution .wav files into something Jriver can work with for all sample rates?

 

What does an ideal step response look like? How can I tell the difference between HF and LF pre-ringing when I look at a step response?

[dallasjustice]

The Acourate Convolver is pretty sweet! Awesome volume control easy to deal with filters. The sound is mega!

[reverendo]

I've had some e-mail contact with Uli through Hans-Martin in 2009, when I first started to think about DRC. It's great to know that Acourate is alive and well. I'm under the impression that the Acourate might be just right for me, especially since I'm thinking of going directly from a NAS to my DAC. This would make everything so much easier.

What would be the difference between Acourate run from a PC and from a NAS?

Best regards

André

[reverendo]

The Acourate Convolver is pretty sweet! Awesome volume control easy to deal with filters. The sound is mega!

dallasjustice,

What equipment did you use measure your room? What are your impressions? Would love to get some feedback from you.

best regards

André

[Bob Stern]

I've had some e-mail contact with Uli through Hans-Martin in 2009, when I first started to think about DRC. It's great to know that Acourate is alive and well. I'm under the impression that the Acourate might be just right for me, especially since I'm thinking of going directly from a NAS to my DAC. This would make everything so much easier.

What would be the difference between Acourate run from a PC and from a NAS?

 

I wonder whether you misinterpreted a statement about using a NAS. I don't see how you can run Acourate on a NAS. I just searched for "NAS" in the archive of the Acourate email discussion list, and I saw no reference to a NAS being used to run Acourate. There were several mentions of using a NAS to store music files to be played by Acourate or other music player software running on a Windows PC or Mac.

 

Uli has a product with the confusing name "AcourateNAS". It is an offline convolver that runs on a Windows PC, not a NAS, that converts your music files into "corrected" music files that embody Acourate room correction. You then can play the corrected music files using any Mac or PC music player without a convolver plugin.

http://www.audiovero.de/en/acouratenas.php

[reverendo]

I wonder whether you misinterpreted a statement about using a NAS. I don't see how you can run Acourate on a NAS. I just searched for "NAS" in the archive of the Acourate email discussion list, and I saw no reference to a NAS being used to run Acourate. There were several mentions of using a NAS to store music files to be played by Acourate or other music player software running on a Windows PC or Mac.

 

Uli has a product with the confusing name "AcourateNAS". It is an offline convolver that runs on a Windows PC, not a NAS, that converts your music files into "corrected" music files that embody Acourate room correction. You then can play the corrected music files using any Mac or PC music player without a convolver plugin.

http://www.audiovero.de/en/acouratenas.php

Hi Bob,

Thanks for the clarification. I had looked at the AcourateNAS, but apparently didn't read carefully enough. I erroneously assumed that it would be kind of a server app on a NAS, but now I see that it actually changes the original files into files that correspond to that specific listening environment. I wouldn't be able to use them in another setting or system and, therefore, would have to double my music library. That's a pity, but I'm still interested in Acourate. I'll probably try to find a good USB measurement microphone, measure my room and send Uli a few tracks just to get an idea of what results I can expect.

Do you have any idea if the Dayton Audio UMM-6 USB Measurement Microphone is any good? I don't think that buying an Earthworks mic solely for this purpose will be worthwhile.

Best regards

André

[dallasjustice]

Andre,

I look forward to showing you my setup next week. Sorry I didn't respond to your questions here. I've complained about this thread before. For some reason, I don't always get notices even though I'm subscribed to it. Weird.

Michael.

 

 

dallasjustice,

What equipment did you use measure your room? What are your impressions? Would love to get some feedback from you.

best regards

André

[reverendo]

Andre,

I look forward to showing you my setup next week. Sorry I didn't respond to your questions here. I've complained about this thread before. For some reason, I don't always get notices even though I'm subscribed to it. Weird.

Michael.

Hi Michael,

Thank you so very much for the chance to listen to your system. In many ways it's the system that does certain things the best I've ever experienced, especially in regards to sound stage, sound stage placement and a very, very clean and deep LF that never ever gets confused, be it with the hugely complicated reproduction of jazz double bass nor organ with timpani in Saints-Saens' Symphony Nº 3. Thanks again!

This visit made me want to try Acourate and yesterday I did the recording of the sweep. My situation, though, is vastly different from Michael's, since I don't have a dedicated room and no room treatment per se, which means Acourate will have to work way harder, since Michael's room is very well treated. I did try to position my speakers the best I could, but I hope that Acourate will be able to diminish the effects of my inadequate room as much as possible. Uli is working on the files and I imagine that I should be able to listen to the modified test tracks tomorrow. I'm very, very curious in regards to the results.

Best regards

[satbox]

Hi,

I'm newbie in DRC and read this very good and helpful article. Thank you Mitcho! Now, I would like to try Acourate in my listening room.

In step 1 of the set up to take measurements, it is advisable to move any chairs, tables, sofas, etc. out of the way between the speakers and the listening position. Why? These pieces of furniture are part of the acoustic environment of the room, no?

Didier

[mitchco]

Hi Didier, thanks for your kind words and sorry for the delay. Yes, while these are part of the acoustic environment, we don’t want to correct their acoustic reflections, especially if they are in the path between the speakers and measurement mic or directly behind the measurement mic like a chair or sofa back. The corrected response is usually suboptimal. Search terms Reflection Free Zone (RFZ), early reflections, and comb filtering in small room acoustics for details.

 

If you desire to hear for yourself, try the following experiment. Take a measurement with all objects in their normal positions. Without changing anything else, and leaving the mic where it is, remove large objects (coffee table, chair, sofa…), including anything moveable between the speaker’s polar response and microphone and anything near or around the microphone. Then take another measurement. Generate a correction filter for each measurement using the same target response and other Acourate parameters. Meaning everything is the same except the two measurement files being used.

 

Put furniture back in normal position. If using JRiver’s Convolution engine, load one correction filter, then while listening to music in real time, load the other filter, there will be a slight gap and then you will hear the different filter. Switching filters while listening is easy to do in JRiver. Which filter sounds the most natural to your ears?

 

Cheers, Mitch

[satbox]

Hi Mitch,

 

Thank you for your answer, I will try with and without furniture and keep you informed.

 

Regarding your step by step procedure, I have some questions (like in your article, I have a 2.0 system):

 

-When starting Macro4 (filter generation), unlike in the article, I can not define different values for left and right channels for the excess phase (I have only one "X / X" displayed on the screen). Is it normal? Change in Acourate?

 

-I do not manage to produce the last graph (frequency response after correction). Please, can you explain how to create this graph?

 

Thank you!

 

Didier

[mitchco]

Hi Didier, again sorry for the delay.

 

Wrt Macro 4 and excess phase fields. Not sure why yours is different. I am using Acourate V1.8.9. I would ask Uli. Lots of good information and helpful members at: https://groups.yahoo.com/neo/groups/acourate/info

 

Oops - edited as I have not had enough coffee and misunderstood your question. To get the frequency response graph shown, run Macro 1 again, but before you do, in the Room Pulse field, click into that and select the pulses from the Test Convolution folder. Don't forget to reset the Room Pulse field back to the working directory when you are finished looking at the simulation.

 

Hope that helps,

 

Mitch

[satbox]

Hi Didier, again sorry for the delay.

 

Wrt Macro 4 and excess phase fields. Not sure why yours is different. I am using Acourate V1.8.9. I would ask Uli. Lots of good information and helpful members at: https://groups.yahoo.com/neo/groups/acourate/info

 

Oops - edited as I have not had enough coffee and misunderstood your question. To get the frequency response graph shown, run Macro 1 again, but before you do, in the Room Pulse field, click into that and select the pulses from the Test Convolution folder. Don't forget to reset the Room Pulse field back to the working directory when you are finished looking at the simulation.

 

Hope that helps,

 

Mitch

 

Thank you Mitch, crystal clear.

 

Didier

[3ll3d00d]

-When starting Macro4 (filter generation), unlike in the article, I can not define different values for left and right channels for the excess phase (I have only one "X / X" displayed on the screen). Is it normal? Change in Acourate?

add

 

Macro4RightFDW=1

 

in the [Expert Mode] block in \Documents\Acourate\Acourate.ini then restart acourate