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Room measurements with KEF R3

EEE272

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Was it this statement? I still stand by it. Above 10k air attenuation also affects reflections that travel a longer way.
There is a drawing in Toole's book. I don't have it here but can give you the page indication later.

Maybe it was not formulated well?
I meant from around 6-10k the fall off no longer follows a straight line.
Oh, now I think I get what you mean. Absorption does NOT affect direct sound. For higher frequencies, direct sound is comparatively stronger, hence the tilt.
Nevertheless, if you take away even more of the higher frequencies, you get a plateau because the direct sound is just much stronger.
Let's take an extreme case. In an anechoic chamber, the response is only direct and thus flat. In a purely reflective environment, far from the speakers, the indirect sound prevails, thus tilted. Was this the misunderstanding?
 

abdo123

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Oh, now I think I get what you mean. Absorption does NOT affect direct sound. For higher frequencies, direct sound is comparatively stronger, hence the tilt.
Nevertheless, if you take away even more of the higher frequencies, you get a plateau because the direct sound is just much stronger.
Let's take an extreme case. In an anechoic chamber, the response is only direct and thus flat. In a purely reflective environment, far from the speakers, the indirect sound prevails, thus tilted. Was this the misunderstanding?
I just want it to be clear that the tilt is 100% a function of the speaker’s directivity.

Have a look at the in-room response of the D&D 8C vs the predicted in-room response. The D&D8C is constant directivity speaker so there is no tilt at all.

1642538912307.png
 

EEE272

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I just want it to be clear that the tilt is 100% a function of the speaker’s directivity.

Have a look at the in-room response of the D&D 8C vs the predicted in-room response. The D&D8C is constant directivity speaker so there is no tilt at all.

View attachment 180019
I would not agree that it is 100% directivity. But I 100% agree that directivity of a speaker influences the tilt.

Nevertheless, so does the room or distance from the speaker.
Take my example of the anechoic chamber. Or what happens when you take a near field measure at low volume. The main factor for the "shape" of the tilt is often directivity though. For example, if it is very uneven, this will come back in the measurement.

Edit: by the way, really cool example! I really like it!
 

EEE272

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Thanks for clarification :) Tomorrow I will do measurements according to your directions. As for the near-field should the mic be placed in the middle of the twitter just a few centimeters away?
Great! In principle, you can do that. Being 20 cm out or so, might make it easier to point to the tweeter. If you use the time window, that should still work perfectly even a bit further out. I think the measure with the 90 degree calibration at the listening position and pointed to the ceiling will be really interesting. Thanks!
 
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Marcin

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@EEE272
I couldn't figure out the time window in REW so I made the measurement the way I did before. Without any EQ.
This is the measurement taken from 20 cm with psychoacoustic smoothing
2022-01-19 10_08_54-Window.png


and with 1/12 smoothing
2022-01-19 10_09_11-Window.png


This is L+R with mic pointed at the ceiling from listening position (1/12 smoothing)
2022-01-19 10_03_19-Window.png


@TurtlePaul Speakers 135cm from the front wall (1/12 smoothing):
2022-01-19 10_32_55-Window.png
 
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EEE272

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That looks really good! All fine with your speakers, as expected! ;)

Just to show you what I meant with the HF falloff that came too early. Your previous graphs with the different calibration really dropped off too early in the HF. I superposed one of the old and the new curve that you just posted. I took here the "before Dirac" figure and superimposed it with the graph above. It is not perfect but I tried to match the scales as much as I could and what I meant is quite visible.
1642587000992.png




While certainly not done with pixel precision, you can see that your new measurements flatten up much more nicely in my opinion.

On a side note, you can also see that the measurement without EQ basically follows already the standard curve that Dirac would propose to you. Thus, your speakers are so well designed that you should not really correct anything above 1000Hz (maybe even 500Hz depending on taste).
Your near-field also shows now how nicely flat the speaker response is - just as it should!
Great setup, the main focus should be on below 1000Hz and with Dirac, you are in good hands. ;)
 

EEE272

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The part that probably needs most work is around 60-80, where your room takes over. That can mostly be addressed with shifting things around, like you already started to do. Down to 100Hz, you are already in a quite good spot.

Regarding the waterfall, I do still think your room could use some absorbers in the high frequencies (maybe at the first reflection points). It will give you a more spatial feel. While this sounds counterintuitive, many modern recordings add reverb/phase shifts for more spatiousness, which you hear best, when the room does not interfere too much.
 

EEE272

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@EEE272 Can you share which page/chapter of the book describes 0.4db/oct roll-off as optimal?
Sure, I have the third edition of the book and don't know if the text differs in previous editions.

On p345 he mentions this 0.4db curve and calls it "an attempt is made to arrive at a room curve that might result from a "perfect" loudspeaker".
How he got there is explained in more detail on p368. He took the 6 top rated speakers and their in room response. They all match up very well (he even makes this point by checking out the measurements of a reviewer).
These curves are all close to the 0.4dB.
The Kef R3 is top rated, so I would have expected it to be similar as well.
p 344 he compares this curve of the 6 top loudspeakers to the "Dirac room curve" and shows that they basically match up.

There is a lot of "might" and "could" here of course... ;)
I also really do not want to claim that there cannot be an excellent sounding loudspeaker with a different tilt. Nevertheless, it seems that the excellent sounding loudspeakers in the HK tests shared the same characteristic in terms of falloff in their standardized test room. As the louspeaker subjective quality correlates with the Olive score, a high Olive score (which the Kef has) is likely to correlate to a similar result. Hence, my expectation.

In any case, one should not temper with the HF, if the on-axis is flat, which he explained in the early chapters. This aligns with p371, where he argues that, above the transition frequency, speakers (if calibration is to be applied) should only be calibrated for on-axis direct sound.

When seeing the first measurements, I did not want to exclude that there is an extreme influence of the room but I was suspecting already that the measurement setup was more likely to be the cause. With the new curves, we see that the room is not "special" and the measurements match up.

That the room can have an influence is shown on p377. It shows the impact of the room and the distance to the speaker using a figure showing indicating how reflections lead to a less flat response and distance leads to a stronger falloff above 6-10K.

For really large rooms, this air attenuation and reflections, seem to be the reason that the "optimal/ideal" curve is also more tilted (this is discussed in the X-Curve chapter, where some researchers even suggest a tilt, flat, tilt as a preferred curve to have influence of air, flat response, and then some bass boost). In our domestic homes the 0.4 seems to match up really well (Toole estimates on p371 that "loudspeakers with flat on-axis and well-behaved directivity will fit within the tolerances, without equalization above about 200 Hz").
 

TurtlePaul

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Marcin, thanks for humoring me and trying. I thought that that positioning would push one of the nulls lower to 60 hz (it did). However, it seems like the dip at 80-90 hz is caused by something other than the back wall distance and it didn't fix that problem.

The measurement just above that (with the blue and brown lines) looks pretty optimal for room placement.
 
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Marcin

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That looks really good! All fine with your speakers, as expected! ;)
Phew, that's a relief!
Thanks a lot for this in-depth explanation.

I did another measurement in Dirac for current placement. I will be doing listening comparisons in the next few days.
First impression is that bass is "thinner". I can hear the bass purr but it's missing the reverb, therefore doesn't sound as punchy. Mids and highs sound cleaner, clarified, but it's probably related to the lack of reverb in lower frequencies.

Marcin, thanks for humoring me and trying. I thought that that positioning would push one of the nulls lower to 60 hz (it did). However, it seems like the dip at 80-90 hz is caused by something other than the back wall distance and it didn't fix that problem.

The measurement just above that (with the blue and brown lines) looks pretty optimal for room placement.
I can assure you this speaker placement looked humorous. Good that my wife did not see it...
 
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Marcin

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The part that probably needs most work is around 60-80, where your room takes over. That can mostly be addressed with shifting things around, like you already started to do. Down to 100Hz, you are already in a quite good spot.

Regarding the waterfall, I do still think your room could use some absorbers in the high frequencies (maybe at the first reflection points). It will give you a more spatial feel. While this sounds counterintuitive, many modern recordings add reverb/phase shifts for more spatiousness, which you hear best, when the room does not interfere too much.
Do you think it's worth to try bass traps like these (30 cm diameter)?

1642769910634.png

BT_Premium_1m_S_Coefficient_2017.png

I know it will not help much below 100 Hz but it might smooth 100-500Hz region.
I was thinking about adding 4 of them (2 stacked on each other like in the picture) in the left side corners. Those are the most "boomy" areas of the room.

1642770466281.png
 

abdo123

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Do you think it's worth to try bass traps like these (30 cm diameter)?

View attachment 180747
BT_Premium_1m_S_Coefficient_2017.png

I know it will not help much below 100 Hz but it might smooth 100-500Hz region.
I was thinking about adding 4 of them (2 stacked on each other like in the picture) in the left side corners. Those are the most "boomy" areas of the room.

View attachment 180748
not really. Perhaps if you cover enough of the walls that ~20% of the room's surface area is covered with them. The only thing that works at that range are these tuned at the frequency that you want: https://gikacoustics.eu/product/gik-acoustics-scopus-tuned-bass-trap-t100/

and you would need a good number of them.

The only other thing that you can use is EQ and getting a subwoofer for more headroom for the EQ. If you want the sub-bass response to be good in multiple seats around the room then you would need multiple subwoofers, typically two or four.
 

abdo123

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@Marcin Almost every company out there over-inflates the capabilities of their porous absorption. for example this is more likely how a 30cm thick absorber would perform

1642771906577.png
 

Jdunk54nl

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@Marcin Almost every company out there over-inflates the capabilities of their porous absorption. for example this is more likely how a 30cm thick absorber would perform

View attachment 180750

We just going to say a 30cm thick thing isn’t thick enough for 100hz and below frequencies, unless it is made of very interesting materials,
 

abdo123

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We just going to say a 30cm thick thing isn’t thick enough for 100hz and below frequencies, unless it is made of very interesting materials,
Some pyramid/triangle shaped can sometimes reach 45 cm at their deepest point, but this circular design is a little off. Maybe they wanted to deflect high frequencies on the cheap.
 
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Marcin

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OK, thanks for quick response.

So, if I would like some acoustic treatment only for frequencies above 100 Hz - should I just focus on standard absorption panels at first reflection points?
What should be the optimal acoustic treatment for a living room? Bearing in mind we don't want to make it look like a recording studio.

Those circulars bass traps could be easily hidden behind the curtains, that is why I thought about them ;)
 

abdo123

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OK, thanks for quick response.

So, if I would like some acoustic treatment only for frequencies above 100 Hz - should I just focus on standard absorption panels at first reflection points?
What should be the optimal acoustic treatment for a living room? Bearing in mind we don't want to make it look like a recording studio.

Those circulars bass traps could be easily hidden behind the curtains, that is why I thought about them ;)
How about just the regular plain broadband corner bass trap? https://gikacoustics.eu/product/gik-acoustics-tri-trap/

If you cover floor to ceiling all the corners that should make a tremendous positive difference. For a domestic space i wouldn't treat any further.
 
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Marcin

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I can only cover corners from floor to ceiling at the left side. Actually such a wide bass trap will cover 1/3 of the balcony door...
At the front right side corner I can have only one trap because of wall mounted shelves. At the back I have doors so nothing can stand there.
 

abdo123

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I can only cover corners from floor to ceiling at the left side. Actually such a wide bass trap will cover 1/3 of the balcony door...
At the front right side corner I can have only one trap because of wall mounted shelves. At the back I have doors so nothing can stand there.
you can also do the junctions between the ceiling and walls, or the floor and walls. they can be hanged horizontally on wall.
 
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