A layman multimedia guide to Immersive Sound for the technically minded (Immersive Audio and Holophony)

[jgazal]

(...)
yet very few people feel like this sounds flat when a headphone is calibrated that way. we have the expected variations from HRTF, an extra variable compared to the average human target, but one we expect and can deal with. but then comes something like the almost universal desire to get more low end that probably comes from a desire to compensate for the lack of tactile bass on headphones. how do we quantify that objectively? how a use tries to turn body vibration into increased low frequency at the eardrum? despite a purely objective approach, the result doesn't work as is because we did not and could not account for all the variables in the system. so what we have is a simplified system and only subjectivity can turn that into something feeling neutral, or not.
(...)
I get the idea of the Realiser A8/A16 where you take one specific room and try to mimic the sound for one specific user with one specific headphone. the target is clear, the reference is clear. it's all user specific. that to me makes sense, it's not a matter of spatial distortion, it's an attempt to simulate the experience of one room for one dude. we lack tactile subs and maybe looking at the speakers, but otherwise it's pretty complete. (...)

(...)
about analogsurviver's comment on subs, Floyd Toole mentioned a few times that we might not even need actual subs to replace the lack of tactile bass. vibrations from any source can subjectively do wonders even if they're not at the proper frequency or rhythm. to dumb it down, if we shake a little, it seems to feel more realistic than if we have only headphones.
(...)
I never got to try the stuff that makes your chair vibrate with the music, was that a total bust or are there people actually enjoying that stuff?

Sorry to cut your great post, but since you are at it, I would like to expand the topic of tactile/haptic/kinetic transducers.

I guess those kind of transducers that propagate low frequencies through solids (your couch, chair or your own body) instead of air have the advantage of avoiding room nodes and bass overhigh and they go deeper in frequencies if compared with subwoofers at the same price.

B. The crosstalk avoidance binauralization route
B.1 The crosstalk avoidance binauralization with headphones
And what you can do with DSPs like the Smyth Research Realiser A16?
(...)
Add tactile/haptic transducers and you feel bone conducting bass not affected by the acoustics of your listening room.

So I was searching for the most linear solution and I have found Crowson Technology tactile transducers, Subpac S2 seated haptic transducers, Subpac MX2 and Woojer Ryg (eta early 2018) wearable haptic transducers:

Crowson and Subpac have more reviews.

See, for instance, Subpac reviews:

so, just got it up and running. The most fascinating thing to me is that it makes me seemingly "hear" the bass with my ears more. Like I know it's an audio illusion, but the bass guitar on Fiona Apple's Criminal sounds louder with subpac on. Because they're running completely independently through entirely different DACs, I can control the subpac's and my HD800's volume completely independently. And when I turn down the subpac without even touching the HD800's volume, it SOUNDS like the bass is going down as well. Like it seems like just in my ears it's less loud without the subpac on. At first I though that maybe I was hearing some bleed through the open HD800s, but the effect still happens with sealed IEMs. And I don't hear anything coming from the subpac if I have the HD800s turned all the way down. But when they're working together, the subpac seems to make bass sound louder, seemingly, to my ears. So funny.

I have also noticed with the M2, wanting to wear it on the front, getting a good tight fit seems key. Just casually having it lay there doesn't have the same effect, it's almost like the bass gets loose and unrefined.

I've noticed that as well. It has everything to do with that being the way we actually hear bass in the real world. We not only hear deep bass, we feel it with our bodies. That's the gestalt ofdeep bass. When the tactile element is missing, our perceptual apparatus tells us something is missing and we don't "hear" the bass.

With the subpac, the trick is to find the right level match so the tactile part is not calling too much attention to itself. When you achieve the sweet spot, it just sounds like really deep bass.

Adds about half an octave of deep bass to the HD 800's, now doesn't it?

Comments on M2 inverted vs. M2 and/or S2?
I just heard about the device, and initially thought all applications would chest-mounted, e.g. using M2 inverted, as it "feels" most instinctive to me. Something feeling rumbling behind you seems a bit off

it's not as big of a deal as you would think, as long as you use the unit subtly (where it is at its best). Your core isn't super sensitive directionally, it mostly just feels an omnidirectional thump. That being said, I do prefer the inverted M2. Especially if I am playing around with it at higher than natural settings.

A lot of people who use this thing go crazy with it, and have impact it produces set at ***several*** times what the natural impact would be. If you use the subpac at a "natural" level, then you almost won't think it is on, as your brain just blends it in with your heard sound, into one coherent whole. If you have it higher, the "spell is broken" and you feel the subpac as its own separate thing, in which case having it on the back is a little off-putting.

All that to say, yes, I prefer in the front, but it actually doesn't matter as much as you would think if you are using it for high fidelity musical enjoyment.

Best tip ever. Makes a huge difference.
Got my M2 this christmas. Love it.
Will also get a Smyth Realizer A16. Backed it a Kickstartert.
Compared to my Lofelt Basslet the SupPac is a bit slower. (https://lofelt.com/) But the Basslet is very small.

What do you think?

 

[bigshot]

Butt shakers! A friend of mine bought those. I gave him the funniest look when he told me. I remember going to the theater to see the Battlestar Galactica movie in SENSAROUND. It was a dog's breakfast. Plaster fell from the roof of the theater on us and there was dust in the air every time they fired up the low end squawkers in the back of the theater.

 

[castleofargh]

@jgazal you need to teach me how to search the forum that effectively ^_^.
you quoted what I think and know on the subject. I'm still very much there as I haven't had the opportunity to try anything of the kind myself. which is a serious limitation when the conversation is about impressions. so for now I can only trust the people providing feedback from uncontrolled experiences(despite how it's always my last resort), and assume it does work like Floyd Toole suggested. I imagine that like most things, the brain of some people may have an easier time assimilating the shakes as being low end rumble from music. but that's just me making an educated guess.

 

[bigshot]

Some people just might like sitting on a vibrator!

 

[jgazal]

I just use the main search bar at the top right corner and filter the result by user.

@bigshot, that Sensurround feedback is funny! I didn’t know about it:

Sensurround

Sensurround is the brand name for a process developed by Cerwin-Vega in conjunction with Universal Studios to enhance the audio experience during film screenings, specifically for the 1974 film Earthquake. The process was intended for subsequent use and was adopted for four more films, Midway (1976), Rollercoaster (1977), the theatrical version of Saga of a Star World (1978), the Battlestar Galactica pilot, as well as the compilation film Mission Galactica: The Cylon Attack (1979). Sensurround worked by adding extended-range bass for sound effects. The low-frequency sounds were more felt than heard, providing a vivid complement to onscreen depictions of earth tremors, bomber formations, and amusement park rides. The overall trend toward "multiplex" cinema structures presented challenges that made Sensurround impractical as a permanent feature of cinema.[1]

Sensurround helped bring wider recognition to established loudspeaker manufacturer Cerwin-Vega,[2] and aided in establishing a strong reputation for new audio amplifier company BGW Systems. The increased awareness of extended low-frequency sound reproduction that Sensurround brought to film audiences was a factor in the increase in subwoofer sales and in the rise in the number of subwoofer designs in the late 1970s and 1980s.

I see it may seem gimmick, but the subpac reviews here at head-fi show a mild subtle use of the technology.

I saw the buttkickers, but I live in a country to which freight is very expensive and on top of that there are high importation taxes. So less mass is important for me. And I guess linear transducers may work better than inertial transducers:

The Speakers With The Deepest Bass: Tactile Transducers
(...)
Linear Actuators are transducers that push against a hard surface. They apply a force directly to an object, in contrast to Inertial Shakers which vibrate themselves, and then transmit that vibration into another object. Commercially available Linear Actuators usually replace the feet of a chair. They operate by pushing against the floor, and directly lifting and dropping a chair. They tend to be more expensive that Inertial Shakers, and they can be only installed under chairs — they can’t be installed under a floor or in a swimming pool like the shakers above.

I know that considering tactile route is tantamount to sacrilege, particularly when you have an acoustically treated room with multiple subwoofers, but unfortunately I need something to work in my small room.

Currently the subpac has more acceptance by dj’s and mastering engineers mixing heavily bass content for dance clubs:

But, differently from @castleofargh, that is what I think I know about the subject. So my expectations might be really wrong.

My aim was to reproduce visceral impact of pipe organs and percussion, with harmonic fidelity and reduced distortion, considering my room and budget constraint...

I will eventually buy one to try it. I just don’t know which one...

I would love to try Crowson transducers because they tackle the issue for multiple users, but it is still out of my budget. Let’s see...

 

[bigshot]

An interesting thing happened last night... I was listening to a new CD with my regular stereo to 5.1 DSP and the album appeared to have been mixed in matrixed surround. I was getting pretty discrete sounds out of individual rears and the vocals were channeled to the center. I wonder if there are other albums that are encoded in matrix surround without the cover of the CD mentioning it.

(Yes the phrase "discrete sounds out of individual rears" was intentionally spoken as the setup line for a joke. Knock it home.)

 

[jgazal]

Is matrixed surround the same as Dolby Pro Logic? I have no experience with those.

Inspired by your enthusiasm with multichannel, I bought three music albums mixed with either DTS, Dolby or multichannel PCM.

 

[bigshot]

There are different types of matrixed systems. The main two are Dolby Pro Logic and DTS Neo:6. Each of them have their own encoding/decoding scheme so they aren't usually interchangeable. There are several varieties of Dolby Pro Logic. The most basic is 3 front channels and one mono surround channel. They developed ways to matrix more channels in later versions, like Dolby Pro Logic Iix. They also have different types of encoding based on different purposes- for example one way to decode movies and a different way to decode music.

It seems that matrixed encoding is rarely documented on the covers of the discs. You have to just try them and figure out if one of them works. A few weeks ago I watched four episodes of a TV series on DVD before I realized that it wasn't just two channel, it was encoded in Dolby Pro Logic II. I started looking through other discs and found one that had the DTS logo on it that decoded using Neo:6 perfectly. It's kind of irritating to have a surround mix in your hand and not have any way to know how to properly decode it.

I remember back in the LP era, there was a thing called the Haffler Doss Sum and Difference Matrix System, which was basically taking a two channel source and adding two rear speakers with the positive lead from the right going to the rear right speaker and the positive lead from the left going to the rear left speaker. Then you connected the two negatives together in the rear. That threw out of phase material to the rear. I read about it in an interview with Brian Eno and discovered that engineers had picked it up and were encoding rear channel material into their albums without advertising it. Progressive rock and New Wave music used it a lot.

 

[71 dB]

Back in 2004 my AV amp needed repair and I had to live a couple of weeks without it. So, I used my old NAD 302 instead. Since I had 5-speaker system, I had the main speakers ground wires connected to amp ground through center speaker and rear channel in "Haffler Doss" - way. It worked "considering the circumstances" and I managed the days before getting my AV-amp back.

 

[71 dB]

It's kind of irritating to have a surround mix in your hand and not have any way to know how to properly decode it.

Well you can test all the decoding methods and choose whatever sounds best.
I have a couple of Andreas Vollenweider discs which clearly say "Dolby Surround" in the back.

 

[gregorio]

Would releasing an specific “binaural synthesis master” (that allow mixing a drum in the cherished way gregorio described, but also conveying at least a 180 degree hemifield sounstage and proximity) represent a competitive advantage? If you say yes, then your offer will match my propensity to buy your mastering instead of an standard stereo one.

There's three problems here:

1. The two assertions here are mutually exclusive. I know of no way to both mix a drumkit in the "cherished way" AND create a binaural master, the processor you posted a screenshot of does not allow this. There are conversion plugins which take a normal stereo mix and attempts to convert it to binaural but I've not generally been happy with the results I've heard.

2. Due to the previous point, we're talking about two completely separate mixes and masters and, would likely require re-recording some of the instruments. This is going to roughly double the time and cost of mixing and mastering and could somewhat increase the time and costs of recording. Would any competitive advantage outweigh this substantial additional time/cost? Probably not but ...

3. It's not my decision, it's the decision of whoever is paying for my services, the record label or artist. Typically, with the state of the industry over the last decade, they are wanting less time and lower costs, not higher and, they're generally very economically risk averse!

The most basic is 3 front channels and one mono surround channel. They developed ways to matrix more channels in later versions, like Dolby Pro Logic Iix.

As far as I'm aware ProLogic is always essentially 4 channels (LCRS). The newer versions, such as ProLogic IIx, can output up to 7.1 (or 9.1 in the case of ProLogic IIz) but they are not matrix'ing more channels, they are simply up-mixing the additional channels (from either LtRt/LCRS or DD 5.1 input). I could be wrong here though, I've never actually worked with ProLogic IIx.

G

 

[jgazal]

@gregorio, please accept my apologies for using the wrong words.

I used that expression because I did not know how to express its meaning in a better way.

I should have said "making artistically the most out of two channel standard stereo".

I wish I had the opportunity to play with those applications. Then I could contribute in a more meaningful way...

 

[pinnahertz]

An interesting thing happened last night... I was listening to a new CD with my regular stereo to 5.1 DSP and the album appeared to have been mixed in matrixed surround. I was getting pretty discrete sounds out of individual rears and the vocals were channeled to the center. I wonder if there are other albums that are encoded in matrix surround without the cover of the CD mentioning it.

(Yes the phrase "discrete sounds out of individual rears" was intentionally spoken as the setup line for a joke. Knock it home.)

Ever heard the term "Magic Surround" on a dubbing stage? You'd have to be mixing for Dolby Stereo/ProLogic to hear that term. It is the re-direction of front material to surround by that material accidentally matching the decode algorithm for surround material. It was always known about, sometimes compensated for if desired. Music did that a lot. There is also another ProLogic anomaly that bears the industry-insider name "Toddisms". Craig Todd was the engineer who developed the original Dolby surround decoder electronics. He used chips designed for Quad matrix steering logic made by Tate Audio. The steering time constants were chosen to be as innocuous as possible, and were basically syllabic in duration. But every so often a transient sound would be miss-steered because the logic was too slow and end up where you didn't want it. That's a "Toddism", and you could compensate by tickling the steering in advance with a low level sound in the same location. The sound would be masked but the steering logic would be pre-coaxed to the right result so when the real effect occurred it was properly steered. Adjacent channel separation in the basic matrix is only 3dB. The Tate chips hyped that to around 20dB, but only over a limited dynamic range. The initial release of the ProLogic chip set improved on the dynamic range of the steering logic to the point that a consumer, analog, ProLogic decoder out performed the Cat. 150 card used in Dolby cinema processors, and the reference decoder used to monitor the mix in the dubbing stage. Toddisms never went away completely, though.

Mixing for ProLogic IIx would only require a reference decoder to monitor through, with the knowlege that the mix would never...ever...hit an optical film track! The surround band limiting and Dolby B NR applied to surround in the original Dolby Stereo and ProLogic was there because of optical slit alignment problems (think tape head azimuth) in projectors. Those limitations became non-issues in consumer audio formats, so consumer variants of ProLogic eventually removed them, at least to a degree that wouldn't create severe incompatibility with older soundtracks. There was also a 20ms basic time delay in the surround, which was added to based on theater speaker locations, to hype surround separation using the precedence (Haas) effect, which I think may also have gone away by now.

I got the joke, butt decided to bunt.

 

[bigshot]

Interesting stuff!

There are two competing blu-rays right now of Dario Argento's Suspiria. The original four track masters were in too bad of a shape to use, but for one of them, they went back to the stems and remixed to recreate the original 4 channel mix. That was released as 4.0 DTS Master Audio HD. The other release only has a stereo DTS Master Audio HD soundtrack. However the stereo track is encoded in Dolby Pro Logic so it expands out to a similar sounding 4.0. The cover makes no mention of the fact that it is in Dolby Pro Logic surround. I can't see any reason why in 2018 anyone would use a matrixed surround format. I think they just stole it off an old laserdisc release and they didn't want anyone to know that was the source because DTS would probably gripe that they were putting a Dolby encoded track in a DTS package.

 

[jgazal]

An interesting video about reverb and mixing with Ambisonics:

edit: first, I listened with headphones. I have just checked with speakers at near field and my crosstalk cancellation pillows and it seems promising.