All of it.
You missed 90% of the explanation.
It explains how the rooms work. They're only hemi-anechoic in the speakers to room and speakers to engineer path - not the engineer to room path. They use a psycho-acoustic principle called self-noises cues. It's a key aspect of the design. These aren't anechoic rooms to the users at all.
We don't share detailed design data with strangers (or competitors for that matter) so you would not have the information and knowledge to read that data since it is simply not publicly available. All of this is proprietary and the reason why we survive as a company in today's pro audio world. We do share 100% with clients though, that have full access to everything, at any point in time.
The whole explanation:
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This is your Front-To-Back [FTB] Control Room and Mastering Suite standard. What would be the basic tenets of construction that guarantee this?
The system is two-fold. I looked at how the room should behave to be problem-free, but also I tied in the subject of how we perceive sound in an entirely different way. In the old Live End, Dead End [LEDE] system, they used the Hass kicker
[see sidebar] and other effects to feed environmental info back to the engineer about the space. In a Reflection-Free Zone [RFZ, a more modern version of LEDE] it is a little bit easier, because you have reflective areas in front of the room. RFZs use geometry to create a reflection-free zone around the sweet spot, so they sound a little more natural than the ones that had been deadened, such as old LEDE rooms with an absorptive front of the room. But the RFZ rooms don't really get rid of energy until it is far down in the room, and they'll still feed back something – a diffused version of the Hass kicker – which is basically like introducing distortion in the system. You're adding a variable between the engineer and the speaker, and that variable is related to the direct interaction between the speaker and the room. To me, that's always been, "Why would you want to do that?" Also, that Hass kicker was related to the size of the live room on the other side. That Hass kicker had to be within a certain time frame compared to the time frame of the live room. It made studios incompatible between one another, due to the time frame of the live rooms being different. There were a lot of very blurry areas, and it was running in circles. You justify Paper A with Paper B, and there was not anything I could grab onto; it was just a matter of opinion, at that point. I didn't like that. I decided FTB was a way to still provide environmental feedback to the engineer that did not involve the speakers, or anything related to speaker-to-engineer and speaker-to-room response. The idea is very basic. What is another source of sound in the room that I can use, besides the speakers? It is us. It's the noise we make when we walk, talk, and enter the room. From studies, I knew quite well what HRTF [Head-Related Transfer Function] is; I knew how long it would take for the brain to actually calibrate to a space, what it needs to do that, and what the auditory system would consider a "natural" space.
AG: Not everyone knows what the idea of a head-related transfer function is.
It's basically the influence of the torso, the head, and the pinna – the shape of the ear – on how we perceive sound. So that's the transfer; the influence of all of that on the way we hear. For example, the pinna will give you a lot of information about elevation from the reflection inside your ear. Another aspect is that it's like a fingerprint – everyone has a different set of ears. Part of the auditory system's response is acquired when you're born; it's embedded in your DNA. The other part you are learning as a kid by moving your head around; your brain learns how to identify objects around you from learning what it sounds like when it comes from this direction or that direction.
AG: Why is that important when you're building a room that is semi-anechoic?
Well, our brains and hearing systems don't like to be in anechoic environments. It's very unnatural. What you see is constantly correlated by the brain to what you hear. If you're in a dead, anechoic space, the cues that your brain receives about the space don't match the visual cues. The whole auditory system will distort its steady state response in a way that it will become a lot more sensitive to small reflections, high-frequencies, and anything that can give the brain detail more environmental data about the space. Everything will be enhanced. If you get your brain in that mindset, and then you play music, what you hear is not flat, in the sense that your brain will add a series of filters in between because it's looking for missing environmental information.
AG: It's overcompensating.
Yeah. That's why engineers complain that they add too much reverb or too much delay in dead rooms. Mixes are imbalanced when they move out of the room. The responsibility is not in the room being dead, because the room might measure flat. But
we don't measure flat in the space. It's a combination of these two things that makes a room translate.
More how humans listen and perceive the space?
Well, by not having an auditory system not in a "stressed" mode – as in "not its usual steady state." It's in a "flat" (steady state) mode; it's not looking for missing environmental information, it already knows where it is. It doesn't accentuate any of the environmental cues. That's partially what they were doing with LEDE. They wanted that to come, they just did it in a very strange way. For FTB, having the reflective front wall and these two diffusers in the ceiling, the two in the back provides just enough information when you make sound in a room that the brain actually calibrates through these reflections. It's able to say, "Okay, I know where I am. The room makes sense. I'm not stressed by the environment. I have control over what's going on." In FTB terms, these are all called "environmental cues." They feed back environmental information by interacting with "self-noise cues" – the noise we produce in the room."
Link to article:
https://tapeop.com/interviews/btg/135/thomas-jouanjean-northward-acoustics/
