2. Hierarchy of Sound & How it relates to True Stereo Recordings

Hierarchy of Sound

True Stereo recordings offer the listener a live acoustically realistic perspective without processing or electronic manipulation of any kind. Recorded with a single pair of microphones set up in spaces that have good natural acoustics, a textural dynamic quality is presented that simply cannot be achieved with multiple microphone techniques. Harmonic and spatial accuracy allow one to almost forget it’s a recording making the artist’s true intentions more approachable

Microphone preamp
Storage Medium (Analog / Digital)

Source (LP, CD, Tape, Hard drive etc)
Power Amp

Like any chain of events, all elements are interrelated and depend on one another for an intended outcome. The vast array of possibilities for both recording and playback are seemingly endless. A firm understanding of the strengths and limitations of such processes are therefore the most important step in any real comprehension for establishing how the intended results are to be achieved.

This class is about these elements, and observing both their strengths and weaknesses in the recording and playback chain; the purpose with which we can further our own abilities to create and interpolate the intentions we wish to use in displaying our final results.

Technology will continue to expand but our intentions will and should remain the same, to derive the desired result.

Exploring the Sound Hierarchy

The first thing to consider is the musicians and event that you have chosen to reflect. The knowledge of the individual performers within the structure of the music and how they interact will greatly aid in the ultimate understanding of what is possible to achieve. The more precise the performance parameters the easier it will be to construct a strategy or framework in which to operate from. In Classical music the formula for set up is generally a performance, because this type of music was originally heard in all acoustic spaces without amplification, and therefore was established with the listening experience in mind. Positioning of instruments are arranged for balance purposes; this indeed makes it easier to establish a good level and harmonic balance of all instruments involved, with the softest most transparent instruments in the front and the loudest, most penetrating in the rear.

Recordings other forms of music such as jazz can be much more challenging; as an example, the balance between drums and non-amplified acoustic bass or acoustic guitar and piano. There are unlimited combinations of instruments that we can encounter in difficult if not near impossible situations for recording in true stereo. There are often solutions to these problems through various manipulations of the musicians’ positions as well as the space it self.

True high quality recording mediums have really only existed for a little over half a century; their techniques and theory are still being explored, cultivated and documented.

The modern criteria for capturing sound allows for a vast amount of manipulations, from multi microphone techniques to the use of computer processing to change and shape the sound in all sorts of directions. Digital editing alone can create just about any desired effect.

The goal of this class is to capture sound by trying to keep the frequency, amplitude and time relationships as intact as conceivable. This includes understanding playback mediums and how they relate to this discourse.

The Space
Next to the music being recorded the space in which to record in is the most applicable. Indeed in trying to create a desired effect in capturing the simple truth (frequency, amplitude & time) is the most challenging and often times the most rewarding experience.

The use of the space is essential and probably no ideal space exits for all parameters. The desire to create a partiticular effect therefore lies in the intended result. Recording an orchestra in a small dry space makes as little sense as recording a Jazz trio in a lively gymnasium.

Finding the right space is not the key to panacea but the next logical step in the securing of a good possible outcome. The use of the musician’s and subsequent positioning of the microphones can only be realized with the knowledge of what lies within the limitations and the ability to access the prescribed outcome.

Microphones are the real limitation of all recorded sound. In True Stereo recording using simple microphone techniques pair matching is the first criteria to address, as it is impossible to construct a solid image if the microphones don’t have near ideal match. Frequency imbalance, phase anomalies, channel balance and tonal qualities will all relate to a matching pair of microphones.

Once this has been established, the polar patterns and stereo pair techniques can be adopted. Understanding the three basic techniques, coincident, near coincident and spaced AB will certainly aid us in calculating the particular result we may wish to obtain.

For mono compatibility and extreme center focus, coincident would be our chosen course. Recording solo instruments up close or trying to eliminate some room problems would also be good reasons. The stereo spread is more restricted typically because left and right is determined by strictly amplitude differences.

For a wider stereo spread and a closer representation of the human ear, near coincident styles can give us great rewards. ORTF in particular creates a fine sense of space and maintains a solid fundamental quality, which brings back a wonderful sense of acoustic geometry and very accurate spatial imaging. Because the spread is determined by amplitude as well as time differences, mono compatibility is not precise and some loss of frequency will occur, but these differences also occur (inner aurally) with our ears and the close resemblance to this helps reconstruct a more life like event.

The most open in room sound can be obtained by using spaced AB techniques. Recording large ensembles or enlarging the image in a small space are some the possible reasons to chose these methods. Stereo spread is determined most of all by time differences, mono compatibility is unlikely to have good results. Precise positioning of instruments is also not normally possible. The use of omni directional microphones, which don’t typically work well with coincident, or near coincident techniques increases the potential for improved bass response and if image specificity is not paramount good results can indeed be realized.

The quality of the microphones and there use will only be obtained by experimenting through which you will gain and recognize their inherent strengths and weaknesses and how to obtain desired results.

Microphone Preamp
The next stage is converting the microphone signal with added gain to our storage medium. The quality of the microphone preamp, like any other electronic device, is subject to individual tastes, assuming impedance matches are compatible. The use of this stage will likely be subject to a particular microphone being employed. Having low distortion and noise is essential. The use of transformer-less , transformer coupled , tube or solid state can be options put into context to judge the over all warmth and clarity of the particular microphone preamp.

Storage Mediums
The world is going digital and although tremendous progress has and is being made, there are those who still feel analog still offers qualities that digital systems have still yet to convey. Tonal qualities, harmonics, warmth, and musicality are all qualities that

digital still seems to not be able to fully grasp. Higher and higher sampling rates are expanding those horizons but don’t quite seem to be there yet.

Analog is certainly not perfect; noise and stability issues have always existed and are unlikely to be solved as the world moves ahead in the digital domain.

Also, transferring from these storage mediums to a consumer source is a question that needs to be addressed. Keeping the whole chain digital keeps noise to a minimum, but the use of analog can add dither and produce a warmer and more pleasant objective result. These decisions will be chosen for various reasons but will all contribute to the end result.


Playback mediums
There is a wide array of playback mediums available. Of course the original master recording, assuming it was designed for the minimum of sonic manipulations, is going to give the best result. CD, LP, tape (analog or digital), DVD, SACD, and DVD audio are all among the growing number of sources and possibilities.

The quality of the playback mechanism is perhaps the most influential and misunderstood. The closer it can fundamentally reconstruct the recording chain the more believable and the easier it will be to follow the music. If you don’t get it right here you will only amplify its problems later in the chain.

Like the microphone preamp the audio playback preamp must have low noise and distortion. Some feel a passive volume attenuator is adequate, and compared to a low quality line stage is preferable, although ultimately loss of bandwidth and transient attack can both suffer from passive devices. The use of high quality solid state or tube devices will maintain proper energy transfer and ensure that the power amp will see a proper signal.

There is now a popular use of passive controls on the amp stage in some modern integrated amps, but some losses generally occur with this compromise. The use of a separate preamp and amp still offers the best result, and having a preamp with a separate power supply is basically essential to create an environment to amplify and maintain the small electronic signal being applied.

Power Amp
The power amp must accept the incoming signal and amplify the loudspeakers. Matching an amp, preamp and loudspeakers is sometimes as much as an art as it is a science. Impedance matching, damping factors and load compatibilities are all questions, which need to be addressed. The selection of a given speaker will greatly affect the parameters of choice. Power output is also a criterion to consider, depending on speaker impedance and efficiency. When mismatches exist, poor bass and overall frequency response deviations can occur and even amp shut down can happen.

The loudspeaker, like the microphone, is a transducer, of course being the inverse in the relationship. The closer it can produce the microphone output, the more accurate it will perform. The use of various speakers is of course related to the quality of the playback equipment and to a greater degree, the recording mechanisms. Aside from amp compatibility, the proper set up and appropriate room will affect the final results.

The speaker offers the most apparent difference in subjective results and is therefore often the most difficult to quantify. Varying amounts of bandwidth and tonal color often determine what we end up preferring. The amount of direct and reflected sound creates the imaging capabilities and precision of such.

As in all things, subjective response is what rules the day, but understanding basic sound and capturing such will go a long way in developing our subjective responses, always going back to the intended results.

Ken Christianson, Pro Musica, Chicago

posted on: 2011/09/14
* 12. True Stereo in Perspective
* 11. Room & Boundary Effects for Playback Systems
* 10. Instrument Positioning & Room Manipulations
* 9. Choosing a Space-Acoustical Considerations
* 8. Troubleshooting True Stereo Sound
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