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Sweet Room - Kill those room modes
#1
The link below is something I posted a while ago in relation to Home Audio Fidelity's Room Shaper plugin.  Now that we have Sweet Room, I am thinking that this might be a useful tool for anyone interested in using Sweet Room to kill those room modes?

The room mode calculator linked below is something that works well for me, although I might be lucky in this regard in that I have a very rectangular room.  For those with more complex room layouts, i doubt it will work too well.  

The great thing about this room mode calculator is that it includes a tone generator that actually allows you to listen to to those room modes.  This is useful as it allows you to actually hear the effect that the room modes make to the sound.  This kind of information is useful in terms of improving understanding of the issue, and it could then be used to test any Sweet Room correction files that you subsequently make, to judge the impact and aurally verify if they are actually having the desired effect.  For the record, this room mode checker makes it abundantly and very aurally clear that my room has a serious issue in the 28Hz region.

To use this you will need some way to send music from your PC to your Devialet, although AIR is fine for this.

https://amcoustics.com/tools/amroc?l=20&...0-%20Music

I have not had time to actually try this in conjunction with Sweet Room, and I suspect it will take to time to get the dB cut and Q value right.

Maybe others have some ideas as to how this could be implemented, or other ways to address those pesky room modes?   I am far for an expert here, for example, I know that I have an issue at 28Hz, but what dB cut and Q value would be recommended to rectify?  Or is it a case that a degree of trial and error is needed?

In terms of trial and error, I tried this link below to generate some test tones, one at the actual mode frequency of 28Hz, then others at slightly higher and lower frequencies.

https://www.audiocheck.net/audiofrequenc...netone.php

I then played these tones to hear the effect of the room mode as the frequencies rise and fall.  Another thing I tried was using Roon's pararmetric EQ to make a dip at 28Hz.  With a bit of experimenting, I found a dip of -12dB with a Q of 5 transformed the resonating room mode into something that sounded like normal bass.  It was not quite right though, the bass was not entirely even when listening to the higher / lower test tones.  I think with a lot of time and experimentation, you could get things "just so" with this method.  The idea here is that once you have fine tuned something that works in Roon, the dB and Q values used could then be transferred into Sweet Room.

I can't help thinking there must be an easier way?
1000 Pro - KEF Blade - iFi Zen Stream - Mutec REF10 - MC3+USB - Pro-Ject Signature 12
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#2
(31-Oct-2020, 13:22)Confused Wrote: The link below is something I posted a while ago in relation to Home Audio Fidelity's Room Shaper plugin.  Now that we have Sweet Room, I am thinking that this might be a useful tool for anyone interested in using Sweet Room to kill those room modes?

The room mode calculator linked below is something that works well for me, although I might be lucky in this regard in that I have a very rectangular room.  For those with more complex room layouts, i doubt it will work too well.  

The great thing about this room mode calculator is that it includes a tone generator that actually allows you to listen to to those room modes.  This is useful as it allows you to actually hear the effect that the room modes make to the sound.  This kind of information is useful in terms of improving understanding of the issue, and it could then be used to test any Sweet Room correction files that you subsequently make, to judge the impact and aurally verify if they are actually having the desired effect.  For the record, this room mode checker makes it abundantly and very aurally clear that my room has a serious issue in the 28Hz region.

To use this you will need some way to send music from your PC to your Devialet, although AIR is fine for this.

https://amcoustics.com/tools/amroc?l=20&...0-%20Music

I have not had time to actually try this in conjunction with Sweet Room, and I suspect it will take to time to get the dB cut and Q value right.

Maybe others have some ideas as to how this could be implemented, or other ways to address those pesky room modes?   I am far for an expert here, for example, I know that I have an issue at 28Hz, but what dB cut and Q value would be recommended to rectify?  Or is it a case that a degree of trial and error is needed?

In terms of trial and error, I tried this link below to generate some test tones, one at the actual mode frequency of 28Hz, then others at slightly higher and lower frequencies.

https://www.audiocheck.net/audiofrequenc...netone.php

I then played these tones to hear the effect of the room mode as the frequencies rise and fall.  Another thing I tried was using Roon's pararmetric EQ to make a dip at 28Hz.  With a bit of experimenting, I found a dip of -12dB with a Q of 5 transformed the resonating room mode into something that sounded like normal bass.  It was not quite right though, the bass was not entirely even when listening to the higher / lower test tones.  I think with a lot of time and experimentation, you could get things "just so" with this method.  The idea here is that once you have fine tuned something that works in Roon, the dB and Q values used could then be transferred into Sweet Room.

I can't help thinking there must be an easier way?

Have you discounted the purchase of a measuring microphone, such as the MiniDSP umik-1?

With an appropriate measurement you should be able to remove most of the trial and error you describe above. It may not be as 'sexy' as all the other accessories you have but used judiciously, the results could be as good, if not better, than those accessories.
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#3
Probably an idea to do a REW/Sweet Room config first and then use this nice tool to verify by ear that the result is good.
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#4
For anyone with an iPhone or iPad there is an app called Audio Function Generator. It’s very configurable and the results can be streamed directly to the amp.
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#5
@alandbush - I have owned a Umik-1 for many years!

Perhaps some explanation is required here as to why I found the AMcoustics Room Mode tool so interesting. If I measure using REW it does pick up that I have some room induced peaks and nulls in the sub 150Hz range. Nothing too unusual about that. Using REW, it tells me that I have a room mode at 27.4Hz, which ties up nicely with the AMcoustics tool which shows me both visually and aurally that I have an issue at 28Hz, so far so good.

Again using REW, this tells me that my most offensive room mode is at 54.5Hz, this too has alignment with the AMcoustics Room Mode tool, which indicates a room mode at 56Hz.

Now this is the bit that I find interesting. Using the AMcoustics Room Mode tool, the 28Hz tone sounds horrific, hugely overblown bass sound and offensive to my ears, whereas the 56Hz tone sound like moderately enhanced bass, and actually rather pleasant. So aurally the AMcoustics Room Mode tool tells me the 28Hz mode is a big problem, whereas the 56Hz tone is less of an issue and maybe something you could happily live with.

So maybe a case of the subjective influence of the room not matching the objective measurement of the room? This is why I found the AMcoustics Room Mode tool interesting, as it provides some insight into what REW is showing related to how this actually sounds in the room.

@ogs - Doing a REW/Sweet Room config first and then using the AMcoustics Room Mode tool to verify by ear is a good idea. I am also wondering if there are other approaches. For example, I could use the room mode tool and Roon to kill the highly offensive 28Hz mode, then measure with REW to judge the impact of this on the overall in room frequency response curve, then work out the overall correction needed to get near to the "house curve" sound of choice. Ah, if only I had more free time at the moment. I think I will give this some more thought and spend what is left of my limited free time to actually listen to music.

As an aside, REW used to work fine on my old lowish spec i5 PC. Running on my current i990K machine, with much higher resolution graphics etc., REW is very buggy, with many of the GUI's displaying incorrectly when playing around with settings. I am sure there must be an easy fix in the settings somewhere, but I tend to lose interest in software when it plays up like this, often you can waste a huge amount of time sorting issues like this, which I find very frustrating.

@Axel - I have just tried the Audio Function Generator you recommended. A nice tip, thanks! It is simple and works a treat, I really like the way it allows you to play a test tone, then toggle the frequency up / down by 1dB. Ideal for hunting down those pesky room resonances.
1000 Pro - KEF Blade - iFi Zen Stream - Mutec REF10 - MC3+USB - Pro-Ject Signature 12
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#6
Be careful when playing with pure sines.

The way the cochlea works inside the ear is almost like a Fourier transform. A pure sine only stimulates a small number of hair cells while a signal with multiple frequencies will stimulate a much larger number, therefore spreading the overall energy across a larger number of cells.

This is to say that you need to be careful because it is much easier to damage your ear when playing with pure sine waves, at lower levels than a musical signal that contains many frequencies.

Jean-Marie
MacBook Air M2 -> RAAT/Air -> WiFi -> PLC -> Ethernet -> Devialet 220pro with Core Infinity (upgraded from 120) -> AperturA Armonia
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#7
@Confused ,

The differences in frequency between measured and predicted for your modes (eg 27.4 Hz measured vs 28 Hz) can be due to one or two things. There could be an inaccuracy with the meter or the AMcoustics software but the most probable cause is that there's some flex in your walls which means that the mode is actually going to be slightly lower than a prediction based on length because the walls bulge out under pressure, increasing the length of the room axis slightly.

As for the 54.5 Hz mode being less offensive than predicted, that also could be due to one or two things but since it's harder to absorb sound as the frequency lowers and since walls//ceilings/floors do absorb some sound, it could just come down to your walls being more effective absorbers at 54.5 Hz than they are an octave lower at 27.4 Hz.

Your software tool will give you an idea of what the frequency of your modes are, and of their severity, but room construction and materials are going to modify what's actually happening in the room to a slight degree and the only way of really knowing how the room actually behaves is to measure what it does. Feeding room dimensions into a mode calculator will not give accurate results because your room surfaces aren't perfectly rigid.
Roon Nucleus+, Devilalet Expert 140 Pro CI, Focal Sopra 2, PS Audio P12, Keces P8 LPS, Uptone Audio EtherREGEN with optical fibre link to my router, Shunyata Alpha NR and Sigma NR power cables, Shunyata Sigma ethernet cables, Shunyata Alpha V2 speaker cables, Grand Prix Audio Monaco rack, RealTRAPS acoustic treatment.

Brisbane, Qld, Australia
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#8
(01-Nov-2020, 13:35)David A Wrote: @Confused ,

The differences in frequency between measured and predicted for your modes (eg 27.4 Hz measured vs 28 Hz) can be due to one or two things. There could be an inaccuracy with the meter or the AMcoustics software but the most probable cause is that there's some flex in your walls which means that the mode is actually going to be slightly lower than a prediction based on length because the walls bulge out under pressure, increasing the length of the room axis slightly.

As for the 54.5 Hz mode being less offensive than predicted, that also could be due to one or two things but since it's harder to absorb sound as the frequency lowers and since walls//ceilings/floors do absorb some sound, it could just come down to your walls being more effective absorbers at 54.5 Hz than they are an octave lower at 27.4 Hz.

Your software tool will give you an idea of what the frequency of your modes are, and of their severity, but room construction and materials are going to modify what's actually happening in the room to a slight degree and the only way of really knowing how the room actually behaves is to measure what it does. Feeding room dimensions into a mode calculator will not give accurate results because your room surfaces aren't perfectly rigid.

I agree that a feeding room dimensions into a mode calculator will not give perfect results, there are two many variables as you mention.  (although in my case with a rectangular room there is perhaps a surprising degree of correlation.)

However, this does distract from the key point I was trying to convey.  REW is actually measuring the room, so will take all of the above into account.  

The REW measurements indicate that my most offensive room mode is at 54.5Hz, whereas the room mode at 27.4Hz (also measured by REW) is subjectively and audibly by far the worst, this is the key point.  This is based on measured results, listening to tones that correlate to the measured results, and hence is completely unrelated to how AMcoustics Room Mode tool is calculating anything.  As for the difference between 27.4Hz and 28Hz, the mode sounds much the same at 27Hz as it does at 28Hz, so I do not think a 0.6Hz difference is much to worry about in practice.
1000 Pro - KEF Blade - iFi Zen Stream - Mutec REF10 - MC3+USB - Pro-Ject Signature 12
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