Does 'envelopment' exist? Can it be measured?

[NTK]

Is that really true, that using manual crossover filter creation for bass management **cannot** get as flat as automated tools?

Both Harman's SFM and MSO use highly computationally intensive numerical global optimizations to arrive at the subwoofer parameters (gain, frequency, Q of PEQ and delay for each sub). I can't say if they are alway superior to manual tuning, but it is pretty much impossible to do the same type of optimization manually.

I don't think DSP profiles need switching, just attenuate / switch speakers on/off, or go to mono on trueSubs as above

Methods based on mono bass (SFM, MSO, ART, DBA, Trinnov Waveforming, etc.) all rely on subs, and sometimes main speakers if they are full-range, working together to tame the room modes. This doesn't work for stereo bass as we can no longer treat the signals to the subs as "correlated", and therefore they can't "work together". So, the EQ parameters for stereo bass will highly likely be different from those that will get the best out of mono bass (i.e. even bass response across a large listening area).

 

[Oddball]

Both Harman's SFM and MSO use highly computationally intensive numerical global optimizations to arrive at the subwoofer parameters (gain, frequency, Q of PEQ and delay for each sub). I can't say if they are alway superior to manual tuning, but it is pretty much impossible to do the same type of optimization manually.


Methods based on mono bass (SFM, MSO, ART, DBA, Trinnov Waveforming, etc.) all rely on subs, and sometimes main speakers if they are full-range, working together to tame the room modes. This doesn't work for stereo bass as we can no longer treat the signals to the subs as "correlated", and therefore they can't "work together". So, the EQ parameters for stereo bass will highly likely be different from those that will get the best out of mono bass (i.e. even bass response across a large listening area).

Not sure what is so special about stereo bass? You drop a sub next to the tower and hope that it will work well? And than when it does not even when EQd, you claim that you are enjoying stereo bass with all the uneven FQ response and excess decay? What exactly is there to enjoy in the "working together" and "correlation"?

Might come as a surprise, but HT people are not actually that dumb. They deal with more channels and problems than stereo. And by overwhelming majority (based solely on my experience on forums though - so worth a quarter of cent or less) all Storm and D&M efforts for directional bass have ended up in failure by popular judgement. Directional bass would be what you refer to as stereo bass.

 

[dagfinn]

Not sure what is so special about stereo bass? You drop a sub next to the tower and hope that it will work well? And than when it does not even when EQd, you claim that you are enjoying stereo bass with all the uneven FQ response and excess decay? What exactly is there to enjoy in the "working together" and "correlation"?

Might come as a surprise, but HT people are not actually that dumb. They deal with more channels and problems than stereo. And by overwhelming majority (based solely on my experience on forums though - so worth a quarter of cent or less) all Storm and D&M efforts for directional bass have ended up in failure by popular judgement. Directional bass would be what you refer to as stereo bass.

 

[NTK]

Not sure what is so special about stereo bass?

Did you read and understand what Thomas Lund was talking about in post #54? Stereo bass is all about low frequency envelopment, and not about locating bass sources (or "directional bass").

 

[Oddball]

If he was using a more technical lingo I might understand it better. But the way it is I must admit it remains a mystery to me. I am actually jealous of you guys that seem to understand it? Any words of wisdom for the ones not so bright?

 

[Sokel]

If he was using a more technical lingo I might understand it better. But the way it is I must admit it remains a mystery to me. I am actually jealous of you guys that seem to understand it? Any words of wisdom for the ones not so bright?

His white paper and experiment about it may be of help:
(references at the end too)

https://assets.swoogo.com/uploads/4646601-673c03ab61c93.pdf

But the easiest way to see what he's talking about is to try it, you have full range speakers, subs are not entirely mandatory but a good treated room is. And that's the difficulty about it, physically treating a room down there is huge and messy.

The middle ground for the "as intended by the artist" aka (usually) flush mounted mains at the control room , is DSP' ing each (of the stereo) channel to a decent response, not summed as mono.

 

[NTK]

If he was using a more technical lingo I might understand it better. But the way it is I must admit it remains a mystery to me. I am actually jealous of you guys that seem to understand it? Any words of wisdom for the ones not so bright?

I discovered this subject through David Griesinger's papers. David is a PhD physicist so his papers are inevitably technical. May be you can try this one. You can skip the math as they are mostly useful for the purpose of his proposed measurement methods.
http://davidgriesinger.com/overvw1.pdf

 

[Oddball]

Many thanks that helps as always. Now treating the room is as you say not really practical for the low end. And also not sure if the tower approach is really the best if you are listening to reference volume. In HT it is a defined volume, but especially with classical music, I understand that peaks might last a bit longer. No passive tower is really good for 105dB at some average 3m distance @30hz.

As I noted, directional subs are a disaster in most rooms. You need 1) to even FQ response, and then 2) control decay. Without 1 or 2 your are pretty much toast in your stereo. Managing subs probably does not take PHD, or at least for now.

 

[Sokel]

Many thanks that helps as always. Now treating the room is as you say not really practical for the low end. And also not sure if the tower approach is really the best if you are listening to reference volume. In HT it is a defined volume, but especially with classical music, I understand that peaks might last a bit longer. No passive tower is really good for 105dB at some average 3m distance @30hz.

As I noted, directional subs are a disaster in most rooms. You need 1) to even FQ response, and then 2) control decay. Without 1 or 2 your are pretty much toast in your stereo. Managing subs probably does not take PHD, or at least for now.

The subject is not about directional bass or even its audibility, is about what this difference down low (demonstrated at the recordings, in other threads as well) does to the scene and the feeling of the scene.

The two main vague descriptions about it is that bass summed to mono is confined and unenveloping, while the (recorded) stereo bass brings more of the recorded space to the table, a more open and enveloping scene.

(lots of towers do 105dB at 3m at 30Hz ,lower is difficult for both loud and low distortion, bigger ones though, like the mains monitors I wrote above, or even a pair of nice KH420 even with some help)

 

[Oddball]

The subject is not about directional bass or even its audibility, is about what this difference down low (demonstrated at the recordings, in other threads as well) does to the scene and the feeling of the scene.

The two main vague descriptions about it is that bass summed to mono is confined and unenveloping, while the (recorded) stereo bass brings more of the recorded space to the table, a more open and enveloping scene.

(lots of towers do 105dB at 3m at 30Hz ,lower is difficult for both loud and low distortion, bigger ones though, like the mains monitors I wrote above, or even a pair of nice KH420 even with some help)

If you want to listen to 105dB towers at 3 m at 30hz - please do so. I have my big towers actually working hard only above 100hz. Never better, and they are no good even at 60hz @105dB, despite its size.

To the point of stereo recording is a valid one. But IME using stereo subs is a mute point. It would have to be a really extraordinary room to accomodate that.

Not sure why people don't take ART more seriously. It's just one battle after another I guess.

 

[Chr1]

Have to say that I find it surprising that this concept of "envelopment" is something new and/or revolutionary.
Surely the fact that two channel music has been recorded "full range stereo" for many years now, means this so called envelopement has been around for ages.
ie. As long as people have had the transducers with the capability to reproduce it properly, said envelopement has been a thing.
ie. Stereo bass ain't exactly new.
Or no?

 

[thcdru2k]

The problem from what I can tell is that people have systems in different rooms. In a large concert hall or a very large open concept room low-frequency envelopments may come through by design while in most rooms they are dominated by modes and decay therefore no advantage over optimized mono bass.

 

[levimax]

Over the years I found that by far the most "enveloping" effect comes from the recording itself - at least in a home scenario where there's never heavy, long reverb unless your place is huge. Differences between room acoustics pale in comparison to the room on the actual recording.

The subjective "enveloping" is indeed phase related and much stronger on bass. I made us an illustrative "test signal":

Dark Dream.mp3 | Powered by Box

app.box.com

That's a rather simple strings/pad patch using two "supersaw" oscillators that are detuned stacks of 7 sawtooth waveforms each. The detuning (dynamically played too via aftertouch on keyboard) alone gives a sense of space, even though the dry signal is mono. Then come stereo phaser, picking that up and widening it further (more phase modulation), and then drowned in stereo reverb making it even "worse".

You will notice the subjective "width" or "hugginess" or "enveloping", whatever you wanna call it, is noticeably more pronounced on the low notes from 0:50. The chaotic phase relations and beating of the whole signal chain is the same, I just perceive it as "more stereo" on bass.

If you're into this sort of thing like me, you'll definitely want stereo bass, either from two big speakers, or ideally two subwoofers. Mono bass is nice and danceable and vinyl and club compatible, but there's some "magic" about stereo bass that's hard to grasp and must have to do with how we perceive direction in that range.

Thanks for the file. I have a 2.2 system with co-located subs with an interface so can sum to mono "on the fly" with the problem being I get a "3-6 dB boost bass" when summing to mono which confounds things in many cases but on this sample there is lot more going on than just "louder bass" when I switch back and forth. In my experience summing to mono varies from no difference to a very noticable differences depending on content. Discarding Hi-Fi information, even for the good intention of smoother FR, has never made sense to me.

 

[Keith_W]

Not sure why people don't take ART more seriously. It's just one battle after another I guess.

We do take it seriously. It's an amazing accomplishment for sure. But some of us also have open minds and are curious about new developments in audio. Yes it is true that you have to forego the benefit of using multi-subs to even out room modes, and you need specific placement of subwoofers that might worsen the situation. But is that sacrifice worth it? And those studies are in anechoic chambers or in the free-field. Are they applicable in listening rooms? I mean, we have people like Lund here, may as well pick his brains like a bunch of hungry vultures!

 

[Oddball]

We do take it seriously. It's an amazing accomplishment for sure. But some of us also have open minds and are curious about new developments in audio. Yes it is true that you have to forego the benefit of using multi-subs to even out room modes, and you need specific placement of subwoofers that might worsen the situation. But is that sacrifice worth it? And those studies are in anechoic chambers or in the free-field. Are they applicable in listening rooms? I mean, we have people like Lund here, may as well pick his brains like a bunch of hungry vultures!

I'd just say that idea is a great (here and broader) , but then how you implement is when it fails. I am ultimately curious, but reserve my right to be conservative in technicalities.

My wife also wants the unlimited ATM line, but unfortunately that is not in the stars.

 

[thcdru2k]

I think it's important not to treat this as purely subjective. There should be measurable indicators. I would think evaluating impulse, phase, and decay between L and R can hint at whether spatial cues are preserved. If the responses from different drivers are identical, it's effectively no different from a mono sum.

 

[Ropeburn]

Thanks for the file. I have a 2.2 system with co-located subs with an interface so can sum to mono "on the fly" with the problem being I get a "3-6 dB boost bass" when summing to mono which confounds things in many cases but on this sample there is lot more going on than just "louder bass" when I switch back and forth. In my experience summing to mono varies from no difference to a very noticable differences depending on content. Discarding Hi-Fi information, even for the good intention of smoother FR, has never made sense to me.

Glad it's of some use. I didn't try switching playback to mono here, maybe tomorrow when neighbours are awake again. Heh. But it won't be very useful anyway because I can't just switch bass to mono here, only the general signal.

Of course you'll get a lot of cancellation and additional phase beating on switching to mono when channels keep dynamically differing so much. It's definitely not mono compatible, so to speak. The artist intended stereo bass in this case, so that's how it should be listened to.

 

[john61ct]

Thanks much!

the EQ parameters for stereo bass will highly likely be different from those that will get the best out of mono bass (i.e. even bass response across a large listening area).

How about if tuning for primary LP only?

 

[Ropeburn]

I think it's important not to treat this as purely subjective. There should be measurable indicators. I would think evaluating impulse, phase, and decay between L and R can hint at whether spatial cues are preserved. If the responses from different drivers are identical, it's effectively no different from a mono sum.

It would be interesting to make a binaural recording of a stereo signal, and compare its stereo correlation with the original. The difference would be room influence. Binaural recording is difficult of course and at best an approximation of how we really hear, but should give some indication of what's going on at least.

 

[john61ct]

Thanks for the file. I have a 2.2 system with co-located subs with an interface so can sum to mono "on the fly"

Yes what I'm looking at, but switchable to 5.x with multiple subs.

I'm thinking now obviously BRuTeS (Bone Rattling fUll-size TruE Sub) from below 30Hz should be mono only, can be freely placed

and my MBM midbass couplers that get bandpassed ~250 down to maybe 60-80Hz are obviously stereo

with a buncha trueSubs between those two functions, maybe not identical before crossovers but whose FR overlap a fair bit

I could then conduct ongoing experimenting, two get colocated front F/R make it easy to switch stereo vs mono

and then more kept in mono to freely place to help with room issues

xover between those two sets can go from 100+ down to 40-50Hz however low they go

If I use MSO (or win the ART lottery) I set ALL the trueSubs to mono and see if removing the front pair from colocated is better

compared to the above mix of stereo bass colocated + mono supplements.