How to find what music has stereo bass (with EasyEffects)

[FrantzM]

Hi

This is new to me and humbling.. I am very satisfied with my mono bass arrangment where everything under 80 Hz goes to MSO-ed dual subs. Happy and content .. and it took a very long time to get there .. how would one integrate, linearize, 2 channels (stereo?) low bass? Are the gains worth it? Are there that many recordings that use it?
Perhaps a bit off-topics sine there seems to be a software that identify stereo bass...

Best.

 

[Hayabusa]

I cannot confirm

I will redo it and check again...

 

[pablolie]

Hi

This is new to me and humbling.. I am very satisfied with my mono bass arrangment where everything under 80 Hz goes to MSO-ed dual subs. Happy and content .. and it took a very long time to get there .. how would one integrate, linearize, 2 channels (stereo?) low bass? Are the gains worth it? Are there that many recordings that use it?
Perhaps a bit off-topics sine there seems to be a software that identify stereo bass...

Best.

I did the experiment and detected no difference, and my personal theory remains that it is interacting with something that causes vibration somewhere that indeed can be heard - basically contamination. There are fundamental physiological reasons why bass under 80Hz is quite non-directional, and that's still the majority scientific consensus out there. The study also says you need an anechoic chamber (no room reflections) and other aspects that make it very unrealistic in a normal listening environment. The study itself states that accuracy (in an anechoic room) drops with frequency but doesn’t hit zero at 50–60 Hz (I think 31Hz was the lowest but TL;DR .
Also curious is that they use "four Genelec 7380A active subwoofers with the low frequency cutoff point at 16 Hz and the high-cutoff at 100 Hz" - why even go so high? That raises the question about "contamination" I mentioned. Note their takeaway is ".. demonstrating that the directional hearing of low-frequency sound sources highly depends on the acoustical properties of the listening environment ..".
I also find it odd to test for directionality with "pink noise", since it by definition ranges from 20-20000Hz (even though the subs are cut off at an arbitrary 100Hz - why?). No one has ever doubted directionality across that entire range, so that part of the experiment seems a waste of time - I'd stick to the sinusoid results.

 

[LSPhil]

It is absolutely settled "sub bass" is *not* directional. Give us a pointer to a source that says it's not. Whether it 80 or 90Hz or such there is silly debate about. But anything under 80Hz being directional (unless there are unwanted room interactions) is not based on any scientific source ever.

In enclosed spaces, bass behaves differently than higher frequencies. At low frequencies, especially in the sub-bass range, we're dealing with pressure zones, peaks and nulls, not propagating acoustic waves in the conventional sense. This is because the wavelengths are so long that the room dimensions are often smaller than the wavelengths themselves.
Only above a certain frequency, known as the Schroeder frequency, does sound begin to behave like a diffuse acoustic field, where it propagates as waves and reflects off surfaces in a more predictable manner.
In professional audio production, no competent mixing or mastering engineer uses stereo bass in recordings. This is because stereo bass can cause phase cancellations or reinforcements (constructive and destructive interference) when played back in real rooms, due to these pressure interactions, not because of any creative or aesthetic reason. That's why bass is always summed to mono below a certain frequency, typically around 80–120 Hz, depending on the system and the intended playback environment.

 

[krabapple]

Power response estimate with pink noise, white noise, whatever, over a window more than 2 milliseconds at 20kHz, and not UNDER 200 milliseconds at 100Hz. The window *must* work according to cochlear dynamics to get the right answer. No options.

Thanks. Do we know whether common (among techy audiophiles at least) consumer room measuring apps (REW, Audyssey, Dirac...) adhere to these criteria in the region below a few hundred Hz?

 

[NTK]

...
In professional audio production, no competent mixing or mastering engineer uses stereo bass in recordings. This is because stereo bass can cause phase cancellations or reinforcements (constructive and destructive interference) when played back in real rooms, due to these pressure interactions, not because of any creative or aesthetic reason. That's why bass is always summed to mono below a certain frequency, typically around 80–120 Hz, depending on the system and the intended playback environment.

You've gotten it backwards. Proper multichannel mix are done with full frequency bandwidth for all the ear level channels. The downmixing to mono bass happens in your system. Check out Morten Lindberg's system, each of the 7 channels is equipped with a W371A, and the single subwoofer is for the LFE channel only.

You need to read some of Thomas Lund's posts.
https://www.audiosciencereview.com/...bass-and-subwoofers.51589/page-5#post-2008100
https://www.audiosciencereview.com/...ass-and-subwoofers.51589/page-10#post-2221928

 

[pablolie]

You've gotten it backwards. Proper multichannel mix are done with full frequency bandwidth for all the ear level channels. The downmixing to mono bass happens in your system. Check out Morten Lindberg's system, each of the 7 channels is equipped with a W371A, and the single subwoofer is for the LFE channel only.

You need to read some of Thomas Lund's posts.
https://www.audiosciencereview.com/...bass-and-subwoofers.51589/page-5#post-2008100
https://www.audiosciencereview.com/...ass-and-subwoofers.51589/page-10#post-2221928

Impressive except for all those plastic cases on thin shelves...? Aren't they likely to react to sub-bass?

 

[goat76]

In professional audio production, no competent mixing or mastering engineer uses stereo bass in recordings. This is because stereo bass can cause phase cancellations or reinforcements (constructive and destructive interference) when played back in real rooms, due to these pressure interactions, not because of any creative or aesthetic reason. That's why bass is always summed to mono below a certain frequency, typically around 80–120 Hz, depending on the system and the intended playback environment.

I tested 26 randomly chosen tracks, and 20 of them contained stereo information right down to the lowest bass region; some had pretty large differences, while others had less. I was a bit surprised by this, as I had expected most of them to be summed to mono, especially since many of those tracks were pop and rock productions.

I have also made some listening tests comparing stereo bass vs mono bass, and to me, it makes an audible difference. Bass summed to mono sounds somewhat "claustrophobic", as if the bass sound is just in front of me in the area around and between the main speakers. With stereo bass, it sounds larger with a greater sensation of envelopment. It's not about detecting directional cues.

 

[olieb]

In professional audio production, no competent mixing or mastering engineer uses stereo bass in recordings.

I agree with the first two paragraphs of your post, but while the quote above might be correct (or not, idk) for most mixed pop, rock, folk and jazz (stereo) recordings, it is not true for those classical recordings of orchestra that I checked. There the amount of channel differences in (sub) bass can be (and is) quite considerable. And I don't think that is because the engineers are not competent.
@NTK commented on the case of multichannel where it seems a bit different again with bass management.

This is because stereo bass can cause phase cancellations or reinforcements (constructive and destructive interference) when played back in real rooms, due to these pressure interactions, not because of any creative or aesthetic reason.

These interferences (aka room mode related uneven FR) happen with mono bass too (just to a somewhat lesser degree) depending on where you put your sub(s).

That raises the question about "contamination" I mentioned.

I also find it odd to test for directionality with "pink noise", since it by definition ranges from 20-20000Hz (even though the subs are cut off at an arbitrary 100Hz - why?)

You might want to actually read the study before commenting on details. They took care of "contamination" and explain the noise test signals.

 

[bmc0]

In professional audio production, no competent mixing or mastering engineer uses stereo bass in recordings. [...] That's why bass is always summed to mono below a certain frequency, typically around 80–120 Hz, depending on the system and the intended playback environment.

I guess there are very few "competent" engineers in the classical/orchestral genre then.

There are fundamental physiological reasons why bass under 80Hz is quite non-directional, and that's still the majority scientific consensus out there.

Not according to the literature I've read.

Also curious is that they use "four Genelec 7380A active subwoofers with the low frequency cutoff point at 16 Hz and the high-cutoff at 100 Hz" - why even go so high? That raises the question about "contamination" I mentioned.

That's just how the subs were set and does not reflect the frequency content of the stimuli. The authors were careful to avoid frequency content which could have contaminated the results.

Note their takeaway is ".. demonstrating that the directional hearing of low-frequency sound sources highly depends on the acoustical properties of the listening environment ..".

Yes, but this does not imply that directional/spatial sensation is absent in the presence of modes/reflections. Note, for example, the 80Hz sinusoidal result: 10° was statistically significant, but in the wrong direction. Since the desired characteristic in concert halls appears to be chaotic fluctuations in ITD and ILD, it seems to me that it doesn't really matter if the detected direction is inaccurate, just that it fluctuates.

I also find it odd to test for directionality with "pink noise", since it by definition ranges from 20-20000Hz (even though the subs are cut off at an arbitrary 100Hz - why?).

As explained in the paper, the pink noise bursts were filtered with one octave wide bandpass filters. The stated frequencies (31.5, 40, 50, 63, 80, and 100) are the center frequencies of the bandpass filters.

 

[pablolie]

Just to make it clear - I *did* find the paper educational and learned from it. I fully accept that under special and tightly controlled circumstances content as low as 31.5Hz can be directional.

In the real world though, If I run with these test tones:

1. I don't hear 20Hz, but if I turn the volume high enough, I sense it. Zero directionality in my room (and I used Dirac to set up the subs).
2. 25Hz I hear clearly, but zero directionality. If I walk around, it's easy to hear the room modes.
Same up to 63Hz. From there on, possibly I can hear directionality, but I can't claim it's not because some other interaction with my room... I have some room treatments, but they are far from perfect, since it's my living room. Anything above 90Hz is directional.

So in a nutshell, I am not sure how useful that study is out in the wild. I am not sure many of us have an anechoic room as our listening room. Certainly I can't verify the results at home. That said, I don't have $25k worth of Genelec subs in my room, either.

 

[LSPhil]

I agree with the first two paragraphs of your post, but while the quote above might be correct (or not, idk) for most mixed pop, rock, folk and jazz (stereo) recordings, it is not true for those classical recordings of orchestra that I checked. There the amount of channel differences in (sub) bass can be (and is) quite considerable. And I don't think that is because the engineers are not competent.

In enclosed spaces, bass behaves like pressure zones rather than directional waves.
Below the Schroeder frequency (typically ~100–300 Hz, depending on room size), sound behaves as standing waves (pressure maxima/minima), rather than freely propagating reflected waves.
This means that directionality doesn't make sense at these frequencies, where there is no clear wavefront to track.
Stereo bass causes phase issues.
But what about instruments like the cello? Isn’t that “stereo bass”?
It plays low notes, like C2 (65 Hz):
Yes, the fundamental frequency is 65 Hz, and that part is non-directional and perceived as mono.
However, the cello also produces a rich set of overtones/harmonics: 130 Hz, 195 Hz, 260 Hz, 325 Hz, and beyond.
Although the bass is mono, the timbre and character of the instrument are stereo, because our perception of spatial placement relies heavily on mid- and high-frequency harmonics.
That’s why a cello can sound “placed” in the stereo field, even though its low tones are non-directional and sum to mono.
The sound’s timbre (coming from directional harmonics) is stereo, and it's what gives the instrument its spatial identity.
You’re hearing stereo sound, but not bass which comes from everything above.

I hope that clears things up!

 

[OldHvyMec]

Very interesting thread. I have been using subs (30-60 <) and Bass columns (60 - 250 Hz) for over 20 years.

I use 2 columns that are DIY (SAT) that range from 42" (3 drivers) up to 84" tall with 6 drivers. I use 6.5, 8 and 10" drivers depending on the size of the room and the customer's request.

If the music is mixed with left and right tracks, there is a definite center phantom that bass columns will provide.

Not all recordings qualify, but there are a considerable number that do. I quit listening for it in my setup, but I can tell the difference when a recording is done that way.

One setup I use that is exceptional with VERY low distortion (clarity for the lack of a better term) is Rythmic plates, GR 8 or 12" servo drivers and OB flatpack by DIY or a couple of CnC artists that will build to spec. 1-6 modules tall) In addition to BASS columns.

I've posted one set before delivery to a customer on this form a couple of times.

The sub placement isn't that difficult using 2-4 dual cabinets and then simply place the columns like you would any set of stereo speakers. I always place the columns to the outside of the mains and forward/backward (depending on the room size, mainly length) to help mitigate arrival times vs adding delays with the processor I use. I use a DCX2496/NU12000 Behringer strictly for OXO/gain settings.

It requires a little tinkering to get the phantom placement correct, but it certainly pays dividends that very few systems offer in a stereo environment and considering it's pure analog.

With adequate room treatment and only HSP (human sound processing), it is something I'll never give up.

I've had a few argue the whole mono/summation concept until they sit and listen to a stereo sub/bass system vs a summed or LTE AVR/AVP system.
Add servo subs to the mix, and it's a very easy non non-fatiguing system I can listen to for hours on end. BTW, the columns are directly coupled, adding the effect, much like a servo-based system. Steep XO point is one of the main tricks to achieving the "Clarity" I was speaking of. 48db. The more gradual the slopes, the more distortion is added. 6-12 dB is the absolute worst to add distortion in the sub/bass regions from my experiments.

It's also amazing how much you miss above 300Hz with a bunch of bloated out-of-phase noise below 300Hz removed.

I don't know, maybe some like that type of sound, I'll pass.

Regards

 

[Sokel]

At Bass and Subwoofers thread there are several ways to check how to look for stereo bass.

It's also a treasure trove of studies and informed observations.

I'll quote a post by @Thomas Lund only without disregarding some of the best posts from @j_j and others and the hard work of OP:

Concerning inducement of AE, absolute LF time and phase isn’t important. It is inter-aural time that matters.

Whether or not loudspeakers should replicate reliably what microphones picked up, or what was built with level panning, I guess depends on application.

In monitoring, you want it to be so. Playback includes inter-aural evaluation; plus at least one requirement for absolute time: Group delay must be constant across cross-over points, at frequencies where listener movement is a factor. As active sensors, human adults reach out constantly to seek meaning. In sound, this involves head and body movement, e.g. to distinguish between direct sound and reflections of the listening room. Therefore, direct sound must never ever be contaminated the same way reflections naturally are; by modulated sound colour and/or time, as result of listener movement.

In recreational listening, it can be argued music should primarily rather sound nice and comforting.

 

[j_j]

Thanks. Do we know whether common (among techy audiophiles at least) consumer room measuring apps (REW, Audyssey, Dirac...) adhere to these criteria in the region below a few hundred Hz?

We've had some annoying discussions. I won't be more specific.

 

[bmc0]

Yes, the fundamental frequency is 65 Hz, and that part is non-directional and perceived as mono.

Sure—in anechoic conditions.

However, the cello also produces a rich set of overtones/harmonics: 130 Hz, 195 Hz, 260 Hz, 325 Hz, and beyond.

I'm fairly certain that everyone here is aware of this.

our perception of spatial placement relies heavily on mid- and high-frequency harmonics

This is certainly true and I'm not disputing that upper midbass through low treble frequencies are the most important for localization. But this range is not the only determinant of spatial quality.

That’s why a cello can sound “placed” in the stereo field, even though its low tones are non-directional and sum to mono.

The low frequencies are certainly not mono if you include the hall.

So in a nutshell, I am not sure how useful that study is out in the wild. I am not sure many of us have an anechoic room as our listening room. Certainly I can't verify the results at home.

Since we're judging the relevance from personal anecdotes: I can clearly hear a spatial difference vs summed mono down to approx. 40Hz in my room (which is not anechoic) with appropriate test signals.

 

[j_j]

As far as 'time delay' you've missed the point. It's room modes in the PLAYBACK room combined with room modes in the original recording that can create large phase shifts across the head. This also corresponds to zeros (but not full zeros, short radius ones) in the room response, both of the original as well as the playback room.

It's not so much "chaotic" although some of that does exist in real rooms with air movement, as it is "incredibly complex structure of the soundfield in a wide venue, or its synthesis".

 

[pablolie]

...
Since we're judging the relevance from personal anecdotes: I can clearly hear a spatial difference vs summed mono down to approx. 40Hz in my room (which is not anechoic) with appropriate test signals.

And yet the study doesn't support that observation, but it's great we have a way to verify for ourselves... which basically is the case in many things audiophile.
Another somewhat weak point in the study is the limited data collection... only 18 test subjects.

 

[j_j]

And yet the study doesn't support that observation, but it's great we have a way to verify for ourselves... which basically is the case in many things audiophile.
Another somewhat weak point in the study is the limited data collection... only 18 test subjects.

There are a number of studies, both published and unpublished, that support both the idea that directionality under circa 90Hz isn't a think, and that a sense of envelopment down to circa 35-40Hz *IS* a thing. Consider the spacing of nodes in a wide, complex room, and what that does to the steady state sensation in any given place.

 

[Robin L]

There are a number of studies, both published and unpublished, that support both the idea that directionality under circa 90Hz isn't a think, and that a sense of envelopment down to circa 35-40Hz *IS* a thing. Consider the spacing of nodes in a wide, complex room, and what that does to the steady state sensation in any given place.

I've been listening to J. S. Bach's works for organ today. That music is played on a pipe organ in a large church, often a cathedral. One of the primary features of this music are bass melodies in the lowest octave. Listening to this music in my small room with a capable subwoofer certainly gives the impression of the tactile quality of deep bass, but the sense of the original room size is absent.