Have you seen the hockey-puck-size wooden discs that, scattered about your room, are supposed to tame spurious energies and make for better sound? Or, more recently, the little brass bowls that are supposed to do pretty much the same thing? As you might expect, neither of these things is anything like cheap, but the real question is: Do they work?
WAIT! STOP! Don’t tell me that you’ve heard them and that they DO work; I’d just tell you the same tired old stuff about “Placebo Effect”, and how we all have the wondrous innate ability to convince ourselves that we can “hear” pretty much anything at all that we have pre-conditioned ourselves to think we WANT to hear or ought to be able to.
Let me instead — like any good Troll — tell you why they can’t possibly work at all.
Think about this: What we have in any listening-room situation is some walls; some enclosed space; a stereo system; and (at least probably) some furniture arranged to provide a listener with a (hopefully well-positioned) place to sit and enjoy some music. When music is played, some air pumps (a pair of speakers) transfer energy (in the form of pressure waves) to the air in the captive space. Of this energy, some portion impinges directly on the ears of the listener; some bounces-around off the walls of the room and either eventually makes it to the ears of the listener or not; and some is absorbed by one thing or another and finally lost as heat.
To make things simpler, let’s consider only half of the picture: Half a room, with half the walls, half the enclosed space, etc. Also, just one speaker. To start our examination, let’s take a look at the energy in the room and how it gets there. Obviously it comes from the speaker, but how? What’s the speaker’s dispersion pattern? How much of the radiated energy will be (directly) radiated into what portion of the room?
Although at VERY low (sub-sonic) frequencies the radiation pattern of any speaker that could actually go that low would be essentially spherical, the radiated sound most real-world speakers will produce will vary with frequency, with the dispersion pattern getting narrower and narrower as the frequency increases and the wavelength of the sound gets smaller and smaller as compared to the size of the driver producing it. (Wavelengths at sea-level range from about 55 feet [16.75 meters] at 20Hz to only a little over 5/8ths of an inch [1.68 cm] at 20kHz.)
Because of this, for most frequencies that are ever likely to played on the hypothetical speaker in our hypothetical half-room, the dispersion pattern is going to be well less than spherical, so let’s, just for fun, say that it’s one-quarter spherical. Now let’s figure out how big that is and how much energy the speaker will be transferring per square inch so we can learn just exactly how much effect it’s possible for a “magic disc” or a “magic bowl” to have on the total sound energy in the room.
The formula for the area of a sphere is A=4(πr2). So, if the distance from the speaker to the disc or bowl is exactly 8 feet, the area of an entire sphere centered on the speaker and extending to the magic thingy would be calculated as follows: The radius is 8 feet. 8 feet squared= 64 square feet. We’re going to need square inches, so let’s re-state that 64 sq. ft. as 9216 square inches. (8ft X 12inches = 96 inches. 96inches X 96inches = 9216 square inches.) 9216 sq. in. X π = 28,952.893 sq. in. (let’s just call it 29,000 sq. in.) Finally, 29,000 sq. in. X 4 = 116,000 square inches, so 116,000 sq. in. is the total surface area of that 8ft. radius sphere. We’re only talking about one quarter of a sphere, though, so, dividing it by 4, we’re back to the original 29,000 square inch figure. What this means is that If the radiation pattern of the speaker has an area of 29,000 sq. in. at 8ft from the driver, and that’s where the magic disc or bowl is positioned, the amount of direct radiated energy that will impinge on the magic device, and which that device will therefore be able to work with in changing the sound of your system will be equal to 1/29,000 of the total energy put out by the speaker for each square inch of the device’s surface.
So now, let’s figure out how much total energy there is and exactly how many square inches of magic device there are. If the speaker has the fairly typical sensitivity of 92dB at one Watt at one meter, and if the listener likes his music pretty loud, there might actually be a whole Watt of energy going out to the speaker. Although no conventional speaker is more than a few percent efficient, let’s, just for now, say that it’s an impossible 100% efficient, and that, therefore, that entire Watt of energy is being radiated throughout the room. If the magic disc or bowl has a diameter of 4 inches and, consequently, a surface area of about 12.6 square inches, the absolute MOST energy that’s going to be available to it will therefore be 12.6/29,000ths of a Watt (0.000434 Watts) – a little over four TEN THOUSANDTHS of a Watt (=0.434 milliwatts or 0.0434% of the total energy in the room).
Now that it has this princely powerhouse of energy available to it, what’s the disc or bowl going to do with it? Well, there are only three possible things that it CAN do: It can reflect it; it can absorb it; or it can, by being excited to resonate at its fundamental resonant frequency, absorb the incoming energy and re-radiate it back into the room.
So that whatever happens will have the greatest effect, let’s assume that each of these possibilities will also be (another clear-cut violation of basic physics) 100% efficient.
If the energy is reflected, so what? Odds are that it would have been reflected anyway, even without “help”. About the only possible difference would be in the arrival time of the reflected energy. Assuming ALL of the reflected energy is reflected directly at your ear (impossible) and that the presence of the disc or bowl increases or shortens the path to your ear by a whole eleven feet (!), that time change (at sea level) will only be about one millisecond. Is it really going to strongly affect your listening experience if four one hundredths of one percent of the total sound energy in the room (0.0434%) hits your ear one thousandth of a second early or late?
If all of the energy impinging on the magic doodad is absorbed, you will have lost forever 0.0434% of the music energy you’ve paid good money to buy, produce, and hear. Do you gasp in horror? Do you call the Better Business Bureau? Do you even notice?
The one thing that can actually have some perceivable effect is absorption and re-radiation at a different frequency. Even so, given the amount of energy available, which, at just 0.0434%, is already better than 40dB down from signal level, and that, of the total re-radiated energy, the amount to actually reach your ear could easily be down another 30dB below that, it seems hardly likely that a (take your pick: spurious, corrected, harmonizing) tone some possible 70dB below ambient signal level will either ruin, help, or in any other way alter your listening experience.
My job as Troll is finished for now, and I will go back to just being Roger Skoff, intrepid whatever. Be warned, though, there are plenty of other things out there that richly deserve to be debunked, and, if you liked this article and tell me about it, I may be back to do so. I may also do just the opposite and write to explain why some much maligned things are NOT voodoo or plots to scam the foolish.