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

[bachatero]

Here's how you can find what music has bass in stereo so you know if you need stereo subwoofers or not. I use Linux so I also use EasyEffects which makes this task shockingly easy.

1. Add a Stereo Tools widget and invert the phase in one channel, left or right
2. Add another Stereo Tools and combine both channels into one mono ("Mono Sum L+R")
3. Add an Equalizer and set it to Low-Pass, 2x slope, and frequency 120Hz or around that

Done! Now you'll only hear stereo bass content. If your music doesn't use stereo bass you'll hear nothing. These steps are so generic that you could apply the same idea to the Mac/Windows equivalent of EasyEffects.

If you get rid of the equalizer, you'll instead hear whatever isn't center panned, bass or not. If you use only the invert phase step, you can test speaker crosstalk.

I tested some of my favorite music and found that there are generally no stereo bass guitars, synths often have stereo bass, and classical recordings have stereo bass if the instruments are bassy (cello and upright bass). For bass guitars, it seems like what little you can hear of them if they're not obviously panned is the residuals of crosstalk in the analog recording equipment.

 

[bachatero]

Is NOBODY interested in stereo bass?

 

[Scytales]

Of course they are people interested in stereo bass !

As a classical music lover, I very much welcome stereo in bass.

One very well known method to obtain stereo in bass is to use the so-called distant AB recording technique : two omnidirectional microphones set widely apart. The great Emory Cook, who has pioneered this technique in the US, used to tell that the distance between the two microphones (and the two reproducing loudspeakers) should be at minimum of 1.83 m : https://www.preservationsound.com/wp-content/uploads/2012/11/Emory_Cook-AIEE-530616-Binaurality.pdf

There are sound engineers who consistently use that technique to record performances in any venue.

 

[Delli]

Stereo bass is an interesting thing.

Can you tell me the frequency range you’re listening to in ‘stereo bass’

 

[DVDdoug]

Is NOBODY interested in stereo bass?

Too rare for me to worry about. There are some good reasons for mono (centered) bass. The main thing is that the "average stereo" NEEDS both woofers for the most & lowest bass possible.

Here's how you can find what music has bass in stereo so you know if you need stereo subwoofers or not.

If you've got a "high end" home theater with full-range speakers, the subwoofer is ONLY used for the "point one" LFE channel with the regular left & right bass going to the regular stereo speakers.

...My setup doesn't qualify for that. And although I have a pair of subs my AVR only has one sub output.

 

[Sokel]

Stereo bass is an interesting thing.

Can you tell me the frequency range you’re listening to in ‘stereo bass’

Have a look at this thread:

Bass and subwoofers

This is the second in a series of follow-up posts to https://www.audiosciencereview.com/...-of-lokki-bech-toole-et-al.27540/#post-950580, this time focussing on bass perception with a brief digression on subwoofers, since there's relevance to (reproduction of) concert hall acoustics. I’ve...

www.audiosciencereview.com

 

[Old_School_Brad]

Is NOBODY interested in stereo bass?

Since this excellent post of yours is geared toward users with subwoofers, maybe consider updating the thread title to better catch the attention of those who’d benefit from looking into it?

 

[SorenTyson]

Is NOBODY interested in stereo bass?

I for one is not. However I appreciate your post since I am only starting to learn about easy effects. Amazing how simple (and free) to work with sound, as the example you just gave

 

[Hayabusa]

Is NOBODY interested in stereo bass?

what good examples did you find? I tried a few songs that I thought had stereo bass, but they all are mono below 70-80Hz

 

[goat76]

There isn't much or anything to lose by having the subwoofers connected in a stereo configuration. You get the bass content in stereo whenever the audio content has stereo information. Whenever the bass is summed to mono in the recordings, your subwoofers will act the same way as if they were connected in a mono configuration anyway. With the subwoofers connected in stereo, it's always a win-win situation, no matter what bass information the audio content contains.

 

[Palmspar]

Under 100hz the bass is omnidirectional in a room, therefore stereo bass under 80hz will be useless.
More subs are great for good base anywhere in the room, use 3 diy subs but they have mono input.
Room correction is used only under 280hz, with house curve 5db boost under 100hz

 

[goat76]

Under 100hz the bass is omnidirectional in a room, therefore stereo bass under 80hz will be useless.
More subs are great for good base anywhere in the room, use 3 diy subs but they have mono input.
Room correction is used only under 280hz, with house curve 5db boost under 100hz

There are more aspects to stereo bass than just directional cues. I think all three of the following gentlemen, David Griesinger, @j_j, and @Thomas Lund, have a thing or two to say on the matter. Or you could just read this thread: https://audiosciencereview.com/foru...ereo-bass-using-subwoofers.11034/post-2241700

 

[j_j]

Under 100hz the bass is omnidirectional in a room, therefore stereo bass under 80hz will be useless.
More subs are great for good base anywhere in the room, use 3 diy subs but they have mono input.
Room correction is used only under 280hz, with house curve 5db boost under 100hz

Try this: Make a 50Hz tone with your favorite gadget. Phase shift it by 90 and 180 degrees in the opposite headphone. (No acoustic mixing needed.) Same level, of course, exactly.

Tell me these sound the same. Just go do it.

Room correction makes little sense above a kHz or two, but for the purpose of imaging stabilization, doing broadband correction of both channels (talking stereo for starter) for timbre (1/2 octave or so above 500Hz, along with standard room correction) based on ***THE DIRECT SOUND FROM THE LOUDSPEAKERS ONLY*** is a very good idea.

Long-term measurements that include the room acoustics are wrong above a a few hundred Hz. Of course, really bad room acoustics are just not very correctable, in particular specular reflections are the pits.

 

[Palmspar]

@j_j 50hz in headphones is not the same as in a room, in a room the soundwave bounces against walls and vloor an therefore the base comes from all directions.

 

[NTK]

There isn't much or anything to lose by having the subwoofers connected in a stereo configuration. You get the bass content in stereo whenever the audio content has stereo information. Whenever the bass is summed to mono in the recordings, your subwoofers will act the same way as if they were connected in a mono configuration anyway. With the subwoofers connected in stereo, it's always a win-win situation, no matter what bass information the audio content contains.

What you lose is schemes like sound field management (SFM), multi-sub optimizer (MSO), or double bass array (DBA) will not work. They all depend on the subs all playing "correlated" signals.

It is a trade off between prioritizing flat magnitude response (often for multiple listening positions) vs low frequency spatial effects.

 

[j_j]

@j_j 50hz in headphones is not the same as in a room, in a room the soundwave bounces against walls and vloor an therefore the base comes from all directions.

Gosh, I do know that. Now try the experiment. It is enough by itself to make the point. How you get that in a room from a single source (say a pipe organ, or a bass viol, etc, I will leave up to you, after saying that yes, it's been observed to exist, and can be heard.

Yes, that's a test of "can you figure it out." The answer is obvious when you think about large spaces.

 

[j_j]

It is a trade off between prioritizing flat magnitude response (often for multiple listening positions) vs low frequency spatial effects.

There really is no conflict there at all, it's just a lot more linear algebra, and when you say "flat magnitude response" what you really mean is flat PRESSURE response. Remember that there are 4 variables in a sound field at any given point, please.

 

[olieb]

Try this: Make a 50Hz tone with your favorite gadget. Phase shift it by 90 and 180 degrees in the opposite headphone. (No acoustic mixing needed.) Same level, of course, exactly.

Tell me these sound the same. Just go do it.

Amazing.
Not that the sound is different, I expected that. And 180° phase difference between ears at 50Hz seemed to be not what happens a lot. But 90° sounds different too.
And then I tried to reduce that and even a delay of 1ms(!) between the ears/channels, that is 34cm of traveling sound, gives a small but distinct difference in direction(!) of perceived source. I did not expect that.
I used sine and with BU8 filtered (correlated) noise. Same result in both cases.
Makes me think about "common wisdom".

What you lose is schemes like sound field management (SFM), multi-sub optimizer (MSO), or double bass array (DBA) will not work. They all depend on the subs all playing "correlated" signals.

Wouldn't these work just fine with the correlated part of the signal? That would guarantee the function when bass is mixed to mono. And when not, the question is how to adjust the uncorrelated part to the subs in such a way that the sound will work out. One can always reduce with a mid/side plugin if it is too much.

 

[NTK]

There really is no conflict there at all, it's just a lot more linear algebra, and when you say "flat magnitude response" what you really mean is flat PRESSURE response. Remember that there are 4 variables in a sound field at any given point, please.

I am aware of acoustic particle velocity, which is usually measured using sound intensity probes. This is a hobby for me. I didn't study acoustics in school nor did anything related to audio to earn my living, so I am fully aware my understanding in this area is full of holes. I do think I've read more on acoustics than the average person, and I rarely encounter any mentioning of sound intensity measurements in audio reproduction. In noise control where people look for noise sources, yes; home audio reproduction or even in room acoustics, not too often.

As a matter of practicality, do we have the information from the recordings to figure out what the acoustic particle velocities should be (or, by extension, the 3-D pressure field around the listener, since velocity and pressure are related by Euler's equation)? Without a reference, how do we know what to reproduce, let alone how?

The 50 Hz signal test is IMHO a bit synthetic. The distance (path length) between the ears is about 0.23 m, and with natural sound coming directly from one side it gives a phase shift of about 12°. I didn't run a blind test, but the difference between 0° and 12° phase shift isn't much. I tried tone bursts with ITD of 670 μs, again no blind tests, and my ability to tell a left/right directional difference seems to stop at about 60 Hz and below.

Wouldn't these work just fine with the correlated part of the signal? That would guarantee the function when bass is mixed to mono. And when not, the question is how to adjust the uncorrelated part to the subs in such a way that the sound will work out. One can always reduce with a mid/side plugin if it is too much.

Below were Dr Toole's settings of his previous setup in California. The level settings of the SFM optimized subs alone were 0 dB left front, -6 dB right front, -12 dB left rear, -12 dB right rear. Each sub also has its delay and one PEQ attenuation filter. I doubt SFM optimized sub settings will work very well in general for stereo bass. (Diagram source)

 

[j_j]

As a matter of practicality, do we have the information from the recordings to figure out what the acoustic particle velocities should be (or, by extension, the 3-D pressure field around the listener, since velocity and pressure are related by Euler's equation)? Without a reference, how do we know what to reproduce, let alone how?

No, we don't, in general, this is one of the points I make repeatedly in talks involving the production and reproduction of envelopement.

The 50 Hz signal test is IMHO a bit synthetic. T

Yet, it proves beyond any doubt that the effects are audible.

Your assumption of a waveform in a free field is pretty much opposite the reality of either a good concert venue, or outdoors, but for different reasons, unless you're completely inside the near field even at low frequencies, however, which is a point you're missing. Consider the effects of pressure zeros, air movement, and the like.