31 Secrets

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Dear Music Lover, These 31 Secrets to Better Sound were gained from nearly thirty years of solid installation and live music recording experience. After hearing the results, clients and staff often asked, Why dont you write that stuff down? Frankly, I never thought it was any big deal. But as the years have gone by, theres still not much thats been said or written about some of these topics. Finally, the time seemed right to do it now that the next millenium is here! The following topics may sometimes be related to Avantgarde Hornspeakers, and sometimes not at all. When appropriate, the topics applicability to the Hornspeakers will be indicated with a symbol . Since some of what you are about to hear goes against common knowledge, I only ask two things: 1) Keep an open mind until youve heard the entire position and youve thought about it a bit. 2) If you disagree with one point, dont assume thatll happen with the rest. I guarantee that youll find some topics thatll have you nodding in agreement.

31 Secrets to Better Sound is divided into two general areas. The first is Optimizing Your Systems Performance, and the second is Thinking Outside the Box. I hope youll find most of what follows to be pretty good advice. In general, its applicable to almost every system, at most levels.



1) Why you should be sour on a wide Sweet Spot A wide sweet spot is almost like having your own harmonic distortion generator! Theres simply no way a serious listener should be satisfied to sit more than a foot away from the equal path length intersection (center point) of sound from a pair of loudspeakers. Inter-channel phase and timing information has just been badly compromised, destroying instrumental timbres. How is it that audiophiles will accept only phase and time-aligned loudspeakers and then expect to sit off the acoustic center-point, totally destroying the inter-channel phase/time information? Look at it this way First, since you probably know this stuff, please forgive the simplified averaged wavelengths, but for purposes of illustration, lets assume that a 1100 Hz tone (or harmonic) has a length of about 12 inches. Then 550 Hz is almost 2 feet in length (from the top of the sound-wave crest to the top of the next). And 2 kHz is almost 6 inches in length, 4 kHz is 3 inches, etc. Imagine that a female vocalist is recorded with her image centrally located in the stereo stage. If you sit two feet off center, that means that any fundamental notes and their harmonics from at least 500 Hz and above have been altered, some dramatically, some slightly. This is audible, and its depressingly measurable! Before we examine the disastrous effects, lets look at whats happened to cause the problem Wait a minute! What about imaging? Lets say that now youre about a foot closer to the left speaker than you are to the right one. Imagine a centrally recorded image that is reproduced at equal volume (amplitude) from both speakers in order to give the illusion of a precise center image. Without going too far into recording techniques, a panned mono center image (such as in a studio) will appear to have shifted left somewhat. While a center image recorded from a stereo pair of mics seems to stay put a little better. But these are phantom images 2

at best, lacking in the ultimate richness of tone and body. Heres why Its not the potential image wander thats troublesome. Its the harmonic distortion! (Technically, its not distortion, but the alteration of harmonic relationships.) The positive cycle (top of the wave crest) of a 1000 Hz overtone arrives at your ear from the (closer) left speaker before it does from the right one. Therell be an audibleand very measurable change at that frequency (or harmonic overtone). Should the distance be equivalent to a half-wavelength further (6 inches), then that particular overtone (harmonic) will arrive exactly out of phase. And you know how your stereo plays less bass when the speakers are out of phase? Well, the effect is exactly the same a reduction in level at that particular frequency. Why is this important? Youve heard of voiceprints. Thats where a recording of your voice can be used to positively identify you, no matter how hard you try to shift the sound of your voice. How does it work? The unique relationships of vocal overtones are different for each voice. For example, the first harmonic may be 87.3% of the fundamental, the second just 48.1%, the third 54.7%, etc. The exact relationship of these overtones (their relative strength, compared to the fundamental) is the identifying genetic code of your voice. Well it turns out that all instruments and voices have their own particular set of harmonic ratios. Thats how we know to differentiate two different instruments that are playing exactly the same notesay A (440 Hz). And thats how an original Guarneri will be chosen over a replicaits all in the tonewhich is actually the harmonicor overtone structure. So, if youre sitting where the path lengths are significantly unequal from the left and right speakers, you are absolutely guaranteed to hear wild shifts in the harmonics, meaning that an instrument or voice will not sound exactly as it should. This is not just some subjective acoustic theory. Its not only audible; its also measurable in your room at your listening seat! In fact, youve just altered your systems harmonic relationships. So why did you buy all that stuff

with vanishingly low distortion if youre going to introduce a far worse version by not sitting in the center point where the path lengths are equal? Incidentally, this is an incontrovertible law of physics that is part of the goodand the badof stereophony. It doesnt matter if your loudspeakers produce a smooth response off-axis. The varying wavelengths at a position off the acoustic center will always produce uneven response on centrally recorded images. Heres a simple test for you. Put on a Sheffield or other disc that contains pink noise in both channels (pink noise is best, because it contains equal energy per octave, just like music). If you can, put your preamp in mono. What you want is equal amplitude in each channel. Now, from the center position, slowly move your head to the left or right. That huge change in tonal balance is exactly what happens if you sit off axis. And because the wavelengths vary according to frequency, the varying time arrivals of harmonics also produce an unpredictable (well, it is predictable in that its never a good thing) cancellation effect. And a wide sweet spot isnt really so sweet Now that weve told it like it is, lets also admit to having wonderful experiences listening to music while others have occupied the best seat. If a system has dynamics, if its effortless, if it at least starts out being pretty accurate timbrally, then it can be quite listenable off-axis. Just remember that the phantom image produced off-axis is only an approximation. Sweet, it aint!


2) Fine tune your tonal balance with stereo separation and toe-in Most audiophiles know, thatby aiming a speaker a bit off-axis (perhaps to crossfire behind you a foot or two)they can take the edge off the sound, when compared to aiming the speakers directly at the primary listening seat. Aiming straight aheadfor some loudspeakersresults in the best overall frequency balance (generally when this is the case, the manufacturer or their dealers will make a point of advising you of this). Aiming more toward the listening position is commonly called toe-in.

But did you know that stereo separationoften a matter of a few inchescan make a difference in perceived warmth? Most audiophiles would suggest moving the speakers a bit further apart (to get closer to sidewalls for bass reinforcement) as a way of warming up the sound. But 30 years of experience contradicts this idea. Getting a bit closer to the sidewalls may add more bass (and more unpleasant reflections), but the overall sound often gets thinner. Actually, if your sound is a bit thin, and youd like a bit more fullness, mid-range body, or warmth, the best way is often to bring your speakers a few inches closer together. Ive encountered situations where only an inch or so apiece toward the center gave me the balance I was looking for. Of course, when you do this, it changes your toein slightly so as to aim more to the center, so if youve picked the angle of your speakers for toe-in, youll need to toe them out just slightly to accommodate for the move. And you may just find that you dont need the speakers as far off-axis as you thought when you originally settled on the toe-in. After doing this for hundreds (maybe thousands) of people, I was still baffled as to why this should be the case. About 18 years ago, after observing the effect with spaced omni microphones (where an inch or two difference in separation could yield a warmer or cooler sound), I at least developed a theory about whats happening. We perceive warm or cool sound to some extent by the amount of energy present in the lower mid-range/upper bass. Well, the wavelengths of these frequencies are fairly long, say 2-6 in length. If we bring our speakers a bit closer together, the reproduced sound couples ever so slightly better, slightly shifting the sonic temperature to warmer. Whether the theory is correct or not, you definitely can change the balance of your system with subtle changes in loudspeaker separation and toe-in.


3) Set up a grid to begin your speaker installation Since stereophony depends on precise time arrival from each channel to a centrally located listening position, as you move your speakers around in the 3

room, youll need a temporary floor grid