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Double Bass Traeger's Soundpost Thoughts

Brent Norton

Brent Norton

Sep 26, 2003
455
1
49
Detroit, MI
www.nortoncustoms.com
#1
In Traeger's new book, he talks about impedance matching as it pertains to the soundpost's relationship to the plates of the bass. He states that plywood basses, having plates with greater impedance than carved instruments, will benefit from soundposts made of a hardwood such as birch or maple. I'm interested in hearing from the TBDB luthier contingent about your thoughts on this.

Also, have any of you experiemented with the concept of the rounded-ends or hourglass shaped posts?
 
#2
Well I haven't recieved my book yet,but I will comment on my experience.Hope to hear from you other Luthier cats.
Ever wonder why Kay bases always had a hardwood [W. the spilt down the side] soundpost? Sometimes that original post sounds better than a softer seasoned spruce post.You can spend lots of time fitting and positioning and then that ol' spit dowel still sounds best.Go figure...I worked on a Kay for John Lockwood years ago and he insisted I keep the original sounpost.He also wanted the original hard wire on the tailpiece,but thats another subject.
As for the tapered [Hourglass] shaped post,I read here on TB that Ron Carter like them and thinks they allow the top and back to vibrate more freely.I tried it on one bass and he may be on to something.But why not just use a smaller diameter soundpost?
It's definatly a challenge w. each and every bass that comes through to try and narrow the choices and help get the maximum sound w. that little soulfull piece of wood.
 
#3
I've experienced a number of Traeger-set soundposts over the years. Many were beveled so severely that only about half the original end surface was intact. My concern is twofold: 1) all the pressure is on a very small area, which makes me worry about top splits, and 2) the bevel makes it nearly impossible to tell if the post fits.

I think too much is made of the soundpost material and its affect on tone. It's only a piston.
 
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#4
Thanks for the input so far, guys. Arnold, you address one of the things that rubbed me the wrong way in Traeger's soundpost chapter: He states that he's seen a lot of basses that were damaged by what he feels is a too-narrow post (5/8"), but then goes on to recommend 5/8" soundposts in certain circumstances, or rounded/bevelled soundposts with 5/8" contact areas...

Back to material... if the soundpost is indeed just a piston - its job being to transfer energy - it seems the relatively soft wood of your garden-veriety spruce post would absorb some of that energy where the harder wood, with its increased rigidity, would more effectively transfer it... Further thoughts?
 
#5
Spruce is a great species because it is rigid, but lower in mass. If you want to transfer any kind of physical energy, wouldn't you want this win-win situation? An increase in soundpost weight would require more energy to do the same thing a lighter post is doing with less energy. I'm not a scientist, nor do I want to be. Just some from-the-bench observations... Or, spruce soundposts work, and have been working for several hundred years.

WWBBD?
 
#8
Well ,I got the book today and yes I didn't mind plunking down the 94 bucks because I have never apprenticed with anyone and thought this might be some good schooling for the buck.It sure is an interesting read and I feel it is sorely over-due to the bass world.There just isn't that much out there in print on bass luthiery.
That being said I may not agree w. every point in the book[I barely had much time to skim though part of it today] but only wish guys like Lou DeLeon or Sam Kolstien would have written down their thoughts on the many subjects of bass repair.Guys like me need this valued info ,so for now I will dig the fact that Traeger has done this book.It is a wonderfull thing that you learn sometihng new every day whether it be on the bandstand or the shop or a book.
Ken,I'm sorry you had a bad experience w. Chuck.Maybe it was a bad day for him or whatever,but I'm sure that you found a luthier that you liked and now have had Arnold do his great service for you and your basses.Respect in the music business is a funny thing,sometimes earned,sometimes assumed.And you know you should never assume...
 
#10
Ken,
Not starting anything w.you, my wife always says "Never Assume,It makes an A.. out of me and you". Just a funny saying,I guess...
Ken ,you are right,I guess I was the guy assumiing that Chuck had a bad day.Service is service,at least I feel this way and you try to be a good guy as much as possible.All I know is you can't please everyone all the time and some people just don't hit it off.
I stopped recommending musician's years ago because sometimes I would build up the players reputation saying 'You'll love this guy,he plays great" and then the person hiring the player hating the cat!!
 
#13
nicklloyd said:
Spruce is a great species because it is rigid, but lower in mass. If you want to transfer any kind of physical energy, wouldn't you want this win-win situation? An increase in soundpost weight would require more energy to do the same thing a lighter post is doing with less energy. I'm not a scientist, nor do I want to be. Just some from-the-bench observations... Or, spruce soundposts work, and have been working for several hundred years.

WWBBD?
Click to expand...

Some things to consider:

Sound travels faster through denser materials. If a material is higher in mass with the same exterior dimensions, then it is more dense and the more efficient (faster) sound conductor. Spruce may be the best choice with carved basses for other reasons than its low density?

I have seen some books and internet articles that recommend that the soundpost come out of a spare piece of the top wood. Also some feel that the bridge should ideally be made from the same wood as the ribs and back. These were apparently the practices of the makers of the lyra instruments that predated violins. Perhaps this is where the standardization of spruce posts and maple bridges came from? Since vilolins usually were made from these woods?

In any case, the exclusive use of spruce sound posts predated plywood instruments and may not apply in the same way it does to carved instruments. It would seem that Kay could have used spruce posts as easily as hardwoods;- when Kay basses were made neither spruce nor hardwood brought a particularly high price for dowel rods. Certainly they had a reason for using the hardwood posts that they used. I guess a plywood soundpost would be the best!

It does cause one to wonder if the original principle of matching the materials of the post to the top as closely as possible and the bridge to the back aren't somehow related to Traeger's "impedance" matching ideas.
 
#15
I'd like to remind everyone again that this thread is about soundposts and Traeger's thoughts about them. If there's going to be any Traeger-trashing here, it should be related to disagreements with his thoughts about soundposts. I don't know Traeger from Adam and have heard some very mixed reviews of his work, but trashing a person who isn't here to defend himself doesn't exactly seem very sportsmanlike. :eyebrow:

On the bright side, I am very interested in learning something about soundposts as this thread continues. :)
 
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#16
arnoldschnitzer said:
I think too much is made of the soundpost material and its affect on tone. It's only a piston.
Click to expand...

Keeping in mind that I know almost nothing about luthiery:

No soundpost is perfectly rigid; it make look like a simple mechanical link, but we're talking about transmitting vibrations over a tremedounsly wide range, over which changing the modulus of elasticity, damping and other charactreristics of the soundpost will have a measurable (if not necessarily audible) effect. It's a very complex filter. So maybe it's something worth investigating further.

YMMV.
 
#17
The article on Tom Kelischek had some of HIS interesting thoughts about soundposts, th eonly one of which I can remember right now is that the one he put in his last bass was almost twice the diameter of a "normal" post.

I'll re -read the article and post pertinent points, pedantically.
 
#18
The input from the bower is very complex but consists of a series of partial resonances. These same resonances appear in the output of the instrument. But the instrument changes them to a great degree resulting in a very distinctive sound to each bass. Everything effects this, from the wood damping to the thickness/graduation of the plates, the stiffness of the sides, the size of the ff holes, the volume of the box.

(If you are still interested, read on, i'm getting to the soundpost)

The force exerted by the bowed strings causes the bridge to rock about the position of the post, causing the other side of the plate (east to west) to vibrate with a larger amplitude. This increases the radiating volume of the instrument and results in a louder sound. It also changes the way the body modes of the instrument vibrate, and effects frequency response of the bass.

This is the physics of it, and you can't change it! :eyebrow:

In practice small differences in arching, plate thickness and mass of the individual plates can result in big changes in the resonant frequencies of the bass. Any little change has the potential to effect the response of a particular bass, from a round end post, to a thinner post, to a change in post material. That is why the post can be tapped a little and that will pop a brighter resonance. If you had the ability to measure the response curve quickly and accurately it would be obvious by an increase in amplitude of one (or more) peaks. Tap it the other way and a partial resonance goes down. That is physics and it can't be changed.

Knowing how to effect the change is the HARD part and is why luthiers exist. It is obviously easier to understand this than to be able to tune a bass!!!! It is like tuning an engine by feel. Also just because a change effects the bass in a desirable way to the owner, does not mean it is good for its longterm health.

(now to Traeger)

" Here's a real shocker. Contrary to popular belief the soundpost does not transmit the vibrations of the top to the back", Traeger writes. And " Because the top and back do not vibrate exactly the same way at the same time, they exert a twisting motion on the sound post. The more you can make the soundpost less resistive to this twisting motion, the better the instrument will sound."

Here is that pesky "Better' prase. But the physics are correct.

Thinner post will resist less, as will one with rounded ends. So will an hourglas shaped post. Writes Traeger. Makes sense.

Plywood plates have a higher impedance (resists bending) according to Traeger. And he states that the higher impedance plates need a stiffer wood to match. This is unclear to me.
 
#19
What it seems like from Ken M.'s post is that the sound post's most important function is as a wave node and a fulcrum. As a wave node, it breaks up partials that can't "fit" evenly on one side or the other of the node. If you think about this as being analagous to a harmonic nodal position on the string, you can see that the "best" position for the sound post is going to be a fixed point without much room for variation. Unlike the nodal point on the string however, you have to find the sweet spot for the sound post.

I have the book on order, but no book yet. Is there a really detailed definition of impedance? I know it is resistance to bending, but I'm wondering how it is quantified and measured. Obviously you can make quick comparisons of two materials and identify greater or lesser impedance, but is there a way to measure it the way one measures (for instance) electrical impedance?

I think as to the use of the term "better", we can safely conclude that Traeger believes "better" is when the instrument is more resonant. While "better" could be different things to different people, resonance is much more objective and measureable. It is sort of obvious to me that if your goal is to make a responsive instrument that amplifies sound, increases in resonance are better than decreases, since resonance reduces the energy required to produce a given amplification level.

As far as the need for a denser post for plywood, well, I'll have to read the book, but it is obvious that the Kay bass company was in agreement with Traeger, whatever the reasoning behind it.
 
#20
Too much "resonance" and a bass becomes wolfy and/or uneven, because the instrument has distinct pitches at which it resonates most strongly, and is therefore louder or more responsive or more wolfy (overblown) at that frequency. Many bass adjusters yank the soundpost far south of the bridge in an effort to stimulate resonance or depth. The result is almost always mud, wolf tones and unevenness. But at first glance it sounds deeper, which many equate to the player as better. "Better" to me is a bass that sounds clear, has depth, rings out, but most of all is even through all registers. Problems occur when we try to make a bass sound like a different bass. I hold to the traditionally accepted soundpost function: a piston to tie the top vibrations into the rest of the instrument; and a counter to the bass bar, acting as a pivot point. Moving the soundpost affects the swinging of the bass bar more than anything else, IMHO.
 

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