Sign in to follow this  
Jack Devereux

Sound Post Stock

Recommended Posts

Re-reading the Triangle Strings article about making a soundpost, which starts with splitting a blank out and working it round. Does anybody have any thoughts on selecting good spruce to start with? Anything in particular to look for? I have an orphan half of a top that looks like Simeon Chambers's stuff in a pile of wood I recently bought from a friend. It's super tight grained and very light, not sure of the density, would this be a good place to start? 

Share this post


Link to post
Share on other sites

Sounds like a great place to start, Simeons wood has always impressed me as high quality.

  In theory you want a high strength to weight ratio , of all the woods, Spruce consistently fits the bill. After that a high rate of speed of sound also seems to be appropriate for the job, spruce again generally falls into that category.Weight is also a factor that must effect tonal production,due to inertial damping, could be good in some respects ,but again I suspect more weight translates to energy loss, translates to reduced plate movement. , Because the post is essentially over engineered in compression.....a 6mm SPLIT post will hold a great deal of weight before collapsing..at that point I'm more worried about the top or back , seen a few posts punched through!..I'd be happy to try a low density, (but not so low it's hard to get a clean end cut) , High RR, SPLIT post, Whatever the difference in the extremes in spruce, they are not going to add up to a lot either, it's(the post) the smallest ,lightest, most overbuilt component in the whole system, Focus on fit ,tension,and placement.  I mean what the heck ...we all need practice anyways...  What I think is a very important element is the split nature of the method , no other method provides that much stability , make sure to split in both directions ,to work with any twist present.   the fitting is the real sticker.

Share this post


Link to post
Share on other sites

There are aspects of structure, acoustics, and what just makes you feel good to do.

For structure, there's no real issue... I've never heard of one failing in compression or buckling, and I'm sure it would punch through the plates before that happened, even if the post had lots of runout.

Acoustics I don't believe are that big of a deal, either.  I recall a discussion about this recently, where a pencil was used with no observable loss.  In testing, I have used hardwood dowels, and reduced a soundpost to 3mm diameter to see what happened.  There did seem to be a very slight difference with the 3mm post (still 6mm at the ends to avoid plate damage), but that might have been due to the fact that it was 1/3 the weight of a normal post.  

What makes you feel good - I just buy decent soundpost stock with fine grain, and use it.  I might process it to look old, but haven't done that yet.  If you like to cut your own soundposts, I see no reason not to, and also see no physical reason why you shouldn't use low-density Engelmann.

Share this post


Link to post
Share on other sites
56 minutes ago, FrankNichols said:

Does the post need to be round? Why not square? 

A couple years ago I saw a fiddle with a square (or maybe slightly rectangular) post. It sounded fine, but there was no way to tell if a normal round one would have sounded better.

Share this post


Link to post
Share on other sites

If the same wood is used a square post is stiffer in bending than a round one of the same weight.  Since these aren't used one might conclude the bending stiffness the post isn't important.  Also one might further conclude that the wood's bending elastic modulus isn't important either.

I've tried a carbon fiber tube which has a really high bending stiffness/weight ratio.  It didn't seem to work any better or different than ordinary spruce ones.  The only property that seems important is that the material has to be soft enough that your sound post setter can stick into it.

I haven't gone the other way.  Someday I'll try a section of rubber hose.

Share this post


Link to post
Share on other sites
1 hour ago, Marty Kasprzyk said:

The only property that seems important is that the material has to be soft enough that your sound post setter can stick into it.

You could use steel and a magnetic setter.

Or any material and a scissor-type setter.

Share this post


Link to post
Share on other sites

The term "sound post" might imply that its function is to transmit vibration from the top plate to the back plate such that the back plate can generate some sound too.

My take on it is half-assed backward:  The function of the sound post is to prevent the top plate from vibrating at that location.  

The back plate is usually made quite thick in the central area.  I believe this creates a solid relatively unmovable foundation for the sound post to sit on.

Share this post


Link to post
Share on other sites
52 minutes ago, Marty Kasprzyk said:

The back plate is usually made quite thick in the central area.  I believe this creates a solid relatively unmovable foundation for the sound post to sit on.

The soundpost does move at some frequencies.  There are mode shapes where the central area of the back is moving, and the soundpost rides with it.  Actually, it's not really separable... the plates are connected together by the post, so the modes are defined by the mass/stiffness of both plates.  And ribs too.

Share this post


Link to post
Share on other sites

As Don stated above, I do not think the material makes much difference in sound.  That being written, choosing a material that is stiffer and less likely to dent or split is helpful.

Share this post


Link to post
Share on other sites

My own little experiments find that the chief function of the sound post is to provide support for the belly at an important point. This support point controls the belly's vibrations and the bridge response. So, you can try different materials and shapes with almost no noticeable changes in tone. Yes, the soundpost does transmit vibrations to the back, but this seems to be less important. However, you cannot neglect the interaction with the back if you want to get the right overall tone output. 

Share this post


Link to post
Share on other sites
10 hours ago, Jerry Pasewicz said:

As Don stated above, I do not think the material makes much difference in sound.  That being written, choosing a material that is stiffer and less likely to dent or split is helpful.

Jerry, thanks for weighing in, that's basically what I was wondering. I remember seeing you give a talk about this a few years ago, where you mentioned that you had a special stash of specific soundpost stock. Was just curious what the criteria were for that wood. 

Share this post


Link to post
Share on other sites
3 hours ago, Luis Martins said:

Has anyone tried carbon fiber? Will not split!

That's not quite accurate. Carbon fiber can split quite severely. And not unlike wooden soundposts, some of that will depend on the "grain" orientation of the carbon fiber.

Monodirectional carbon fiber composites are quite easy to split.

Share this post


Link to post
Share on other sites

I think the movement  of the  back, thrown into motion  by the  post, is of crucial  importance to the  sound, especially on the lower strings. Players will  try the upper reaches of the G and D  strings, and they're  really testing how the back works.

I tend to use spruce with strong defined grain, but not too close. I made my own for  years, but I  mostly buy them now, unless I want one of an unusual  thickness.

Share this post


Link to post
Share on other sites
6 hours ago, JacksonMaberry said:

... how do you avoid run-out? ;)

Reorder while you still have some in stock.  :P

Share this post


Link to post
Share on other sites
On 03/25/2017 at 6:30 PM, David Burgess said:

That's not quite accurate. Carbon fiber can split quite severely. And not unlike wooden soundposts, some of that will depend on the "grain" orientation of the carbon fiber.

Monodirectional carbon fiber composites are quite easy to split.

Sorry for the delay. 

Attached is a photo of some easily split unidirection (mono, uni, single, one direction) carbon fiber composites :  solid rod, tube, and tape.

IMG_1772. small, jpg

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
Sign in to follow this  

  • Recently Browsing   0 members

    No registered users viewing this page.