Room measurements and what to make out of them

Roust_m

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Feb 25, 2022
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Hi,

I've purchased a calibrated microphone and did my room measurements with REW. Here is the link with my measurements:
I've measured all 6 seats around both right and left ear position 2 times, one time for the right speaker and one for the left.

I got curves like this one:
curve.png
This one is shown with 1/24th smoothing. My room has no acoustic treatment apart from thin acoustic foam on the front wall behind the acoustically transparent screen.

What should I make out of this?
A local shop suggested a combination of the following Artnovion products to deal with the problem:

My main concern is that the first 3 absorption panels don't absorb well in the range between 100Hz and 250Hz. Sparta for example has absorption coefficient of .75 at 250Hz and only .2 at 100Hz. And my curves are very spiky in that range.
Also, I have doubts about even those declared values. I have the below screenshot from one of Anthony Grimany's videos where he says that a panel which is 100mm thick can absorb down to 250Hz.
Absorbtion1.png
I am not quite sure how Artnovion can claim that their 60mm Sparta can absorb down to 200Hz? It's foam thickness is even thinner than 60mm, perhaps only 30mm, the rest is just gap. I went to a demo room with these kind of panels on the walls and they said they spent $180,000 on equipment (speakers, projector, processors, amps) and even to my unsophisticated ear the sound was not very good.

I've looked at another product (Sonitus Legatto 12):
This one claims to go down to 160Hz and seems to be much more solid product being 120mm this (at its thickest part)

Artnovian Wall Bass Trap being 143mm thick claims to deal with range of 80 Hz to 120 Hz. This sounds like its breaking laws of physics.

I also don't understand how the corner bass traps work given that the area of their maximum thickness is very small. One of the Audiholics videos suggested that to treat high and mid frequencies you need to cover about 15% of wall surface in the room. How can a corner bass trap treat lower frequencies if the coverage may only be 2-3
% of the wall surface?

Did anyone have any experience with Artnovion products? Do they really work on the declared frequencies?

Thanks.
 

Bruce B

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First thing I would do is work with what you have. Start moving the speakers around if you can't move your listening position. You can hang curtains and even tapestries at your 1st reflection points. Nice area rug/carpet as well would help.

Then, I would start using 2 subs. The JL Audio subs with digital correction would be great.

Something like diffraction could work well also. The hardest part is correcting below 250Hz. The rest is easy!
 

ecwl

Member
Mar 20, 2021
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I'm unsure what issues are trying to be addressed. is it the frequency response? Is it the RT60 in the bass or the RT60 in the midrange and trebles?
I'm guessing pretty much any brand of 4" absorber panels would address most of these issues?
But having read the other related posts, I wonder if contacting a professional is a better way to go?
I found this website to be fairly helpful with their articles. I hope they still provide services:
 

Roust_m

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Feb 25, 2022
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First thing I would do is work with what you have. Start moving the speakers around if you can't move your listening position. You can hang curtains and even tapestries at your 1st reflection points. Nice area rug/carpet as well would help.

Then, I would start using 2 subs. The JL Audio subs with digital correction would be great.

Something like diffraction could work well also. The hardest part is correcting below 250Hz. The rest is easy!
I already have 2 subs. I don't have much flexibility in moving either the seating position or the speakers. I have front speakers behind the screen, surround speakers on the sides and the back and 4 Atmos speakers in the ceiling, my room looks like this:
room dimensions.png
I already have a carpet, but it only serves as high frequency absorber. Curtains are not suitable in the first reflection point and they are not going to absorb even mid frequencies properly.
And yes, going below 250Hz is hard, so this is what my question is all about.
 

Roust_m

New Member
Feb 25, 2022
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I'm unsure what issues are trying to be addressed. is it the frequency response? Is it the RT60 in the bass or the RT60 in the midrange and trebles?
I'm guessing pretty much any brand of 4" absorber panels would address most of these issues?
But having read the other related posts, I wonder if contacting a professional is a better way to go?
I found this website to be fairly helpful with their articles. I hope they still provide services:
I want to address everything I possibly can. I am even considering making a bass trap out of the riser. The shop I went to provided an advice from a professional. They recommended those Artnovion panels. My concern is how a panel which is only 60mm thick, most of which is air gap, is going absorb frequencies below 250Hz. I want to check facts before accepting the professional advice.
 

MTB Vince

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May 11, 2019
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Dundas, ON Canada
What part of the world do you live in that you provided all your dimensional info in metric @Roust_m?
 

MTB Vince

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May 11, 2019
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Well I'm willing to provide some guidance but I'm in Canada and so am inconveniently located. I think you are wise to be skeptical about Artnovian. The performance claims they are making for a number of their products do indeed defy physics.

Honestly though, I think the best advice I could give you in light of where you seem to be in your acoustics journey, would be to engage a friendly & collaborative pro like Nyal Mellor of Acoustic Frontiers. He offers a reasonably priced remote consulting service that could work for you. The money you would spend on his services would likely be entirely offset by your satisfaction in the sonic end result... And the money you won't have wasted by having bought the wrong sorts of treatments or treatment products that look pretty but fail to live up to their wishful marketing claims!
 

ecwl

Member
Mar 20, 2021
49
42
23
I want to address everything I possibly can. I am even considering making a bass trap out of the riser. The shop I went to provided an advice from a professional. They recommended those Artnovion panels. My concern is how a panel which is only 60mm thick, most of which is air gap, is going absorb frequencies below 250Hz. I want to check facts before accepting the professional advice.
So I have definitely found many local "professionals" to know very little about room acoustics and are just there to sell you acoustic treatment products and then maybe hang them up for you.
That's why I recommended the Acoustic Frontiers link because they seem to know what they are talking about and they're willing to work with somebody who has already made REW measurements of their home.
As to your question about what bass traps can and cannot do, I find that the best and reliable source actually came not from a home theatre specialist but a YouTuber who focuses on studio acoustic treatment with the channel Acoustics Insider. His first few videos answer your question of what those 4" deep panels can and cannot do and why they can still work in your situation. But because you're not building a studio, your use would be different. Regardless, I think if you're asking these questions, you should be contacting a service like Acoustic Frontiers.
 
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Roust_m

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Feb 25, 2022
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Well I'm willing to provide some guidance but I'm in Canada and so am inconveniently located. I think you are wise to be skeptical about Artnovian. The performance claims they are making for a number of their products do indeed defy physics.

Honestly though, I think the best advice I could give you in light of where you seem to be in your acoustics journey, would be to engage a friendly & collaborative pro like Nyal Mellor of Acoustic Frontiers. He offers a reasonably priced remote consulting service that could work for you. The money you would spend on his services would likely be entirely offset by your satisfaction in the sonic end result... And the money you won't have wasted by having bought the wrong sorts of treatments or treatment products that look pretty but fail to live up to their wishful marketing claims!
Before I engage a consultant, I would like to understand the issue myself. Like how bad my room currently is and what a well treated room would look like in REW measurements. Will the curve be 2-3Db variations between the dips and the spikes? Will the RT60 be under .2 etc. What are the standards here?
 

StreamFidelity

Active Member
Jun 30, 2020
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Rostock, Germany
griggaudio.de
Will the curve be 2-3Db variations between the dips and the spikes? Will the RT60 be under .2 etc. What are the standards here?
I'm not an acoustics expert, but I've done a lot of work with measurements and with Acourate digital correction filters. I am not familiar with REW. Here are my findings.

Reverberation

Although many say that reverberation in one's home should not exceed 0.6 sec and in studio max. 0.2 sec, bat it's only a rough approximation. The size of the room and the intended use are decisive. In my case, the room is not too dry and is well damped for speech and music (ca. 0.45 sec).



Room modes

Every room has modes. This can be mitigated somewhat with bass traps and by moving boxes. A correction with convolution filter was the solution for me.

The picture below shows the frequency response once uncorrected (thin line) and corrected (bold red line). Without correction the bass mode around 60Hz would excite the room too much. Valuable detail information in the mid and high frequencies would be lost.



Step response

In the image below, you can see in the step response that the tweeter comes first in a reversed polarity, and then the midrange and bass drivers.


Source: https://www.stereophile.com/content/sonus-faber-amati-futura-loudspeaker-measurements

In all HiFi test magazines you usually only get to see the step response of "one" loudspeaker. In the picture below, the digital correction with Acourate brings all loudspeaker drivers in line. The step response of both speakers (left/right) is perfectly optimized and synchronized.

 
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Roust_m

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Feb 25, 2022
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I'm not an acoustics expert, but I've done a lot of work with measurements and with Acourate digital correction filters. I am not familiar with REW. Here are my findings.

Reverberation

Although many say that reverberation in one's home should not exceed 0.6 sec and in studio max. 0.2 sec, bat it's only a rough approximation. The size of the room and the intended use are decisive. In my case, the room is not too dry and is well damped for speech and music (ca. 0.45 sec).



Room modes

Every room has modes. This can be mitigated somewhat with bass traps and by moving boxes. A correction with convolution filter was the solution for me.

The picture below shows the frequency response once uncorrected (thin line) and corrected (bold red line). Without correction the bass mode around 60Hz would excite the room too much. Valuable detail information in the mid and high frequencies would be lost.



Step response

In the image below, you can see in the step response that the tweeter comes first in a reversed polarity, and then the midrange and bass drivers.


Source: https://www.stereophile.com/content/sonus-faber-amati-futura-loudspeaker-measurements

In all HiFi test magazines you usually only get to see the step response of "one" loudspeaker. In the picture below, the digital correction with Acourate brings all loudspeaker drivers in line. The step response of both speakers (left/right) is perfectly optimized and synchronized.

Your curve is pretty smooth, even untreated. How large is your room? Is it a cinema room or a studio? Not sure why it has negative values on the vertical axis on the second picture. Also, what kind of treatment did you put into your room?
 

StreamFidelity

Active Member
Jun 30, 2020
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Rostock, Germany
griggaudio.de
Your curve is pretty smooth, even untreated. How large is your room? Is it a cinema room or a studio? Not sure why it has negative values on the vertical axis on the second picture. Also, what kind of treatment did you put into your room?
It is a normal small living room with an adjoining kitchen behind the listening position. The dimensions are 4.2m x 6.7m = approx. 28 m² (approx. 92 squarefeet).

Except for an acoustic curtain in front of the TV and a fluffy carpet, bookshelf and couch with cushions, there is no special damping. The stool in the middle should go, but there's not enough room.

I make sure to sit exactly in the sweet spot. The speakers are angled toward the listening position to minimize sidewall reflections.

 
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cjf

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Nov 19, 2012
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I already have 2 subs. I don't have much flexibility in moving either the seating position or the speakers. I have front speakers behind the screen, surround speakers on the sides and the back and 4 Atmos speakers in the ceiling, my room looks like this:
View attachment 92801
I already have a carpet, but it only serves as high frequency absorber. Curtains are not suitable in the first reflection point and they are not going to absorb even mid frequencies properly.
And yes, going below 250Hz is hard, so this is what my question is all about.
Out of curiosity, have you confirmed the acoustic transparency claim of the screen that sits in front of the main Left/Right/Center channel speakers while using REW?

Also, I'm curious what exactly is the limiting factor on where you can place the existing Subs within the room? Is this due to it just not being visually appealing or you would trip over them if placed elsewhere or is this placement limitation due to a hardware limitation (ie...forced to use Line Level RCA connections to the Subs, not enough electrical plugs in other parts of the room..etc)?

I'm not saying this is what you did here but too many people place Subs where they think is best without confirming via measurements using REW or similar if that placement is indeed "ideal". You may or may not be surprised at what a better Sub placement strategy can do to that existing Freq Resp curve without spending another dime in the process to find out.

Maybe you have already done this and your current placement is already the best spots within the room but if you have not done this yet I would start there first (ie...confirm the existing Sub placement cant be bettered). Extension cords can be used as a temporary band aide just to find those ideal spots.

If it turns out there are indeed better places in the room for your existing Subs then the current locations you can then decide on next steps (is the difference in the curve between a new spot vs the existing spots worth whatever headaches that come along with the new placements...if any.

Are you currently or are you planning on using Room correction software in this system?
 

Roust_m

New Member
Feb 25, 2022
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It is a normal small living room with an adjoining kitchen behind the listening position. The dimensions are 4.2m x 6.7m = approx. 28 m² (approx. 92 squarefeet).

Except for an acoustic curtain in front of the TV and a fluffy carpet, bookshelf and couch with cushions, there is no special damping. The stool in the middle should go, but there's not enough room.

I make sure to sit exactly in the sweet spot. The speakers are angled toward the listening position to minimize sidewall reflections.

What smoothing did you apply to the room frequency response curve? What did you do to correct it? I am not sure if your room is indicative to mine, as mine is a dedicated cinema room with 7.2.4 speaker set.
 

Roust_m

New Member
Feb 25, 2022
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Out of curiosity, have you confirmed the acoustic transparency claim of the screen that sits in front of the main Left/Right/Center channel speakers while using REW?

Also, I'm curious what exactly is the limiting factor on where you can place the existing Subs within the room? Is this due to it just not being visually appealing or you would trip over them if placed elsewhere or is this placement limitation due to a hardware limitation (ie...forced to use Line Level RCA connections to the Subs, not enough electrical plugs in other parts of the room..etc)?

I'm not saying this is what you did here but too many people place Subs where they think is best without confirming via measurements using REW or similar if that placement is indeed "ideal". You may or may not be surprised at what a better Sub placement strategy can do to that existing Freq Resp curve without spending another dime in the process to find out.

Maybe you have already done this and your current placement is already the best spots within the room but if you have not done this yet I would start there first (ie...confirm the existing Sub placement cant be bettered). Extension cords can be used as a temporary band aide just to find those ideal spots.

If it turns out there are indeed better places in the room for your existing Subs then the current locations you can then decide on next steps (is the difference in the curve between a new spot vs the existing spots worth whatever headaches that come along with the new placements...if any.

Are you currently or are you planning on using Room correction software in this system?
How can I confirm the screen acoustic transparency using REW?

I can move subs around the room. I used to have them in the front two corners, now I moved one to the back corner diagonally opposite the first one. REW measurements show improvement in the lower frequencies curve.

What do you mean by room correction software? The EQ in the AVR? I will do it in the end. The problem is, you can improve one spot in the room using EQ and make others worse. This is why I am focused on room treatment at the moment.
 

StreamFidelity

Active Member
Jun 30, 2020
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Rostock, Germany
griggaudio.de
What do you mean by room correction software?
I drive the corrections with an Audio PC. In case of interest to read:

What options does an Audio PC offer for improving room acoustics ?

Why can an Audio PC optimize the speaker ?
 

cjf

Well-Known Member
Nov 19, 2012
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How can I confirm the screen acoustic transparency using REW?

I can move subs around the room. I used to have them in the front two corners, now I moved one to the back corner diagonally opposite the first one. REW measurements show improvement in the lower frequencies curve.

What do you mean by room correction software? The EQ in the AVR? I will do it in the end. The problem is, you can improve one spot in the room using EQ and make others worse. This is why I am focused on room treatment at the moment.
The easiest way to confirm the acoustic transparency of the screen would be to do a Freq Sweep using REW from, say 20-20Khz, with the screen in its normal position and then do another with the screen retracted or removed. You can then overlay both sweeps in REW to look for any worthwhile differences for better or worse.

OK..good to hear that you've played with multiple placement options for the Subs. If you haven't done so yet, with your current Sub placement (ie..one at one end of the room and the other at the other end) you should confirm they are not out of Phase with each other. Sometimes this placement will result in one Sub being some degree out of Phase with the other Sub ( And Main Speaker Channels). This is more true when/if there happens to be a "Null" at some point in the room between the two Subs locations. If your lucky and there is no Null then it may be fine as is. On some Subs Phase can be adjusted from 0-180deg to account for such issues and this can also be confirmed using REW. You would want to run a sweep of each Sub alone then with both at the same time at minimum then use the Phase chart to see any out of Phase behavior. If doing that is too much work then you can just adjust Phase by ear. It should be fairly obvious which Phase setting sounds better.

In terms of Room Correction software, some AV Integrated units have baked in Room Correction options but IMO their flexibility is pretty limited. The best option here would be to use a program like Audiolense or Acourate installed on the same PC as REW. These programs can offer much more accurate and better sounding Room Correction files which are then fed into a playback software like Roon or JRiver using their Convolution feature. Granted, this is far more complicated but the results are significantly better in terms of SQ, again IMO.
 
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cjf

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Nov 19, 2012
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I forgot to mention that attempting to make each seat in the room sound the same or very similar does have its drawbacks. I believe trying to make this as a primary requirement ultimately results in a system that cant sound as good as another system that first focuses on the SQ at the sweet spot only.

In my view, the casual listeners who typically sit in those others seats can live with what they are hearing. When I have guests over to do some listening to music I usually sit in other seats in the room. My setup is tuned strictly for the main listening position and does sound quite different when sitting anywhere else but the main listening position. But even then, it still doesn't sound horrible. Just something to consider.
 
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