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#31
11-25-2020, 07:25 AM
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#32
11-25-2020, 08:03 AM
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Quote:
The Yamaha LL16 and LL16M is another example of the same guitar with different b/s. If people honestly think the tonal differences is in the variances of individual tops, then play a dozen of these two in different shops and see for yourself. Same goes with the Yamaha A3R and A3M etc, watch comparison videos of you can't get a hold of them, it's plain as day. Anyway, I digress lol
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#34
11-25-2020, 02:23 PM
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The back can have a big influence on the sound, depending on how it is braced. As said there are active backs that vibrate with the top and ones wrongly called reflective, a better term might be rigid back. The wavelengths of sound in the body are too short for the back to 'reflect' the sound. These 'rigid' backed guitars would be better for throwing the sound into an audience as no sound is wasted being radiated off the back. Mind you if the back of an active guitar is played against the player the guitar acts almost as a 'reflective' backed guitar. It would not matter much with a reflective guitar what the back is made of, mahogany, rosewood or laminate.
The active backed guitar is a little more complicated. The difference in stiffness and mass of the back alters the resonances and how prominent they are. But the bracing on the back has a great influence on how much the back contributes to the sound. If the makers adjust the bracing for the material, be it mahogany like woods (maple, whatever) as compared to the rosewood end of the spectrum they can get the same bass response although the heavier woods will have the bass vibrate longer. There we get the dry or wet sounds. The interesting thing is the lower bout of the guitar has one main resonance and the upper bout another, more in the midrange. I won't go into too great detail but a cheap plywood guitar that is sold in bulk as starter guitars have 'reflective' backs. And tops that barely vibrate but hey, what do you want for under $100? (Actually I bought the guitar for $30, with case. I really bought it for the case and just could not throw the guitar away.) Anyway I 'slightly' modified the guitar. I gave it an arm bevel and belly cut (OMG is it ever comfortable now) and while I was inside I took a trick from Alan to get some bass response.  I took about a third off the top of the back braces off. Now even with the plywood back there is a more drum-like sound when you tap the back but importantly also more from the top. I still have to modify the bridge a little to hold a regular saddle but I already know that the guitar will sound fuller, even with the cuts into the body. Freeing up the back by shaving the braces helped it out. On the top, just for curiosity sake, has no braces other than the bridge plate and a horizontal brace just below the sound hole. If the top is thick enough there is not much need for other braces. But don't expect too much sound out of it. So on the contribution of the back, yes the type of wood can effect the sound and one wood will sound different than another. But the maker can adjust how much contribution they want off of it. Even a plywood back can be made to help the top out. I have to try it myself but I am sure that if a luthier wanted to make a decent sounding plywood backed guitar they could. So just to add, I did a half-arse fret job and strung it up. It turned out pretty well, better than I thought it would. I could take down the saddle a touch but it plays not bad and sounds much better. It is not great on the low E string, the box needs to be tuned a little lower. But I can live with it. Fingertips are already saying enough. It has been quite a while since I picked up a guitar. A day later. The issues with the bass was a bad fret, not bad now. Pretty happy for plywood.
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Fred Last edited by printer2; 11-26-2020 at 08:30 PM.
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#35
11-26-2020, 10:24 AM
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printer2 brings up the 'active/reflective' debate, and that certainly has a lot to do with it. IMO the most important properties of the back wood are the density and stiffness, which go together to some extent. Those work together in establishing the pitches of the resonant modes of the back, which, in turn, determines how the back and top work together. This is particularly important in pumping air in and out of the sound hole in the low frequency range, but back resonances also seem to help in producing 'tone color'.
Ovations are the only guitars I've ever tested that had no back resonances in the range below about 1000 Hz. Basically on those all of the sound is coming off the top. IMO it greatly restricts the range of available tone color: it's a nice enough sound as far as it goes, but doesn't allow for much range of expression. So far as I can tell, the back only enhances the output in the lowest 'bass reflex' range of the guitar, and then only when it's flexible enough. Above that (say, above the pitch of the open G string) it's mostly stealing energy from the top. The 'dips' in the output spectrum at back resonant pitches help to shape the sound, so they're good in that respect, but they also cost output, so you want to sort of minimize them. One way to do that is to use a fairly heavy back; it only 'eats' energy when it's moving, so if it's hard to move maybe it eats less. Another thing that could help is to reduce the damping; the amount of energy the back dissipates in the process of vibrating. A good start there is to use a low damping wood, such as a rosewood. Material damping only really sets a sort of limit to the structure: you probably can't get the damping of the structure to be lower than what is inherent in the material, but it's all too easy to make it higher, say, by messing up the bracing. So there's the rationale behind using dense, stiff, low damping woods like BRW for the back. We could discuss the properties of B&S woods all day, and probably not settle many of the endless debates. Just as one f'rinstnace : my measurements suggest that soft maple and black walnut are very similar in every respect in mechanical and acoustic properties, but maple guitars are said to sound 'bright' while walnut is 'dark'. Is this an example of people listening with their eyes? Can it be determined what 'bright' and 'dark' mean objectively? I doubt it.
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#36
11-26-2020, 10:49 AM
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I was just about to contribute to this discussion because over the past 2-3 years, I switched from laminated b/s guitars to solid b/s guitars. But then I realized I also switched from "lower end" guitars to more "higher end" guitars.
Could that be it? It turns out all I can contribute is to say I like the sound from my all solid guitars more than those with laminated b/s. It's not that I disliked my lam b/s guitars' tone, but rather I just like the tone of my current all solid guitars. Is that because they were made of all solid woods rather than solid tops vs. laminated b/s? Or maybe it's because of the bracing patterns of Gibson and Martin are different enough from Ibanez and Alvarez to create a sound I like? Or maybe it's because the inside surfaces are less rough in texture? Or perhaps its because of the actual pieces of wood. In short, I dunno ... Best, PJ
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A Gibson A couple Martins
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