Countermeasure missing right / left side balance in living room theatre

T

TheSound

Audiophyte
Hi @gene, hi @Mathew J Poes,

i would like to refer to the youtube video about optimizing small rooms:


I have here in our living room exactly the scenario, that Matt described (left side windows to the garden / right side open "L" shape to the kitchen).

Since 2016 i did step by step to raise the theatre and now more or less the final item went in, the curtain to the window side. Not only for the acoustics but at least as much to maximize the joy watching the projection screen with my JVC X7900 projector :) And it works marvelous, having the complete left side darkened watching a movie is real pleasure... And that of course means, that it is always completely closed while watching movies.

I expected of course, that with the courtain

a) the acousting characteristic of the room changed significantly
b) that i have to take measures against it by re-calibrating my AVR / speaker setup with REW

What i observed then exactly as Matt said in the video, i got an audible mis-balance between right and left speaker side in presence and also a bit sound characteristic. Due to the curtain and the reduced reflections, the left speakers seemed to get a lot more present as before (of course having the speaker level at the main seat perfectly aligned with REW before WITH curtain closed).

And then i remembered a discussion with the people from Patrick Schappert from Grobi, telling me that acousting treatment always brings a reduction in auditory spaciousness and an increase of focus the the speaker near to the treatment.

So, for a first quick countermeasure, i increased the speaker levels of FR, SR and SBR while listing to some well known music step by step until the presence of left and right side was equalized. But that ended up in 2,5 dB more level of these 3 speakers compared to left side FL, SL and SBL.

How would you see it? As i cannot really play with the position of the curtain (always completely closed on watching movies) and no presets in my SR7010 to change between situations, do you think, that increasing the levels for the right side of the room was a good measure? Of would you recommend to do something different?

Wish you all the best for 2020 and would be happy to read your feedback, Holger
 
Last edited:
Matthew J Poes

Matthew J Poes

Senior Audioholic
Hi @gene, hi @Mathew J Poes,

i would like to refer to the youtube video about optimizing small rooms:


I have here in our living room exactly the scenario, that Matt described (left side windows to the garden / right side open "L" shape to the kitchen).

Since 2016 i did step by step to raise the theatre and now more or less the final item went in, the curtain to the window side. Not only for the acoustics but at least as much to maximize the joy watching the projection screen with my JVC X7900 projector :) And it works marvelous, having the complete left side darkened watching a movie is real pleasure... And that of course means, that it is always completely closed while watching movies.

I expected of course, that with the courtain

a) the acousting characteristic of the room changed significantly
b) that i have to take measures against it by re-calibrating my AVR / speaker setup with REW

What i observed then exactly as Matt said in the video, i got an audible mis-balance between right and left speaker side in presence and also a bit sound characteristic. Due to the curtain and the reduced reflections, the left speakers seemed to get a lot more present as before (of course having the speaker level at the main seat perfectly aligned with REW before WITH curtain closed).

And then i remembered a discussion with the people from Patrick Schappert from Grobi, telling me that acousting treatment always brings a reduction in auditory spaciousness and an increase of focus the the speaker near to the treatment.

So, for a first quick countermeasure, i increased the speaker levels of FR, SR and SBR while listing to some well known music step by step until the presence of left and right side was equalized. But that ended up in 2,5 dB more level of these 3 speakers compared to left side FL, SL and SBL.

How would you see it? As i cannot really play with the position of the curtain (always completely closed on watching movies) and no presets in my SR7010 to change between situations, do you think, that increasing the levels for the right side of the room was a good measure? Of would you recommend to do something different?

Wish you all the best for 2020 and would be happy to read your feedback, Holger
can you share pictures of the space. I think it would be easier for me to see what is going on. I can best help when I have a clearer image in my head of the acoustics of the space.
 
T

TheSound

Audiophyte
Hi Matt,

thanks for your answer! Pls let me get back to you a bit later, theres something on the topic, that i need to check a bit more...

cheers, Holger
 
Matthew J Poes

Matthew J Poes

Senior Audioholic
Hi Matt,

thanks for your answer! Pls let me get back to you a bit later, theres something on the topic, that i need to check a bit more...

cheers, Holger
No problem. There are very logical reasons for why an acoustic asymmetry between the left and right will lead to an imbalanced soundstage. The spaciousness and imaging are dramatically damaged. However fixing the problem requires understanding what the asymmetry is.
 
Pogre

Pogre

Audioholic Warlord
TheSound brought something up that never occurred to me before. I have sliding glass door on the wall next to my left speaker. If I were to get some thicker light blocking curtains that would change my room acoustics enough to recalibrate?

It'd be nice to be able to darken the room some more anyway and it'd give me something new to OCD on, lol.

20170823_092038-1305x734.jpg
20170914_070929-1305x734.jpg
20190930_112024-816x459.jpg
 
Matthew J Poes

Matthew J Poes

Senior Audioholic
TheSound brought something up that never occurred to me before. I have sliding glass door on the wall next to my left speaker. If I were to get some thicker light blocking curtains that would change my room acoustics enough to recalibrate?

It'd be nice to be able to darken the room some more anyway and it'd give me something new to OCD on, lol.

View attachment 33265View attachment 33266View attachment 33267
well it would depend on what we mean by recalibrate. When the reflections are asymmetric in the lateral direction (not the same from side to side) the soundstage doesn’t sound even or consistent. Pans across the azimuth (side to side) will be uneven. Some of this effect is related to how reflections cause us to perceive the space. Some of it is the shift in response to one side. So from that standpoint, a recalibration might help even things out. In addition, If speakers are very close to side walls (yours are not) then strong early reflections off the sidewall can cause increased output. The reflections combine with the direct sound more intensely basically because they are happening within the same time window as perceptual integration. If you then absorb these reflections in one side and not the other, the image shifts and the absorbed side will be perceived as quieter. Because curtains absorb more at high frequencies than low frequencies, the imbalance is also a shift in tonal balance (the absorbed side will sound dulled).

this is why it can be a good idea to make the left and right side acoustically similar. Let’s call it acoustic equity, but not equality. They won’t be physically the same necessarily but we want them to sound the same. So if one side is open to another room, put curtains or absorbing panels on the walled off side. If one side has windows and curtains, put curtains on the other side too, and because the window itself creates a cavity, the walled side will need more absorption at low frequencies to have acoustic equity side to side.

how is this achieved you might ask? Measure the spectral response of the reflection. You measure the reflection of the left and right side and compare. Then design the absorption to compensate. It will never be exact but at least close enough. To measure a reflection you simply window out the direct sound and compare each side.

most eq systems only woke in the amplitude domain. They don’t work in the time domain other than the fact that sound is largely minimum phase in a room. Especially at low frequencies. Currents absorb down to about 150-250hz with sufficient weight, thickness, and depth. However they are not great bass absorbers so a curtain won’t change the low frequencies much. That is best fixed with subs and eq.

hopefully this helps. You all are making me think I should do a video on acoustic asymmetry. What it is, when it matters, how to fix it.
 
Pogre

Pogre

Audioholic Warlord
well it would depend on what we mean by recalibrate. When the reflections are asymmetric in the lateral direction (not the same from side to side) the soundstage doesn’t sound even or consistent. Pans across the azimuth (side to side) will be uneven. Some of this effect is related to how reflections cause us to perceive the space. Some of it is the shift in response to one side. So from that standpoint, a recalibration might help even things out. In addition, If speakers are very close to side walls (yours are not) then strong early reflections off the sidewall can cause increased output. The reflections combine with the direct sound more intensely basically because they are happening within the same time window as perceptual integration. If you then absorb these reflections in one side and not the other, the image shifts and the absorbed side will be perceived as quieter. Because curtains absorb more at high frequencies than low frequencies, the imbalance is also a shift in tonal balance (the absorbed side will sound dulled).

this is why it can be a good idea to make the left and right side acoustically similar. Let’s call it acoustic equity, but not equality. They won’t be physically the same necessarily but we want them to sound the same. So if one side is open to another room, put curtains or absorbing panels on the walled off side. If one side has windows and curtains, put curtains on the other side too, and because the window itself creates a cavity, the walled side will need more absorption at low frequencies to have acoustic equity side to side.

how is this achieved you might ask? Measure the spectral response of the reflection. You measure the reflection of the left and right side and compare. Then design the absorption to compensate. It will never be exact but at least close enough. To measure a reflection you simply window out the direct sound and compare each side.

most eq systems only woke in the amplitude domain. They don’t work in the time domain other than the fact that sound is largely minimum phase in a room. Especially at low frequencies. Currents absorb down to about 150-250hz with sufficient weight, thickness, and depth. However they are not great bass absorbers so a curtain won’t change the low frequencies much. That is best fixed with subs and eq.

hopefully this helps. You all are making me think I should do a video on acoustic asymmetry. What it is, when it matters, how to fix it.
I think that might be a good one! I actually understood at least... half of what you explained, lol. I probably would need to recalibrate, but whether the end result is any better than it is now is, as usual, "it depends".

I'm familiar with rew and have a mic so I can do the measurements you're talking about but understanding them and making them useful is where I personally could use some help.
 
Pogre

Pogre

Audioholic Warlord
well it would depend on what we mean by recalibrate.
Oh, it just never occurred to me that curtains would or could make enough of a difference to where a recalibration is necessary. If it is necessary then obviously I've changed my room acoustics whether positively, negatively or not really impactfully at all and that makes things interesting for me. You did a good job of explaining it to me. Thanks.
 
Matthew J Poes

Matthew J Poes

Senior Audioholic
Oh, it just never occurred to me that curtains would or could make enough of a difference to where a recalibration is necessary. If it is necessary then obviously I've changed my room acoustics whether positively, negatively or not really impactfully at all and that makes things interesting for me. You did a good job of explaining it to me. Thanks.
I do my best. I do need to put out more articles and videos on acoustics. Maybe even showing the impact of stuff like this.

I can help people interpret results from REW if they share with me the mdat files, take pictures of the room, and carefully label each measurement.

curtains are actually very effective absorbers. Especially at mid and high frequencies. The absorption is on par with 1”-2” fiberglass panels depending on space. In fact, heavy velour curtains with a thick (1/8”) liner and a 4” air gap can about equal a 4” panel.
 
lovinthehd

lovinthehd

Audioholic Slumlord
Oh, it just never occurred to me that curtains would or could make enough of a difference to where a recalibration is necessary. If it is necessary then obviously I've changed my room acoustics whether positively, negatively or not really impactfully at all and that makes things interesting for me. You did a good job of explaining it to me. Thanks.
Seeing how I can see your blinds thru the curtains, wouldn't expect them to do much....or is it just that blazing AZ sun? :)
 
Pogre

Pogre

Audioholic Warlord
Seeing how I can see your blinds thru the curtains, wouldn't expect them to do much....or is it just that blazing AZ sun? :)
Those are older pics. The curtains behind the tv have been replaced with thicker light blocking curtains. I'm thinking about getting some for the glass door too.
 

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