Bass direction is audible

[Titurel]

A more practical question might be how one makes subwoofers difficult to localize. Regardless of the consensus opinion regarding bass directionality in the abstract, real world audibility is often a different question. For example, sympathetic excitation of objects near a subwoofer can give away its position, particularly at high levels. Similarly, port noise, cabinet harmonics, and imperfect physical grounding of the sub can also give clues to its position. While such effects may be transitory, once noticed, it may be difficult not to continue associating bass transients with the "revealed" source(s), in effect "hearing" directional effects not actually manifest.

 

[Justdafactsmaam]

I'm not sure if this would work. For L-only and R-only signal a proper DBA is formed, but as far as I can see for a mono signal we end up with N mono subs all playing the same low-level comb-filtered signal. The cancellation signal for the other channel almost kills the main chain signal as it is an inverted and slightly delayed copy.

I think we really need different and independent traveling wave directions for the DBAs to work and create a proper wavefront for mono signals, traveling from front to back and passing the head on the way. 90 degrees offset of propagation directions seem to be the natural choice then, at least as a starting point.

You are pretty much describing the Trinnov wave firming technology

 

[Keith_W]

I'm not sure if this would work. For L-only and R-only signal a proper DBA is formed, but as far as I can see for a mono signal we end up with N mono subs all playing the same low-level comb-filtered signal. The cancellation signal for the other channel almost kills the main chain signal as it is an inverted and slightly delayed copy.

Hmm. I see what you are saying, but I am not sure if I agree 100%. The left and right channel would simultaneously output the same sound and can be adjusted so that they are in-phase at the listening position. Likewise the cancellation signal. I do think you would lose the benefit of the DBA though - the DBA completely eliminates room modes everywhere in the room. I think that the setup I proposed would only eliminate room modes at the listening position and produce comb filtering everywhere else.

I am not smart enough to figure this one out by myself so I could be totally wrong here. Would appreciate comments.

 

[andyc56]

Griesinger talks about an envelopment effect with bass when it is set up a certain way. @Matthew J Poes tested this and didn't think the juice was worth the squeeze because of 1) how small the effect was, 2) how little content could take advantage of it, and 3) that setting up your system in such a way precludes summing bass sources for modal smoothing.

There's a video with Matthew where he discusses this. Todd Welti is also sitting in for the discussion. Here's where the discussion begins.

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At around 51:14 he talks about how Griesinger had him set up a stereo bass arrangement in his bathroom to try to hear it.

 

[Tom C]

Room modes do not categorically destroy the effect, according to Griesinger (page 41-45), but most modes are detrimental. He claims that "it is usually—but not always—possible to find loudspeaker positions that work adequately in a particular room."

So, just now, after reading this paper, I pulled the stereo subs on my two-channel bedroom system out of the corners, and placed them hard left and right (90 degrees) of the listening position. Well, there is quite a large improvement in bass clarity. couldn’t tell much difference between middle of the room right next to the mains vs. corner placement. But now, there is also less masking of the mid and upper bass played by the mains. Hard to make a solid conclusion after 15 mins of listening, but right now sure seems to be a significant improvement.

 

[ElJaimito]

I don't know where this assurance that bass frequencies are non-locatable comes from. IME it is entirely false. It can be argued to be partially true in a very small listening room due to the room response, but try standing outside with a distant thunderstorm going on. The very low rumble is clearly directional. I have to place my (sub 50Hz) sub very carefully so as not to disturb the stereo image. The best solution is multiple subs in my view, but my present room has no, err, room.

 

[dasdoing]

I don't know where this assurance that bass frequencies are non-locatable comes from

I think people are confusing omnidirectional transmission with omnidirectional arrival. somehow people seam to think they are the same

 

[Chromatischism]

I don't know where this assurance that bass frequencies are non-locatable comes from. IME it is entirely false. It can be argued to be partially true in a very small listening room due to the room response, but try standing outside with a distant thunderstorm going on. The very low rumble is clearly directional. I have to place my (sub 50Hz) sub very carefully so as not to disturb the stereo image. The best solution is multiple subs in my view, but my present room has no, err, room.

We are indeed talking about the context of listening to audio in a room.

But the thunderstorm example isn't the best. There is always higher frequency content that tips you off to the direction as well.

 

[Sokel]

Just for the shake of testing and for one sample (my room + gear) is entirely different to measure a continuous sine at 60Hz for example than a short rapidly intermittent one with some pause in between (like a drum kick duration for example,but heavily filtered above 60Hz or so )

The first one probably builds-in in the room making it difficult to locate after the first few ms,that's my explanation.

 

[Flaesh]

When using a bass array and an absorber at the back, the traveling wave moves from front to back.

 

[Flaesh]

something like this:

Or simply use [thick] absorbers on the side walls. Left and right SBAs.
The useful and pleasant traveling wave effect will completely disappear with monophonic bass.

 

[Flaesh]

What happens when using subs this way?:

Both will acts as DBA if bass is mono.

 

[Paffi]

Well that's not the concept of a plain wave and wouldn't work

 

[Flaesh]

like this

with the main listening position in the middle of the room

- it doesn't seem necessary(?)

 

[sigbergaudio]

So, just now, after reading this paper, I pulled the stereo subs on my two-channel bedroom system out of the corners, and placed them hard left and right (90 degrees) of the listening position. Well, there is quite a large improvement in bass clarity. couldn’t tell much difference between middle of the room right next to the mains vs. corner placement. But now, there is also less masking of the mid and upper bass played by the mains. Hard to make a solid conclusion after 15 mins of listening, but right now sure seems to be a significant improvement.

That might as well be due to different frequency response as a result of alternative placement of the subs.

 

[sigbergaudio]

This directional bass discussion feels a bit similar to the "can we hear above 20khz" discussion.

It's possible to find various papers implying that it is possible, but there's roughly zero evidence that it has practical, real world implications for domestic sound reproduction.

 

[Sokel]

This directional bass discussion feels a bit similar to the "can we hear above 20khz" discussion.

No comparison between the two,the above 20kHz discussion has (usually) age limitations,very little research,etc.
Directional bass on the other hand has a lot more research and has proven valid.

Lots and lots of this research right at the first post of this threads:

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

Refining a listener and loudspeaker model based on readings of Lokki, Bech, Toole, et al

Model I have been trying to educate myself a little more about concert hall acoustics recently, so I’ve been skimming papers and presentations from David Greisinger (http://www.davidgriesinger.com/) and Tapio Lokki (https://users.aalto.fi/~ktlokki/). I’ve also had a long-standing interest in...

www.audiosciencereview.com

 

[audiofooled]

A good way to objectively literally see that bass transients have tactile directional force, is the empty coke can on a table test.
Depending on displacement of the sub, the distance can be anywhere from 2-5m. An important factor is to have sufficient rear, and side wall clearance, so that virtual subs are not being formed.

A big bass drop or hard kick, can/will blow the can straight away from a single sub, on axis.

If the can is in between a stereo triangle, using the same transient stimulus at the same SPL at can, i've watched the can move unpredictably, wonkily, maybe back some, but most often as much sideways as back.

Adding a sub in the rear of the room, going MSO etc,.... makes the can want to vibrate in place....and erratically hover around some..

In addition to my post #98, IME it's not just about subs, although it highly depends on what job you give to them and some important qualities required. I'm sure you know what I'm talking about, i.e. some shortcomings of commercial subs that are of poor quality. And it's about the mains also.

As an analogy to an empty can test you describe, in attachment you may find a (very poor quality), but importantly a real time recording of some transients and what goes on about vector gravitational components of a device placed on a hard surface, about 3,5 meters away.

Sadly the device is unable to capture audio at low frequencies (100Hz is already severely rolled off) and there's some latency in processing and rendering the data. Just another inconvenience, devices mic is only couple of mm away from the surface it's sitting in, so it captures mostly the reflections off it, also distorts audio because of the force. Video is 60 fps. But still, this gives a better audio/visual clue than, for example, if I were to mix in the original audio track.

The track is this one:

As you may notice, it contains both quick bass drops and quite low frequencies, but it's not about stereo bass for this purpose. I didn't look into it, but I suspect it's mono bass most of the time.

From what I can observe, the energy is almost instantaneous because of high sound propagation velocity trough hard surfaces. But what sets things in motion is physics of high/low air pressure, acceleration, velocity and displacement, complex phase relations and acoustic impedance mismatch between air and solids. This is highly complex as the room is being the part of the system, so good luck in trying to model this...

So yes, bass energy can have a direction even in a room. In this case, device is placed upright, oriented left to right and turned towards the system laterally (arrow to the right means the device is being pushed away). Note that the low frequencies, even though not recorded, are also absorbed in a timely manner, not letting it flapping about. Regarding your observation, empty can I suppose on a capable system could be pushed away with enough force to be tilted out of balance, not being able to return to it's equilibrium state.

Important thing to consider is that the setup must be such that the energy is distributed in a controlled manner and absorbed rather quickly. Indeed the device shows complex gravity vectors acting like a shock absorber on a bumpy road. However, room modes (if they are supported) want to do exactly the opposite, i.e. behave like a ride with broken shock absorbers. Surely someone had experienced that.

IMHO, the key is in having net displacement (ports in room are kind of messing this up) as shown in a room gain analysis by @René - Acculution.com . Also, for audibility of stereo bass I think vertical plane must be considered and it's a better job for the mains, rather than the subs. Subs on the other hand have a job of not smearing it up. But to set things up in a remotely practical manner, one may have to start from scratch. Because of that, I would think one should first experience this and then decide if it's worth the trouble, or cost, for that matter.

EDIT: Note - Audio in attachment is quite compressed and loud!

 

[gnarly]

In addition to my post #98, IME it's not just about subs, although it highly depends on what job you give to them and some important qualities required. I'm sure you know what I'm talking about, i.e. some shortcomings of commercial subs that are of poor quality. And it's about the mains also.

As an analogy to an empty can test you describe, in attachment you may find a (very poor quality), but importantly a real time recording of some transients and what goes on about vector gravitational components of a device placed on a hard surface, about 3,5 meters away.

Good stuff !

I have to admit that I've given up trying to analyze the force of soundwaves that are stronger than just hearing.
I just observe room object movements and feel tactile body vibrations.
It's waaay too complicated I think, to be able to model in a real-world space that isn't some very simple geometric form.

It's crazy the way I've seen objects response to cranking tunes...
Like a roll of paper towels unwinding about 1/4 revolution at a time from Alex Clare's "Too Close", mounting around the corner on a wall 20+ft from speaker/sub stack.
Craziest I've ever seen, a huge drop in the middle of Lindsey Stirling's "Crystallize", reached out 35 feet away and opened a kitchen cabinet in the next room mounted up near ceiling, and plucked a single champagne glass down to the ground. Dozen others unmoved. Same song outdoors will make make a 50ft deck handrail and pickets writh like a snake when it hits. Yes, I did say cranking !

I see the same crazy stuff with wave phenoms, watching them on the lake we look out at. Big rolling waves hit walls one way, waves with breaking crests another.
Combinations, all vectored together, are like moguls on the ski slopes, only they are constantly moving as you trying to ride whatever thru them.

The science of waves, vibrations...too much for this old mellon to master. So I just play with, and enjoy them.

edit: PS, have meant to thank you for the track by Smilk you posted some time back. I really like it and it's a good demo song for my rig. Gives guests some real grins.

 

[Chr1]

Nice one fella. I love your thinking... And am jealous of your ability to be able to move sh** around your domicile with bass/SPL.
Splendid.

I love that I can play loud where I live but reckon I'd have the cops round sharpish if cupboard doors started opening/loo rolls unravelling etc tho, as I live in the city centre.
(Chuffed that I have the potential/gear to do so however.) One day.

Kudos!