Capturing air

May 13, 2019
 by Paul McGowan

We're happiest when recordings and systems capture the space as well as the music.

Mastering and recording engineer Gus Skinas and I have been playing with microphones as of late and the biggest differences we hear are in the air, the room, the space. Sure, there are big differences between tonal qualities microphones capture (or don't) but those quickly pale in comparison to how much air is recorded.

We seem to "see through" the tonal differences rather quickly, forgiving the microphone for its colorations. But it is the recorded air that makes the magic.

One such microphone must have been handcrafted by wizards. It's an AKG C24 as modified by Tim de Paravicini on a sort of bet between Tim and its owner, Dan Schwartz. I don't know the details but they involved replacing its guts with Tim's transformers and Dan's handpicked vacuum tubes. But I could have easily just said it used Eye of newt and toe of frog, Wool of bat and tongue of dog, Adder's fork and blind-worm's sting, Lizard's leg and owlet's wing.

The recipe that made it doesn't matter. The instrument captures the air and the moment, unlike any device I have ever heard.

Whether it's a stereo system that faithfully reproduces air or a microphone that captures it, it's the sound of the environment that often is more important than the main venue.

How is the air in your listening room?

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36 comments on “Capturing air”

  1. In contrast to a multi-way loudspeaker with different driver technologies and most complex crossover designs it should be easy to measure reliably (in a measurement chamber) the performance of a microphone. I guess the “air” you mention could be seen in the shape of tone burst measurement revealing the resolution of transients. Thus Tim de Paravicini must have been quite sure where to make the tweaks!

  2. The aforementioned recipe was used for malign purposes, for deception, but home audio is deception, so it may be appropriate.
    The sound of the environment was exactly what Cage's 4'33" was all about. He any others at the time were exploring the idea that music was the sum of the composer's designs and external influences, unique on every occasion, so one extreme was to eliminate the composer and the music is just the environmental factors. Or something like that.
    Because my digital system is now so free of noise, I've finally gone the final step and ordered some low noise power cables. I had one on demo and was impressed. Back to the theory of dynamics being dependent on how quiet you can go, not just how loud.

    1. I assume that the distortions produced by the drivers (nonlinearities of motors and membrane break-ups) are the most critical elements here. Just compare the pure (!) dynamics of a spherical horn speaker having tiny movements of the membranes compared with other speaker designs. And then there are the resonances of the speaker’s cabinet.

  3. Reproducing the "air" (connected with "space around instruments", "ambience retrieval", "holographic imaging") more or less means what I understand by the "magic" a system delivers. It's the final important step in performance (of a recording or a setup) for me.

    When we speak about the situation at home, actively adressing the HF radiation and noise fields to/within equipment, cabling and room(!) means a lot in order to achieve this when the setup is already on a high level!

  4. A mic has to faithfully capture the ambiance, the essence of the room, for the recording to have any hope of being magical. If the mic doesn't get it right, it will never be right.

  5. For me at least, the "air" in the room is also the place where the magic happens. I hope you all are going to use the mike for new recording projects, and I look forward to hearing them!

  6. The air in my music room is excellent. Like Tim it relys on vacuum tubes, thirty to be precise - and solid state for the bass. I wouldn't change a thing (except tubes when it comes to it, but its a price worth paying).

  7. In my dedicated listening room, "The Air" is so near perfect that 3 weeks of testing 2" thick AbFuser panels were returned for credit. Could not enhance or improve the ambiance, the soundstage or the holographic presentation imaging, only diffuse\confuse it!

    If the Microphones capture "the venue", my set up recreates it!! Will be exciting Paul to hear more of these recorded magical achievements!!!

  8. Interesting that such a solid state guy finds a tube microphone so enamoring. I’ve gone full circle and back to tubes in the preamp section for ~45Hz and up (solid state power amp for speaker control) and all solid state below 45Hz.

    I’ve been downloading some great remastered recordings from the late 50’s and early 60’s as there seems to be ‘something’ from those days and techniques that conveys the ‘air and magic’ in a lot of those recordings.

    I also have some modern recordings that surpass the remasters.

    The 1st requirement though is ensuring I enjoy the recording content.

  9. Maybe you should use that microphone to record a recital of John Cage's controversial "composition" 4'33" for silent piano. Cage's instructions were for it to be "played" with the windows open, in order for the audience to experience what sounds a lot like your description of the "air" in the room .... 🙂

    1. Go ahead and laugh at Cage. He wrote an epic piece that is being performed called "As Slow As Possible."

      The performance of the organ version at St. Burchardi church in Halberstadt, Germany began in 2001 and is scheduled to have a duration of 639 years, ending in 2640.

      Here's something interesting. It probably belongs in Ripley's Believe it or not.

      There are certain professors of music who actually take this stuff seriously. Who is crazier, them or Cage himself? Is he putting us all on or is he for real? I say he actually believes in what he does. As someone once told me no one ever went broke underestimating the intelligence of the American public or put another way by someone else you cold glue two pieces of anything together and someone in America will buy it. Anyone still have their pet rock? Mood ring? Duncan Imperial Yoyo?

      1. Here's an interesting thought. If Gus Skinas wanted to record the St. Burundi Church version, presumably he would want to record it in 5-channel DSD256 sound in order to fully capture all this "air". I did a quick back-of-the-envelope calculation, and it turns out that the final recorded file would occupy some 23,372 PetaBytes!!

        The only problem I can see is that Dan Schwartz's microphone might not last the full 639 years. I'm guessing the tubes might burn out.

              1. Oh, absolutely. These will be 45rpm audiophile pressings on 180g vinyl. Approximately 11 million discs in total. The vinyl alone will weigh nearly 2,000 tons, and the full set will require about 52 miles of shelf space. I am told that shipping will actually be free, but you are advised that delivery will come in 90 full-sized container trucks, and the drivers will anticipate access to a loading dock. But the good news is there will only be just the one booklet, although there won't be all that much in it. But I believe Soundmind will be writing the foreword, if he's still around. Pricing not yet announced.

                1. Very impressive maths. They could always do it by weekly instalment magazines. A mere 210,815 years. It will have to be a limited edition as I'm not sure there are enough trees and a digital version would take away all the fun.

                  I prefer Hurtag. I heard Isserlis play some of his pieces, which he stretched out to about 30 seconds or so, a handful of notes and one of the few times people were leaning forward to try and hear a bit better. That was in Row C. 20 rows back they probably missed the whole experience.

                    1. I used to listen to Bill Bryson and sometimes before the hour was out I'd have the thought that at some point during the broadcast I'd died and been reincarnated. I have a book arrived yesterday by Willy Vlautin and I expect the experience will be similar. Some music is like that. One of my favourites is The Magic Fields' 69 Love Songs. They're all over quite quickly. Some of them were choreographed in a piece by NDT1 called Schmetterling, here:

                2. To be honest, I've been sitting in the office all day with the window open and it sounds a bit like your typical bit of John Cage. A bit of traffic, rusting of leaves, etc ..

                    1. Strangely it's spring and it's not raining. There's a heatwave in Bonnie Scotland. I'm sure the birds are whistling the opening theme to Mahler 4.

  10. Naturally the first thing I did after reading today's post was to research this microphone. And it is quite unique, flexible, adaptable, neutral, with many adjustable pickup patterns. It is a stereophonic microphone with two condenser elements about 1 1/2 inches apart. Their close proximity makes time of arrival differences negligible and reduces phase differences. They are capable of many different pickup patterns including omnidirectional and figure 8 among others. They have many applications. The design is from the 1950s and this must be among the most valuable microphones ever. Out of production for decades, used examples in excellent condition sell for around $12,000 to $16,000 and from what I've read if you need them it's worth every penny. I had a hunch it had at least some adjustments that were omnidirectional pickup patterns. BTW, there are no modern equivalents available.

    Able to record reverberation of live spaces, this is what audiophiles call "air" comes from. Optimal placement and adjustment are critical for the best results. From vocals to jazz ensembles to symphony orchestras this is one great microphone.

    All this being said, and regardless of the engineer's skill in using them, they cannot accurately record concert hall reverberation. The reason is simple. The arriving sound field has sound varying in amplitude with time arriving in all three planes from every direction at different times. These are the reflections and their directional properties classify them as vectors. Like every other microphone the electrical signal they produce only has amplitude varying with time and has therefore lost all of the directional characteristics of direction of arrival in the sound field. The signals are classified as scalars meaning they have no directional properties. The directional properties of the arriving field on playback cannot recreate the vectors of the sound that was recorded and cannot separate the source of sound arriving directly from one direction from the reverberant field arriving from many directions. When reproduced through loudspeakers the perception of being immersed or enveloped by sound is almost completely lost. So what vectors the loudspeaker produces is completely different from what was recorded.

    The ambisonic principle uses three figure 8 microphones and one omnidirectional microphone. The figure 8 microphones are on three axes, left minus right, front minus back, and up minus down. The omnidirectional microphone is used for a reference of overall loudness. By vector algebra the system could theoretically derive any vector from any direction. Systems like Dolby Atoms and similar use this concept. The ambisonic system I described here has shortcomings and is now referred to as a first order ambisonic system. More figure 8 microphones are added at different angles to better fill in the gaps producing higher order ambisonic systems. The playback system requires a processor and many speakers and amplifiers in all directions. It's been used in theaters but isn't practical for a home. Ambisonic systems are not like other multichannel systems such as quadraphonic, SACD, and further derivatives which record sound from different directions directly.

    Scroll down to the picture on the right side. This shows the different Ambisonic sound pickup of different orders. A problem with this concept is that unless you have a very large number of directions, and a large room with a high ceiling, aiming speakers directly at you gives you focused directional sound. This is what you'd hear from background music in a supermarket where there may be dozens or even over a hundred speakers but the only one you hear is the one closest to being directly above your head. This is because the sound does not arrive with the diffusivity of direction natural reverberation does.

    So far the only successful methods I'm aware of are Wave Field Synthesis and my own invention EEAS. These methods reconstruct the reverberant sound field based on a mathematical relationship for a given space between the direct and reverberant sound field. Neither of them are practical for home use by audiophiles.

  11. Oh how I do agree with this 100%. And it's just as important that your system from the source to the interconnects to the preamp to the amp to the speaker wire and to the speakers can preserve that air that is captured by the microphone and not destroy it along the way.

  12. It was quite controversial in recording studios when the mic was first introduced. Some saw it as coloration.. Amongst some of the recording engineers, Tim de Paravicini and Dan Schwartz were seen as...................... "Air-etics." 😉

  13. Honest question...

    Is "air" being used as audiophile jargon for sounds of reverberation? Or does it mean something else?

    Could someone list out two or three easily streamable tracks with great "air", and then list out two or three lacking in "air", so that we could all listen to them? This will allow those of us not sure how the term is being used to "grok" it, and may have the side benefit of allowing everyone to agree they are describing the same thing. If possible, it would be great if those listing the "air" tracks also clarified what it is in the track that sounds like "air" to them.

    Thanks in advance for helping to put some clarity to a difficult to grasp topic.

        1. Cookie could probably give the best answer...I’d say what you hear is achieved by microphones able to catch the space and ambience between instruments and singers as well as of the room. And certainly also needed are other involved following electronics with highest resolving capabilities.

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