Bass direction is audible

[dualazmak]

Do you have the measured (not calculated) responses NF or at the LP?

Here is the actual room air sound SPL response measured at my listening position; you would please visit my post here for the details of present/latest system setup including the Fq-SPL response of air sound at LP and "measured" at upstream digital domain, analog line-levels as well as SP high-levels;

Spoiler: Where in the signal chain/path I should measure/check Fq responses?

- Frequency response measurements by "cumulative white noise averaging": #392, #404, especially the end portion of #297(remote thread) by Dr. Floyd Toole, #315(remote thread) by Dr. Floyd Toole, #125(remote thread)

- Where in my multichannel multi-driver (multi-way) multi-amplifier stereo system should I measure/check frequency (Fq) Responses? #393

- Frequency (Fq) responses in the completed system measured by using “cumulative white noise averaging method” under the present standard crossover configurations and relative gains_Part-1_Fq Responses in EKIO’s digital output level: #394

- Frequency (Fq) responses in the completed system measured by using “cumulative white noise averaging method” under the present standard crossover configurations and relative gains_Part-2_Fq Responses in DAC8PRO’s analog output level: #396

- Frequency (Fq) responses in the completed system measured by using “cumulative white noise averaging method” under the present standard crossover configurations and relative gains_Part-3_Fq Responses in amplifiers’ SP output level before protection capacitors: #401

- Frequency (Fq) responses in the completed system measured by using “cumulative white noise averaging method” under the present standard crossover configurations and relative gains_Part-4_Fq Responses in amplifiers’ SP output level after protection capacitors: #402

- Frequency (Fq) responses in the completed system measured by using “cumulative white noise averaging method” under the present standard crossover configurations and relative gains_Part-5_Fq Responses in actual SP room sound at listening position using one measurement microphone: #403

- Frequency (Fq) responses in the completed system measured by using “cumulative white noise averaging method” under the present standard crossover configurations and relative gains_Part-6_Summary, discussions, and a little step forward: #404, #405-#409

As for present Fq response (calibration curve) of my "specially selected in 2008" BEHRINGER ECM8000 measurement microphone, please refer to my post here.
- Frequency response of my BEHRINGER ECM8000 measurement microphone (specially selected unit in 2008): #831

Spoiler: Pros of cumulative recorded white noise FFT averaging for Fq-SPL measurement

In my post #404 on my project thread, I wrote;
Throughout these careful measurements, I confirmed and validated that primitive "cumulative (recorded) white noise averaging method" is really powerful and reliable in terms of;
1. the method is universally applicable in the stages of digital out of crossover software (EKIO), DAC's analog out, amplifier SP out, and of course in the actual room SP sound,
2. the method is accurate, sensitive and reproducible, having little or no statistical fluctuation, because of the FFT averaging analysis on the "accumulated rich data" of the recorded sound,
3. the recorded "white noise tracks" can be re-analyzed any way, anytime, afterwards,
4. flexible mix-paste (sound mixing) can be done to virtually simulate any combination of the channels, especially in amplifiers' SP out signals before going into SP drivers,
5. if needed, the environmental "continuous room back ground noise" can be reduced/removed by the Adobe Audition's "noise capture - noise reduction" function,
6. if needed, suitable gain/level adjustment can be applied for "level matched comparison" of Fq response shapes between the different series of the recorded data,
7. flexible and suitable FFT size (as smoothing intensity) can be selected depending on the frequency zone of interest.

Spoiler: Dr. Floyd Toole's comment on "cumulative white noise averaging" for Fq-SPL measurement

Dr. Toole kindly wrote here in response to my inquiry;
> If properly done both swept tone and noise analysis should give identical answers. It is a choice. The principal difference is in the heating of the drivers in sustained tests at high sound levels - power compression. Low frequencies require longer averaging times.

Are you using 96kHz sampling rate to apply these 25kHz brickwall filters?

Yes, you would please carefully read my post here.
- Summary of rationales for "on-the-fly (real-time)" conversion of all music tracks (including 1 bit DSD tracks) into 88.2 kHz or 96 kHz PCM format for DSP (XO/EQ) processing: #532
- Again, summary of my rationales and pros of analog-level relative gain (tonality) controls in addition to gain controls in DSP configuration: #911, #317(remote thread), #313(remote thread)

Recently (nowadays) I almost always convert (on-the-fly) sampling rate of all the tracks of my digital music library (ref. here) into 88.2 kHz 24 bit PCM by JRiver MC's DSP Studio settings (see the below attached screen capture); 88.2 kHz (i.e. up to Fq of 44.1 kHz in L & R channel) is much more than enough since I have -48 dB/Oct low-pass (high-cut) Linkwitz-Riley filters at 25 kHz, as you pointed.

Just for your convenience and reference, please find here and here (exactly the same contents) the Hyperlink Index for my PC-DSP-based multichannel multi-SP-driver multi-amplifier fully active stereo audio project.

 

[gnarly]

To me, subwoofers are absolutely directional and betray their position regardless of their level and Fc. In my experience, most subwoofers also have considerable residual noise.

Personally, i would call a sub with any residual noise a bad sub, and one not really worthy to use for assessments.
A good sub should be rock quiet, other than it's low/sub bass acoustic output of course.

Subwoofer/s in a room, are only acceptable if the subwoofers are placed under the mains or extremely close to the mains. Mostly, my subwoofers sit gathering dust. They have all been a waste of money in reality as my preference is listening to my many loudspeakers full range, regardless of their capabilities.

I too will only use subs underneath the mains. But my mains crossover directly to the subs at 100Hz, and do not play lower. All low/sub bass comes just from the sub.
So Colocation is critical to achieve 1/4 wave-length summation throughout the critical xover region, to prevent comb filtering.
Different location issue than when mains reach all the way down.


Must say, your experience that your subs have been a waste of money makes it sound like they have all been bad noisy subs..???? Which on it's own doesn't make a lot of sense ??

I seldom hear a main speaker with enough bottom-end displacement, that it can play at its rated SPL without the low/sub bass becoming anemic or distorted sounding.
For me, a sub is necessary to get the needed displacement to produce sub frequencies without compression or distortion.
Reflects the simple physics of posttonic displacement needing to increase 4X, per octave decrease, for equal SPL.
...which leads me to quote you again below, with something that also seems amiss to me...

Exactly. My current mains have twin woofers which cover just one octave and are completely crossed over by 115Hz. Their THD was measured (reviewed) at 0.9% at 110Hz and 1.5% at 42Hz. 9% THD at 30Hz. They have way less inherent distortion than many expensive powered subwoofers, so I have little to gain, and plenty to lose.

At what SPL were the mains measured? And what size woofers, sealed or ported, if i may ask?

The thing is, clean undistorted, uncompressed sub bass all comes back to displacement.
If mains have less displacement than a sub, they will have higher distortion at the same SPL and frequency. (assuming a good sub again )
The lower the frequency, the greater the disparity of course.
So really, there is everything to lose letting mains try to carry the bottom end load on their own, ime/imo.

An example....the ported double 18"s I have under each of my mains.
Taken just now @1m indoors, with mic about 1m off floor. (So not as clean as outdoor ground-plane, which is best way i know to measure.)
105dB is accurate.
Cursor is on 30Hz, showing 0.11% THD. Probably most of the THD is noise floor of 0.089%.
More relevant I think, is second harmonic of 0.090%, and third of 0.046%.
I doubt I could find any main speaker capable of the distortion levels shown for 105dB.

I think the only way a sub doesn't help towards cleaner sound, is if one always listens at low enough SPL to stay in the uncompressed & undistorted SPL range...
or if the sub is noisy, not implemented so well, etc, etc

Just my take...not trying to be confrontational/controversial etc...

 

[krabapple]

Start at “considering” and go from there. Without further real investigation of thresholds of audibility of bass directionality and levels of room reverb anything you “consider” ultimately is speculative. Any conclusions drawn from such speculation is a leap

By that standard any conclusion drawn from the paper, other than the authors' own is a leap.

Here are their conclusions:

Conclusion
This study has demonstrated that room modal resonances have a strong effect on the localisation of very low-frequency sound sources and are the cause for the little directional information exhibited in this frequency range. The psychoacoustic experiment conducted in an anechoic environment using pure sinusoids of 31.5, 50 and 80 Hz show that the direction perception is negatively impacted by the minimum pressure node of the standing wave, whereas the maximum pressure node has a more nominal effect. In the presence of a minimum pressure node, the localisation ability is dependent on the level difference between the standing wave and the direct sound, where relatively large level differences still have a strong effect depending on the frequency. The results of this research suggest that the localisation of lowfrequency sound sources is not so strongly a question of our auditory system’s ability, but more so of the acoustical properties of the listening environment.

One can reasonbly infer from this that if one has a listening environment with few or no modal minima that impact the sound, then LF directionality might be perceived.

To support a claim that one IS perceiving it, one would have to demonstrate the absence of interfering modal minima in their setup, and rule out the usual suspects of audible distortion from the subwoofer itself, or inadequate low pass filtering

Good luck with all that.

 

[levimax]

I have DIY 3 way active speakers plus 2 subs on the sides of the listening area crossed at 80 Hz LR4. Here are my observations:

1. If I play noise only through the subs I can tell the noise is coming from the sides but very subtle. With full range music playing there is no way I can tell where the subs are.

2. Since my system is 4 way active and DIY one of the easiest things to mess up is the phase of the 8 channels. The most reliable way for me to test phase is listening to test recording that go in and out of phase one set of drivers at a time i.e. only tweeters, then only mids, then only woofers, then only subs. Surprisingly to me it was just as easy to hear "in phase" and "out of phase" difference on the subs as it was on the other drivers! With all the talk about "sum to mono" for subs as the way to go I am surprised no one mentions the "lost imaging" from doing this.

My conclusions is that LF "localizing" is different from LF "imaging" which doesn't make sense to me but it is very obvious when listening. From this testing I don't sum my subs to mono and I keep them on the sides of the room where they help smooth out some room modes. This does seems consistent with the study results and like everything else with LF the room has so much of an effect that hard and fast rules are probably not appropriate.

 

[gnarly]

To support a claim that one IS perceiving it, one would have to demonstrate the absence of interfering modal minima in their setup, and rule out the usual suspects of audible distortion from the subwoofer itself, or inadequate low pass filtering

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..

 

[Chromatischism]

Tend to agree. I have my sub crossed too high (almost 200hz) and it's not like it throws the stereo image off entirely, but it's noticeable on some tracks. And, I might be imagining it, but I feel like there's a slight sensation of pressure coming from the direction of the sub but not the other side, even for really low notes. I'm thinking I might add another sub to the other corner to even it out and just go for stereo bass because at that point, why not.

Your sub's crossover isn't a brick wall, I'm sure you know. So if you run it up to 200 Hz, it is putting out content up to 400 Hz at only -24dB down. Even a crossover above 100 Hz runs into clarity issues for this reason.

But what I'm seeing in this thread is that we're basically rehashing another thread on directional bass and stereo subs

 

[Chromatischism]

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..

This could be easily repeated and put on YouTube, right?

While I've never experienced this (aside from port wind), I have a front/rear sub arrangement as that has always gotten me the best bass quality.

 

[Chromatischism]

My conclusions is that LF "localizing" is different from LF "imaging" which doesn't make sense to me but it is very obvious when listening. From this testing I don't sum my subs to mono and I keep them on the sides of the room where they help smooth out some room modes.

Smoothing out room modes only works with mono signals (both subs acting together).

This does seems consistent with the study results and like everything else with LF the room has so much of an effect that hard and fast rules are probably not appropriate.

Tough to make hard and fast rules, yes, but some have narrowed it down. You may enjoy this summary from a few years back: https://www.avsforum.com/threads/localizability-of-bass-frequencies-in-rooms.3205312/

 

[dlaloum]

Smoothing out room modes only works with mono signals (both subs acting together).


Tough to make hard and fast rules, yes, but some have narrowed it down. You may enjoy this summary from a few years back: https://www.avsforum.com/threads/localizability-of-bass-frequencies-in-rooms.3205312/

HT focus has driven sub performance towards an LFE focus - the LFE channel is not supposed to be directional... it is for flash-bang effects...

Directional bass, is recorded into the main base channels - and depending on the bass management of the setup, may be lost, or mixed into the non directional LFE channel.

Subsequent LFE oriented tuning (including multiple subs) then further obfuscates any directional bass cues.

I am ever more convince that the optimal approach, is to use full range speakers if at all possible, or if not, to position subs at the speaker positions (or as close as possible) and configure them as part the base chanel, and NOT as part of the LFE.... and then set the LFE to mix into the base chanels rather than crossing the base channels over into the LFE.

Does this complicate things... absolutely - we are no longer trying to resolve nulls and nodes for a single channel - now we have to try to resolve them for 4, 5, or 7 channels... This is where one hopes that Dirac ART will come to the rescue! (eventually?)

 

[Chromatischism]

HT focus has driven sub performance towards an LFE focus - the LFE channel is not supposed to be directional... it is for flash-bang effects...

Directional bass, is recorded into the main base channels - and depending on the bass management of the setup, may be lost, or mixed into the non directional LFE channel.

Subsequent LFE oriented tuning (including multiple subs) then further obfuscates any directional bass cues.

I am ever more convince that the optimal approach, is to use full range speakers if at all possible, or if not, to position subs at the speaker positions (or as close as possible) and configure them as part the base chanel, and NOT as part of the LFE.... and then set the LFE to mix into the base chanels rather than crossing the base channels over into the LFE.

The point here is that once we are in a room, we lose the ability to distinguish direction of bass frequencies, so the best approach is to combine bass sources to improve quality by flattening the response. Doing so results in better sound quality than the alternative.

 

[Justdafactsmaam]

HT focus has driven sub performance towards an LFE focus - the LFE channel is not supposed to be directional... it is for flash-bang effects...

Directional bass, is recorded into the main base channels - and depending on the bass management of the setup, may be lost, or mixed into the non directional LFE channel.

Subsequent LFE oriented tuning (including multiple subs) then further obfuscates any directional bass cues.

I am ever more convince that the optimal approach, is to use full range speakers if at all possible, or if not, to position subs at the speaker positions (or as close as possible) and configure them as part the base chanel, and NOT as part of the LFE.... and then set the LFE to mix into the base chanels rather than crossing the base channels over into the LFE.

Does this complicate things... absolutely - we are no longer trying to resolve nulls and nodes for a single channel - now we have to try to resolve them for 4, 5, or 7 channels... This is where one hopes that Dirac ART will come to the rescue! (eventually?)

Good old two channel stereo solves that problem

 

[Rja4000]

why would the results w/o room reflections be relevant to our listening environments w/ room reflections?

It may be important for open air PA.

 

[Chromatischism]

It may be important for open air PA.

Bass sources are often arranged to direct bass in controlled directions. They may want to reduce bass leakage to the sides of the venue, for example.

 

[Sokel]

The point here is that once we are in a room, we lose the ability to distinguish direction of bass frequencies,

Not according to this (already posted it in the first page) :

Bass and subwoofers

tested, and of those, only 5-6 turned out to be any good. David told me the problem was the microphone technique they used. If I were to provide a subjective impression of the sound of those recordings, the ones that turned out to be "good" were the ones that had the lowest direct to reflected...

www.audiosciencereview.com

An explosion, thunder or other natural sources can provide outdoor opportunities to notice direction of even infrasound; or a subwoofer in an open field may be used in controlled experiments. Either way, the azimuth of a VLF sound source is easy to tell, also for a child, and that superpower is not lost when we step into a room.

The new research about it is about to be published if I understood correctly.

 

[gnarly]

This could be easily repeated and put on YouTube, right?

While I've never experienced this (aside from port wind), I have a front/rear sub arrangement as that has always gotten me the best bass quality.

The 'can being blown' test is the only thing I've ever considered trying to youtube.
I'm an old geezer who hasn't made a single phone video yet, much less put anything on YT. Maybe someday...Lol

My guess is that the directional hit is a combination of both the port and the direct radiator for bass reflex. I want to try the test with front loaded horn subs, which are basically sealed subs, but the ones I have are large enough it will require outdoors.

Switching gears....in another post you pointed out how a sub crossed at 200Hz, would be down only -24dB at 400Hz.....which is probably true for a great majority of setups using a stand LR24 crossover.
A really cool thing ime, is using steep linear phase xovers to assess subs sonically. It let's us separate the remaining post crossover higher frequency content from the sub's fundamental range. Which also helps with comparisons of audible THD as SPL is increased.

With the example you gave for instance, my routine 96 dB/oct xover is down the -96dB at 400Hz. (Not that I'd ever cross a sub that high...)
At say 80Hz, down -30dB occurs at only 100Hz... Steep low pass makes sub audibility experiments more meaningful ime.

 

[levimax]

Smoothing out room modes only works with mono signals (both subs acting together).

I have near full range mains and 2 subs on the sides of the listening position. The way the mains woofers and the subs excite room modes at the LP is quite different and by using both with DSP I can get a smoother bass response. So while mono may help in some cases I think "mono is the only way to smooth room modes" is overstating things.

 

[Chromatischism]

Not according to this (already posted it in the first page) :

Bass and subwoofers

tested, and of those, only 5-6 turned out to be any good. David told me the problem was the microphone technique they used. If I were to provide a subjective impression of the sound of those recordings, the ones that turned out to be "good" were the ones that had the lowest direct to reflected...

www.audiosciencereview.com

The new research about it is about to be published if I understood correctly.

That statement is being overextended. It doesn't mean the research of Toole and others is not valid. Quite the contrary.

 

[audiofooled]

It has been my experience that in room, low frequencies can have a perceived dimension of width and that the transients that normally reach the low frequencies can have a perceived dimension of depth. It's a combination of what the system does, and what the room does.

In room, we need to keep in mind that we have a physical dimension of height which can have an effect that subs (usually positioned close to the floor) and mains (which may have multiple woofers aligned vertically), interact with the room in a different manner. I suspect that floor bounce may be one of the key factors, being such a large plane. Also, front wall would have a profound effect depending on the physical placement of mains and subs (long wall, short wall, proximity of sound sources to it), and back wall can have a profound effect with regards to MLP and the amount of reflection/absorption.

And then there's signal. It has been my understanding that, at least in electronic music where everything is fabricated, there's a general consensus that you make a kick (quick bass drop, mono) and then you blend it with sustained bass lines so that they are in phase in the transition area. Now, the bass lines which are low in frequency tend to be mono as well to avoid translation problems, but not always the case. There are numerous tools which can be utilized to make the bass lines stereo, increasing perceived width or envelopment or "weight" if you will. This I think is the key factor which makes good bass.

As for a sense of direction, I think it is quite rare in music that something is panned in the low frequencies, but there are all kinds of effects for perceived width.

Transients are a different story. In room they can have a sense of depth, combined with tactile response. If you think about it, outdoors you have ground plane. In room you also have it. The energy has to go somewhere and through solids sound propagates many times faster. In room it is up to your setup how it propagates, where it gets cancelled (or not) and at what frequency.

So, there are pros and cons to everything and ultimately it goes down to use case and preference. But IMO it's well worth experimenting and then decide what to go for.

EDIT:

Something to ponder when it comes to perception of transients and potential spaciousness of sustained bass notes are the techniques which are quite commonly used when the two are sharing the same bandwidth. For example:

This way transients are further emphasized at the very moment they kick in and it goes without you even knowing. Perhaps this can provide a sense of direction if your setup is such that it does not cancel it. I mean, with regards to observations from people who tried front vs rear subs.

 

[Sokel]

That statement is being overextended. It doesn't mean the research of Toole and others is not valid. Quite the contrary.

No one is invalidating Dr Toole's research.
Is just that in a (small?) percentage of music bass is not mono,lots of examples about it at the other thread.

And I don't see any overextension,statement is pretty clear.Let's wait for the new research and see.

 

[Chromatischism]

No one is invalidating Dr Toole's research.
Is just that in a (small?) percentage of music bass is not mono,lots of examples about it at the other thread.

And I don't see any overextension,statement is pretty clear.Let's wait for the new research and see.

Well I need to add more detail to this. I was referring to the part about us having super powers to hear direction of bass in rooms. According to the research I've read from Toole and Geddes, rooms make that impossible below around 80 Hz. So it's possible for the upper bass area, but our resolution or ability to pinpoint the direction doesn't get good until closer to 200 Hz.