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Double Bass Tilting bridge: does north tilt or south tilt lower string height?

#3
What GW says. And, as you've said Chris, it's pretty rare to see a bridge tilting south.

FWIW, you'd have to have some fairly significant tilt to make a noticeable difference in string height. And if you have that much of a tilt in your bridge, step away from the bass!
 
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#4
I’m more curious of the question. Are you looking to lower the strings? If it’s a fixed bridge, you would want to remove some material or slot the strings a little deeper. If it’s adjustable, it’s just the turn of screws. I know you probably know all this, so back to the original sentence in my post - curious of the question
 
#6
Just a tangential question: why are folks saying it's rare for a bridge to tilt south? If my bridge is tilting, that's usually the way it's going. I check it at the start of every gig and adjust if necessary.
 
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#7
This thread made for interesting reading given I just clicked the title on the home page and didn't realise at first that it was about double basses. I only play bass guitar, and was having trouble figuring out how a bridge could tilt at all...
 
#8
Kenan said:
Just a tangential question: why are folks saying it's rare for a bridge to tilt south? If my bridge is tilting, that's usually the way it's going. I check it at the start of every gig and adjust if necessary.
Click to expand...
Bridges tilt north (toward the fingerboard) with regularity because tuning the strings up to pitch usually pulls it that way. Tilting south is a rarity because there is no natural built-in tension to pull it that way as there is with northern tilt. It would take an outside force to influence it in that direction. Perhaps something about how you bag/unbag your bass or the way you stuff it in your car might provide that, I don’t know.
 
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#10
BassFalcon said:
It would take an outside force to influence it in that direction.
Click to expand...

Interestingly different neck-angle geometry and/or a really short bridge and/or a really high saddle (under the tailpiece cable) could potentially reverse what most of us consider "normal" tilting tension, pointing it southward. And these don't have to be that different. It could even simply be a function of low action adjusted at the bridge on some double basses. Also, some strings almost completely stop stretching after they are broken in.

Given all that, it could be said that setup is what determines which way the bridge will tilt.
 
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#11
Thinking twice about it, the string action will go up a bit when tilted towards the fingerboard before it goes down again.
Why?
There are two reasons.
The main one is that the bridge in its normal state is not perpendicular to the vibrating length of the string. If it would be perpendicular it would be the highest point and any tilting would lower the action. But it isn’t for a good reason.
So tilting the bridge towards the fingerboard gets closer to the perpendicular state and therefor raises the bridge.
The second reason is that a tilted bridge sits on the edge of the bridge foot that rises the middle of the foot and makes the distance from string to top at the middle of the bridge foot higher. Just a minor effect but somebody asked …
 
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#12
My bridge has a tendency to lean towards the south and coming back to almost straight. It’s a cyclic behaviour happening over a period from a couple of weeks to a few month. It also has longer periods of rests, not moving at all. I have started to percieve the double bass (or any acoustic instrument) as a co-existing, living organism for some time now; and as we all know, not all forms of life obey to the rules of physics but rather respond to how they are dealt with.

BassFalcon said:
Bridges tilt north (toward the fingerboard) with regularity because tuning the strings up to pitch usually pulls it that way. Tilting south is a rarity because there is no natural built-in tension to pull it that way as there is with northern tilt. It would take an outside force to influence it in that direction. Perhaps something about how you bag/unbag your bass or the way you stuff it in your car might provide that, I don’t know.
Click to expand...
 
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#13
On my main bass the fixed bridge was tilted towards the FB for perhaps 30 years when I got it. The bridge was bent like a Thonet chair and had to be made brand new. The luthier told me, that the bridge tends to tilt towards the FB with string tuning, and that I should check whether the bridge is straight from time to time. He also told me that when (fixed) bridge is tilted, the legs touch the body on smaller area, resulting in worse sound. Adjustable bridge is more tolerant to tilting, but still not desired.

Also, check whether the bridge is in its right position east -west, and whether the adjust pins are symmetrically adjusted, so that the bridge top is in its right shape compared to FB curvature.
 
#15
The stretching of a string over time means that more string is wound onto the peg and also that the movement of the string towards the pegbox happens to a lesser degree as well at the contact point of the string at the bridge.

The relatively high friction of the string at the bridge catches the bridge crown which can result in tilting towards the bridge.

But there are also forces that want to move the bridge crown due to the angled string at the bridge. They cancel each other out if the string to bridge angle (at the straight side of the bridge) are the same but if not have a tendency to move the bridge in one or the other direction, depending on the additional forces from the stretching string.

Since the bridge angle could be easily corrected (unless the angle difference is so extreme that the bridge needs to be screwed to the body as with my Clevinger EUB without a raised saddle) and friction keeps it in place, the luthiers don’t care too much about an exactly equal bridge to string angle at both sides of the bridge.

A raised saddle can change the angle at the tailpiece side but would change the string pressure to the bridge as well which is often more important and generally the reason to change the saddle height. A changed overstand does the same in the fingerboard side of the bridge.

Use a line with a roll at weight, hold the ends of the line so that the roll goes down making a v-shape of the line. The angle between line and weight will always be the same on both sides because otherwise forces from both sides are different and the weight will move so that such a equal force state could be reached.

BTW, the force is determined by the tension of the line/string (constant across the length of the string/line unless there is some friction) and the angle.
 
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#16
This has reminded me to check my own bass. I have adjusters and noted that the feet were fully in contact but upper part of the bridge had pulled forward a little, noted because the gap between upper and lower parts of the legs was not parallel. After releasing some tension and returning the gaps to parallel the string heights were about a mm lower and there was less tension. I have noticed that rarely are the string angles on each side of the bridge equal and that the angle on the tailpiece side is generally more acute. Over a period of time there is a resulting force that pulls the top of the bridge towards the fingerboard IMO. And afterwards my bass sounded better too.
 
#17
A brief look at the other side...

As ugly as they are compared to an expertly carved adjustable wooden double bass bridge, if installed as designed the oft derided Deuce bridge does successfully resist tipping over, but they actually can be caused to tilt enough to raise most of the treble foot off the table. I've seen this happen once with my Deuce bridge while breaking in new strings, was of course quite surprised and hustled to straighten it, and now keep an eye on that treble foot. So with that experience I can reliably say that my Alcoa tends to tilt my Deuce bridge northward...

Also perhaps of interest, some double bass strings are both low-tension enough and smooth enough that they do not apply sufficient friction or tension to the top of the bridge to prevent it from tilting. I've seen this happen with some very smooth wackers.

It's worth mentioning, a conventional wooden double bass bridge with installed adjusters could also have one foot (most likely this would be the bass side foot) pointing cattywampus north and south in contrast to the other foot. I've never seen this done but there isn't much preventing it being intentionally installed that way. This would probably help resist having a bridge flip, but the big question in my mind is whether the thickness of the rest of the bridge leg involved in this change would be sufficient to withstand splitting because of tilting tension on the internal adjuster post; in the case of the Deuce bridge that part of the bridge is thick aluminum and the adjuster post is a 1/4" bolt shaft, so everything is beefier.

D'A-PW Tuner.jpg

I also play banjo and mandolin, both which also have "floating" bridges. Bridges on both instruments can also end up tilting and even eventually flipping. The mandolin bridge is also often fitted with adjusters, which while making it handy for action adjustments can also affect tone and volume. Adjusters on mandolin bridges also tend to allow the bridge top (called the saddle on guitars and mandolins) to tilt more. Manual adjustments, frequently required, are affectionately called "burping the bridge" by mandolin players. Four and five string banjos tend to have nonadjustable (often also laminated one, two or more piece) bridges, sometimes with a middle, perpendicular, keyed ebony foot that prevents the bridge from tilting.
 
#18
Many years of experience with this phenomenon has taught me that over time tuning the strings causes the top of the bridge to edge north (towards the fingerboard). This always results in a slight raising of the action and perceived tension. Moving the top of the bridge south to bring the bridge back to optimal position always lowers the action and perceived tension. This bridge movement can also be diagnosed and corrected by measuring the string length, assuming that you know what that should be for your bass. Upton always provides a handy measuring stick for this purpose for all the basses they build.
 
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#19
There will be a difference in effect because the bridge is asymmetrical north-south, with more foot on the north side than the south. So northward tilt will raise the action more than the opposite. At the point where the bridge is tilted enough to noticeably lower the action, it's already too unstable to stand, either way.

The way to affect the action is to move the bridge rather than tilt it, which alters the scale too, of course. Moving northward raises, and southward lowers.
 

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