Author Topic: Using room correction...  (Read 1092 times)

Offline Jason Willemse

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Using room correction...
« on: April 09, 2018, 11:21:32 PM »
Itís a funny game this. The rabbit hole just goes on and on and on...

Iíll skip all the early stories of the quest to put together a decent stereo system. What Iíd like to tell is hopefully some good learning for others.

Without making the room look like a studio, I really wanted something special. The room is small, around 3 x 4m. The wall behind the speakers is fully curtained with heavy material - top to bottom, left corner to right. The back wall is treated with three large panels covering most of the wall. Side walls have one large panel each. The floor, a shaggy rug covering about 60%.

Aside from the record player, the system runs digital via usb from a Mac-mini, with content made available through Amarra4 Luxe and using the Dirac powered Impulse Room Correction (IRC).

Lots of experimenting, but eventually figured out what was probably the biggest learning of all. Getting the room acoustics right to the best ability without any processing, then ice the cake.

On all my initial tests, I picked up distortion at even low volume as the IRC was overcompensating. I placed speakers at every position I could imagine from around 1.5m out, back to 30cm from the wall. Paying attention to how IRC maps out the room frequencies before correction is fascinating and will pay big dividends toward your final setup.

Funnily enough, the best positioning turned out to be almost exactly what the speaker manufacturer recommended fro the specific model - 50cm off the back wall to achieve the best out of the lower end of the spectrum.

A member on this forum posted something or other about placing your seating position twice the distance away from the speakers as they are part. Coincidentally, this worked out incredibly, though was far from my staring point.

Another spoke of the centre of a room being a less than ideal listening position... clever guys on here!

The final product saw IRC making minimal changes, but just providing that bit of airiness that it need to bring out its full potential.

It has been very frustrating at times... and this would be a looooooong post if I had to go through all the hiccups.

In the end, itís just hauntingly beautiful what can be achieved without going too crazy. (Relative)

Iíve learned a lot from many on this forum, and for that I am truly grateful.


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Offline Rodney_gold

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Re: Using room correction...
« Reply #1 on: April 13, 2018, 05:13:19 AM »
if using the dirac based correction , you need to reduce digital gain by at least 6db or more so as to allow headroom and avoid digital clipping.. I looked at the amarra user manual .. I see the IRC filters have a gain slider , did you reduce gain using them?
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Offline XL1000

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Re: Using room correction...
« Reply #2 on: April 13, 2018, 06:48:35 AM »
Well done Jason. I am about to go down the rabbit hole myself on the same journey.
I am resigning myself to settle on the equipment I have now and see what the absolute best sound is I can get from it.
Still need to get the Mic and learn the software, but the room will get the most attention first.

I may call on you for some PC knowledge if you can lend a hand with that. Also running a Mac Mini late 2012 Server for the source and then into DAC/Amp.
Rodney's question is already HG for me so I have a long way to go. Happy for the result you have achieved.
Music is a moral law. It gives soul to the universe, wings to the mind, flight to the imagination, and charm and gaiety to life and to everything. Plato

Offline Jason Willemse

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Re: Using room correction...
« Reply #3 on: April 13, 2018, 07:22:18 AM »
if using the dirac based correction , you need to reduce digital gain by at least 6db or more so as to allow headroom and avoid digital clipping.. I looked at the amarra user manual .. I see the IRC filters have a gain slider , did you reduce gain using them?
Yes - IRC does indeed have a gain slider that you can use to adjust to the point of no digital clipping. For me, and please pardon me as I am far from an expert, it is a good indication of how much digital correction is needed in the room. The more gain reduction you need to apply, the more things are ďwrongĒ.

In my first (and worst) attempts, I was having to apply a -8db gain to not have any digital clipping. This was based on an auto generated target curve. Studying the graphs generated allows one to see where the problems are, and by moving the speakers around one can compensate for these, particularly in the lower frequencies.

Mapping it out by moving the speakers 5cm at a time and repeating the test, I was able to get a good understanding and prediction of what each movement would do.

A few days and about 20 or so tests later, I was able to apply the room correction with zero adjustments to the gain.

The best thing was how much I learnt about the room dynamics in the process. Regardless of the starting point, small adjustment at a time and careful noting of the results takes one a long way.


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Offline Jason Willemse

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Re: Using room correction...
« Reply #4 on: April 13, 2018, 07:28:18 AM »
Well done Jason. I am about to go down the rabbit hole myself on the same journey.
I am resigning myself to settle on the equipment I have now and see what the absolute best sound is I can get from it.
Still need to get the Mic and learn the software, but the room will get the most attention first.

I may call on you for some PC knowledge if you can lend a hand with that. Also running a Mac Mini late 2012 Server for the source and then into DAC/Amp.
Rodney's question is already HG for me so I have a long way to go. Happy for the result you have achieved.

No problem! Youíre welcome to contact me anytime. The software itself is surprisingly easy to navigate, so donít stress yourself out too much about that. I have to admit that it is rather expensive to apply at 5.5k for the software and then still the price for a mic. But then, like anything, the higher up the ladder you go, the pricier it gets for each improvement. If you consider it from that perspective, itís sensible.

A good choice to give the room as much attention as possible first, then apply the room correction.


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Offline Air

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Re: Using room correction...
« Reply #5 on: April 15, 2018, 11:37:49 AM »
Hi Jason, your journey is enlightening and I think it might be of interest and value if you can share more of the specific milestones in the process.

There were some heated debates in the past about the topic of how much intervention through digital room correction is ideal. Your approach seems sensible, or at least admitting to my bias, in line with my own views, namely as little as possible. I believe that getting the basics right such as a careful selection of components in the context of the room, careful placement of transducers in the room and room treatment is important. Then room correction could be the cherry on the cake. I am an advocate for medium powered amplifiers for various reasons and to have a -6db or more gain reduction require that more and more power is required for targeted loudness levels. To me, it sounds like slapping a plaster on a wound without taking care of the underlying problems involved.

The reason why I think that the share you detail is important for all of us is, for example, your comment on the negative consequences of listening in centre of the room. I, for example, found encourage all my customers not to place speaker symmetrical in room, and to for example put speakers not equal distances from side walls.

if you have time.. it would be of nice if you can provide more detail and don't forget to give more detail of speakers and other equipment(I wonder for example why manufacturer recommends 50cm away from back wall.. is it a standmount, port of speaker etc.)
Cheers
Stefan

Offline chrisc

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Re: Using room correction...
« Reply #6 on: April 15, 2018, 11:51:25 AM »
I found a DSP extremely useful for "ironing out" speaker deficiencies.  Frequency levels, crossover points, coupled with speaker placement transformed the sound

Last week I was called in to "sort out" as it were, a fellow in Constantia who had cobbled together bits and pieces which sounded horrible.  The first thing I did was to make him fit three large rugs over the tiles and fit curtains to the two large windows on either side.  Then I moved the speakers away from the wall, some 1.5 metres in.  Using REW with a calibrated microphone, I saw a large (+12db) honk at 130Hz which was his main speakers and sub playing the same frequency.  Moving the main speakers to start at 180Hz and the sub to roll off at 120Hz and reducing the level of the bass by -6db (he has a Marantz AVR which allows this), it made an astonishing difference

His first set of speakers were FANE units, a 15" woofer and a single tweeter, sounded like disco speakers.  He now has a pair of Triton speakers and the sound is even and balanced, you can now hear the singer sing instead of being so recessed that you thought you were listening to an instrumental recording

I also discovered he only had 6 CDs.  How can you possibly enjoy music with such a poor selection.  I also fitted an FM aerial and FMR comes in loud and clear.
Even duct tape canít fix stupidÖ but it can muffle the sound

Offline Rodney_gold

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Re: Using room correction...
« Reply #7 on: April 15, 2018, 05:08:01 PM »
The -6db hit is in the digital domain..any active pre will compensate
Asymmetrical speaker placement  in a room is what one wants to avoid if possible , you are guaranteed to have imbalances that way.
what dsp did you use to correct the 6 cd system ?

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Offline chrisc

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Re: Using room correction...
« Reply #8 on: April 15, 2018, 05:21:13 PM »
Mini DSP 4-10, I think it once belonged to you
Even duct tape canít fix stupidÖ but it can muffle the sound

Offline Rodney_gold

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Re: Using room correction...
« Reply #9 on: April 15, 2018, 06:09:06 PM »
thats a good all rounder unit.. he can use it to replace a dac and pre as well
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Offline Jason Willemse

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Re: Using room correction...
« Reply #10 on: April 15, 2018, 06:25:48 PM »
Hi Jason, your journey is enlightening and I think it might be of interest and value if you can share more of the specific milestones in the process.

There were some heated debates in the past about the topic of how much intervention through digital room correction is ideal. Your approach seems sensible, or at least admitting to my bias, in line with my own views, namely as little as possible. I believe that getting the basics right such as a careful selection of components in the context of the room, careful placement of transducers in the room and room treatment is important. Then room correction could be the cherry on the cake. I am an advocate for medium powered amplifiers for various reasons and to have a -6db or more gain reduction require that more and more power is required for targeted loudness levels. To me, it sounds like slapping a plaster on a wound without taking care of the underlying problems involved.

The reason why I think that the share you detail is important for all of us is, for example, your comment on the negative consequences of listening in centre of the room. I, for example, found encourage all my customers not to place speaker symmetrical in room, and to for example put speakers not equal distances from side walls.

if you have time.. it would be of nice if you can provide more detail and don't forget to give more detail of speakers and other equipment(I wonder for example why manufacturer recommends 50cm away from back wall.. is it a standmount, port of speaker etc.)
Cheers
Stefan

Hi Stefan. Iíll try and provide as much relevant information as I can, then perhaps discuss with more detail on some of your points. I will admit that I am a little intimidated by this, as Iím sure you give my level of expertise more credit than itís worth. I still have much to learn.

Iíll start with the room. Itís internal dimensions are 346cm (w) x 434cm (l) x 285cm (h). Concrete walls, tiled floor and a standard ceiling. This represents 70m^2 worth of surface area.

Five absorption panels measuring 195cm x 90cm are in place, and are 10cm thick. One on either side wall, and another 3 at the back. This represents just short of 9m^2, around 12% of the rooms total surface reflections.

The front wall to wall curtains provide cover of another near 10m^2, and a 280cm x 190cm shaggy rug provides another 5m^2. In total, about 35% of the rooms total surface area is treated in he usual key areas, with none on the ceiling.

The room feels very quiet to be in, and measures just over 41dB average at the listening position with all equipment switched on at no volume... for what itís worth.

For reference and a better visual perspective, here a couple pics.



Next up, some info on the equipment. I started with a 350w x 2 @ 8 ohm Perreaux P350 into a pair of large Jamo Oriel towers. The Oriel speakers are 210lt cabinets in a 3-way configuration with 4 drivers, 87db / 6 ohm with 2 internal 8Ē bass (reflex) drivers, a 6.5Ē mid and soft dome tweeter. They were very big units to have a such a small space, and were moved out to become another system at a later stage.



At this stage I was just playing around with positioning and temporary acoustic treatment, so to be honest never did any tests with them and room correction.

The components were changed to the following which I will discuss piece by piece and provide spec where I have it.

Apple MacMini: Self explanatory, running Ammara4 Luxe with Dirac Impulse room correction. The microphone used for calibration is a Mini DSP Umik-1 mounted on tripod at 90 degrees, ie directly facing towards the speakers. Digital content is via Tidal Hi-Res, or purchased flac and dsd from HDtracks. A usb cable provides the content to the DAC.

DAC / Pre: This is Perreaux DP32 with the following spec.



Amplification: Perreaux 100p 2ch 100w x 2 @ 8 ohm. Some info.



Turntable - standard Rega P3.

Phonostage: Perreaux VP3 MM / MC with adjustable gain, load, RIAA etc.



Cables: Audioquest Red River XLR,Van den Hul  speaker cables 2 - 2.

Speakers: Monitor Audio Platinum 100 bookshelf on sand-filled original stands.



Ok, so where did I start. Basically with what looked right, and with some simply applied rules. Give the speakers some breathing room, apply the equilateral triangle listening point, mark the reflection points with mirror detection, and off we go. What is important to know is that this basically put the listener right in the centre of the room.

I was feeling ok with what was going on, but the frequencies below 130Hz were a mess. There was a ďblack holeĒ in the centre of the room that I just couldnít figure out. I pulled the speakers a third of the way into the room, pulled the seating position closer and basically created a big set of headphones. For a while I was pretty impressed, but it quickly lost its appeal. Bass was still a mess, but a bit better as the black hole was gone.

I measured the room with IRC with the mic at the listening position, and saw a big fall off at 100Hz. I pushed the speakers in increments closer and closer to the wall, watching as the fall off moved up towards 130Hz, though falling off less than before.

The speakers are bookshelf units with rear porting, so placing them closer to the wall certainly has quite an effect on lower frequencies. I found a sweet spot which gave me a nice bass feel, which coincidentally fell in line with the manufacturer recommendation of 50cm. The emptiness in the room centre still existed, but by moving back to around 100cm from the back wall, I found my happy place.

The limited size of the room left with little option as far as width placement goes for the speakers. I tried to keep the stage as wide as required to meet at my desired listening position, meaning I had to sacrifice a bit of the side wall breathing space. I settled with 50cm off, in line with the minimum recommendation of the manufacturer. This gave me the sweet spot I needed at my listening position.

Speakers are now 210cm apart, 22 degrees toeíd in directly at the listener who is 260cm away from the middle of the two speakers. About 45 degrees wide from the listener.

The following graphs show the outcome.


The 7 measurements overlaid.


The applied correction on the 7 measurements.


The 7 corrected measurements with target curve.

To be continued...








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Offline Jason Willemse

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Re: Using room correction...
« Reply #11 on: April 15, 2018, 06:41:38 PM »
Hi Stefan. Iíll try and provide as much relevant information as I can, then perhaps discuss with more detail on some of your points. I will admit that I am a little intimidated by this, as Iím sure you give my level of expertise more credit than itís worth. I still have much to learn.

Iíll start with the room. Itís internal dimensions are 346cm (w) x 434cm (l) x 285cm (h). Concrete walls, tiled floor and a standard ceiling. This represents 70m^2 worth of surface area.

Five absorption panels measuring 195cm x 90cm are in place, and are 10cm thick. One on either side wall, and another 3 at the back. This represents just short of 9m^2, around 12% of the rooms total surface reflections.

The front wall to wall curtains provide cover of another near 10m^2, and a 280cm x 190cm shaggy rug provides another 5m^2. In total, about 35% of the rooms total surface area is treated in he usual key areas, with none on the ceiling.

The room feels very quiet to be in, and measures just over 41dB average at the listening position with all equipment switched on at no volume... for what itís worth.

For reference and a better visual perspective, here a couple pics.



Next up, some info on the equipment. I started with a 350w x 2 @ 8 ohm Perreaux P350 into a pair of large Jamo Oriel towers. The Oriel speakers are 210lt cabinets in a 3-way configuration with 4 drivers, 87db / 6 ohm with 2 internal 8Ē bass (reflex) drivers, a 6.5Ē mid and soft dome tweeter. They were very big units to have a such a small space, and were moved out to become another system at a later stage.



At this stage I was just playing around with positioning and temporary acoustic treatment, so to be honest never did any tests with them and room correction.

The components were changed to the following which I will discuss piece by piece and provide spec where I have it.

Apple MacMini: Self explanatory, running Ammara4 Luxe with Dirac Impulse room correction. The microphone used for calibration is a Mini DSP Umik-1 mounted on tripod at 90 degrees, ie directly facing towards the speakers. Digital content is via Tidal Hi-Res, or purchased flac and dsd from HDtracks. A usb cable provides the content to the DAC.

DAC / Pre: This is Perreaux DP32 with the following spec.



Amplification: Perreaux 100p 2ch 100w x 2 @ 8 ohm. Some info.



Turntable - standard Rega P3.

Phonostage: Perreaux VP3 MM / MC with adjustable gain, load, RIAA etc.



Cables: Audioquest Red River XLR,Van den Hul  speaker cables 2 - 2.

Speakers: Monitor Audio Platinum 100 bookshelf on sand-filled original stands.



Ok, so where did I start. Basically with what looked right, and with some simply applied rules. Give the speakers some breathing room, apply the equilateral triangle listening point, mark the reflection points with mirror detection, and off we go. What is important to know is that this basically put the listener right in the centre of the room.

I was feeling ok with what was going on, but the frequencies below 130Hz were a mess. There was a ďblack holeĒ in the centre of the room that I just couldnít figure out. I pulled the speakers a third of the way into the room, pulled the seating position closer and basically created a big set of headphones. For a while I was pretty impressed, but it quickly lost its appeal. Bass was still a mess, but a bit better as the black hole was gone.

I measured the room with IRC with the mic at the listening position, and saw a big fall off at 100Hz. I pushed the speakers in increments closer and closer to the wall, watching as the fall off moved up towards 130Hz, though falling off less than before.

The speakers are bookshelf units with rear porting, so placing them closer to the wall certainly has quite an effect on lower frequencies. I found a sweet spot which gave me a nice bass feel, which coincidentally fell in line with the manufacturer recommendation of 50cm. The emptiness in the room centre still existed, but by moving back to around 100cm from the back wall, I found my happy place.

The limited size of the room left with little option as far as width placement goes for the speakers. I tried to keep the stage as wide as required to meet at my desired listening position, meaning I had to sacrifice a bit of the side wall breathing space. I settled with 50cm off, in line with the minimum recommendation of the manufacturer. This gave me the sweet spot I needed at my listening position.

Speakers are now 210cm apart, 22 degrees toeíd in directly at the listener who is 260cm away from the middle of the two speakers. About 45 degrees wide from the listener.

The following graphs show the outcome.


The 7 measurements overlaid.


The applied correction on the 7 measurements.


The 7 corrected measurements with target curve.

To be continued...








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Letís talk I about symmetry and the centre is the room phenomenon.

The room is why it is, and will always have certain characteristics.

Perfect Symmetry means that the way the room reacts will be just that... the positives and negatives happening equally at both channels, and not allowing for one to compensate for the other because of each having a different reaction to the room. I get that. This room doesnít allow for much adjustment in this regard. It is symmetrical, space limited and I have to do a with what I have. At least itís not square school would be a whole lot worse.

The centre of the room could well be far better suited in a different room, but the centre most point of any room will always be subjected to the most amount of reflections and phase issues imo. Bass loads in corners, and one can expect bass to be less in the centre.

The back wall on the other hand, being closer to it will give better bass, but subject you to strong reflections. Hence the large amount of absorption.

One thing that was really impressive with regards to IRC. Once applied, the sound in the centre of the room was greatly improved, and when switched off returned to that ominous black hole.





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Offline Air

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Re: Using room correction...
« Reply #12 on: April 15, 2018, 08:06:18 PM »
Thanks, Jason for the effort of sharing the detail. Once again I get the impression of a thoughtful approach to getting the best sound. The operative phrase in your 1st post that also appeals to me is to get some magic without the room looking like a studio. You certainly achieved that.

The measurements are also excellent after the correction! I am sure it sounds great.

So the 1st major principle for me at play is about the careful selection of the speaker in the context of the room, hence a question in my mind would be, why not keep the big Jamo's in place and apply the room correction? Have you tried that or was it purely the aesthetics that made you get the 2-way standmounts?

Secondly, I get it that the room leaves you little room to manoeuvre and symmetry is often also more pleasing to the eye. It feels right, however, I often try to substitute balance for symmetry. What would happen if you move the left speaker, let's say 5cm to the left and the right speaker also 5 cm to the left, the seating obviously would also then move slightly to the left? I would be curious to see how it impacts on the valley at 130Hz that you find before applying the room correction. Maybe the room is just to small as you said and the 5cm to little to really have a significant impact.

Lastly, and this is really pedantic but have you investigated what the impact of closing the curtains are on the measurements?

Stefan


Offline Rodney_gold

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Re: Using room correction...
« Reply #13 on: April 15, 2018, 10:23:59 PM »
You can use those handles in the DIRAC target curve screen to limit correction..have you tried using dirac to just do correction up to , lets say,  300hz..?
 
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