Temperature changes and neck movement

[lbpesq]

Hi, Keith.  I have three early Alembic guitars, 72-10, a ‘76 MSG Series I, and a ‘77 LSG 12 String Series I.  They are all quite stable and the weather here in the Bay Area is mild, so it is rare that I have had to adjust relief after the initial set up when I first acquired each.  Unless it’s way out, when I adjust a truss rod I usually turn it about 1/8 turn and then wait 24 hours before any further adjustment.  I assume my early Alembics are robust enough that they can handle such a gentle approach to truss rod adjustment without sustaining damage.  Of course one should inspect the adjustment nut and lubricate it, if needed - especially on a vintage instrument. 

OTOH, I wouldn’t want to cause any damage unnecessarily by tightening the rod instead of manually pulling the neck and then tightening the nut.  (Brother Paul, tbo’s elusive “third hand” would sure come in handy in this procedure!). Anyone else ever heard of this?

Bill, tgo

[bigredbass]

A tip you may find useful (and may be at work here):

Just as we always tune up to pitch (as can happen, tune down to get in tune and it just may keep creeping down a wee bit), whenever I loosen a truss rod to get it back to there, I always snug it up just slightly to cinch it.  Not enough to change the action, only to set the nut.

Weather / season / temp-related action changes will vary from axe to axe depending on the particular wood in a given bass.  My red Spoiler (made in 82) was virtually unmoveable once the action was set.  My green Elan was much newer and would move around a bit as it was a much newer build and a different neck recipe.

[KR]

Bill, In So Cal, where I live, I hardly touch the truss. If I do it's very small turns, similar to your Alembics. I agree Bigredbass about the truss nut. I'll tighten the truss again slightly after loosening the nut.

[edwin]

I toured my Alembics (and other basses) all around the country and they traveled in unheated or cooled trailers most of the time. So, long trips in very high or very cold temps and wild swings in humidity. I have to say that my Alembics really didn't require that much adjustment compared to the others. Instruments can put up with a lot, not that I recommend it, if it can be avoided.

[jazzyvee]

I have a classico and over the past year approximately, I have noticed  the note E on the D string and note A on the G string have a buzz in sound and I can feel it under my finger when playing those notes. It is also a bit lower in volume and i guess what people may refer to on an electric bass as a dead spot.  It's more noticeable if I'm sustaining either of those notes or playing them seqentially in the same position but not if I'm passing through either of them on the way to the next note.
As a beginner I fully accept that it may be all or partially down to bad technique on my part and i'm tryng to be aware of what I'm doing in that position, but I do wonder if it has anything to do with the change in humidity within the room.
Last year late November I bought a large warm water aquarium for the room the bass set up in and I have to top it up about once per week with about a 1/2 to 1 itre of water due to evaporation and humidity in the room according to my not very accurate gauge is 62%.
Could that be causing any issues?,  is this what people refer to as growl?. There is no truss rod adjustment and it is a substantial neck and I haven't found any issues elsewhere.
Any suggestions ?

[garyhead]

I've had a 6 String Classico for 22 years and haven't had this problem.....could there be some deterioration / failure in the string winding's?
Had an interesting conversation with Ron W last fall when the bass was at the shop.  He said it would be possible to use Gut strings if metal was inserted into the strings around the pickup area.....now That would a unique sound!
A quick voltage check of your batteries would also be in order.....ie.  check the simple stuff first! 

[edwardofhuncote]

Jazzy, if the relative humidity in the room with your bass is 62%, it is almost certainly affecting the neck geometry. No experience with a Classico (yet!  ) but I wouldn't expect the neck of one to behave any differently from an upright. Higher levels of moisture will usually cause a neck to bow back, placing the strings closer to the fingerboard. I wouldn't rule out a string winding either, but this sounds like a good ol' geometry problem. Put it in another room for a week or two, and see if the buzzes diminish.

[BeenDown139]

just noticed this thread, thought i'd jump FWIW. 
Here in denver we're getting set for a wild weather swing: 90°+ every day for the last month or so, < 15% humidity.  I took a bike ride in 95° heat yesterday, today it's gonna snow.  So i know i'm gonna be tweaking truss rods when i get home from work tonight.

I have two basses that sit in my living room/practice space that get played every day - a '95 5-string fretless essence and a '19 MK 5-string fretted.  I've had the essence for a couple of years now, and i've come to refer to it as my barometer.  I keep the action on it as low as i can (~ 3mm at the 12th fret) which probably doesn't help.  Every time we have a weather change, either i'm adjusting the bridge & nut or if the fingerboard buzzing gets too bad, tweaking the truss rods.  I used to live in an apartment that had a swamp cooler that ran most of the time.  As long as it ran and kept the humidity up around 60%, the fretless neck was nice and stable.  Now that it lives in a more ventilated environment, it changes as the weather does.  I've owned 10 various models of alembic basses over the years and this is the only one that's ever given me trouble like this.  Usually when i get a chronic temperamental instrument like this, i either get at the root of the problem or it goes on the auction block.  This one's different, because once the action's dialed in, it plays and sounds like no other instrument i've ever owned.  so i've come to live with it (kinda like having a beautiful wayward girlfriend - gotta look past the part you can't change). 

They symptoms of rising humidity with that bass is: i'll check the tuning and the whole bass will be sharp, sometimes almost a whole step.  Sight down the neck and i'll have a back-bow, almost to the point of being unplayable.  out comes the wrenches and away we go.  Falling humidity just the opposite: the whole bass will be flat a half step or so, the action will be be up to about 5mm.
When we have stretches of variable weather, i'll just leave the truss rod cover off of it because i know i'll be tweaking the truss rods.  I've getting pretty good at dialing the action in, it's not that difficult and so i just live with it.  The MK seems to hang in there pretty well, its action movement is noticeable when i play it, but usually not enough to warrant an adjustment.  But it's essentially a brand new instrument (still has that wood smell) and i'd imagine it'll be a few years before it completely stabilizes.

Over the years, i've gigged with a lot of instruments, not sure i'd wanna be on the road with something this temperamental. A few years ago, i owned a steinberger XL-2 and i could take that thing out of a car trunk (boot, for you across the pond) in sub-zero weather, pull it out of the case and not even have to tune it when showtime came around.  now that bass was a real road-dog!  i miss that bass. :-(

[Jonnio]

In my limited experience with bass guitars, but with a more engineering background, temperature differential on the bass mainly affects the strings over a shorter period of time. I suppose if you have gone outside and then into a warm room, the coefficient of expansion of the metal is greater than the wood. When it comes to expansion of wood, things take on a different perspective. Along the length, wood expends very little with heat, and by only a small amount, it is not a good conductor. But because wood takes up heat slower than slim metal strings, which expand quicker, they will go slightly flat, in that short period of time. Humidity is a far greater player, it will slowly expand and contract the fingerboard across its width and also to a lesser extent along the length, hence the edge of the fret wire can be felt in some seasons and not in others. Over in the UK, we have wet soggy winters, but although the relative humidity is slightly higher then, the absolute humidity is higher in summer, and wood pulls in more of this out of the atmosphere. My basses, both Series 1, and Epic, (to a lesser extent), have required the truss rods to be loosened slightly in summer, due to the fretboard growing slightly with the uptake of moisture. The adjustments to the truss rods will always be needed, but in fairness, it is not too difficult. Any experiences from others welcome to either support or refute my findings, as I do think it is an interesting subject for study and debate. Cheers

[pauldo]

I live in Wisconsin and our winters are cold and dry, summers are hot a humid.   I have yet to have a scenario where I needed to adjust the truss rod (30 some years of ownership). 

Admittedly (although reasoning assures me it is false) I am intimidated by the idea.  But truthfully I can only recall adjusting string height (maybe 1/32") a handful of times to compensate for fret buzz because of temperature/ humidity changes. 

My favorite saying is that my bass darn near plays itself.  A true testament of the attention to detail that went into it when it was birthed back in 1984.  Thank YOU Alembic people!

[s_wood]

As others have said, neck movement is a natural and unavoidable consequence of drastic humidity changes (temperature changes are, in my experience, a very minor factor here).  Wood is hygroscopic, meaning it absorbs and releases moisture to the atmosphere.  When the air is very humid, the unfinished fingerboards of our Alembics will absorb moisture over time and slightly increase in size.  When it's dry, the fingerboard shrinks a bit. Those movements will change the relationship between the neck and the truss rod tension, which will affect relief.

Geek alert: the hygrometers that many of have in our homes, or that we scan on one weather website or another, measure what's called "relative humidity."  It's expressed in a percentage. Relative humidity is essentially a measure of how more much moisture the air can hold at a particular temperature.  It is NOT a measure of how much water is in in the air.  That's called absolute humidity.  All that means we can't simply look at the relative humidity % and say that there is more or less water in the air, and it's the quantity of water in the air that affects the movement of the neck.

Anyway... a couple of typical factors that affect humidity. Forced air heat and air conditioning both dry out the inside air.  On the east coast of the US (where I live) and in England, (where Jazzy lives), it's typically pretty humid outside, especially in the summer and fall (because warm air holds more water than cold air).  So if we keep our basses inside where HVAC systems keep the air pretty dry and then take our basses outside to play an outdoor gig they will experience a significant humidity change pretty quickly, and the neck will likely move.  It's less of a problem in the winter because the outside air has less moisture in it.  And even with HVAC systems, it's drier inside in the winter because the colder air is drier.  That's why those of us who live in humid climates where it also gets cold(the US East coast and Midwest, Great Britain, France, Belgium, and parts of Germany) have more of an issue with neck movement.  Where the air is always dry it's much less of a problem.So, if you live where I do - or where Jazzy does - the truss rod wrench is your friend.