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Below is an article by one of our members, Izzy Marrone (windowman99), that he wrote at a member of the NJ Audio Society. I thought it was very interesting and worthy of posting here for discussion and/or comments, with his permission of course.

Logic, Semantics, Conclusions and Philosophy
(For the sake of this discussion, I am assuming acoustical instrument recordings in a hall)

The last meeting got me to thinking about a few things in this hobby of ours. I’d like to share them with you. If you’re old enough, you may remember an early ad campaign for that favorite audiophile whipping-boy product, the Bose 901 speaker (version 1!). I remember a particular ad which tried to explain why this was such a “breakthrough” speaker. You see, Bose researcher’s found out that at a live concert, only 11% of the music that reaches your ears gets there in a direct path from the source. The overwhelming majority comes from various reflections in the hall. So, the ad stated, our speaker is better because it “mimics” the live hall in that only 11% of its’ sound is direct. Hence the phrase “direct/reflecting” speaker. (Remember the Bose has only 1 out of 9 drivers (exactly 11.1%) facing directly forward). You’ll see why this is relevant soon.

Fast forward to present day. A new audio company’s researchers discover that the best instrumental sources of live music have a quality called “harmonized resonance”. And further, this resonance is “perfectly balanced”. So, a “new approach to the treatment of resonance” is realized by treating it as “an essential element that adds warmth and fullness to the sound”.

What do BOTH companies (incorrectly) conclude? That the reproducing system (the home stereo) must have the same characteristics as the original event (the live concert). This seems to make sense at first glance. Shouldn’t we pursue as a reference in our home listening the original source? But the flaw lies in bad logic. The two events have VASTLY different physical characteristics. Production of sound is VERY different that reproduction. In fact, in many ways they are diametrically opposed.

In the first example, a home speaker’s dispersion should have nothing at all to do with the original event. Why not? Well, the very act of capturing sound changes the original event, and demands completely different rules upon playback. For example, the microphone(s) pickup patterns, the number of playback channels, and other variables can affect what the “optimum” dispersion should be. Speaker designers to this day do not agree on the ideal model (line or point source, for example). And the recording itself imprints a certain amount of reflection cues (the “89%” factor). Deliberately superimposing new, unpredictable ones via the speaker is not necessarily an advantage. Complicating this is the fact that a typical home system’s room is nowhere near as large as the original. The acoustical properties of small rooms are VERY DIFFERENT than large ones. (I am speaking primarily of reverberation decay times and reflections). You don’t really want it to (nor can it) have the same qualities (ie, 89% reflective) of the original. And even “bad” recordings with little or no “hall” sound will not be helped by this idea; if the original ambience is not recorded, your home room will never get it back. You’d be better off in these situations trying to electronically generate ambience. (Surround sound/DTS/Dolby, anyone?)

In the second example, since resonance is a given in all acoustic instruments, shouldn’t it be a desirable quality in reproduction? By all means NO!! (Here is where semantics may come into play). Engineers have a very specific definition of this word, and it DOES NOT have a pleasant, positive connotation. To explain: All physical things have a frequency of vibration at which they naturally want to move. This is called the “resonant frequency” (“RF” for short). A good example to think of is a guitar string. The RF changes depending on its’ tension as it is tuned. This is literally “tuning” the RF. When all the strings are tuned to each other, the guitar sounds “right” and pleasing. I believe some people think this tuning can be done to a stereo system by assorted “tweaking”.

But in a PLAYBACK situation, any part of the system that gets its’ RF excited will superimpose that RF over the desired signal. This is bad news. By definition it is a distortion of the signal. It cannot be correct to “tune” the RF here. Philosophically, you should want to KILL it! (Or at the very least damp the hell out of it). What competent designers try to do is make sure that a devices’ RF will never be excited by the signal passing through it, or that if it does, it will be well damped. Think of damping as putting a brick over the guitar string as you strum it. The string will try to vibrate, but be prevented by the weight of the brick. This is called mass-damping.

It gets more involved when complex things are assembled. Ideally, you’d want to design a complex thing (like a speaker) so that each parts’ resonant frequency, when assembled together, would “cancel” out, or at least not add up in the same place. To a designer at the reproduction end, resonance is BAD, something to be AVOIDED at all costs. On an absolute basis, the less resonance there is, the less distorted the signal will be. This is why I cringe at the idea of “tuning” the RF instead of trying to reduce or eliminate it. So why would this idea (of “desirable” resonances) be pursued? I think maybe this is an area where non-technical people may be guilty of misusing the language. Maybe they are describing a pleasing “warmth” or “fullness” to reproduced sound that they call “resonance tuning” when a system is pleasantly tweaked. But I’d call this “voicing” a system, which I’ll define as assembling a group of components together that complement one another in sound quality. It shouldn’t be called “resonance tuning”, unless you want to hear certain distortions, even if they’re pleasant. Then it would truly be a case of assembling a bunch of “desirable” resonances. As pleasant as this might be, it is nothing more than a collection of colorations, which ultimately limits the purity of the music. The difference is philosophical. I don’t want to tune multiple resonances in a system like a tuned guitar, but to minimize them. This maximizes resolution, which should go hand with hand with greater purity and more ultimate enjoyment of the music.

The difference in philosophies is crucial, because it acts as a guide to what types of things one would consider doing in a system to improve it. Someone trying to “tune” a RF might be more prone, let’s say, to put a preamp on a wooden base or foot, to hear the “desirable” resonance of it. I, on the other hand, would hardly consider it. First give me something heavy and (acoustically) dead to put on top, for mass-damping (like the brick mentioned above). Second, something underneath that would have some self-damping properties and very little resonance of its own, with the added ability to dissipate any resonances reaching it from above. (Hint: it’s not hard, is ridiculously cheap, and not an audio-related product). More sophisticated and costly products specifically made for audio are also available. An excellent article about such matters is on Stereophile’s website, titled “Bad Vibes!” by Shannon Dickson, November 1995.
 

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Logic, Semantics, Conclusions and Philosophy
Fast forward to present day. A new audio company’s researchers discover that the best instrumental sources of live music have a quality called “harmonized resonance”. And further, this resonance is “perfectly balanced”. So, a “new approach to the treatment of resonance” is realized by treating it as “an essential element that adds warmth and fullness to the sound”.
“Best instrumental sources” – what on earth does that mean? That some musical instruments are better than others? :huh: Sure, all instruments have “resonances,” but the only job of a sound system is to accurately reproduce what the instrument sounds like, plain and simple. For a sound system to try to mimic the resonances of musical instruments is plain silly.

What do BOTH companies (incorrectly) conclude? That the reproducing system (the home stereo) must have the same characteristics as the original event (the live concert). This seems to make sense at first glance. Shouldn’t we pursue as a reference in our home listening the original source? But the flaw lies in bad logic. The two events have VASTLY different physical characteristics. Production of sound is VERY different that reproduction. In fact, in many ways they are diametrically opposed.
An excellent response to those misguided people who think a sound system should “convey to the listener at home what is heard at a live performance,” to paraphrase one notable contributor on the Audyssey discussion thread.

That’s one reason I’m not big on acoustical treatments. An overly-dampened room as about as far from a performance venue as you can get.

What do BOTH companies (incorrectly) conclude?...
... In the first example, a home speaker’s dispersion should have nothing at all to do with the original event.
I wouldn’t necessarily say that Bose’s philosophy is totally incorrect. If a speaker designs-in reflection as a means to bring the live experience closer to home, what’s wrong with that? (That’s not to dismiss other problems with Bose designs, of course.) After all, other companies attempt to do something similar with bipolar speakers (Def Tech for instance). But I think I’d agree that doing it electronically with surround sound is a better method that gets much more realistic results.

Regards,
Wayne
 

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Logic can lead you anywhere, depending on the assumptions. All conclusions, opinions, and perspectives are based upon the prior knowledge, beliefs, and underlying assumptions that are often simply accepted without question. These are great examples of how a statement taken as fact, then applied out of the context can be used to generate the desired logical outcome. It IS logical IF you accept the premise, and the unstated assumptions along the way.

Many of the debates that we find in the A/V business revolve around opposing underlying assumptions, with far less testing of the limits of the viability than needed to come to the conclusions that many reach. Many of the problems that people have trouble solving also have their root in faulty assumptions. We see it all the time in service. We operate on limited information and make assumptions constantly. When we fail to test them, it can often create more headaches. The real problem is when someone is incapable of understanding that everything that he/she believes about a particular matter is based upon some set of assumptions.
 

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...But I think I’d agree that doing it electronically with surround sound is a better method that gets much more realistic results.


I'd say predictable, rather than realistic. I don't think that realism is very easy to define. Otherwise, I agree.
 

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Live auditoriums designed to have the audience hear what the orchestra wants you to hear are going to be tough if not impossible to reproduce in your home. Yamaha has be trying since the late 80's using surround and has done a fairly good job.

Your right Wayne when you say "but the only job of a sound system is to accurately reproduce what the instrument sounds like, plain and simple. For a sound system to try to mimic the resonances of musical instruments is plain silly".
You can not expect a pair of speakers to reproduce the sound of a live recording. It is much more likely to be able to hear what the sound engineer in a recording studio wants you to hear than a live recording because the studio is much more like a home listening environment unless of course you live in a huge open loft.

The Bose 901's were particularly cleaver and using reflection off of the wall behind the speaker did reproduce some interesting results. I do not think that Bose ever thought that taking a series of samples around an area and making a digital recording in 5.1 or even 7.1 channels was even going to be an in home reality.

I remember the first movie I saw that made a real impact with real surround sound "Top Gun" I immediately went home and started to plan out how I was going to get that sort of sound in my own room and thus went out and bought my first Prologic receiver made by Yamaha that had front effect speakers that mounted up high on the walls outside the main channels and had two rear channels a centre and sub channel. The Yamaha had many surround modes for music that Yamaha spent years testing and sampling many world famous theaters and stadiums that worked very well. Did they accurately reproduce them in my room? No. However it was a much better job than trying to get a single pair of speakers to reproduce the music as it sounded during the live event.

When I have done live recordings of our Christmas production at our church (a 40 piece orchestra along with 200 voice choir) not only placing mic's on the interments them selves I have always used several area mic's that capture the sounds that are naturally reflected around the auditorium. This has always given me a much more live sound. Playing the recording back on a two channel system looses almost all the dynamics of the original recording however even expanding it to 5.1 prologic made the recording come alive. I do not believe that there is a single two channel setup can do that.
 

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“Best instrumental sources” – what on earth does that mean? That some musical instruments are better than others? :huh: Sure, all instruments have “resonances,” but the only job of a sound system is to accurately reproduce what the instrument sounds like, plain and simple. For a sound system to try to mimic the resonances of musical instruments is plain silly.
In the context of the article, I took this to mean the venue. :ponder:
 

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As a hobbiest and not a physicist I have to go by observations and my gut feelings. I have always thought that the goal for the reproduction system is accuracy, at least as a baseline. It doesn't mean that a system can't have optional and configurable methods of modifying the source data in an attempt to recreate the live experience.

So speakers should be designed to reproduce the electrical signal as true as possible for a wide a variety of rooms. This is why I never bought into the 901 design. That was until I heard a friend's B&O system that used traditional speakers for mains and Bose for the "Ambio" channels. This was back in the 70s and sophisticated DSP for audio was yet to come. But the attempt by B&O to introduce ambience through a primative bucket brigade delay showed merit. Using Bose for the delay channels created an impressive effect for back in the day.
 

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Logic can lead you anywhere, depending on the assumptions. All conclusions, opinions, and perspectives are based upon the prior knowledge, beliefs, and underlying assumptions that are often simply accepted without question. These are great examples of how a statement taken as fact, then applied out of the context can be used to generate the desired logical outcome. It IS logical IF you accept the premise, and the unstated assumptions along the way.

Many of the debates that we find in the A/V business revolve around opposing underlying assumptions, with far less testing of the limits of the viability than needed to come to the conclusions that many reach. Many of the problems that people have trouble solving also have their root in faulty assumptions. We see it all the time in service. We operate on limited information and make assumptions constantly. When we fail to test them, it can often create more headaches. The real problem is when someone is incapable of understanding that everything that he/she believes about a particular matter is based upon some set of assumptions.
As someone who formerly ran an audio service center, I fully agree with your point.
 

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There is a saying in the service business about which part of the anatomy will be bitten by assumptions that I am sure you are familiar with. When I was a math teacher, I always emphasized the process of solving problems. It was almost always the case that the first step, understanding the problem, was where most students have problems with problem solving. Usually, the issue was with assumtions made that were inconsistent with what is actually the information given. It continues to amaze me how otehrwise intellegent people can get hung up on ideas that are based on assumptions that they don't ever test. It is one of the most basic concepts in logic, mathematics, and philosophy that many never really get. The best service techs definitely do...or at least keep learning the lesson repeatedly.:innocent:
 
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