Bass and subwoofers

[Chromatischism]

Please take note that for stereo bass, the optimal position for the subwoofer is LR - to the left and right of the listener.

Now take a look at Welti's 2002 paper. The link can be found in the first post of this thread. I have highlighted the relevant configuration from the conclusion:

View attachment 524423

Welti's paper assumed that both subwoofers were reproducing the same signal. But this essentially proves that @NTK is correct. If you set up your subs at the midpoint of the wall on either side of the listening position, a simple flick of a switch can load a different DSP profile and you can decide for yourself if you want stereo bass or mono bass.

And back to my post—in order to avoid bass interference that will happen when not aligning and equalizing the subs as one, you need a huge room. The subs need to be 20-30 feet apart. Otherwise, the huge swings in the response will degrade the experience. Almost no one has such a room, which, going back to my original post, is why "stereo bass" is mostly not possible for most people.

 

[flightops]

I’ll be installing a second sub, but not for a “stereo” sub effect.

The second sub will be to help try and excite a “null” in my room at 50-51Hz that a single sub can’t overcome completely.

 

[levimax]

And back to my post—in order to avoid bass interference that will happen when not aligning and equalizing the subs as one, you need a huge room. The subs need to be 20-30 feet apart. Otherwise, the huge swings in the response will degrade the experience. Almost no one has such a room, which, going back to my original post, is why "stereo bass" is mostly not possible for most people.

There is another way for stereo bass and subs. If the subs and mains are colocated (stacked to create a shared baffle effect) with 1/4 wavelength or less of the crossover frequency distance between the sub and the mains woofer and use a of a linear phase crossover (proper close colocation will allow pre-ringing cancelation) and with the sub having significantly more SPL capabilities than the mains. This will allow for a point source for the entire frequency range, a much larger sweet spot in the room, much better time domain performance especially group delay (felt as slam), ability to fill dips with DSP ( carefully), and stereo bass if desired.

 

[NTK]

The concept of stereo bass (and low frequency auditory envelopment) is based on decorrelated bass signals from (at least) the left and right channels. Since they are decorrelated, i.e. there is no set relationship between the left and right bass signals, we cannot predict how they interact or interfere with each other. That's why the normal bass management techniques (time/phase alignment, etc.) do not apply.

 

[levimax]

The concept of stereo bass (and low frequency auditory envelopment) is based on decorrelated bass signals from (at least) the left and right channels. Since they are decorrelated, i.e. there is no set relationship between the left and right bass signals, we cannot predict how they interact or interfere with each other. That's why the normal bass management techniques (time/phase alignment, etc.) do not apply.

What could be better than 2 ( or more for MC) point sources accurately transfering the original signal which presumably contains the original spatial information into the room accurately in both the frequency and time domain? Yes the room may mangle it but you have to start somewhere. Fixing the room if the original signal is not transfered accuratley will never work.

 

[NTK]

What could be better than 2 ( or more for MC) point sources accurately transfering the original signal which presumably contains the original spatial information into the room accurately in both the frequency and time domain? Yes the room may mangle it but you have to start somewhere. Fixing the room if the original signal is not transfered accuratley will never work.

For auditory envelopment, it is not about locating the direction of the sound source (even in the original concert hall). It is about the spatial sensation. Here is how Dr Griesinger described it. And (mono) bass management is also not about sound source location either, because its working principle is dependent on bass not being localizable.
http://davidgriesinger.com/asa05.pdf

 

[levimax]

For auditory envelopment, it is not about locating the direction of the sound source (even in the original concert hall). It is about the spatial sensation. Here is how Dr Griesinger described it. And (mono) bass management is also not about sound source location either, because its working principle is dependent on bass not being localizable.
http://davidgriesinger.com/asa05.pdf

View attachment 526118

For auditory envelopment, it is not about locating the direction of the sound source (even in the original concert hall). It is about the spatial sensation. Here is how Dr Griesinger described it. And (mono) bass management is also not about sound source location either, because its working principle is dependent on bass not being localizable.
http://davidgriesinger.com/asa05.pdf

View attachment 526118

What are are the minimum requirements of a system and room to be able to create the envelopment effect?

 

[NTK]

What are are the minimum requirements of a system and room to be able to create the envelopment effect?

Dr Griesinger has a paper on it titled "Loudspeaker and listener positions for optimal low-frequency spatial reproduction in listening rooms".
http://davidgriesinger.com/asa05.pdf

 

[Chromatischism]

There is another way for stereo bass and subs. If the subs and mains are colocated (stacked to create a shared baffle effect) with 1/4 wavelength or less of the crossover frequency distance between the sub and the mains woofer and use a of a linear phase crossover (proper close colocation will allow pre-ringing cancelation) and with the sub having significantly more SPL capabilities than the mains. This will allow for a point source for the entire frequency range, a much larger sweet spot in the room, much better time domain performance especially group delay (felt as slam), ability to fill dips with DSP ( carefully), and stereo bass if desired.

Yes, of course you can just use "full range mains". But that ignores all of the frequency response smoothing benefits of multiple subs and their placement along the walls.

It's been said ad nauseum: the best place for your speakers is almost never the best place for bass.

 

[levimax]

Dr Griesinger has a paper on it titled "Loudspeaker and listener positions for optimal low-frequency spatial reproduction in listening rooms".
http://davidgriesinger.com/asa05.pdf

So the big trick is working with speaker placement, room modes, and LP and some rooms won't work. The rest is standard stuff. Conclusion quoted below:

Conclusions; Although widely held to be unnecessary or impossible, reproduction of envelopment at low frequencies in small rooms can be achieved, particularly with a multi-channel sound system. Successful results depend on: 1. having an input recording that includes at least two channels where the reverberation is independently recorded, and thus uncorrelated with the other channels. 2. The presence of independently driven room modes that overlap in such a way that the lateral pressure gradient of one mode combines with the pressure of another. In the case of two channel stereo, the best results usually occur when an asymmetric lateral mode (driven by the difference signal between the loudspeakers)creates a pressure gradient at the listening position, and a medial mode (usually a front/back mode) supplies the pressure. Ideally both modal systems should be broad enough in frequency that there is a substantial frequency overlap, as well as a spatial overlap. Such spatial and frequency overlaps occur in rectangular rooms of various dimensions, but are rare in rooms that are close to square in dimension. Putting the front speakers along the long wall of a small room can be helpful, as can a somewhat asymmetric speaker layout. In many rooms it can be helpful to place low frequency drivers at the sides of the listening position rather than at the front of the room. Where high Q modes exist it is useful to damp the modes electronically by an inverse filter with precisely the same frequency and Q.

 

[levimax]

It's been said ad nauseum: the best place for your speakers is almost never the best place for bass.

I know that is the common wisdom but I am surprised it is not questioned more as there are big problems with separating the mains and the subs, everything is compromised for "smooth FR" and pretty graphs. While smooth FR is "the biggest" determinant of perceived sound quality that doesn't mean other things don't matter. Once FR smoothness is "smooth enough" then what? Ignore all the other issues?

1. No longer a point source.
2. Inability to use linear phase crossovers/ high group delay.
3. Much smaller "sweet spot", basically only one in the entire room.
4. Sum to mono / destruction of information.
5. Time domain issues (never able to get sound to arrive at same time for "Impact / Slam" effect.)

I would argue you can get smooth enough FR with point source like transducers.

 

[Fidji]

So the big trick is working with speaker placement, room modes, and LP and some rooms won't work. The rest is standard stuff. Conclusion quoted below:

Conclusions; Although widely held to be unnecessary or impossible, reproduction of envelopment at low frequencies in small rooms can be achieved, particularly with a multi-channel sound system. Successful results depend on: 1. having an input recording that includes at least two channels where the reverberation is independently recorded, and thus uncorrelated with the other channels. 2. The presence of independently driven room modes that overlap in such a way that the lateral pressure gradient of one mode combines with the pressure of another. In the case of two channel stereo, the best results usually occur when an asymmetric lateral mode (driven by the difference signal between the loudspeakers)creates a pressure gradient at the listening position, and a medial mode (usually a front/back mode) supplies the pressure. Ideally both modal systems should be broad enough in frequency that there is a substantial frequency overlap, as well as a spatial overlap. Such spatial and frequency overlaps occur in rectangular rooms of various dimensions, but are rare in rooms that are close to square in dimension. Putting the front speakers along the long wall of a small room can be helpful, as can a somewhat asymmetric speaker layout. In many rooms it can be helpful to place low frequency drivers at the sides of the listening position rather than at the front of the room. Where high Q modes exist it is useful to damp the modes electronically by an inverse filter with precisely the same frequency and Q.

Indeed, is very simple, known since decades for anybody willing to experiment and it has been done and discussed thousands of times since then. It gets resurrected in cycles, sometimes with catchy names like “bassiousness” or “affective touch”.

What are are the minimum requirements of a system and room to be able to create the envelopment effect?

Multichannel.
If we talk “envelopment” in sense of “what you experience in good concert hall”. This is how I understood D. Griesinger research.

EDIT: I really encourage everybody with opportunity to experiment - have 2 subs, can drive them in 2.2. config - place them best you can, do some critical listening and enjoy your newly found envolopment. Then visit real concert hall and be honest to yourself.

 

[kyuu]

For auditory envelopment, it is not about locating the direction of the sound source (even in the original concert hall). It is about the spatial sensation. Here is how Dr Griesinger described it. And (mono) bass management is also not about sound source location either, because its working principle is dependent on bass not being localizable.
http://davidgriesinger.com/asa05.pdf

View attachment 526118

If I'm not reading this passage wrong, this seems to be entirely about replicating a particular effect of a concert hall. One would never experience this in a small room, or in an outdoor venue. And of course, any recording that wasn't done in a concert hall-like environment would seem to lack this effect unless it was added in post-production. There's a lot of brouhaha about a lot of decorrelated bass being present in recordings that plainly aren't recordings from such an environment, so is including it deliberate? Some accident of the production process? Does it have a similar "swirling" effect? What's the deal?

 

[Sokel]

If I'm not reading this passage wrong, this seems to be entirely about replicating a particular effect of a concert hall. One would never experience this in a small room, or in an outdoor venue. And of course, any recording that wasn't done in a concert hall-like environment would seem to lack this effect unless it was added in post-production. There's a lot of brouhaha about a lot of decorrelated bass being present in recordings that plainly aren't recordings from such an environment, so is including it deliberate? Some accident of the production process? Does it have a similar "swirling" effect? What's the deal?

1958-1960 recording, 1996 put on this CD analyzed here, Reiner's Scheherazade, presumably from the original analog tapes recorded at the venue:

L-R Spectrum

L-R phase delta from DC to 400Hz

If there's a chance for "venue" sound, old recordings like this is a good index.

 

[MayI]

And back to my post—in order to avoid bass interference that will happen when not aligning and equalizing the subs as one, you need a huge room. The subs need to be 20-30 feet apart.

Evidence? Repeating the same error doesn't make it right.
https://audioroundtable.com/misc/icad2005F96.pdf

The cabinets housing this 3-way loudspeaker system, which were never moved between conditions, were placed on the floor, with the low-frequency
driver (15-in diameter) at a distance of 200 cm from the listening position.
These subwoofers, which were never moved between conditions, were placed on the cement floor, with the driver (15-in diameter) at a distance of 200 cm from the listening position.

That's less than 7' away.
Clearly not reading the evidence, nor understanding.

Otherwise, the huge swings in the response will degrade the experience.

Evidence?

Almost no one has such a room, which, going back to my original post, is why "stereo bass" is mostly not possible for most people.

The only thing preventing perception of non mono bass in domestic sized spaces is signals and most likely, room decays, based on the scientific evidence so far.

 

[NTK]

If I'm not reading this passage wrong, this seems to be entirely about replicating a particular effect of a concert hall. One would never experience this in a small room, or in an outdoor venue. And of course, any recording that wasn't done in a concert hall-like environment would seem to lack this effect unless it was added in post-production. There's a lot of brouhaha about a lot of decorrelated bass being present in recordings that plainly aren't recordings from such an environment, so is including it deliberate? Some accident of the production process? Does it have a similar "swirling" effect? What's the deal?

The deal, at least for classical music, is that the hall in which the music was performed and recorded is an integral part of the performance. That's why there are highly acclaimed concert halls and there are also ones not so highly acclaimed.

Audio reproduction in domestic listening rooms is one demanding task (if not impossible if you think about it for a moment). We are asking our equipment to not only reproduce the sounds of the musical instruments and voices of the performers, we are also asking it to suppress the acoustics of our little rooms, and replace it with a convincing facsimile of the acoustics of the original venue in which the music was recorded, which can be hugely different from one place to the next, and to do that with recordings that often lack the necessary information.

For music in which there is no "original performance" and is assembled inside a DAW, the session played in the studio at the final sign off would be the "original performance". Acknowledging the existence of the "audio reproduction circle of confusion", why wouldn't one want to be at least able to experience something close to what was heard in that session?

 

[tifune]

Is it possible that XTC enhances this effect?