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Acoustics of the Shoebox

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bombdiggity:
Not quite sure what general subject thread this fits but it may be closest here. 

There's an interesting study how room design affects the audient's experience summarized here (and apparently published in the Proceedings of the National Academy of Sciences in 2014):

https://www.concertgebouw.nl/uw-bezoek/gebouw-geschiedenis/beroemde-akoestiek/nrc-handelsblad-akoestiek-van-de-schoenendoos

Google translate seemed to do a pretty good job with it. 

The impact of the reverb from the shape of the room on differing segments of the frequency range in conjunction with the type of music lays out (and in their study measures) a number of the factors that interact before our mics even enter the picture. 

Gutbucket:
A coffered ceiling and niched sidewalls are important detail elements as well, apparently.  David Griesinger is a expert on concert hall acoustics as well as a recording engineer, and always a good read on these topics- www.davidgriesinger.com/


--- Quote --- The six Finns measured the famous acoustics of the Concertgebouw. [snip] The more than thirty loudspeakers on the stage together formed a 'loudspeaker orchestra'. Mozart, Beethoven, Bruckner came from the speakers, but without an orchestra being involved.
--- End quote ---

No Sibelius?

wforwumbo:
Cool to see David Griesinger cited here - David is a good friend of mine, and I've had the pleasure of interning for him. Just saw him a few weeks ago, he's been working on a cool new mechanism for playback of binaural stimuli.

Regarding the purpose of this post... I actually have a plan. Given my degree is in architectural acoustics and I've both taken and TA'd multiple semesters in the topic, I might try to put together some notes on room acoustics for tapers, and contributing it to the knowledge base. That is, if people are interested in reading about it and want to learn more about the topic.

bombdiggity:
^ That would be fun and probably useful (particularly to the extent we can choose our location/s at any given event).  The audience may be a subset even here but there are a few of us... 

The David Griesinger information is excellent.  I liked this brief piece: https://www.classical-scene.com/2011/10/11/9243/  I seem to have stumbled into this aspect myself: You cannot use any type of first-order microphone without putting the microphones much closer to the music than would be ideal for concert listening. This increases the direct to reverberant ratio and widens the image enough that the recording begins to have the clarity of natural hearing.  It is highly unlikely I'll be in settings where running multiple mics is feasible and I'm not likely to want to do that anyway, so I tend to focus on how to get the most from a pair within the myriad limitations I have to deal with.  I've learned how to pretty consistently get what I like, which might not be everyone's exact cup of tea, but I feel satisfied that I accomplished my goal. 

I am growing more curious about how to get the coloring useful reverberance might provide but too often there is too much rather than too little of that. 

wforwumbo:

--- Quote from: bombdiggity on December 05, 2017, 01:00:29 PM ---^ That would be fun and probably useful (particularly to the extent we can choose our location/s at any given event).  The audience may be a subset even here but there are a few of us... 

The David Griesinger information is excellent.  I liked this brief piece: https://www.classical-scene.com/2011/10/11/9243/  I seem to have stumbled into this aspect myself: You cannot use any type of first-order microphone without putting the microphones much closer to the music than would be ideal for concert listening. This increases the direct to reverberant ratio and widens the image enough that the recording begins to have the clarity of natural hearing.  It is highly unlikely I'll be in settings where running multiple mics is feasible and I'm not likely to want to do that anyway, so I tend to focus on how to get the most from a pair within the myriad limitations I have to deal with.  I've learned how to pretty consistently get what I like, which might not be everyone's exact cup of tea, but I feel satisfied that I accomplished my goal. 

I am growing more curious about how to get the coloring useful reverberance might provide but too often there is too much rather than too little of that.

--- End quote ---

Yup, happy to contribute what I can. I'll LaTeX all my notes into PDFs, and gear the discussion and topics (with sources) to specifically gear it towards live tapers, and specifically those without a background in differential equations.

Something you - and everyone here - should know about David, is that he really ONLY thinks about recording music in the sense of classical and opera. So for one thing, instrumentation is obviously different. For another, it is frequently unamplified (and when it is, the amplification definitely isn't at the volume or speaker array placement of most rock PAs). And for a third - possibly most importantly - the audience is almost always pindrop silent in a classical/opera performance, which obviously isn't the case at, say, a rock gig. For David's work recording classical music, his way of thinking makes a lot of sense. He wants a HIGH degree of accuracy in spatial information presented in a stereo field, and he thinks about room reflections as a way to enhance that. Not to mention, for stuff like classical music the thresholds of binaural perception (for example, binaural sluggishness) are radically different....

When you put a rock band with live PA reinforcement in any venue (ie the type of music that tends to be discussed around here), a room reacts VERY differently. I've had some discussions with David about the types of shows I attend (which are usually modern ambient/electroacoustic, and Phish), and he's admitted it's an entirely different ballgame, with a different set of variables that change the way of thinking about capture and playback. Not that David's points are invalidated particularly for our discussion here and the ones I tend to have with him, but take lots of what he's talking about with a grain of salt when thinking about your own tapes.

There is another point I want to mention here too, which is brief but more academic than it is practical: David's usage of the words "Clarity" and "Presence" are not the commonly-agreed-upon definitions. Rather, he has re-defined them to fit more conveniently with his own thoughts of recording and listening. It's not worth getting into the nitty-gritty details of the distinctions, but just know that he has his own definitions for those terms.

What IS worth thinking about, as far as David's theories and applying them to the type of music we tend to tape, is the TIMING of early reflections. note: what follows is my opinion based on experience, knowledge of theory, and personal testing; it is by no means law, and it certainly isn't necessarily rigorous, rather it's my beliefs on the matter. The time at which an early reflection arrives is sometimes more important than its strength. If early reflections arrive too late, then we perceive them as separable auditory events rather than as directional cues for the volume of a room or distance from side walls. This is what we commonly refer to in live performance as a slapback echo; it can sound disorienting and a bit confusing when you're trying to get a sense of the balance of a live performance. Diffuse reflections, as a corollary, if in too great of a strength will blur the stereo image, make things sound distant, and cause instruments to start becoming one giant smudge rather than a balanced stereo image.

All three components of an impulse response - direct sound, early reflections, and late reverberation - work closely together in concert (no pun intended) to produce the resulting sound field perceived by a listener. This is more or less the foundation of David's work - trying to get a good balance amongst all three to optimize the playback experience. Put another way, he's trying to understand the entire system from origin of sound propagation (as well as its potential contents) all the way to neural firing, and he's trying to reverse-engineer all the pieces of the puzzle to get it to all fit together in a manner he can control. Hell, it's why he created random hall and the Lexicon 224 (he's shown me pictures of him literally hand-building the RAM, creating his own compiler/assembler for TI DSPs, and his custom command line/controls for creating complex DSP code from when he designed the 224). I'm not gonna give away any of his DEEP secrets, but I'll happily discuss whatever he shares openly within the academic community.

I know I ranted a bit non-linearly here, and some of the topics I mentioned and how I spoke about them might be a bit hand-wave-y (I'm currently on a massive 4-day coding binge with about 9 hours of sleep in that time span). If you want to know more about anything I've just mentioned, please let me know and I'll happily explain in further detail and at a lower level.

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