Someone e-mailed me a post about an idea for enlarging a room wanting to know my thoughts on it. First, it would have been nice to know where it came from, but regardless after reading it I do have some opinions FWIW.
Quote:I am guessing it’s time to simply get to the meat of this fantasy of mine: that of electronically enlarging the size of the room. I am assuming we all understand the why of it, and now let’s go to the how of it. I want to state up front that I have never tried this, I only envision how this will work and as many of you have pointed out, to make it work properly is a major challenge – both physically and technically.
First though, let’s review and think about what it means to have a larger room. Imagine yourself standing in a room with 5 other people talking and chatting it up. The room is 10×10 feet and with your eyes opened or closed you can sense the size of the room. You sense this because of how your voice feeds back into your ears. You hear how your voice and movements interact with the surrounding walls. This has everything to do with the wall’s surfaces and proximity.
What I didn’t tell you is that in our imaginary room, the walls can be moved. As you are chatting it up with the other folks, I have people behind the walls that pull them apart, expanding the room size to 20×20, effectively doubling the size. You would immediately know you are in a larger room because the time it takes your voice, and the voices of your mates to reach the walls and bounce back would be doubled. That’s how you know the size of the room. Same for the ceiling – if I were to pull the ceiling up you’d know that as well.
Well, I don't have any issues with that, except to say in a properly done listening room you would not be aware of the rooms size. It would be the recording, specifically ambience in the recording, that determines the size of the space you perceive.
Remember, a common mistake is to attempt to make a recording sound like it's playing in your room. No residential rooms are large enough for this to work to a degree that would fool a listener into thinking it's real -
except perhaps a recording of a solo guitarist sitting on a stool.
The idea is to transport the listener to the venue of the recording, not the other way around. To do this involves acoustic treatments that make your walls disappear. This is btw, done with quadratic theory diffusion on all four walls. That said, if you wanted to manipulate the size of the room you would have to manipulate the size of the room in the recording since you can't hear your own walls.
How do you manipulate the size of a room in a recording? Reverb.
Quote:Therefore, in theory, all I need to do is place 4 very flat wall loudspeakers – one against each of the 4 walls in our room – and internal to those loudspeakers is a microphone and some circuitry to make the microphones and speakers work. The microphones would “hear” your voice and movements and send a duplicate signal back to you at the same volume level and timing as would a wall reflection. If you did this, you wouldn’t really know anything was happening – your ear hearing what it was expecting to hear from a surface 10 feet away.
OK, this where we start to get into trouble. The flat loudspeakers would have to be the same size as the walls.
The internal "circuitry" must be the same quality as the playback gear, and of the same design so that the signatures, harmonics, timbres all match the main loudspeakers.
The biggest problem is however, that the flat speakers in front of the walls must be able to absorb sound at every frequency, like a black hole absorbs light. Otherwise reflections from the panel (assuming they are panels) would ruin the intended effect. That's nearly impossible to do, if not completely impossible.
The only way to handle it is anti-noise. Using the entire speaker panel AS THE MICROPHONE, you would have to store the sound and then using the same panel AS THE SPEAKER, play the sound back out of phase to cancel it. You can now introduce your digital delay and then re-launch the same playback but in-phase into the listening space.
Quote:To expand the size of the room I now need only to delay the output of my wall mounted loudspeakers, playing back what the microphones pickup, the appropriate time difference you would normally get when the walls moved twice the distance from where you stood. Done properly, your ears would not hear anything different than if the actual physical event happened. In a darkened room, you would swear the walls had moved – because every auditory sense you have is giving you the correct cues for exactly that to happen.
Quote:If you move your head, move closer to one wall and further from the other wall, the effect would be identical to what would happen should you actually move the wall.
This would depend on the software you write and if you have a GPS locator taped to your forehead. Otherwise, no. Where you stand in the room would not be the same as moving the walls. And if that was the intension and you did it that way, the question would then become why?
Quote:If you change the volume level of the “reflected” sound you effectively control the nature of the wall’s reflectivity. So in this one system you can both control the size of the room as well as what the walls are made of. One could then program the system to track the recordings you play – add the approximate size and nature of each room to the metadata of your tracks and when you play something that was recorded in Carnegie Hall, the room changes to simulate that size – a cozy nightclub, a large outdoor concert, a deadened recording studio, etc. Let your imagination run wild.
OK, this is clearly the mind of a stereotypical engineer - I call them "math guys" who fall victim to the human urge to overcomplicate everything.
Understanding that it is possible to take a small room, treat it with diffusion, and make it sound like any size space the recording suggests would keep ones mind from even going here. Imagine having a sound stage that is arced around you 50 feet and a depth of 80 feet in room that's 15x13. Changing the size of the room to larger or smaller simply depends on the recording you pick. Should you want to manipulate that for some unknown reason, you could EASILY do it electronically with a single knob connected to a reverb effect that was inserted into the signal path.
I've seen it many times, audiophiles restlessly exploring ways to improve their playback experience, because they haven't found nirvana with the gear they're listening to. IF someone came to me with this idea, I would sell them some diffusers and a Decware amp so that they could stop thinking about the room and gear completely.
For those not familiar with quadratic theory diffusers, they are based on prime number sequences designed to capture and relaunch reflections into a hemi-disk pattern tangent to the orientation of the well dividers (what?) Sorry - let's try again. The are wood panels with slots that both diffuse energy across a 180 degree pattern as well as reduce the amplitude of sound energy (reflections). Both are required to have a holographic soundstage that defies the physical size of your room.
The reason for this is because in an untreated room with hard wall surfaces, sound from the speaker hits your ears (direct energy) and then hits the back wall behind you, followed by the side walls, followed by the front wall, followed by that same wave traveling past your head a second time. That's bad. The brain can not tell if the second wave was the same as the first because the two are too close in volume and too close in time. The result is a fuzzy sound stage and listener fatigue. Delay the reflection by a several milliseconds and reduce the reflection by several dB and the brain knows instinctively that it was ambience, not the original sound (direct energy). This is what makes everything pop into 3D and creates a sound stage that goes anywhere from 10 to 100 feet behind your speakers despite their only being 3 or 4 feet out from the wall.
My guess is that if whoever had this idea decides to develop it, they will after lots of time and money find it easier to accomplish with special open back headphones. Delay the reflection at the ear instead of at the wall which would be possible since the computer is faster than the neurons in the brain and would have the capability to distinguish direct from reflected energy. Meanwhile the rest of us will be enjoying recordings with a minimal amount of complexity and zero negative feedback amplification.
Steve
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Electronically Enlarging a Room (Read 14778 times)
