A U D I O... P A P E R


THE GRAND ILLUSION - PART I

PLAYBACK SYSTEMS

by Steve Deckert
December 2000

 

All of us have different criteria for judging and enjoying high fidelity playback systems. For some it is overwhelming volume and dynamics - trying to re-create the live performance in it's proper scale. For others it's imaging and soundstage - trying to re-create the live performance in it's original space. For some it's both.

This paper will deal with observations relating to the desire and ability of all audiophiles to re-create the original performance as close as possible on their playback systems. It will discuss imaging, soundstage and recording techniques as well as try to determine what is reasonable to expect and what is not.

Interestingly enough we all admit to wanting to create the illusion of live music in our living rooms, but each go about it in different, usually unsuccessful ways. A reason for the lack of consistency in technique could be a lack of understanding of what it actually is that you're trying to re-create. Obviously before you can make any serious moves in the progress of your playback system or it's setup, you have to know exactly what it is you are trying to accomplish.

Some of the first things to consider are the types of performances you wish to re-create. Live Rock Concerts, Small Jazz Clubs, Live Classical works or perhaps small instrumentals?

In order to increase your chances of success, you might want to choose one that has some chance of being recreated in your listening space. Naturally if you have a small listening room in your home, it's going to be difficult to actually recreate the live pressures, and space of a large rock concert or classical symphony.

This is very much a room size issue and a listening style decision. For example, given most peoples idea of a proper listening room setup, it would be rather difficult to re-create a full orchestra in your 16 x 24 listening room. Even more difficult would be a 12 x 15 room.

The goal is to hear the recording and nothing else. To do that you must make pain staking efforts to NOT hear your room, or artifacts generated by your speakers and electronics. Well right there you're screwed because your listening room is responsible for altering 60% of what you hear from your playback system. Low level ambiance cues and harmonic trails that give a recording it's sense of space will be drowned out by the tones and resonance's of your listening room.

Since your room is going to be the biggest key to your success or failure, you want your room to be generally as large as possible, and of course acoustically compatible with your intended setup. If you were to dedicate your room to your playback system and one listening chair and got very serious about acoustic treatments that started with the basic architecture of the room you could get fairly close to the grand illusion some of the time.

But, if not, you have to make some choices as to how you set up your listening gear. Most of us would like to have it sound like the musicians are actually there in the listening room between and behind the speakers, while we sit 8 or 12 feet back (a psychologically safe distance). This only works in rooms that are around 500 square feet or larger unless you don't care about scale. It is possible to create a miniature scale illusion of the performance that is very pleasing but it will never give the illusion of being real because the scale is off.

In smaller or normal size rooms, you have two ways you can setup your speakers and listening chair for the grand illusion. One works and one doesn't. The common way, where you try to bring the performance into your room can be replaced with a near field setup that largely reduces the negative effects of your listening room acoustics on the recording. In a near field arrangement, you are transported to the performance and the size of your room has little bearing on the illusion. In this setup, any kind of recording can be properly rendered.

The Grand Illusion is what every audiophile and high end manufacture chases. Few actually master one, as they seem fragile and hard to maintain with consistency. That doesn't keep us from trying though, and it is the intent of this paper to help people understand what it is that they're chasing. Most audiophiles chase their tails because they've never actually considered what is possible and what is not, let alone how to correctly judge results.

Many speaker manufactures have concluded that the evils of your listening room acoustics will always be a reality and try to use your room acoustics to enhance the sound. Obviously the perfect way to listen would be to hear only the direct sound from your speakers, not the reflected sounds of your room. Headphones being the closest thing I can think of to that ideal. However, the delivery system of headphones is incapable of creating the illusion of depth from a sound stage that exists in space in front of you (vs. inside your head).

It stands to reason then that if you're listening to your speakers, the louder you play them, the louder the reflections and other nasty acoustic issues of your room become. In contrast, if you were to listen to your system set up in a near field arrangement late at night when the noise floor is lowest, you would be about 100 times more likely to witness the grand illusion.

Some are wondering what specifically I mean by near field so let me site an example. In a 13 x 15 dedicated listening room, you would place your speakers around 6 to 7 feet apart and your listening chair about 3 to 4 feet back from the speaker plane. The speakers would be toed-in to intersect at an imaginary point just in front of your nose, or just behind your head. When you sat on the very edge of your chair and reached forward you would be just about able to touch your speakers. There would be about 4 to 5 feet between your front wall and the speakers.

Speakers that use your room, or more specifically the walls in combination with direct radiation often are more successful in getting close the grand illusion than conventional designs. Bipolar and or panel speakers being a good example of this, create their own illusion of space and size using your room dimensions to dictate the accuracy of the results. Any sound you hear from your room is not sound true to the recording because it becomes imbedded with new spatial and timing cues. If you are the type who feels secure only when perfect accuracy is achieved, these types of speakers would insure that it never happens. But, as you will someday discover, the grand illusion has little to do with perfect accuracy, or the specs of your playback gear.

Creating the perfect illusion requires much more than the right speakers and room setup, it is in fact a fragile balance of your entire audio chain and always in the hands of the weakest link. This can be cables, amplifiers, preamps, sources, speakers, room, listening style, dirty power lines, ambient noise levels, or the most common of all, the interaction of all the gear in your audio chain with each other, better known as synergy.

Identifying the weak link is usually all but impossible unless you take suspects one at a time and do careful documented replacements of each and analyze the changes.

Assuming that you have a playback system and room that stands a chance at creating the illusion, you need to start thinking about a way to measure the results so you can continue to tweak things in the right direction. This is where many audiophiles who've been fortunate enough to have the money to buy great gear get lost. They get lost because they have no real reference.

A simple grand illusion would be to set a stool between and behind your speakers and record a singer or musician playing an acoustic instrument in your room. The recording would be done using a stereo pair of good ribbon microphones and recorded live onto two tracks. The recording would then be played back using the two track machine as your source. This simple recording would carry the acoustic signature of your room, so when it is played back IN your room it pending the quality of the gear involved could become the grand illusion.

With that ideal as an example, you need to have a long hard think about what you're listening to. Recorded CD's and LP's from major or popular artists are an illusion in themselves in that you'll never know if what you're hearing is accurate or not.

This is a large contributor to the fact that audio playback systems are judged subjectively. If playback systems were all setup and optimized to transport you to the performance and we all had the same live two track recording to listen to, and we all had been to the actual performance at the exact time it was recorded and all sat just below the microphones it would be about a 1000 times easier to judge the quality and accuracy of high fidelity playback systems. It would certainly be nice from the perspective of reviewers in magazines who's information is usually all but worthless in letting us know what that same gear will sound like in our homes.

When the first high fidelity playback system was married with the concept of stereophonic recordings it was demonstrated and measured in an auditorium where live classical works were performed for a live audience. The recording technology of the day was inferior so they wired the recording to another auditorium in real time. The second auditorium was outfitted with speakers on the stage arranged in a stereo array and played to a live audience. That was the first Grand Illusion, and was very enthusiastically received.

Since it is neither practical or possible for most to create live recordings in their own listening rooms, or listen to recordings that they themselves have made in world class studios it is all but impossible to accurately rate the accuracy of your playback system. That is not to say it is impossible to create a good illusion, just difficult to know if that illusion is fictitious or based solely on the merits of the recording.

Since most of us have only CD's or LP's to listen to, and most of us have not had the luxury of attending multiple live performances, the better we understand exactly what we're listening to on a recording the better chance we'll have of tweaking our systems to achieve a consistent and accurate illusion on all good recordings.

If you're in a small untreated listening room, sitting far away from your speakers you have no chance of creating the illusion regardless of the quality of your gear, so don't waist any more money trying to get there. Learn to listen in the described near field arrangement and do it on gear that is conducive to lucid soundstages. Don't expect to chase the grand illusion in a family room with all the associated comforts of home, or in a home theater/stereo system. The grand illusion is the summit for only serious climbers who are willing to dedicate a room to the task.

In part II of this paper we will discuss recordings and how they effect imaging and soundstage accuracy, and or how they effect the illusion of imaging and soundstage accuracy. Once you discover what a recording is, you can learn to hear what's probably right, and probably not right with your playback system on most decent quality recordings.

 

 

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