Eastman MD605 - 44% Humidity

[TheGrayFox]

I suspect some of the nerds among us have done this, but I've concluded via some weeks-long testing that my mandolin simply sounds the best between 42% and 44% humidity. This is room humidity, and not case humidity.

Over 44%, it starts to sound a bit muffled. The overtones start to diminish, and the sound is generally less "sparkly." Under 42%, and the instrument sounds curt and, in some ways, cheap. Granted, the difference within 1 or 2% on either side isn't huge, but as you get to 3, 4% on either side, it starts to get significant. Sonics exhibit a clear difference at 1% difference in humidity, however, on either side of that range. My partner has confirmed this.

Where do you all keep your rooms / homes to keep the mando happy?

[sunburst]

If a mandolin stays in 42% relative humidity long enough to reach equilibrium moisture content, that would be roughly 7.6% moisture. If the relative humidity is then changed to 45% and the mandolin is left in that environment long enough to reach equilibrium moisture content, that would be roughly 8% moisture.
While it is true that drier wood is relatively stiffer and relatively lighter than wood that is more moist, I'm having trouble thinking that half a percent difference in moisture content could make much difference in the sound.
To what do you attribute the difference in sound?
(BTW, of the half dozen or so hygrometers that I have (3 in the shop), none are accurate enough to be confident that readings are better than within maybe 10% of actual. That's why I have three of them in the shop.)

[Charlieshafer]

I'm with John that getting that accurate a reading is a little wishful thinking. Humidity affects everything in a room, as sound guys know, like baseball players, that warm, moist air transmits baseballs and sound better. The temperature is not all that critical indoors, it's a molecular thing where more water vapor affects the sound waves, and it could also be all the furniture and carpeting within a room. As far as trying to keep a stable humidity environment that doesn't require you to seal yourself in a room, much like antiques in museums? Forget it. You live in New England. Today, relative humidity is 100%, tomorrow back down to 40%, and if the temperature drops below freezing some clear night over the next week or two, 20%.

[sunburst]

OK, I'll buy that the room could sound different under different conditions of relative humidity, but noticeably different outside of a range of 42% to 44%?

[NursingDaBlues]

Our music room is humidified and runs between 39% and 49%. It’s the best we can do considering it’s not sealed, and it also has the cycling of central heat/air. However, our instruments hold tone pretty well in or out of the room.

Except…

A couple of my Webers like it dry. I really haven’t precisely measured, but the more humidity they’re exposed to the duller they sound. My wife’s Webers don’t react this way. On the other hand, I have a Martin J-65 that’s really sounds better with higher humidity conditions. Go figure. I can’t cater to these special sensitive souls, so they just have to learn to live in the same conditions as the rest of the choir.

[Charlieshafer]

OK, I'll buy that the room could sound different under different conditions of relative humidity, but noticeably different outside of a range of 42% to 44%?

I agree, not sure the measuring going on is all that accurate.

[MikeZito]

I once read/heard that both Taylor guitars and Gibson keep their factory humidity at 46%, so if I can keep my room anywhere within 5 or 6% of that, I am happy . . . but since my practice studio is in an commercial office building that takes in very little outside air, it is sometimes very difficult to keep that range - especially in winter. The best advice that can be had is to do your best to keep the room properly humidified, and keep your instruments in a case when not being played - especially in seasons/locations where humidity is way off the 46% mark.

[Charlie Bernstein]

How in the world do you adjust your room's humidity? For my house, it depends on what the weather is doing outside and what the furnace is doing inside.

[sunburst]

How in the world do you adjust your room's humidity?

Humidifier - dehumidifier, whichever is appropriate at the time. It helps (a lot) to have a well sealed room.
Right now, with the spring weather coming in, I am not having to actively maintain a good relative humidity level in my shop. I've been running a humidifier for months, and when the RH starts to rise in the shop I'll start up the dehumidifier. The shop is pretty well sealed with sprayed foam insulation and good weather seals.

[dhergert]

Keep in mind that temperatures have an effect also. While your wooden parts are pretty stable in temperatures, your metal parts are not, including your tuners, your strings, your frets, your truss rod (if present) and your tailpiece.

Wood expands with high humidity and contracts with low humidity while metal expands with heat and contracts with cold.

Discussion here has pretty well covered wood and humidity. Temperatures are going to change your tuning first, but then they may also change your tone.

This is especially true related to a truss rod if you have one. If the wood in your neck is expanding due to humidity and your truss rod is contracting due to cold temperature, that part of the mandolin is getting constricted, restricting vibration, possibly causing the instrument to sound pinched and muted.

This can also affect your tailpiece, mostly for tuning, but to a lesser degree for tone, depending on the tailpiece design and what metals it is made of. Again, this is a resonant surface, so if you have metal parts expanding against metal parts, these parts are going to get tighter against each other, which will affect tone.

The big question about changes in metals due to temperature is whether these changes are extreme enough to where you can tell a difference. The easy way to find out is to warm the instrument up. If the humidity remains the same and the instrument temperature increases by 10 degrees, and if the tone improves, you have your answer.

[sunburst]

Wood expands with high humidity and contracts with low humidity while metal expands with heat and contracts with cold.

True.

This is especially true related to a truss rod if you have one. If the wood in your neck is expanding due to humidity and your truss rod is contracting due to cold temperature, that part of the mandolin is getting constricted...

Wood moves very little in the direction of the grain, which is also the direction of the truss rod. Wood movement in the direction of the grain in wood is so small that it can be ignored most of the time. (For example, when I built my first shop in Virginia, I calculated the amount of lengthwise shrinkage of my 16'6" rafters from green (fresh off of my sawmill) to dry (19% moisture) and it was about 1/16". Negligible.) Not sure what "getting constricted" means, and I don't feel like taking the time to figure the movement of a steel truss rod in response to temperature, but my feeling is that under normal room conditions, or even fairly extreme room conditions, the difference in interaction of the truss rod and the neck is not huge.

This can also affect your tailpiece, mostly for tuning, but to a lesser degree for tone, depending on the tailpiece design and what metals it is made of. Again, this is a resonant surface, so if you have metal parts expanding against metal parts, these parts are going to get tighter against each other, which will affect tone.

Once again, under normal or even extreme room conditions, I don't think tailpiece expansion and contraction amounts to much. Furthermore, try as I might (as a maker of tailpieces), I can't hear much difference in the sound of a mandolin attributable to the tailpiece.

I'm still just not seeing anything that would make a mandolin sound noticeably different within normal room temperatures (even a wide range of normal) outside of a 3% range of relative humidity.

[Charlie Bernstein]

Humidifier - dehumidifier, whichever is appropriate at the time. It helps (a lot) to have a well sealed room. . . .

We have a dehumidifier is dry out the basement and a humidifier to keep us from getting colds. I have a couple of little Dampits, too.

But that doesn't mean that we can dial in a particular humidity. That sounds like science fiction!

It's not that I want to be able to do it. It's just surprising that anyone would want to. You can really hear a difference based on a percentage point of humidity? You're good!

(I do believe you. They say Eric Johnson can tell from the sound what kind of battery is in his stomp box.)

[FLATROCK HILL]

...I don't feel like taking the time to figure the movement of a steel truss rod in response to temperature, but my feeling is that under normal room conditions, or even fairly extreme room conditions, the difference in interaction of the truss rod and the neck is not huge.

My guess is that you are correct. Not much change in the length of a truss rod with a few degrees of temperature change. Or even "fairly extreme room conditions"

A motorcycle pushrod tube is similar in length to a mandolin truss rod. I'll go out on a limb and assume that the truss rod is steel (as stated). An aluminum pushrod will expand slightly more than a steel one and even the aluminum pushrod won't expand much more than a few (10) thousandths or so. And that change in length takes place during several hundred degree change in temperature.

Not sure how valid this comparison is but it makes sense to me.

[sunburst]

...They say Eric Johnson can tell from the sound what kind of battery is in his stomp box.)

[dhergert]

... The big question about changes in metals due to temperature is whether these changes are extreme enough to where you can tell a difference. The easy way to find out is to warm the instrument up. If the humidity remains the same and the instrument temperature increases by 10 degrees, and if the tone improves, you have your answer.

Sorry to quote myself there.

Changes in metal due to temperature aren't theoretical, they do happen. And don't get me wrong, I don't think anyone is questioning that it happens, we're all just unsure if it happens enough to matter.

In practice on the mandolin, these changes are sufficient to noticeably cause tuning deviation with just a ~5-~10 degree temperature change, but mandolin strings are under significant tension.

So is the tailpiece though, and, sometimes the truss rod is too.

If it were me and one of my mandolins was exhibiting this behavior, I'd be curious to test this. If the OP's normal ambient temperature in the house is 68F, and if there's a warmer room in the house (for example, due to sunshine, etc.), it would be pretty easy to put the mandolin in that room for an hour or more to acclimate and test.

Of course that does assume the humidity remains the same as the rest of the house in that warmer room, which may not be a fair assumption.

The bulk of my instrument time is with the banjo which typically has some wood and lots of metal doing lots of crazy things inside. Especially with certain banjos I can quite easily demonstrate this tone effect due to temperature changes. But the mandolin is a very different animal.

[sunburst]

...that doesn't mean that we can dial in a particular humidity...

It depends upon the size of the space and how well sealed it is. A sealed box just big enough for a mandolin (or a museum exhibit) can be dialed in pretty well (they do it in glass museum cases). A room or house with doors and windows, leaks and drafts, people going in and out, heating and cooling systems cycling on and off... yeah, sounds kinda like science fiction.

[fscotte]

And it all changes as soon as you start breathing.

[Phil Goodson]

Perhaps eardrums perceive sounds differently when the humidity changes; membranes swelling up and all.
Just saying ....

Honestly, I can play an instrument and go into the kitchen for a drink of water, and when I get back, the instrument sounds different. I think we trust our ears a little too much at times. Look at those Loar or violin blinded acoustic studies.

[MikeZito]

Yes, Phil is right. Somebody once described it to me as something like 'Fresh Ear Syndrome'. After repeatedly listening to an instrument (or playback of a song in the studio), your ears almost get numb to the sound - so, you have to get up and walk away from it, for a while - and when you come back, you will hear it with 'fresh ears' again.

[TheGrayFox]

I admit, my measurements are not up to scientific standards. Just two meters to measure humidity. Though I have a small, approx 1000 sq ft apartment. It was recently sealed and insulated via green energy initiatives, so it isn't dumping too much out the window. I generally find that running my humidifier at a similar setting each day (it remains on all day- as some noted, New England is tough for indoor humidity in winter) I can keep it pretty much in the same, possibly incorrect, reading range on my meters.

It's absolutely possible I'm hearing things, though. I suppose it could be a thousand factors, really, and I'm just attributing it to humidity. Am I sitting at a different angle while I play, firing sound at the walls in a different way? Is my picking hand any different than yesterday? Are the strings going dead? Certainly, it could be more than the humidity!

My initial post was partly in jest at my own expense- here I am monitoring my humidifier and meters like a hawk, when I should probably just be playing.