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Elias Foppa

All spruce violin

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6 hours ago, Marty Kasprzyk said:

About two thirds of the instrument's sound comes from the front half of the instrument and about one third comes off of the back half.  This forms a front to back output ratio of about two.

This happens because a high density maple back plate weighs about twice the weight of the low density spruce top plate so it doesn't vibrate as fast as the top plate thus it producing less sound.  Their weight ratio is the inverse of their sound output ratio.

This is an intentional outcome to prevent a lot of sound from being produced from the back where much of it would be wasted and not projected to the listener audience.  For a violin or viola much of the back plate's sound would be lost by being absorbed by the players shoulder, arm, and chest.  For a cello much of the sound would be absorbed by the player's body.   

If the backs were also made light by being made out of spruce both the top and back would produce similar amounts of sound and even more of the total sound would be wasted.

The same thing happens with guitars--the body and back are made relatively heavy and the top light so that most of the sound is produced by the top and the player's body absorbs very little sound producing vibration.

But sexually deviant players might prefer spruce backs.

 

The above discussion assumes that the spruce top and spruce back have the same average thicknesses and therefore close to the same weight.

However the spruce back could be made thicker and therefore heavier than the top to maintain the same ratio of sound production that a typical violin has.

However as Don pointed out the anisotropic longitudinal elastic modulus to radial elastic modulus ratio for spruce is much higher than for maple so various mode frequencies would be different thus producing a different sound character.  Don correctly points out that "different" is often considered "bad".

However completely identical duplication of sound character isn't very good either.  An argument could be made that some amount of variation is desirable and a spruce backed might be well liked by some people.

I expect that all Big Mac hamburgers should taste the same but that all hamburgers shouldn't taste like Big Macs.

 

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1 hour ago, not telling said:

 

4 hours ago, PhilipKT said:

That’s the best simile I’ve heard since “when she dances she looks like a squirrel trying to cross a freeway.”

Uh...gee...thanks...I think. Both are evocative images, I guess. 

 

 But that’s the whole point of a simile, to evoke an image. Your’s was marvelous, the squirrel one always makes me laugh.

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My last viola has a bass bar (treble bar?) on the inside of the back plate plate on which the sound post rests.

The idea came from a Dutch violin maker on the internet and it seems to work.

In China I saw a phD scientist friend praying for his first time at a Buddhist temple. I asked him why he was doing that and he said he would try anything if it worked.

 

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A while ago I read here about Testore cello with quatered spruce top and slab cut spruce back. Does anyone have more information or better at least any photo of the instrument? I've heard it is still used by some sololist.

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Once saw an old hill cello, I think it was Lockey Hill, which had an original spruce back. Sounded ok but not really good. 

More interesting for me was the Balsa wood cello by James Ham. This looked to me like a concept car. 

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6 hours ago, Dominik Tomasek said:

A while ago I read here about Testore cello with quatered spruce top and slab cut spruce back. Does anyone have more information or better at least any photo of the instrument? I've heard it is still used by some sololist.

It was Manfio who mentioned this instrument, I believe it's in Brazil somewhere.

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2 hours ago, joshuabeyer said:

It was Manfio who mentioned this instrument, I believe it's in Brazil somewhere.

Yes, I guess so. Unfortunately Manfio is not answering my messages thus I am seeking information elsewhere. 

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On 7/2/2019 at 3:58 PM, Elias Foppa said:

I have been wondering for quite some time about why maple is used for the back plate. Would making the back plate spruce give the violin better acoustic properties?

Think of a drum.  The drum skin and sides have different roles, and are mostly made of different materials.

Now I violin is more conplicated, but the top is and needs to be more like a drum skin.  Spruce is better at this.

The sides and back, and even neck are more like the drum sides.  However, more complicated.

Now think of using a plastic industrial bucket as a drum. These work fairly well, but the sides and bottom are the same material.  Both material and shape determine musical behavior.  The material of plastic bucket is stiff enough and flexible enough to do both jobs, given the right shape.

The back and sides of a violin are something like the bucket drum.  

The tradition shape and arrangenent of the violin evolved to maximize performance using the traditional Spruce and maple.

 

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On 7/2/2019 at 8:55 PM, not telling said:

Apparently the all-spruce fiddle has happened. I bet it sounds like several pounds of cold butter thudding on granite after being dropped about two feet. But I don't know for sure.

:lol:

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On 7/2/2019 at 11:55 PM, not telling said:

Apparently the all-spruce fiddle has happened. I bet it sounds like several pounds of cold butter thudding on granite after being dropped about two feet.

Ahh.  Borax, right?  [Disappears at high velocity yet again.] :ph34r::lol:

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I have some Sitka that's over .5 density, in the range of maple.  I'd guess I could make a violin with a back out of that, and it would sound pretty normal.

But why?  I don't imagine I would learn anything terribly useful, and end up with a fiddle for the wall.

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