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#46
01-12-2020, 08:27 PM
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All I'm doing is helping him design better guitars, without requiring customers of custom instruments to become rocket scientists before placing their order. 
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#47
01-13-2020, 10:19 AM
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Oscar made an observation in this thread that has me wondering. He refers to an "epicenter of vibration." I think this is something different than the mathematics of scale and intonation. And I'm not sure if there is an epicenter.
I've made a number of guitars and experimented with the placement of pickups. Using a suction cup pickup I found that every part of the guitar vibrates and transmits sound. Some positions made louder sound than others, some positions were more treble while others were more bass. It seems to me that the epicenter would depend on the sound a player preferred. I can imaging a guitar with multiple epicenters, more than the traditional one or two accepted as centers. Ten pickups distributed throughout the guitar would produce quite a variety of sound, any one of which could be the focus, the epicenter of a particular vibration and sound. Just wondering.................
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#48
01-13-2020, 08:20 PM
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In general, you are correct. Epicenter of vibration is different from the mathematics of scale. However, when the bridge location is shifted from its original design to accommodate a longer scale, these two facets of guitar design become inseparably linked. For simplicity, let's imagine the lower bout of a guitar as an elliptical drum head. The physical center of this drum head is the point of maximum excursion, or the "epicenter of vibration." It has the least resistance to movement, and is the most efficient location for converting the energy of a strike into the vibration of tone. It's so efficient, however, that the tone is dominated by the longer wavelength fundamental frequency with very little energy available for exciting the shorter wavelength overtones. As we move from the center towards the rim, excursion becomes limited. If we strike the drum with the same amount of force, less of that energy goes into the fundamental, and more of it goes into the shorter overtones that thrive in spaces where excursion is limited. The rim itself is a zero excursion node. It's primary function is to reflect energy back into the drum head in order to produce resonance. When struck directly on the rim, the tone produced is mainly caused by the body of the drum ringing, not the head vibrating. Whatever head vibration is created, it's entirely made up of overtones with no energy transferred to the fundamental frequency. This is why a skilled dumbek player has total control over the drum's tone, simply by choosing where to strike the head. As guitar players, our control comes from how far from the saddle we choose to pluck the string. Plucking it directly over the 12th fret produces maximum excursion with a strong fundamental frequency and few overtones. Plucking it near the saddle produces lots of overtones with less energy going to the fundamental. When designing a guitar, choosing where to locate the bridge on the lower bout is equivalent to choosing where to strike the drum head. The only difference is that this choice is permanent. The "epicenter of vibration" is still the physical center of the lower bout, but a guitar tone dominated by the fundamental with few overtones is often not the most desirable. This is why we have the two traditional bridge locations, typically identified as 12 or 14 frets to the body (even though frets to the body has nothing to do with it). The 12 fret position is in the center of the lower bout. It produces a faster attack, stronger fundamental, subdued overtones, and less sustain. The 14 fret position is shifted away from the center of the lower bout, towards the waist. Because this is a less efficient location, it transfers energy from the string to the body more slowly, producing a weaker attack, subdued fundamental, plenty of overtones, and long sustain. In theory, the bridge can be located anywhere between the center of the lower bout and the waist, as a form of permanent physical EQ. This location is chosen by the luthier and doesn't need to be attached to any particular scale length or number of frets to the body. It defines the primary tonal quality of the guitar regardless of scale length. From here, either a fixed neck length determines the scale length, or a fixed scale length determines the neck length. One important thing to note here is that the adjustment is always made by locating the bridge between the center of the lower bout and the waist, not by locating it between the center of the lower bout and the tail block. To understand why, lets go back to the drum analogy. The rim of a drum is a zero excursion node. It prevents the drum head from vibrating. On a guitar, this rim is created where the soundboard connects to the sides. Moving the bridge towards the waist keeps it a safe distance from the sides, and allows the soundboard to vibrate. Moving the bridge towards the tail block nestles it in a bowl defined by the curved intersection of the soundboard and the sides. Vibration here is nearly impossible because the bridge is surrounded by a continuous zero vibration node that is only a few inches away. Lifeless tone is guaranteed. No one wants this. Think about it. We've all seen guitars with the bridge located in the center of the lower bout, such as the standard Emerald X7. We've also seen guitars with the bridge shifted away from the center of the lower bout towards the waist, such as the standard Emerald X20. But has anyone ever seen an acoustic (not electric) guitar with the bridge shifted away from the center of the lower bout towards the tail block. I haven't. This is an appropriate home for a tailpiece, not a bridge. And yet, this is precisely what Mountain received. And, shifting the bridge towards the tail block also redistributed the frets to create an 11 fret guitar. I've never seen one of those either, and I can't imagine that anyone would want one. If the longer scale had been achieved by lengthening the neck, preserving the standard bridge location, this would have produced a 13 fret guitar with nice playability, and the bridge would be in the center of the lower bout, which is precisely the sweet spot where all classical nylon bridges are located. Plus, the longer scale requires higher string tension, which benefits nylon strings greatly because their inherent soft quality reduces acoustic energy, and tone suffers from a shorter scale. This is nylon guitar design 101. It's not something that a customer should be required to specify when all he wants is a slightly longer scale. The thing is, I know that Alistair already understands this. He shared his knowledge on this forum while designing Evan's guitars. He was sensitive to scale length and bridge location, and was even hesitant to make the body as shallow as Even wanted. He also shared why he preferred his design approach, and did not proceed with the build until agreement was reached. I can't imagine that he would ever design or build a guitar like Mountain's X7N. My guess is that he didn't. We all know that Emerald has increased production, and this means that Alistair must delegate more and more tasks to other people. Mountain's customization was probably implemented by someone without sufficient experience. A few years ago, nearly all reports from new Emerald owners were glowing. Now, dissatisfaction is clearly on the rise, as others have pointed out. To be continued ... Finally, to address Evan's point of locating pickups in multiple locations, yes this is possible. From a purely acoustic perspective, locating the bridge is a one time, permanent choice. Wow, that was long. I hope it was at least entertaining.
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#49
01-13-2020, 08:43 PM
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__________________
When I was 5 years old, my mother always told me that happiness was the key to life. When I went to school they asked me what I wanted to be when I grew up. I wrote down, “happy.” They told me I didn’t understand the assignment, and I told them they didn’t understand life. —John Lennon
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#50
01-13-2020, 09:17 PM
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Here’s a relatively recent ad for one from the classifieds: https://www.acousticguitarforum.com/...n+Norman+Blake -Ray
__________________
"It's just honest human stuff that hadn't been near a dang metronome in its life" - Benmont Tench Last edited by raysachs; 01-13-2020 at 09:29 PM.
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#51
01-14-2020, 01:00 AM
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I took a look at this ad. Look at the first photo, and mentally draw a horizontal line straight through the center of the lower bout. The bridge is slightly above that line, closer to the waist than to the tail block. They did shift the bridge down relative to its 14 fret location, but this shift did not cause the bridge to be located below the center of the lower bout.
What I'm talking about is shifting the bridge so far down that it's below the center of the lower bout. I've never seen any guitar with a bridge that low, and I probably never will because its a very poor design. In fact, its not a design at all. It's just a mistake, and Emerald would do well to admit it instead of just passing it on to the customer.
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#52
01-14-2020, 10:25 AM
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Tom2;
More than entertaining; thank you. At the end of the discussion I find myself wondering how the placement of the sound hole reflects placement of the bridge.
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#53
01-14-2020, 03:03 PM
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#54
01-14-2020, 09:23 PM
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#55
01-15-2020, 05:05 AM
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Ok so i better jump in here before things get out of hand.
Firstly I'm dissapointed my ethics have been questioned here. I would have hoped my dedication to my art form would have shown through. This is a guitar i worked on personally and i indeed selected the bridge location myself. Every X7 Nylon we have ever built with a scale over 24 inches had the bridge moved back. Its our standard practice and its what i find works best on the X7. I think the big issue is how we communicate with our customers. Its not uncommon for us to have 100 email exchanges in the consultation of a custom guitar build and we are happy to do that but perhaps we still need to look at how we can communicate better. We have already been discussing creating some design drawings and videos to explain how we modify our custom builds. Believe me im not in the business of taking short cuts when it comes to custom work. Custom work is what we love and live for. Alistair
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#56
01-15-2020, 07:11 AM
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How many founders of a guitar company have read threads here and posted replies about their instruments? I don't know, however kudos to Alistair Hay for jumping in.
__________________
When I was 5 years old, my mother always told me that happiness was the key to life. When I went to school they asked me what I wanted to be when I grew up. I wrote down, “happy.” They told me I didn’t understand the assignment, and I told them they didn’t understand life. —John Lennon
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#57
01-15-2020, 08:01 AM
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#58
01-15-2020, 10:10 AM
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Karen;
Actually, a number of makers have shown up on this and the previous McNichol forum. Ashvin representing Rainsong, Joe representing Blackbird, and so forth including representatives of Journey, CA, and Peavey. The other makers have not had the presence of Emerald, probably because of the customization which makes for a wide variety of unusual, and often stunning instruments (rather than a stock portfolio with a limited range of options to discuss). Another way of looking at it is that Alistair may be the only player-driven maker which encourages player-maker conversation.
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#59
01-15-2020, 10:21 AM
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Thanks for addressing this -- I always appreciate hearing your thoughts directly. If you have the time, I'm wondering if you might talk a bit about why this solution works better on an X7 than extending the neck would (since this seems to go against conventional wisdom with wood guitars). How does the tone, sustain, projection, etc., of an X7 nylon with an extended neck compare to one with the bridge position moved back? Thanks again. -SK
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#60
01-15-2020, 10:23 AM
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Alistair;
I believe in argument, think it often leads to greater understanding. I've found myself informed by some of the provocative statements made on this forum. Sometimes those statements are hurtful, but often the hurt reveals genuine concerns that do lead to refinement and understanding. I've rather enjoyed the argument regarding the placement of the bridge and think all parties acquitted themselves well. Carry on with joy in your heart knowing that you have a lot of people watching and playing your art, and feeling comfortable enough to quibble. And the best of the new year to you.
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