Room measurements and what to make out of them

[StreamFidelity]

Hi to everybody ! I recently moved into a new apartment, and installed my system in the main room.

My congratulations for the very nice tastefully decorated room. The YG speakers should sound very good.

But of course all speakers can only sound as good as the room acoustics allow. My opinion.

1. room modes

In the frequency response (left or right speaker?) there is a peak (+20dB) at about 30Hz and a heavy dip (-30dB) at about 50Hz.

A loudspeaker is placed in the corner of the room (left) and thickens the bass. The other (right) has a door in the back and should have very little bass.

2. reverberation

This one is very high. This is not surprising given the many reverberant surfaces (floor-to-ceiling windows, TV) and the less furniture. I prefer a reverberation of 0.4 sec., 0.6 sec. should generally not be exceeded.

3. symmetry

In rooms it is important to get as much direct sound as possible in "equal proportions" from left and right. Otherwise there will be no phantom center and no stage in depth and width.

This setup is unfortunately very unsymmetrical to the walls. On the left, the window that creates diffuse sound. On the right, no wall, but a large dining table, which reflects the sound totally differently.

Proposed solutions

The solution shown with perforated absorbers and diffusers and the curtains will certainly reduce the reverberation. But the problems with the dip at 50Hz and the missing symmetry will remain.

So I would consider putting the speakers on the window side. And with equal distances to the back and side walls, if possible. The curtains should be closed for listening to music. The listening position should be closer to the speakers. The closer, the more clear sound. No more glass table in the middle reflecting sound unfavorably. And if the TV has to be in the middle, I would cover it for listening to music.

I know you probably don't want to hear this. But it's basically simple physics. I'm planning my listening room right now, too. If you're interested: Planning a new listening room – Grigg Audio Solutions

 

[ecwl]

Hi to everybody ! I recently moved into a new apartment, and installed my system in the main room. Although the acoustics seem fine, the sound gets muddy at high volumes. So I took some measurements with REW, and here are the SPL curve(basal) and RT60 ( before and after panels on wall behind listening place).
If I place absorbent panels on the rear wall, the RT60 decreases and listening improves.
Here's a proposal (Artnovion) to improve things. Thanks for your comments

I see lots of glass that would bounce sound towards you (large bay window to your left) and the coffee table in front of you. That would keep the RT60 pretty high. I think that's why Artnovion suggested that you put curtains to your left.

I also suspect you're just sitting at a position with a 31Hz peak and 52Hz null which would require lots of extremely thick absorbers to improve which I doubt you have the space for. Also, they'll probably ruin the aethestics. I think that's why Artnovion recommended all these corner bass traps but I just don't know if they'll be big/thick enough to deal with such low frequency issues. And ultimately, if you're playing loud and the sound gets muddy, it's probably coming from the 31Hz peak? (Although it could also be from the 120Hz RT60 of 700ms, not sure).

I'm sure the Artnovion suggestions would help quite a bit for all frequencies but not sure if it'll be to your satisfaction.

If I were you, (because I'm quite frugal and prefer minimal intrusions to my living room aesthetics), I would put the curtains on the left first. I would also explore whether I can move the sofa 6" more forward or even 12" more forward. You should use your microphone to measure the frequency response to see if the 31Hz peak and 52Hz null smooths out more if you move 6-18" forward. To me, those are the two things that'll give you the most bang for your buck. If you can't move the sofa, you can't move the sofa. If you don't want curtains across the window, you don't want curtains. And those are compromises you'll have to decide on.

If you are able to do the curtains and move the sofa and you still can't get great sound, I would probably re-measure the new frequency response and see where the bass peaks are. If it's still pretty high at 31Hz, you may want something like the PSI AVAA C214/C20 active bass traps to reduce that bass peak. But once again, you may need several of them which can get very expensive. And ideally you should wander around your room and take the microphone to measure which corners/walls the 31Hz is amplified the most and put the PSI AVAA where the 31Hz peak is loudest.

 

[Rotatoubib]

Thank you.
There are 2 problems: a certain harshness on some soprano voices when the level rises, and a certain lack in the upper bass. This is improved by placing absorbent panels on the 2 tables.
Artnovion's idea is to absorb on the rear wall, with 3 absorbers, 2 wall basstrap, 1 corner bass trap on either side, and a bass trap for very low frequencies, on the floor.

 

[ecwl]

Thank you.
There are 2 problems: a certain harshness on some soprano voices when the level rises, and a certain lack in the upper bass. This is improved by placing absorbent panels on the 2 tables.
Artnovion's idea is to absorb on the rear wall, with 3 absorbers, 2 wall basstrap, 1 corner bass trap on either side, and a bass trap for very low frequencies, on the floor.

So the problem with trying to absorb really low bass frequencies (<55Hz) is that you need really really thick passive bass traps to be effective, e.g.
Mega Bass Trap VMT XXL - Vicoustic
And you'll have to put them at the right spot.

Now in theory, you can put a ton of 4" bass traps all over the wall and each of them might absorb a little bit of the <55Hz resonance and if you have enough of them, eventually, you can get the resonance down. But that'll turn your living room into a recording studio.

At the end of the day, it's just a matter of what compromise you're willing to live with.

As for the harshness in the sopranos, curtains on the window would help. Just as you tested putting the absorbent panels on the tables, you can also try to place/lean an absorbent panel on the left bay window. The key is finding the right spot. The first reflection is where sound bounces from your left speaker off your window into your listening position. If you have a friend/spouse/kid with a mirror, you can sit in the listening position and ask them to move the mirror along your bay window and look at the mirror and see when you can see your left speaker tweeter. That's where your first reflection point is and where you would want to test your absorbent panel first. But for aesthetic reasons, curtains would work better even if an absorbent panel would sound better at the left first reflection point.

 

[sigbergaudio]

@Rotatoubib

With regards to absorbers or bass traps in order to fix the issues below 100hz: Forget about it. There is zero chance you can get anything that will practically fit in your living room that will make any meaningful impact on that huge peak and huge dip.

In order to fix the issues below 100hz you have three options (from easy to more complicated):
* Move listening position and/or speakers to a position where the response is better
* Introduce EQ/DSP that can even out the response
* Purchase one or two subwoofers and high pass the mains, so that the subwoofers (that can be placed in a more optimal positions) can handle the response below 80-100hz.

Harshness: This is probably due to the generally high reflectiveness of the space. As others mention, this can be improved by natural absorbers (curtains, carpets), and/or acoustic panels (walls, ceiling). You will need quite a lot for significant effect.

If you can find something that are visually acceptable that can cover either the entire ceiling or at least the area above the listening position, that will likely have significant effect. Covering the entire wall behind the speakers with a fake wall that have at least 2 inches of insulation and covering that with narrow wooden bars like the picture below (Not sure what that's called in English, I'm Norwegian), that will have a positive effect as well, and also looks good (subjectively at least).

 

[Rotatoubib]

Thanks to all for your kind contribution. How do you explain this feeling of a certain lack of substance, especially on the double basses, based on the SPL curve and the piece?
I mean a lack of foundation on a large symphony orchestra

 

[sigbergaudio]

Thanks to all for your kind contribution. How do you explain this feeling of a certain lack of substance, especially on the double basses, based on the SPL curve and the piece?
I mean a lack of foundation on a large symphony orchestra

The tonality of your system appears to be quite lean, starting from the lower midrange / upper bass / midbass.

The "correct" frequency response is hard to predict given different speakers and different rooms. But to perceive a full sound I'd expect to see at least something along these lines (blue line indicating general response/tonality). Basically you're lacking 3-5dB from ~500hz and down to the bass. I can certainly see how that will come across as "lacking foundation".

EDIT: An interesting test could be to move the speakers closer to the wall (for instance cutting the distance between the speakers and the wall behind them in half) and see what happens with the response.

 

[StreamFidelity]

With regards to absorbers or bass traps in order to fix the issues below 100hz: Forget about it. There is zero chance you can get anything that will practically fit in your living room that will make any meaningful impact on that huge peak and huge dip.

Absolutely correct. The point is that the wavelength is simply too long.

At 100 Hz it is 3.43 m (343 m/sec : 100 Hz)

At 30 Hz it is 11.43 m! (343 m/sec : 30 Hz)

Room modes are caused by reflections of sound waves off the walls, ceilings and floors of a room. These reflections cause the waves to amplify in certain areas of the room and attenuate in other areas.

At half the wavelength (back and forth) between two parallel walls, there is an increase in loudness (peak).

At a quarter wavelength between the walls, there is cancellation (dip) as the waves travel back and forth.

 

[Rotatoubib]

The green SPL curve is what we get with panels on the wall behind listening point: seems better , no? Next, the red one is YG Sonja 1.3 SPL during Stereophile review : you see it goes down under 200 Htz, so maybe its related to the speaker?

 

[ecwl]

Thanks to all for your kind contribution. How do you explain this feeling of a certain lack of substance, especially on the double basses, based on the SPL curve and the piece?
I mean a lack of foundation on a large symphony orchestra

Lack of foundation is probably from the 52Hz dip. But to get a front row symphony hall feel at home, you usually need a slight bass bump which you can’t achieve without DSP and/or subwoofers. If you want the best balcony seat sound from a symphony hall, once you removed the 52Hz dip by moving your seating position, you should have a fairly balanced sound, especially when played at louder volume.

And I’m a master at helping other people spend their money. So feel free to upgrade to Magico M6. But if you put the speakers at the same spot and you sit at the same spot, you’re still going to have the same 52Hz dip because it’s the physics of the room not the physics of the speakers that causes the acoustic issue. Even if you’re to get a subwoofer, there is a chance that it won’t eliminate the 52Hz dip even with optimal placement. That said, it is definitely possible this specific YG model doesn’t have sufficient bass from 200Hz down. I hope not because that would be a pretty poor speaker design then.

 

[sigbergaudio]

The green SPL curve is what we get with panels on the wall behind listening point: seems better , no? Next, the red one is YG Sonja 1.3 SPL during Stereophile review : you see it goes down under 200 Htz, so maybe its related to the speaker?

I guess. The level above 500hz is reduced on the green curve. I assume these are stereo measurements? You will get a more accurate result (closer to what you are hearing) by measuring left and right indivdually and then using the average feature in REW (button in the lower left corner of the graph area).

With regards to Stereophile measurements: The nearfield measurements looks pretty flat. The graph you are referencing is a listening room measurement

.

 

[ecwl]

The green SPL curve is what we get with panels on the wall behind listening point: seems better , no? Next, the red one is YG Sonja 1.3 SPL during Stereophile review : you see it goes down under 200 Htz, so maybe its related to the speaker?

Stereophile reviewers room acoustics are suboptimal in my humble opinion. I guess one can argue that so are most of our rooms so that’s okay?!? But I think it leads to many problems like a reviewer liking a problematic speaker just because its distortions work synergistically with the reviewer’s poor room acoustics. They do try to compensate by showing another pair of speakers so that you can sort of see what is coming from the speakers and what is coming from the room.
So yeah, I would ignore the stereophile in-room measurements.

 

[ecwl]

The green SPL curve is what we get with panels on the wall behind listening point: seems better , no? Next, the red one is YG Sonja 1.3 SPL during Stereophile review : you see it goes down under 200 Htz, so maybe its related to the speaker?

I just realized with the panels, you reduced your 52-54Hz dip by 7dB but you increased your 105Hz? dip by 3dB. This is why room acoustics is so complicated. And why you really want to see if moving your listening position/sofa forward a bit would significantly improve these issues. Which you can test by playing pink noise and measure with a microphone quickly without going through a full measurement process.

 

[Rotatoubib]

What surprised me is that red and green SPL curves are not very different, but listening improved really; maybe its related to SPL 60 ( mean from 700ms to 600)
As you see below, before and after panels

 

[ecwl]

What surprised me is that red and green SPL curves are not very different, but listening improved really; maybe its related to SPL 60 ( mean from 700ms to 600)
As you see below, before and after panels

Yes. Reducing reverberation/resonance would mean the previous musical notes would not hang around in the room for as long and blur the current notes. So all the notes sound clearer.

But notice how your panels affect the midrange and trebles reverberation/resonance much more than the bass. This is because you just need a lot of thick panels to absorb bass.

 

[Rotatoubib]

I agree with you. 30 Htz peak is related to room size and will remain anyway ; maybe the wall and corner bass trap could "equalize" bass?

 

[Rotatoubib]

The 3 bass trap they recommended

 

[sigbergaudio]

I just realized with the panels, you reduced your 52-54Hz dip by 7dB but you increased your 105Hz? dip by 3dB. This is why room acoustics is so complicated. And why you really want to see if moving your listening position/sofa forward a bit would significantly improve these issues. Which you can test by playing pink noise and measure with a microphone quickly without going through a full measurement process.

That is likely due to a slightly moved microphone / other measuring anomaly rather than any effect of the panels.

 

[Rotatoubib]

And absorbing panels

 

[ecwl]

I agree with you. 30 Htz peak is related to room size and will remain anyway ; maybe the wall and corner bass trap could "equalize" bass?

I would argue that we technically don't know that the 30Hz peak "will remain anyway". The possibilities are plenty and I think chances are it's a combination of the following:
1) Your left speaker is so close to the left front corner that it's inciting a 30Hz peak because of the geometry and speaker position
2) You are sitting at a 30Hz peak
3) Your room naturally has a 30Hz resonance that would be amplified regardless of where you sit without very deep bass traps
Since it is likely a combination of these 3 problems, you may have to attack all 3 to improve the problem.
And you may approach some of the problems and be able to sufficiently reduce the 30Hz peak that it's no longer as big of an issue.

But what I think everybody who has posted so far agree is that to use passive bass traps to treat the 30Hz peak would be the hardest thing to do (or near impossible) compared to everything else to try.