Overseas Shipping

by Bart on October 3, 2011

Here at Experimental Musical Instruments, we use the United States Postal Service for shipping to our customers. There are several reasons for this choice. One is that for shipping within the United States the U.S. Postal Service has consistently proven to be admirably timely and dependable for us (contrary to the complaints of anti-government crusaders). Another is that its services are quite modest in cost, and we’re happy to pass these savings on to customers.

The story for overseas shipping is more complex.  The cost savings in shipping through the Post Office’s Priority Mail International service, as compared to private international shippers like FEDEX or DHL, are huge.  We’re able to ship a good percentage of our orders abroad for US$13.95 (that’s where our $14 shipping fee on overseas orders comes from), while shipping the same package with one of the private shippers would cost many times that at least. The problem is that the best that the US Postal Service can do is to deliver the packages to the recipient country’s customs service in a timely fashion.  That done, it’s anybody’s guess how long the package will take to clear customs. Some packages, we’ve found, arrive at the customer’s door halfway around the world in a few days; others take as much as a month.  The situation isn’t much different even when we use the Post Office’s more expensive Express Mail service.

And another drawback: more and more of our customers these days are requesting tracking numbers, which Priority Mail does not offer.  While Express Mail service does provide a tracking number, that number doesn’t do much to speed the package through foreign customs or provide detailed information once the package is in the hands of the recipient country’s postal service.

There is yet another level of service offered by the United States Postal Service in partnership with FEDEX. It’s called Global Express Guaranteed (GXG).  With this service, the US Postal Service delivers the package to FEDEX overseas, and FEDEX shepherds it through customs and does the actual delivery.  It’s a lot more expensive than our current $14, but still less than working directly with FEDEX or DHL would be.  The claim is that it offers good tracking as well as dependably timely delivery.  We are currently looking into this the strength of those claims. If it looks promising, we’ll consider offering overseas customers a choice of services – our usual, wonderfully affordable $14 overseas rate, with no tracking and the understood risk of delays, or a more costly but more dependable GXG rate. 

In truth, offering this choice will be quite a hassle for us. Revamping our website to offer a choice of shipping options will be a lot of expense for a business as small as we are, and managing multiple systems for order fulfillment will be a chore. But if difficulties continue with overseas delivery, the hassle will be justified.

In the meantime, our very affordable overseas shipping rates remain in effect, and we greatly appreciate our overseas customers’ patience in those occasional cases where delivery is slow.

This may be useful information: the countries where delivery tends to be slowest are Italy, Belgium and (surprisingly, for a neighbor) Canada. Deliveries to small developing countries also are sometimes unpredictable.

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Back Again with Faster Download Times

by Bart on August 16, 2011

Over the last month or two this website had been getting increasingly slow to load and appear on your computer screen.  The problem steadily worsened, to the point where, during times of high traffic, it actually became difficult to access the site at all.  The problem was with our server, which had was doing a very poor job of managing traffic flow.  We’ve now upgraded and switched to a new  server, and you’ll find that the site now loads with gratifying speed.   Apologies to all for this frustrating problem, and thanks to our programmer, Frank Vera at http://verainteractive.com/ for speedy and competent fixes.

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Chip Bag Sound

by Bart on March 13, 2011

A few months ago I chanced upon news blurb posted somewhere concerning potato chip packaging. According to the article, the makers of the Sun Chips brand of potato chips had started selling their chips in an eco-friendly bag made from plant-based materials. Rather than lingering as litter in landfills for generations to come, the bags are designed to decompose into compost after a suitable amount of time. But high hopes for this excellent innovation were dimmed when complaints started coming in that the bags are way too loud! It seems they produce hugely distractingly irritating scrunching and crackling noises with routine handling. As a result, they are now being phased out.

Naturally, I was eager to hear what these bags sound like.  So I went to the grocery store and found my way to the potato chips aisle. There I found several varieties of Sun Chips which had already been changed back to traditional packaging, plus one flavor still in the eco-friendly, crackle-prone bags. I bought ‘em, brought ‘em home, and started scrunching and crackling.

And it’s true – these bags really are quite loud, and the sound has a crispness to it that’s more satisfying, to my ear than other types of scrunchable plastic packaging. Definite possibilities here for music and sound-work! But it remains to be seen how long the compostable bags will be available – perhaps they’ll be off the shelves entirely by the time you read this – and also how long an existing bag will retain its sound qualities before decomposition sets in.

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Acoustic Amplifiers

by Bart on December 28, 2010

 The term “acoustic amplifier” is sometimes used to describe sound amplification systems that don’t use electricity. I recently had some communication from Monte Thrasher on this subject (Monte is sound-adventurer/thinker/researcher, as well as visual artist, in the Los Angeles area). It got me thinking again about this rather fascinating topic. 

In the late19th and early 20th century heyday of pre-electronic inventiveness, several people came up with purely mechanical schemes for amplifying sound. Some of them worked in a manner analogous to electronic amplification systems that came later. In electronic tube amplifiers, a tiny electronic signal gives rise to a much stronger version of itself by means of a sort of gating system: through the use of vacuum tubes acting as gatekeepers, the relatively weak voltage fluctuations of the original signal are used to modulate the strength of a much larger voltage from an external source, thus recreating the pattern of the signal on a larger scale. A similar gating idea used in pre-electronic acoustic amplifying devices.

In the early devices, the external power source was compressed air. Imagine an air-gating system that can shut on and off the flow from a compressed air tank … or from a blower of some sort, or even human lungs.  If you can get the gate to open and shut at a frequency in the hearing range, then the resulting puffs of air will create an audible tone. If you can get it to open and shut in a pattern analogous to the wave form of a given sound, you’ll get a replication of that sound. In this way, the relatively small force required to operate the gate can be used to modulate the much greater power of a strong compressed air source, creating a stronger sound. Very clever!

Sound waves in the air typically have small amplitudes (the back-and-forth motion is small); and the force they exert is weak and diffuse. The same is often true (though a bit less so) for the vibrating bodies that generate those sound waves. So if you are to use these sources to operate an air gate, you’ll need to create a gating system that requires very little power to operate.

Let’s think about this: how can you create an air-gating system that requires the smallest amount of movement to let through a substantial puff of air? If you think in terms analogous to a garden gate or doorway, or even a faucet turning on and off, you’re not going to do very well – too much motion required to create an opening of any size. Somebody thinking about this in the early days came up with the idea of a dual-plate grid system. Imagine two flat, rectangular plates, perforated with identical grids of small rectangular holes. When the two plates are placed squarely one in front of the other, the holes line up and air is free to pass through.  When one plate is slid a bit to the side, the holes no longer line up, blocking the flow-through. If the holes are quite small, the amount of sideways motion required for blockage is small; yet if the number of holes is large, the amount of air allowed through when they line up can be substantial. With this approach a clever fabricator can create a gating system that allows a powerful air flow, yet requires relatively little force or amplitude of movement. And notice that this is not a simple on-off system; it’s capable of gradual closure and closure to varying degrees. This suggests that, in theory at least, it should be capable of reproducing the wave forms of the original signal with some subtlety.

Of course it helps to capture the strongest possible signal to begin with, since a stronger signal is more likely to have the power to operate the gate effectively.  This leads us to a question which perhaps should have been our starting point: what sound sources were these acoustic amplifiers being used to amplify … and, for that matter, what could they be used to for today?

For starters, acoustic amplifiers of this sort were workable with the phonograph disk sound recording systems of the day.  In these systems, most readers will know, the sound waves of the sound-to-be-recorded were captured by a diaphragm, whose motion in turn was transmitted to a stylus. The stylus was used to carve a wavering groove in the surface of a rotating disk or cylinder made of soft material, later hardened. (Notice that all of these pre-electronic systems faced the same problem: how to get the most, mechanically, out of sound waves that carry a minimum of mechanical energy.) For playback the process was reversed, with a stylus tracking in the groove and transmitting its motion to a diaphragm positioned at the base of a flared horn for projection into the air.  For a much stronger sound in playback, a similar stylus-based playback system could be used to operate the air-gate of an acoustic amplification system.

A system similar to first stage of the phonograph recording system could also be used for live amplification in real time. For this, the soundwaves of the sound-to-be-amplified were captured by a diaphragm, and the motion of the diaphragm used directly to operate the air-gate of the amplification system. 

Acoustic amplifiers were also used with musical instruments. I find this interesting to think about: long before anyone dreamed of making an electric guitar pickup, there were people anticipating the idea non-electrically. Many of these instrument amplification efforts, it appears from surviving information, centered on cellos and perhaps basses. These instruments are suitable candidates because their oscillating systems – the way the string drives the bridge and soundboard – are robust and forceful. The mechanism for transmitting motion to the air gate was attached directly to the cello or bass bridge.

So what did these acoustic amplifiers sound like?  Given a strong enough air source, according to contemporary reports, they could indeed be very loud; no one seems to dispute that. The sound, as reproduced, was accurate enough to be recognizable – e.g., speech amplified this way could be understood – but it appears that the frequency response was limited: great in the midrange, not so good toward the extremes.

You need links! Here’s a good article: http://www.aqpl43.dsl.pipex.com/MUSEUM/COMMS/auxetophone/auxetoph.htm

And to actually hear a phonograph with compressed-air amplification: http://www.youtube.com/watch?v=J7SV65DFNy8

 It’s tempting to think about the possibilities here for new musical instrument design.  I’ve long had an interest in instruments with forced oscillation. By that I mean instruments in which the vibration happens not because of the natural flexing back and forth of a string, membrane, bar or enclosed body of air, but because it is forced mechanically in some way. This could apply here: it’s not hard to imagine a gridded air-gate device with some sort of audio-frequency mechanical driver moving one of the grid plates back and forth.  This idea happens to be very similar to traditional sirens, which you can read about here:  http://windworld.com/features/gallery/musical-siren-built-by-bart-hopkin/. For such an instrument, in the tradition of wind instruments everywhere, human lungs might be a sufficient source of air flow.

Whatever the approach, there’s some fun to be had here with musical applications. Maybe some day I’ll try my hand at making something along these lines.  If you get to it before it do, be sure to let me know how it goes.

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A couple of years ago Experimental Musical Instruments put out a book called Making Marimbas and Other Bar Percussion Instruments. My co-authors and I tried to cover as much of the world of marimba making as we could, including the various systems for mounting percussion bars. But it has since occurred to me that there is one bar-mounting system we neglected. I’ve seen a few makers use it; it’s a very easy one to implement, and it’s quite effective in its way. I say “in its way” because this system produces a distinctive sound, suitable for some applications and not others. 

The system consists simply of laying the bars out flat on a surface of soft eggshell foam. That’s the kind of foam rubber that has a pattern of peaks and valleys on one side, reminiscent of an egg carton. In other circumstances it’s used for mattresses and sometimes as a wall covering for sound damping. With a suitably sized rectangle of this foam spread eggshell side up on the floor or on a table top, you can lay the bars out in whatever arrangement you wish. With vigorous playing the bars may dance around a bit on the foam, causing them to eventually get out of position, but the problem turns out to be minor. They don’t move all that much and they’re easily repositioned if they do.  

Naturally, the bars are heavily damped in this arrangement – but not hopelessly so, as the crests of the foam hold the bars in a rather yielding, non-rigid sort of way. In fact, the tone of a bar on eggshell foam can be quite appealing. It has relatively little sustain, giving it a rhythmic, percussive quality. The overtones tend to damp out more rapidly than the fundamental, so the overtones aren’t as dominant as they might otherwise be. 

The system has most often been used with metal bars, but it’s worth trying with other materials, and in a variety of sizes. It’s particularly practical for assemblages of found objects, since you can try resting just about anything on the foam to see how it sounds.  In fact, foam mounting can be effective not only for bars, but for un-bar-like objects as well (think of pot lids, bells, and other oddly shaped objects from the scrap yard or hardware store).

In its typical usage, the arrangement isn’t set up in a permanent way. More often, someone shows up with a rolled up piece of foam and a box of bars or other sound objects, and sets them up on the spot. It only takes a minute or two.

 

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A few days ago on this news page I posted a two-part article called Overtone Tuning for Lamellaphones. I later decided that the article belongs not here on the news page, but rather  in EMI’s Tools and Resources pages. I also got out the old editor’s pen and made a few improvements in the article as originally written. You’ll now find the improved version  there, along with a lot of other useful articles, resource lists and software tools for instrument makers. 

This particular topic — how to tune the overtones to get a clearer tone in mbiras, kalimbas, sansas and non-traditional home-mades in the lamellaphone family — is a valuable one, and under-rated in importance (I’ve always thought), so I’m hope a lot of people will take note and have a look at the article.

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World Listening Day

by Bart on July 5, 2010

Sunday, July 18 is  World Listening Day. 

World Listening Day is a project of the World Listening Project, in partnership with the Midwest in Society for Acoustic Ecology. The purpose is to celebrate the practice of listening as it relates to the world around us, as well as bring forward issues relating to the acoustic environment.  Many people will participate in the day in private or individual ways (practicing a little extra conscious listening); many others with take part in specific activitiesThe thinking behind World Listening Day has its roots in the work of R. Murray Schafer, one of the founders of the acoustic ecology movement and a truly inspring thinker.   

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Floating Soundboards

by Bart on April 30, 2010

Lately I’ve been experimenting with string instrument soundboards that are not attached the sides of the sound box all around the periphery, but are attached only at the ends.   The illustration below will give you the picture, using a rectangular sound as an easily visualized example.  I know I’m not the only person to explore this sort of design, but I can’t recall where I’ve seen it before. 

The idea is to allow the soundboard freer vibration than would be the case if it were rigidly attached all around.  This is in keeping with something I’ve long been interested in: string instrument soundboards that are unusually light and/or flexible, so that the strings can easily activate them and drive them to large amplitudes. Because the strings deliver their energy to such soundboards rapidly, the resulting sound tends to have relatively short sustain and the tone may be kind of punchy. For lower notes there may be a bit of a thump in the attack.  The tone tends to be strong in the fundamental, de-emphasizing higher overtones. In theory such soundboards should be louder than more rigid, longer-sustaining soundboards. I haven’t always found that to be the case, but greater volume isn’t the main reason I’m interested.  The main reason I’m interested is, I like the punchy, saturated tone.

A very weak soundboard is likely to distort or collapse under the pressure of the strings.  So what I’ve been doing with these semi-detached soundboards is placing supports of dense sponge rubber under the sides of the board at selected points. (This is the same dense sponge that we sell here at EMI.  It’s great stuff.)  This prevents the soundboard from collapsing under the pressure of the strings, yet it still allows high degree of flexibility. It also adds damping to the board. The damping is probably a good thing, evening out the response and reducing the likelihood of wolf tones (wolf tones = disproportionately loud notes resulting from pronounced resonances at certain frequencies). 

Soundbox with floating soundboard

Soundbox with floating soundboard

So far I’ve built three box zithers this way and a guitar-like instrument, as you can see in the photos. The soundboards are redwood, about a tenth of an inch thick.  They have no strutting or ribs underneath, except for a little cross-grain strip for added strength under the bridge in the guitar. On all but one of the zithers I added magnetic pickups, custom made to accommodate the required pickup width. (I tested piezo pickups as well as little on-board microphones with these instruments, but the magnetic pickups sounded best to me.)

So how do they sound?  You can hear them in the samples below.  I totally love the sound of the zithers, both unamplified and amplified. They really do, to my ear, have the saturated, punchy sort of tone I was after.

The sounding results with the guitar suggest a rather different story. Unamplified, the guitar sounds pretty blah. The mechanics by which the strings drive the soundboard are quite different in zithers and guitars, and what worked so nicely for the zithers is noticeably less pleasing in the guitar. But when it’s played through the pickup, I like the tone more than that of a typical electrified guitar. To my ear it sounds a lot less electric and more acoustic even than an acoustic guitar with a soundhole pickup.  The main reason is the way the highly compliant soundboard interacts with the strings and colors the string sound that the pickup hears. In addition, a couple of other design features contribute to a more “acoustic” tone, namely: 1) I’ve strung the guitar with an unusual set of soft steel strings (more about this in another posting sometime in the future).  2) The pickup is positioned as far from the bridge as possible – adjacent to the 16th fret, which is much farther from the bridge than is typical. This contributes to a warmer tone.  (If you look back at the zithers, you’ll notice that the pickups are right at mid-string, for a similarly warm sound.) 

(About the use of the word “floating:”  duclimer makers sometimes use the phrase “floating soundboard” to refer to a soundboard which isn’t affixed to the sides of the box, but held there only by string pressure.  I’m taking the floating idea a step further, with soundboards that don’t even touch the sides all around.  The term “floating bridge” is occasionally used for guitar bridges that stand on two feet rather than lying flat against the soundboard; one again I’m taking things a step further with a bridge that doesn’t touch the soundboard at all.)


A Pair of Floating Zithers. These two box zithers are made as a pair to be played together by either one or two players. The ranges complement each other, providing three and a half octaves between them.  With seven strings per octave, the tuning is diatonic, but sharping levers on the left allow for quick and convenient retuning to different scales.  The weighted steel arm on the larger zither adds a vibrato to the tone. Give the weight a little push and it will bob up and down because of the way it's anchored in the strings. It continues to bob as you play, wavering the tension on the strings to create the vibrato. The weighted arm doesn't work as will on the smaller zither, so it has an unweighted arm that the player can flex to provide the vibrato manually.

A Pair of Floating Zithers. These two box zithers are made as a pair to be played together by one or two players. The ranges complement each other, providing three and a half octaves between them. With seven strings per octave, the tuning is diatonic, but sharping levers on the left allow for quick and convenient retuning to different scales. The weighted steel arm on the larger zither adds a vibrato to the tone. Give the weight a little push and it will bob up and down because of the way it's anchored in the strings. It continues to bob as you play, wavering the tension on the strings to create the vibrato. The weighted arm doesn't work as will on the smaller zither, so it has an unweighted arm that the player can flex to provide the vibrato manually.


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floating-guit72

Floating Guitar. This guitar has a rather poor tone unamplified, but the amplified tone is, to my ear, natural sounding and appealing. For more details see the description in the main text above.


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Over-Under Zither. This zither is almost identical to the smaller of the zither pair above, but it has a mid-string bridge in the form of a weighted bar. The string segments on one side of the center bridge are twice as long as on the other side, so the notes on either side are an octave apart. The weighted center bridge isn't anchored to anything but the strings themselves. It's free to wobble and bob, creating  pitch-shifting and tremolo effects in the strings.Because of the unfixed bridge, the tone is a little thin and plinky, and the tuning is pretty seriously unstable, but the peculiar wobbly effects appeal to my ear nonetheless.

Over-Under Zither. This zither is almost identical to the smaller of the zither pair above, but it has a mid-string bridge in the form of a weighted bar. The string segments on one side of the center bridge are twice as long as on the other side, so the notes on either side are an octave apart. The weighted center bridge isn't anchored to anything but the strings themselves. It's free to wobble and bob, creating pitch-shifting and tremolo effects in the strings.Because of the unfixed bridge, the tone is a little thin and plinky, and the tuning is pretty seriously unstable, but the peculiar wobbly effects appeal to my ear nonetheless.

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 IMPORTANT NOTE: The following post has been superceded with better information in a subsequent posting.  Get the updated version here.

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I’ve been making an effort lately to get useful information on piezo films into these pages for the benefit of anyone who may want to use them.  Here’s one more posting along those lines. The question I get most frequently from customers regarding the piezo film is, is it OK to trim a piezo film pickup to a smaller size?

The quick and safe answer to this question is “Beware: cutting a piezo film pickup may ruin it.” But a more complete answer is, sometimes it’s OK to cut the film, sometimes it’s not; it depends on how you cut it. Read on for details.

The piezo film pickups we sell are made up of a very thin film of piezoelectric material protected by a layer of clear plastic lamination on both sides. It’s hard to see this unless you look quite carefully, but the piezo under the plastic is actually a double layer, in the form of a single piece of very thin piezo film folded back on itself. The two terminals for the wire connections, located alongside one another at one end of the pickup, are actually at opposite ends of this underlying piezo film, brought next to each other by the folding. (Think of a towel folded in half: the folding brings the opposite ends together.) Now imagine that you decide to shorten the pickup by snipping off the end. By cutting off the point where it folds, you are (unknowingly) cutting the piezo film into two separate sections; it’s then no longer a single sheet. The electrical continuity between the two terminals is broken, and the pickup will not function

So that’s the big negative: you can’t shorten the pickup by snipping off the end; that will destroy the pickup

However, you can trim in other ways, and as long as you do so without compromising the electrical continuity, the pickup will still function. First of all, you can always trim off the clear plastic borders; there’ll be no ill effects because there’s no piezo material in those clear portions anyway. Second of all, if you want a narrower pickup, you can usually get away with trimming the sides, as long as you make sure that the folded end isn’t snipped off

Keep in mind, too, that the piezo film pickups are quite sturdy. If it’s necessary to give the pickup a sharp bend or something of a fold to make it fit in the intended application, that’s ok.

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A couple of months ago I did a posting titled “Wiring Multiple Piezos Together.”  That post has information on how many piezos you can run to a single output before you start to lose signal strength and fidelity, followed by suggestions on how to wire such hook-ups.  The other day it occured to me that I didn’t address one important aspect of the topic.     

What I neglected to discuss was phase cancellation.  In multi-piezo installations where the piezos are on  independent sounding bodies — say, different bars on a marimba – then phase relationships aren’t an issue. But when you have two or more piezos on the same vibrating body — as, for instance, on a soundboard – it’s likely that the signals coming from the piezos will not be perfectly in phase. Then there will be some cancellation when you join them, resulting in a loss of signal strength. Depending on circumstances, the cancellation could be negligible or serious.  

The rest of this post discusses this issue.  To simplify the discussion, I’ll use the case of two piezos mounted on a soundboard as an example.   

There are two ways cancellation can come about when two piezos are mounted on a soundboard: 

1) Phase reversal.  Something about the way the piezos are positioned or wired could result in the piezos capturing opposite phases of the soundboard’s vibration.   This could happen for any of the following reasons: a) one piezo is positioned on the inside of the soundboard; the other on the outside.   b) One piezo is reverse-wired relative to the other. c) One piezo is attached upside-down relative to the other – that is, the two piezos are  mounted with opposite sides against the soundboard.  In any of  these cases, if the piezos are located reasonably close to each other, then their two signals will be close to 180 degrees out of phase, and serious cancellation will occur.

2) Phase offsetting. If the two piezos are somewhat far apart on the soundboard, then each will, at any given instant, be picking up different phases of the waves as they travel through the soundboard.  The phase difference will most likely be much less than 180 degrees, so cancellation will not be severe.  More interestingly, different partials within the sound (with their different wavelengths in the soundboard) will have different and variable phase relationships at the pickup locations.  Keep in mind that this kind of effect occurs naturally in the acoustic sound coming off the soundboard anyway; it’s part of the sound our ears are used to hearing and not necessarily a bad thing.  In spite of being less efficient, with luck it will contribute to a sound that is warmer and more natural than what a single pickup would capture. 

Practically speaking, what can you do to manage these phasing questions in multiple piezo hookups?

First, regarding the 180 degree cancellation described in #1 above: This is normally an undesireable situation and it’s easily remedied by reconfiguring things so that the two piezos are in phase.  Do this by reversing the phase on one of the pickups. One easy way to do that is simply to turn one of the piezos over so that its other side presses on the soundboard.  Another way to invert the phase of the signal from one of the pickups is to reverse the wires coming from the pickup – take the wire that had been the hot lead and wire it to ground, and take the former ground lead and wire it to the hot terminal.  On the other hand, if you’re interested in a weird hollowed-out sort of sound and are willing to accept a serious loss in signal strength, you might enjoy exploring the possibilities of a deliberately out-of-phase hook up.

Regarding the subtler phase interactions described in #2 above:  In theory you could try to analyize oscillation patterns and their interactions as a way of determinining ideal soundboard locations for two or more piezo pickups. In practice this isn’t very realistic, given the almost infinite complexity of possible tones and all their harmonic and inharmonic partials in interaction. Instead, it’s usually worthwhile to spend a little time in trial-and-error mode, testing different locations for the piezos, including varied distances apart, in search of the most attractive sound. In addition, try reversing the phase relationship by inverting of one of the pickups. , Do this either by turning it upside-down or reversing the output wires as described in the previous paragraph.   

In most cases and for most musical tastes you’ll find that having two or more piezos on the same soundboard can yield a warmer and more satisfying sound than a single piezo would.  An exception is the case where you want a particularly bright and edgy tone with a sharp attack. That’s because the cancellation with multiple piezos happens most in the higher frequencies/shorter wavelenghts (as is the case in the natural acoustic sound as well).  A single piezo, being free of these high frequency cancellation effects, tends to sound brighter.  Also, multiple piezos do a better job of capturing the complexity, variablility and non-static nature of the natural sound. This makes for a softer attack,  and contributes to what the our musical ears hear as a warmer and more alive sort of sound. A single piezo, by contrast, will tend to have a slightly more “clinical” feel to its sound.   

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