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#31
10-20-2017, 04:17 PM
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Yes you can lose volume and tone from lowering by saddle Yes you can lose volume and tone from taking relief out of the neck Finger stylists love low action, and so do I on my finger style guitars, but not my Jumbo. She is a strummer and does it better, louder, and bigger than anything else I have. |
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#33
10-20-2017, 04:59 PM
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#34
10-20-2017, 05:27 PM
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#36
10-20-2017, 05:58 PM
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#37
10-20-2017, 06:06 PM
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#38
10-20-2017, 06:21 PM
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#39
10-21-2017, 04:24 PM
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This is turning into a can of worms: Victory Pete's experimental results contradict what I've gotten.
I did an experiment a few years ago specifically to look at the relative effects of changing the string height off the top and break angle. People would say that changed the break angle, and got a certain result, bu when asked how they did it, they say that put in a taller saddle, so two things were changed. I wanted to separate them out. The most straightforward way to do that was to use a Classical guitar with a tieblock bridge. Using an 18-hole setup allowed me to tie the strings either 'over' or 'through' the block, getting two different break angles (in this case ~25 degrees, and ~6 degrees) without changing the saddle. I then put in a tall saddle with the 'low' tie, to get back to the 25 degree break, but with the strings 18mm off the top instead of 11. That gave three cases: A - 11mm string height off the top with 25 degree break, B - 11mm off the top with 6 degree break, and C - 18mm off the top with 25 degree break. So there were two cases with the same string height, and two with the same break angle. I used a mechanical plucker to activate the strings in such a way that they started out vibrating 'vertically' with respect to the soundboard plane, plucking in the same place with the same force every time. I plucked each open string six times, and recorded the sound on my computer, using the same mic and setup each time. This allowed me to average the results and see if there was any significant variation (there wasn't). I made up a 'synthetic strum' for each case, and played them back in random pairs through headphones, asking people to judge whether they were 'the same' or 'different'. I also looked at the wave forms and compared them for: rise and fall time, total duration, maximum amplitude, and frequency mix. Basically, there was no significant difference in rise and fall, duration, or maximum amplitude, between any two cases for the same string. Changing either the string height off the top or the break angle did not change the power output of the string. What did change was the frequency mix, but only when the string height off the top was changed. As has been said, this alters the torque on the top, and thus the way the string drives it. Most of the actual power of the string derives from the 'transverse' motion; the string moves up and down, and pulls the top along with it like a loudspeaker cone. This produces a reasonably large force, and applies it in the way that drives the top most effectively to produce sound. In contrast the things that drive the bridge in a torquewise rocking fashion produce much less force. One is the twice-per-cycle tension change of the string that pulls the bridge toward the nut when the string is either 'up' or 'down'. This varies from string top string, but is generally about 1/7th as strong as the transverse force. There is also a high frequency longitudinal pressure wave in the string, usually up around the 7th-8th partial, that pulls on the top of the bridge, but it's normally not strong. However, because it is often dissonant it can be quite audible at low power. Bridge rocking is inefficient at producing sound, since it pulls on half of the sound board 'up while pushing the other half 'down', so that much of the motion cancels out without producing sound. Also, we build tops to resist this sort of distortion, so it's hard to move the top that way at lower frequencies, since it's so stiff. Add the fact that the forces involved are low, and you just don't see much power output from them. Keep in mind, too, that there's only so much horsepower in a plucked string. If it comes out in one way, it's not there to drive something else. So, what happens is that when the string height off the top is changed the frequency mix is altered a bit, without any measureable change in the actual power produced. You get more sound in the second partial and at the longitudinal wave frequency when the strings are higher off the top, but, it seems, less power elsewhere. The timbre of the note changes, and may sound louder, but it's not. Thus, in the listening tests, when presented with two 'strums' with the same string height off the top , but different break angles, people were guessing, and said 'same' or 'different' about equally. When the string height off the top was changed virtually everybody heard the difference. Some might object that this was done using nylon strings, rather than steel. Certainly the two string types sound different, but they drive the top in the same way. The difference comes, as far as I can tell, from the much lower damping in steel strings, which enhances the upper partials and sustain. As always, when I do one of these experiments I learn two things: 1) there's something I didn't expect happening, and 2) I should have done bigger experiment and gotten more data. Considering how long that one took, it's not likely that I'll br able to scrape up the time. So there you go. The results I got make pretty good sense to me in light of what I know about how strings and guitars work. Unless somebody can show me what I got wrong that's my story and I'm sticking with it.  Finally, I note that the original question was about action height, not string height or saddle height. I excuse the long off-topic post on the grounds that the tread had already been hijacked. |
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#40
10-21-2017, 04:36 PM
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#41
10-21-2017, 04:50 PM
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The OP does indeed relate to saddle height and volume. Saddle height has a lot to do with the action. It also affects the volume as many have mentioned here and on other forums. Some people, like I used to think, think it is because of break angle, but my experiment shows break angle does not effect volume in any way. The height of the saddle and strings determine the volume. A typical problem with older guitars is having to shave down the saddle as the top rises, hence losing volume. A neck reset allows a taller saddle to be used and the results are a louder guitar, everyone here knows that I am sure.
Here is some useful information: http://www.esomogyi.com/principles.html Last edited by Victory Pete; 10-21-2017 at 04:56 PM. |
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#42
10-21-2017, 05:08 PM
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This is getting good now, I am not sure I have seen this Thread before. I really do love to learn all about guitars.
http://www.acousticguitarforum.com/f...62&postcount=9 |
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#43
10-21-2017, 05:29 PM
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Sorry for the rapid fire posts but I keep finding more tidbits of information, all from this Forum. This is where I learned about the ideal 1/2" measurement from top to D and G string. All my guitars have this spec and they all are quite loud and clear.
http://69.41.173.82/forums/showthread.php?t=201163 |
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#44
10-22-2017, 01:32 PM
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OK: we need to be clear that 'volume' or 'loudness' is NOT the same thing as 'power'. Volume and loudness are perceptions; how it sounds to you. Power is something you can measure. A dB meter gives an indication of power, although actually measuring it is more complicated, and actually rather difficult to do for guitars.
In my experiments I used a dB meter as a microphone, since it has a 'flat' frequency response and the ability to adjust the gain. What I compared was the actual amplitude of the sound waves at the location of the mic. Since that was the same, as far as I could determine, and the rise and fall time and duration of the sound was the same, I infer that there was no differecne in power with variation in either string height off the top or break angle. Loudness could well be quite different, and what I saw in the spectra of the notes gave some justification for that. As I say, when the strings were higher off the top there was more energy in the second partial of the notes, and also at the high frequency of the longitudinal wave of the string. This seems to have been compensated by there being a little less energy in the other frequencies, as I mentioned. At ant rate, the point is that there was more energy at higher frequencies In general, high frequencies are easier to pick up at a given sound level for people with 'normal' hearing; our ears tend to be more sensitive to the higher frequencies (unless you have high frequency hearing loss). The longitudinal wave is especially easy to pick out, since it's high enough to be near the frequencies where our ears are most sensitive, and it also tends to be dissonant, so that it stands out. It is stronger, and somewhat higher in frequency in steel strings, so it probably stands out even more with those. This, in itself, could easily be enough to make the guitar sound 'louder', even though there was no more power in the signal. Victory Pete didn't specify how he determined that raising the saddle made the guitar 'louder'. I assumed he meant that he was talking about his perception; that it 'sounded louder', but I didn't want to put words into his mouth. As I mentioned, so far as I can tell, all of the differences between Classical and steel string guitars go back to the difference in the strings, which is primarily one of damping. Nylon, as a material, tends to dissipate vibration energy faster than steel. Also, nylon strings, being thicker, have to move more air as they vibrate. This doesn't produce sound, but it wastes energy, in the same way that running in knee deep water doesn't produce much current, but it sure tires you out. One way that damping is measured is to count the number of vibration cycles it takes for a wave to die out by a certain proportion; say to 1/2 the initial amplitude. In most cases this will be independent of the frequency involved: if the sound dies out in 100 cycles it's the same whether you have something that vibrating at 100 Hz or 1000. However, the 1000 Hz tone will die out ten times quicker simply because it's making ten time as many cycles per second. Thus damping tends to 'eat' high frequencies. You can see this if you do a spectrogram of steel and nylon strings. If you pluck them both in the same place the initial wave form will be the same. The initial relative energy content of each partial is determined by the pluck point, and not by the string material. After a second or so the nylon string will have very little energy left in the high frequency range, while the steel string will still have plenty of high end after a couple of seconds or more. This pretty much determines all the differences in the design and construction of steel and nylon string instruments. With steel strings the problem is to get enough bass to balance out al of the high frequency in the strings. You do this primarily by making the box bigger. This requires some extra beefing up of the top, so a somewhat stronger brace pattern is used. With nylon strings the issue is making the most of the small amount of high frequency the strings produce. A smaller box that accentuates the highs helps with this, and also allows for somewhat lighter construction, which also aids in getting a bit more power. Here you can take advantage of the somewhat lower string tension that's normal with nylon strings as well. Other than that, the kinds of forces the strings put on the bridge top are quite similar: I know, I measured them. All strings drive the top in the same basic ways. There are differences in detail, and those make all the difference in the way the guitars sound. However, in an experiment to see how the strings drive the top either sort of string can be used and give valid results. I used nylon strings in that experiment because it was the easiest way to get the data. In the end, if raising the strings off the top adds to the power output of the guitar it has to be done through making it more efficient. Since, as I pointed out, bridge rocking is a less efficient way of driving the top than the vertical motion driven by the transverse wave, shifting energy from 'vertical' to 'rocking' driving would hardly be the way to increase efficiency. It could well make the guitar 'louder', as I say, but that's different. Note, too, that there are limits as to how far you can go in raising the strings off the top. Torque is what kills guitar tops and rips off bridges. If you want o increase the torque beyond normal limits you'll need to use a bigger bridge and a beefed up top, and both of those tend to kill sound. There's evidence that it's actually more productive to go the other way: Flamenco guitars are notably loud, and use a much lower string height off the top than standard Classicals: generally 7mm or so instead of 11-12 for Classicals. The low bridge allows for the use a thinner and more lightly braced top which is more responsive and punchier: just what you need for those loud Saturday night parties. |
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#45
10-22-2017, 01:50 PM
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This just confirms to me why I should take my guitars to someone who knows what they're doing.
sm |
