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Double Bass fixed vs. adjustable bridge, perspectives?

#21
bonaventura said:
i'm not posing as Arnold :D but i would like to say that many do share his view.

...
Franz Moser took part in those tests as well, as you can see on his website here: Invalid Link Removed

in a nutshell, the ability of the bridge to conduct the vibrations of the bass strings is apparently even better with a good set of bridge adjusters.

you might want to check out F. Moser's site: he has aluminum and titanium adjusters. He told me there is essentially no difference between the two in terms of sound.
Click to expand...


Thanks for the link. :hyper: I had been thinking about this for a month and unsuccessfully Googled for such a device just last night.

Moser's adjuster is a giant leap beyond a one-axis height adjuster. It also has ball pivot joints that allow the bridge to be out of perfect alignment without applying lifting forces to edges of the feet. As long as the foot fits the body the fit is always tight and full. The bridge can even be raised on one side w/o binding or affecting the foot fit.

How can this not be great? Someone just this week in this forum posted to the effect ". . . my bass sounded thin because the bridge has over time crept up the strings and tipped the bridge foot onto the top edge".

I was about to alter my adjusting screws to incorporate a ball and socket joint on the bottom. Was trying to figure out the socket part. I am encouraged and if it doesn't work I now know where to get one.
 
#22
I've had a Moser aluminum and now use a Moser titanic adjuster. They're pretty much the same, except the titanic looks more like steel than aluminum.

The ball mechanism works just like in the web page picture. The bridge can bend up or down, the feet stay flat against the top of the bass. The feet can also flex laterally. The total vertical amount of adjustability for the bridge is about 5 or 6 mm.

Be warned though, the ball mechanism means the top part of the bridge is no longer joined to the feet. They cannot be for this adjuster to work. The top is held against the feet by the pressure of the strings only. So when changing strings it is more important than ever to prevent the bridge from falling, because if it bends too far forward -- ker-thunk! -- the top part can fly forward off the feet. :eek:

Btw, I doubt that any other luthier can install it. Takes some special drilling equipment. You'll need to send your bridge to him. He does it the same day as receipt and sends it back by mail. After calling him I packaged my bridge up with all kinds of padding and sent it off.
 
#26
I would take with a grain of salt the results of the all of the tests performed thus far focusing on listener discriminability and/or preferences for bridges with and without adjusters. This is an area where I certainly do know of what I speak. The objective physical measures, on the other hand, are what they are. As I see it, the good news is that there seems to be no demonstrable or even anecdotal sonic down-side to the adjusters. If anything, the evidence might even suggest a benefit. There is, however, certainly great benefit from adjusters in terms of being able to get your string heights "just right."
 
#27
gbaker said:
Moser's adjuster is a giant leap beyond a one-axis height adjuster.
Click to expand...

I think not. To my mind, a simple one-axis adjuster does the best job keeping the bridge intact as a single vibrating unit. And the fact that it does not allow for tilt is a good thing, as it will encourage the player to keep his bridge properly positioned. A wrongly positioned bridge changes the string length, which adversely affects intonation and tone. Then there is the cost...
 
#28
Chris Fitzgerald said:
I can't explain the physics involved, but on every bass I've ever owned, the strings get further away from the fingerboard in the summer and closer to it in the winter. Spring and fall, the height is all over the place. My suspicion is that it has to do with humidity more than temperature, but take that with a grain of salt.
Click to expand...

Humidity is the answer. As the average humidity level goes up, the wood absorbs the excess moisture and swells. As the humidity drops in the winter, it dries out and shrinks. When it swells, the body pushes out slightly, pushing the strings further away from the fingerboard (a soundpost adjustment might be needed around this time). As it shrinks, the body pulls in a bit and the strings get closer to the fingerboard (requiring another soundpost adjustment). It's probably a bit more complicated than that (different woods expand and contract at different rates) but that's the basic idea.

I usually don't need soundpost adjustments done with the season changes but I do need to raise the action in the winter and lower it in the summer.

mark
 
#29
arnoldschnitzer said:
I think not. To my mind, a simple one-axis adjuster does the best job keeping the bridge intact as a single vibrating unit. And the fact that it does not allow for tilt is a good thing, as it will encourage the player to keep his bridge properly positioned. A wrongly positioned bridge changes the string length, which adversely affects intonation and tone. Then there is the cost...
Click to expand...

Good points, sir. Like every different (I can't say new) concept, there are trade-offs. In addition, there is a lot to say for simplicity, if there is less there is less to go wrong.

I haven't tried it yet, But I THINK the high tension force of the strings (what 40 lbs or more?) will keep the bridge vibrating well intact in the important up/down axis. I don't think there is any question that well fitted feet and therefore the bridge angle is very critical to a full sound. In stringing up my bass it seems that as little as 1/4" along the strings can tilt the feet, even with normal height adjustment screws installed.

Experience has demonstrated that bridge stiffness in the along the axis of the string doesn't effectively prevent bridge creep toward the fingerboard eventually causing sound degradation. A ball and socket-like joint at the foot removes the critically of the bridge angle (within reason). There may be some down side in keeping good sound quality while the bridge is going out of angle but as with the rather recently accepted height adjusting screws, to each his own.

I agree the cost seems high for what seems to be a rather simple concept.

As a experiment, in an old bridge, I am going to fit #10 screws, either carriage bolts or round heads, threaded into the higher bridge legs and with the domed head resting in a mating indentation in the foot. Thus an adjustable height and a ball and socket joint. It may not be too pretty but it should demonstrate the concept. If anyone has already tried this, please let me know. Thanks.
 
#30
I was thinking of doing some routing for a tremelo bar on my bass... or just getting a high mass bridge...

kidding of course...

for the record I like my adjusters and would never play with anything else if I'm given the choice for the rest of my life as I do adjust the height on occasion when I find It seems the strings feel to close or far away form the fingerboard. I should be able to cover any indesrepencies with technique (IMO/E of course)
 
#31
Btw, I doubt that any other luthier can install it. Takes some special drilling equipment. You'll need to send your bridge to him. He does it the same day as receipt and sends it back by mail. After calling him I packaged my bridge up with all kinds of padding and sent it off.[/QUOTE]

So what kind of special equipment are we talking about? Jig Borer?
 
#32
calivox said:
Humidity is the answer. As the average humidity level goes up, the wood absorbs the excess moisture and swells. As the humidity drops in the winter, it dries out and shrinks. When it swells, the body pushes out slightly, pushing the strings further away from the fingerboard (a soundpost adjustment might be needed around this time). As it shrinks, the body pulls in a bit and the strings get closer to the fingerboard (requiring another soundpost adjustment). It's probably a bit more complicated than that (different woods expand and contract at different rates) but that's the basic idea.

I usually don't need soundpost adjustments done with the season changes but I do need to raise the action in the winter and lower it in the summer.

mark
Click to expand...


There are so many anecdotal explanations for the seasonal "rising" and "falling" of the "top". For good measure, throw this one in the hopper:

The luthier who made my German flatback bass told me that the wood swells in summer due to humidity (like you've pointed out). He says the especially the back expands vertically in the summer, such that the neck is pushed up and forwards. Thus, the fingerboard closest to the bridge moves down closer to the top. Thus, he says, the top of the bass doesn't rise, the FB comes down closer to the top, creating more string height. The reverse process would then explain the phenomenon of "lower" string height in winter.

If this is so, then you wouldn't expect to need a seasonal soundpost adjustment, only a string height adjustment.
 
#33
I feel that part the reason the Moser adjuster is considered at all is simply because so many bridge height adjusters aren't installed well. Common problems: The faces where the top and the bottom of the bridge meet aren't squared up; the holes for the adjuster posts aren't drilled square to the faces;the bridge wasn't fit well and wasn't placed at the proper angle to the top before it was sawn in half for the adjuster. People are looking for a better adjuster but what they could do is demand that the job is done right in the first place.
 
#34
bonaventura said:
There are so many anecdotal explanations for the seasonal "rising" and "falling" of the "top". For good measure, throw this one in the hopper:

The luthier who made my bass told me that the wood swells in summer due to humidity (like you've pointed out). He says the back and top expand laterally and vertically in the summer. In doing so, the neck is pushed back such that the fingerboard closest to the bridge comes down towards the top. Thus, he says, the top doesn't rise, the FB comes down closer to the top. The reverse process would then explain the phenomenon of "lower" string height in winter.

If this is so, then you wouldn't expect to need a seasonal soundpost adjustment, only a string height adjustment.
Click to expand...


This is really interesting. I've never heard that before. I'd love to hear what the esteemed Mr. Schnitzer has to say about this.
 
#35
Esteemed? Why would I be angry?...

Seriously, though, I think both factors are real. There is no doubt that soundposts loosen up in the humid summer. I do also believe that there are changes in the back and in the neck angle that occur. Basses that are really deep at the neck joint, exposing lots of end grain in the neck, move more and seem to require more of a bridge adjustment season-to-season.
 
#38
All woods change dimension in reaction to climatic changes. Some species change more than others. Maple is not particularly stable. Wood mainly changes across its grain, in other words primarily in width rather than length. Wood that has been dried to a moisture content lower than it is likely to encounter in real-world conditions becomes more stable than wood that has not. Wood that has been air-dried in a humid environment never reaches a moisture content dry enough to be suitable for use in string instruments. I don't know of any correlation between grain width and seasonal swelling/shrinking.
 

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