Effect of sofa on room measurements

[Deleted member 48726]

I think you are misinterpreting that graph. The two graphs are left channel and right channel, not before and after. Acourate does not boost nulls, it only cuts peaks. But thank you for taking the time to think about my post, I appreciate it

Are you sure it doesn't? I know they are the two channels and target in the graph. I've marked the delta between the target and the nulls.

I guess it's like REW where it looks at the nulls Q. Then it's adjustable and I would make sure it doesn't boost any of them.

 

[Philbo King]

Nulls are not minimum phase, and are not fixable with EQ. Read the Minimum Phase section of the REW online manual for a comprehensive explanation.

 

[Bjorn]

A chair/sofa will not only add some very early reflections but will also attenuate some later ones. Mainly because it's stopping some reflections from the rear with its back.
It makes sense to include it in the measurement but knowing that it will be different when sitting in it.

It's also another reason why applying EQ to peaks and dips especially above the bass region of the room response generally doesn't work well.

 

[Keith_W]

Are you sure it doesn't? I know they are the two channels and target in the graph. I've marked the delta between the target and the nulls.

I moved the target there so that it is easier to compare the sweep with the target. The actual target is referenced to the original uncorrected sweep.

 

[Keith_W]

Lol, no worries. The frustration and excitement of setting up speakers with active filters is known to many of us.

Have you tried measuring with MMM method to see how things smooth outside of your listening position? I find it to be a brilliant reality check sometimes when I get too far into the weeds. Not sure about the pre-ringing, not something I've had to deal with in my system before.

Sorry, I missed your post. I haven't tried the MMM method. What is it good for? Frequencies above Schroder? Removing comb filtering?

 

[Deleted member 48726]

I moved the target there so that it is easier to compare the sweep with the target. The actual target is referenced to the original uncorrected sweep.

Ahh, that's essential information, if you didn't know..

 

[tmtomh]

I moved the target there so that it is easier to compare the sweep with the target. The actual target is referenced to the original uncorrected sweep.

Ah! Okay, that makes a lot of sense!

In that case, I can only say that there are a good number of folks here (not to mention Floyd Toole) who do not recommend full-range auto-correction because it can produce unpleasant-sounding results in the mids and/or treble. I've seen a few reports in various threads around here about how full-range correction produced poor-sounding results in the 4-5kHz region in particular, and I have experienced that myself. In particular, the problem I've had with full-range correction is that the result either sounds too nonlinear in the upper mids and treble (peaky, sibilant, or otherwise just not smooth), or else it sounds smooth and linear but too dull.

I wonder how the result would sound to you if you had Acourate do its thing from 20Hz to 200-300Hz (the Schroeder frequency), as many suggest; or alternatively from 20Hz to about 800Hz, as Genelec's GLM seems to do.

Then you could try working on the rest of the response manually using PEQ. At first glance I'd say you'd want a high shelf starting at 6 or 7kHz, to match your target curve. (Because you've shifted your target curve up in the graph, I can't say how much or how little the cut would need to be.) And then I'd say you'd need to apply a peak cut or boost in the mids to address the fact that the speakers are down in the 2-4kHz range compared to their overall output just below and above that. (Again, because I don't know where your target curve actually is supposed to be, it's hard to say whether 2-4k needs a boost or the other areas need a cut.)

 

[Keith_W]

By the way, Uli (author of Acourate) saw this thread and sent me an email.

Hi Keith,

I've seen this thread and I have some comments:

It makes sense to either take the sofa away or at least to cover it with a soft fabric during the measurement. Be aware that when you sit there for listening your body will not reflect as the sofa and it will cover the reflecting area around the mic.

Dips in the frequency response below 300 Hz may be caused by the reflecting floor. You can easily test it by e.g. by placing a bedspread at the floor at the speaker foot and/or at the reflection point.
The floor would anyway benefit of a long hair rug

Pre-ringing video and step response:
please check first the step response of the measured pulses. If they show up preringing already you have to check for the reason.

He asked me to send him my workspace.

I think going forward, I will put a stack of cushions on the sofa to simulate having a person sitting there. It's easier than sitting there myself.

 

[Keith_W]

Ah! Okay, that makes a lot of sense!

In that case, I can only say that there are a good number of folks here (not to mention Floyd Toole) who do not recommend full-range auto-correction because it can produce unpleasant-sounding results in the mids and/or treble. I've seen a few reports in various threads around here about how full-range correction produced poor-sounding results in the 4-5kHz region in particular, and I have experienced that myself. In particular, the problem I've had with full-range correction is that the result either sounds too nonlinear in the upper mids and treble (peaky, sibilant, or otherwise just not smooth), or else it sounds smooth and linear but too dull.

I wonder how the result would sound to you if you had Acourate do its thing from 20Hz to 200-300Hz (the Schroeder frequency), as many suggest; or alternatively from 20Hz to about 800Hz, as Genelec's GLM seems to do.

Then you could try working on the rest of the response manually using PEQ. At first glance I'd say you'd want a high shelf starting at 6 or 7kHz, to match your target curve. (Because you've shifted your target curve up in the graph, I can't say how much or how little the cut would need to be.) And then I'd say you'd need to apply a peak cut or boost in the mids to address the fact that the speakers are down in the 2-4kHz range compared to their overall output just below and above that. (Again, because I don't know where your target curve actually is supposed to be, it's hard to say whether 2-4k needs a boost or the other areas need a cut.)

Yes, which is why I created a separate thread on whether we should correct to Schroder only, or full range. We should discuss this there. But in brief, I have done both and I much prefer only correcting to Schroder. However, I am open to the idea that I have screwed up all my attempts at full range correction which would explain why I do not like it.

 

[Ron Texas]

There are two schools of thought. One is to measure and do room corrections with the sofa in place, the other is to remove it. Having the sofa in place seems to be the logical answer, but what is the argument for removing it?

 

[Keith_W]

Well, what do you know. Turns out that @sejarzo started a thread on trying to simulate a body at the listening position for measurements. I chuckled a bit when I saw this photo:

The thread is here: https://www.audiosciencereview.com/...at-listening-position-for-measurements.41827/

 

[tmtomh]

Yes, which is why I created a separate thread on whether we should correct to Schroder only, or full range. We should discuss this there. But in brief, I have done both and I much prefer only correcting to Schroder. However, I am open to the idea that I have screwed up all my attempts at full range correction which would explain why I do not like it.

Ah, I didn't remember that it was you who started that other thread - thanks! Didn't mean to go off-topic here; it just seems like a natural extension of the discussion since you are asking what might have gone wrong or what you might do differently, and since the "target curve is set too high" idea turned out to be mistaken, the full-range correction issue seems to be the only (or most likely) remaining explanation.

I'm guessing enough folks have already weighed in on the sofa question to give a clear consensus, but for what it's worth, absolutely keep the sofa in the room, in its normal position, for the measurements. It's no different than a door, a window, a wall, or any other piece of furniture - it will be there during actual listening.

In fact, because I do the vast majority of my listening by myself, I've tried taking listening-position measurements both with the mic on a stand at my listening seat, and with me actually in the listening seat, leaning back slightly and holding the mic where my ears would be. The resulting measurements are very similar, but they're not identical - my body no doubt adds some small amount of absorption (and maybe a little diffraction?). I doubt it makes much if any of an audible difference though - for all I know, the differences between the mic-stand measurements and the me-holding-the-mic measurements are within the margin of run to run variations or within the margin of differences created if the mic is 1/4" higher or lower run to run etc.

EDIT: Just saw your posts above about Acourate recommending putting a covering on the sofa, and @sejarzo using that very clever dummy! My personal opinion is to keep it simple - why simulate the effect of me sitting there when I can just sit there during the measurement?

 

[dasdoing]

EDIT: Just saw your posts above about Acourate recommending putting a covering on the sofa, and @sejarzo using that very clever dummy! My personal opinion is to keep it simple - why simulate the effect of me sitting there when I can just sit there during the measurement?

any surface close to the mic that is reflective will create comb filtering, including you head.
not sure if a cover on the sofa will be absorbive enough, but sounds like the best compromise

 

[dasdoing]

, I am open to the idea that I have screwed up all my attempts at full range correction which would explain why I do not like it.

Effect of sofa on room measurements

Yesterday I decided to look at the effect of having the sofa at the listening position on measurements. This is where the sofa is located: And without sofa: These are the measurements. I applied some smoothing to make the measurements more legible: The mic was not moved from the...

www.audiosciencereview.com

if you corrected a FDW with excess phase than you created artificial peaks where frequencies are delayed

 

[tmtomh]

any surface close to the mic that is reflective will create comb filtering, including you head.
not sure if a cover on the sofa will be absorbive enough, but sounds like the best compromise

Makes sense. But why compromise with a cover on the sofa when you can just use yourself?

Of course if you regularly listen with other people, or you regularly listen from multiple seats in your listening room, then you shouldn't be seated on the sofa during measurements. But if you feel your own body does need to be accounted for, then why not just use... your own body?

 

[dasdoing]

if you feel your own body does need to be accounted for, then why not just use... your own body?

we have to be careful here.
you listen to a live saxofone, the effect of your body will be there.
you record it and play it on your system, you want your body effect to be there, too...because you want it to sound the same

the sofa on the other hand will absorb stuff in the low end, so there is a real probem here. unless, like I said, we imagine ourselfs listening to the real sax on a sofa lol. than we have the real event again

 

[tmtomh]

we have to be careful here.
you listen to a live saxofone, the effect of your body will be there.
you record it and play it on your system, you want your body effect to be there, too...because you want it to sound the same

the sofa on the other hand will absorb stuff in the low end, so there is a real probem here. unless, like I said, we imagine ourselfs listening to the real sax on a sofa lol. than we have the real event again

Which is precisely why you want the sofa there when you measure - so the room correction and/or your own manual PEQ can compensate for the absorption of the sofa. The logic is no different from taking room measurements with the carpet, windows, wall hangings, and bookshelves in your room, even if the saxophone was recorded in a space with hardwood floors and no windows.

 

[sejarzo]

What concerns me more now is that a leather sofa is perhaps more reflective than absorptive in the critical range above Schroeder but below around 1kHz. As I move the mic closer to the speakers...without any dummy in place, LOL...the curve from 400-1KHz tends to flatten. The closer the mic is to where my ears would be when seated in prime listening position, the deeper the dip, and the frequency fairly well correlates to a reflection from the sofa cancelling the direct sound from the speaker.

Maybe the moral of the story is that leather seating is sub-optimal?

 

[JeremyFife]

What concerns me more now is that a leather sofa is perhaps more reflective than absorptive in the critical range above Schroeder but below around 1kHz. As I move the mic closer to the speakers...without any dummy in place, LOL...the curve from 400-1KHz tends to flatten. The closer the mic is to where my ears would be when seated in prime listening position, the deeper the dip, and the frequency fairly well correlates to a reflection from the sofa cancelling the direct sound from the speaker.

Maybe the moral of the story is that leather seating is sub-optimal?

What difference does it make? If that's in the room when you listen, then leave it there to measure... if you change your sofa then just remeasure

 

[dasdoing]

Which is precisely why you want the sofa there when you measure - so the room correction and/or your own manual PEQ can compensate for the absorption of the sofa. The logic is no different from taking room measurements with the carpet, windows, wall hangings, and bookshelves in your room, even if the saxophone was recorded in a space with hardwood floors and no windows.

but it IS problematic as allready said. we don't want sofa comb filtering in the measurements