Jump to content
Maestronet Forums

Sound Posts and the Escher Effect


Brad H
 Share

Recommended Posts

Am I the only one whose eyes are tricked when viewing sound posts?    One minute, it may appear the post is leaning forward, but if I keep looking at it - just like an Escher drawing - I can almost see it leaning the other way.   Or, picking up a violin  and re-examining a previously set post and thinking, " OK, how did I do that?".   I mostly look through the treble f-hole, but will use the bass f-hole, too.

The other Escher effect occurs for me when setting a post sans bridge, and then viewing the post after installing the bridge.   Usually, I see the post in a more backwards leaning stance after installing the bridge.

 

Link to comment
Share on other sites

Its because the image in your mind is created by both your eyes together if you look with one eye only then look with the other eye it will appear to lean at different angles. 

You can try this out by looking at anything with one eye closed, then look with the other eye, while  closing the first, what you look at will appear to move slightly, my opthalmologist explained this to me,it can also be due to differences in strength of vision in each eye.

Link to comment
Share on other sites

Yes I have noticed this, but I also figured out its a function of your visual reference point.  There are multiple surfaces on a violin, all at different angles, and the sound post isn't square to any of them except the garland, which isn't much help.

Your process will be most repeatable if you deliberately compare the sound post position against a specific reference point(s) on the violin.  This keeps your brain from using whatever you looked at last as the reference point.

Link to comment
Share on other sites

13 minutes ago, Shunyata said:

Yes I have noticed this, but I also figured out its a function of your visual reference point.  There are multiple surfaces on a violin, all at different angles, and the sound post isn't square to any of them except the garland, which isn't much help.

Your process will be most repeatable if you deliberately compare the sound post position against a specific reference point(s) on the violin.  This keeps your brain from using whatever you looked at last as the reference point.

What would you suggest as the reference point, since even the garlands on most antique violins are not consistent or straight?

Link to comment
Share on other sites

I usually wear reading glasses when working on violin setup...and keep both eyes open.   Yeah, I get the deal with different reference points.    I have learned not to react to my first impression when viewing a post.    I also usually hold the violin in as close to horizontal position as I can get.   After an initial view, I usually rotate the violin slightly, dipping c-bouts up and down, and can go back to the exact same initial view...and sometimes get a different reading.

Additionally, I think we all have our own idea of a "straight" post (assuming we are aiming for straightness).  

Link to comment
Share on other sites

Some suggestions for reference point include:

* edges of top block (when end pin is out),

* inserting a vertical reference stick through either f hole, located at a consistent point.

*looking at post angle versus back plate at the point of contact (deliberately ignoring the appearance of the post overall)

* using a flat shim to measure position of post relative to f hole notch, both N-S and E-W.

* bending your post setter so it is at right angles to garland when post is in proper location.

None of these are scientifically precise, but together they produce rapid, repeatable results.  And that is all we really need to achieve... quick, consistent placement that is in the right neighborhood for fine adjustment.

 

Link to comment
Share on other sites

1 hour ago, Shunyata said:

* inserting a vertical reference stick through either f hole, located at a consistent point.
 

How do you know that your vertical reference stick is vertical? Do you attach two bubble levels to the stick, and two more to some place on the violin to determine the straightness on two axis?

In other words, I can relate to Brad's challenges, and after many decades in the business, don't find this to be anything close to easy.

Link to comment
Share on other sites

On 2/9/2021 at 6:53 PM, David Burgess said:

What would you suggest as the reference point, since even the garlands on most antique violins are not consistent or straight?

I hadn't thought about this much, more just doing it, so I went and looked in some violins I'd set posts in.  I found that I'm subconsciously referencing to the bridge vertical, which means ultimately to a plane tangent to the top curve at the f-hole notches.  :)

Link to comment
Share on other sites

This thread begs the question as to why it matters if the post is not absolutely vertical ?

The only practical reason I can think of is that the bevel end of the post might did into the top or back a bit leaving an indentation in the wood.

Apart from that is it likely to have an observable effect on sound quality or something else ?

Link to comment
Share on other sites

I'm another who doesn't believe "vertical" is a hard-fast rule, though I tend to do my best to start with that when cutting a post.

As far as "getting it straight", I work on many old instruments where finding a reliable reference point could be classified as "challenging".  It's great when I do, of course.  :) 

Straight looking from the endpin hole is, in my opinion, less difficult than straight from the side (f hole).

If things are wonky (rib corners off 90 degrees, a dip in the rib/plate joint around the c bouts, twisted body, etc... and it doesn't take much to throw off the view) and I can't get a good reference, I sometimes use a china marker to draw a light line across the stop between the ffs. If you hold the violin squarely, directly, in front of you and rotate it away from you, the china marker line can be compared to the post position as a reference point as you go.  Not a perfect solution, but a solution non the less.

The usual warnings: Don't use a china marker if there are open cracks or exposed wood in the stop area.  They are wax, after all.  Easily removed from varnish though...

Hope this helps.

 

Link to comment
Share on other sites

7 hours ago, David Burgess said:

Wasn't me. Sound posts sound best at the location and the angle they sound best, which varies from instrument to instrument.

I looked it up and you were talking about fit, not angle.  I was remembering angle instead.  Sorry.

https://maestronet.com/forum/index.php?/topic/339473-deliberately-angled-soundpost/&do=findComment&comment=785084

 

Link to comment
Share on other sites

2 hours ago, Mark Norfleet said:

No.  And it's even worse after having had surgery to repair a torn retina, but hopefully will improve after cataract surgery that will be needed to address a side effect of one of the drugs I took post surgery.

I've had a few WTF moments in the last few years looking at sound posts....

Might you be up for helping me glue another cello top on sometime soon, or might it come out all wonky? :o:D

Link to comment
Share on other sites

7 hours ago, Jeffrey Holmes said:

Straight looking from the endpin hole is, in my opinion, less difficult than straight from the side (f hole).

Yep.  My challenge is N/S orientation.   The other factor which affects my perception is lighting.   I can sometimes get different readings if I am just bringing light in through the bass f-hole from a lamp versus when using my luthier's light.

 

13 hours ago, Delabo said:

This thread begs the question as to why it matters if the post is not absolutely vertical ?

The only practical reason I can think of is that the bevel end of the post might did into the top or back a bit leaving an indentation in the wood.

Since the plates converge as they get nearer the bottom block (are not parallel), a post that is cut perfectly perpendicular on both ends (only considering N/S line)  will not fit perfectly if set in a vertical  position.    I agree that the perfect fit of the post ends is more important than whether the post is in a vertical position.   I usually cut compound angles on the post ends, so that the tailpiece side of the post ends are cut  incrementally "lower" than the bridge sides.

How do others deal with the non-parallel plate convergences at the post position.   

Link to comment
Share on other sites

4 hours ago, Mark Norfleet said:

Sure, so long as I don't have to make anything straight.
Likely next week some time, if you really want to risk it...

How much risk do you think would be involved?
Jill helped me glue the back on, with the ribs still on the form (which she has done many times, and this is much easier than gluing on a plate with the ribs removed from the form). But this most recent time,  she said afterward, "Don't ever ask me to do this again". :o

WTF? I didn't yell at her or beat her all that much either during or after the procedure. :lol:

Sidebar: Norfleet can do many things as well with his eyes closed, as many other people with their eyes open and with 20/20 vision can do.

Link to comment
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...
 Share

  • Recently Browsing   0 members

    • No registered users viewing this page.


×
×
  • Create New...