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  #31  
Old 07-15-2013, 09:13 PM
spuerspeedo spuerspeedo is offline
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  #32  
Old 07-15-2013, 09:14 PM
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  #33  
Old 07-15-2013, 09:15 PM
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  #34  
Old 07-15-2013, 09:17 PM
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  #35  
Old 07-15-2013, 09:19 PM
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  #36  
Old 07-15-2013, 09:21 PM
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  #37  
Old 07-16-2013, 02:42 AM
Jim.S Jim.S is offline
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I can't answer your question Spuerspeedo but as the thread touched on the use of pine as a top I though some of you guys might find this interesting. This recording has no effects added and the guitar is a Radiata Pine top With (I think you guys call it Oregon Pine bracing or Douglas Fir(Pseudotsuga menziesii)) The recording is a good representation of the instrument but as I have recently had a bit of a play on this guitar it is even more impressive live. The "Shed Guitar" http://www.goreguitars.com.au/attach...Going_Back.mp3
Jim
Darwin Strings
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  #38  
Old 07-16-2013, 01:41 PM
Alan Carruth Alan Carruth is offline
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printer2 wrote:
"But dampening and Q can be frequency dependent. I see the woods as a tuned filter network. One wood may have the same dampening or resonance as another but they may have their resonance in different bands. "

According to Daniel Haines, who did a lot of measurements of wood properties some time back, most softwoods have relatively low damping at low frequencies, and the damping factor rises with frequency. In his measurements there was a 'dogleg' in the plot at around 2kHz, with the damping rising much faster above that pitch. Nobody can think of a good reason for that, and it may be simply an artifact of the measurement protocol.

As I understand it, one of the things that Q number tells you is the proportion of energy lost per cycle of vibration. If the Q is 75, then 1/75th of the energy is being dissipated per cycle.

We often check the Q value by the 'bandwidth' method, looking at the behavior of the material near a resonant frequency, but that's just because it's an easy way to do it. If you re-size the sample, and make another test (which is what Haines did) at the new frequency, you should get substantially the same Q value. The wood, of course, dissipates energy off resonance too.

Any guitar will, in any case, have lots of resonances to work with. Usually they will have somewhat different Q values, since they are affected by the structure and other things. The Q of the wood used probably simply sets an upper limit in practice: if you're using a set of Redwood or BRW that has a Q of around 150, then you're unlikely to see any resonances of the assembled instrument any higher than that. Most likely they'll be lower, and can be a lot lower. It gets hard to sort out: As you get up around 500-800 Hz the resonant bands overlap, and it's impossible to say for sure what's what. The higher the Q of the structure, the 'peakier' the spectrum will tend to be, and that has an effect on the perception of the sound, This stuff gets complicated...
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  #39  
Old 07-16-2013, 07:29 PM
printer2 printer2 is offline
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Quote:
Originally Posted by Alan Carruth View Post
printer2 wrote:
"But dampening and Q can be frequency dependent. I see the woods as a tuned filter network. One wood may have the same dampening or resonance as another but they may have their resonance in different bands. "

According to Daniel Haines, who did a lot of measurements of wood properties some time back, most softwoods have relatively low damping at low frequencies, and the damping factor rises with frequency. In his measurements there was a 'dogleg' in the plot at around 2kHz, with the damping rising much faster above that pitch. Nobody can think of a good reason for that, and it may be simply an artifact of the measurement protocol.

As I understand it, one of the things that Q number tells you is the proportion of energy lost per cycle of vibration. If the Q is 75, then 1/75th of the energy is being dissipated per cycle.

We often check the Q value by the 'bandwidth' method, looking at the behavior of the material near a resonant frequency, but that's just because it's an easy way to do it. If you re-size the sample, and make another test (which is what Haines did) at the new frequency, you should get substantially the same Q value. The wood, of course, dissipates energy off resonance too.

Any guitar will, in any case, have lots of resonances to work with. Usually they will have somewhat different Q values, since they are affected by the structure and other things. The Q of the wood used probably simply sets an upper limit in practice: if you're using a set of Redwood or BRW that has a Q of around 150, then you're unlikely to see any resonances of the assembled instrument any higher than that. Most likely they'll be lower, and can be a lot lower. It gets hard to sort out: As you get up around 500-800 Hz the resonant bands overlap, and it's impossible to say for sure what's what. The higher the Q of the structure, the 'peakier' the spectrum will tend to be, and that has an effect on the perception of the sound, This stuff gets complicated...
Sure does get complicated. Doesn't surprise me about the Haines dogleg thing, sounds like a multi-order bandpass filter to me. We need some bright guy that can put it together like Thiele did for speaker tuning in the dark ages when it was more art than science. Not that it changes much for us, nature determines what the wood can do no mater how much we understand it. I do find it interesting though.
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  #40  
Old 07-16-2013, 07:31 PM
printer2 printer2 is offline
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Cool guitar. You'll get the hang of the picture thing yet.
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  #41  
Old 07-16-2013, 07:40 PM
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Quote:
Originally Posted by Jim.S View Post
I can't answer your question Spuerspeedo but as the thread touched on the use of pine as a top I though some of you guys might find this interesting. This recording has no effects added and the guitar is a Radiata Pine top With (I think you guys call it Oregon Pine bracing or Douglas Fir(Pseudotsuga menziesii)) The recording is a good representation of the instrument but as I have recently had a bit of a play on this guitar it is even more impressive live. The "Shed Guitar" http://www.goreguitars.com.au/attach...Going_Back.mp3
Jim
Darwin Strings
Douglas Fir is another wood that caught my eye. I have some more or less quarter sawn wood that I am using for a neck and in its raw state (I really have to start working on it again) it rings out when you hit it. I am even more impressed at the piece of old growth Fir that I found in my mother's garage, twice the rings per inch as my neck wood. It is even more resonant. Not sure what guitar I will use it on yet.

Oh yeah, sounds good.
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  #42  
Old 07-16-2013, 07:48 PM
stuw stuw is offline
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Quote:
Originally Posted by Jim.S View Post
I can't answer your question Spuerspeedo but as the thread touched on the use of pine as a top I though some of you guys might find this interesting. This recording has no effects added and the guitar is a Radiata Pine top With (I think you guys call it Oregon Pine bracing or Douglas Fir(Pseudotsuga menziesii)) The recording is a good representation of the instrument but as I have recently had a bit of a play on this guitar it is even more impressive live. The "Shed Guitar" http://www.goreguitars.com.au/attach...Going_Back.mp3
Jim
Darwin Strings
That was beautiful.. thank you..
It would be fun now to compare you playing the same song under the same conditions on a Martin, Taylor, whatever etc etc. where traditional woods were used.
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  #43  
Old 07-16-2013, 10:10 PM
Jim.S Jim.S is offline
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That was not me playing Stuw it was a young man by the name of Tom Langford. Personally I see no use in comparison, for a start the guitars you mentioned vary in tone across the brands as well as within the brands.

Jim

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  #44  
Old 07-17-2013, 08:49 AM
John Arnold John Arnold is offline
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My first 'serious' guitar build was a J-45 copy with a four-piece Ponderosa pine top cut from shelving board. Although the density is essentially the same as Sitka spruce, I found that the stiffness is less along the grain. It also tends to be very stiff across the grain, making it respond more like a hardwood top. Not necessarily bad, just different.
Pines are very resinous, so all the associated problems apply. Baking the tops or aging them for a long time will reduce the damping from the resins.
Besides the resin, another possible reason pine is not as desirable for a top is the strength along the grain. At similar density, pine is not as strong as spruce, and is more likely to break across the grain when subjected to impact.
The term "pine" encompasses a wide range...from sugar pine, which is softer and as light as Engelmann spruce, to Southern yellow pine, which can be as hard and as dense as oak.
Because I have a propensity for building guitars from local woods, I have dreamed of a guitar made from trees in my own neighborhood. Although hardwoods are abundant where I live, spruce is not native. Until two years ago, my best prospect for the soundboard was a white pine, which being a yard tree, was very wide-grained. But the tornado super outbreak in 2011 brought down a Norway spruce a block away, and it should make an excellent guitar. It also was a yard tree with wide grain, but the wood is very stiff and light.
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  #45  
Old 07-17-2013, 11:13 AM
Alan Carruth Alan Carruth is offline
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I've tested a few samples of both 'old' and 'new' White pine, and found no particular difference in damping, so I'm not sure about the 'resin' thing. The 'new' wood sure does have more resin in it, though! The mass might be a factor, although, again, I didn't see any real difference. I probably need more samples...

Interestingly enough the 'old' pine came from Tom Thiel, who's selling wood these days. I'm looking forward to making the guitar!

Doug Fir is an interesting wood, and I've used a lot of it over the years in dulcimers and hammered dulcimers. It does tend to be much denser than most of the other 'usual suspects', and if it obeys the same rules relating long grain stiffness to density, it would tend to make a heavier top. I've only seen a few guitars that were made with Doug, and, although they sounded OK, they were not very loud, which is what I'd expect from a heavy top. It also tends to be splitty...
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