Resonant Frequency and the "Opening Up" Phenomenon

[man dough nollij]

I was about to post this in one of the latest "Tonerite" threads, but thought it might be a hijack...

I've been reading all these treads about "opening up", and the various things people have done to keep 'em warmed up, like hanging it in front of a loud speaker, various vibrators, etc.

I should say that I'm a little skeptical about the breaking-in, or opening-up phenomenon, strictly from an engineering background. Enough high level players and world class luthiers believe in it, so I'll go along with idea. I'm not a builder or much of a player, so what do I know?

Someone posted a while back about an interesting phenomenon that I think might tie into the preceding discussion. He said that he noticed that if he sang or hummed into his mandolin's soundhole, it "sang back" at a certain frequency. I've noticed that, too, but never nailed down the resonant pitch.

Here's my idea: try to find out what frequency/note makes a mandolin resonate. Then use a tone generator hooked up to a loudspeaker to blast the little bugger with that exact tone. We should be able to really feel it shake and hear it sing at just the right note.

If anything is going to "wake up" an instrument, I would think (based on wild intuition) that would do it.

Anybody out there sing into your mandolin and figure out what note makes her quiver?

[Bigtuna]

Didn't they use some device to more or less do that to the "Red" violin in the movie the Red Violin?

[foldedpath]

The resonant frequency, as I understand it, is a function of the air mass inside the instrument body being energized by the string/top vibrations. It can be tuned (somewhat like the "bass port" on a speaker cabinet) by the size and shape of the holes in the top.

This primary resonant frequency (and its harmonic series) sits "under" the fundamental tone of any note you play, and it helps establish the timbre or voice of your instrument. I've done recordings of a single note on my guitar and run the waveform through an editor like Wavelab, which can plot it on a graph. There's spike that's always there at the resonant frequency, regardless of the pitch of any other note you play.

Here's where it gets tricky. That resonant frequency isn't necessarily part of the normal equal-temperement series. I haven't tested my mandolin, but the resonant frequency of my steel string guitar is just about exactly at 100 Hz. That's roughly in the vicinity of a "G" note, and a lot of guitars have resonant frequencies more or less in that area. But it's not exactly a G note. A G2 in equal temperament is 98.0 Hz, and G# is 103.8 Hz. This falls somewhere in the middle.

If I built a gadget that vibrated my guitar at the main resonant frequency, how do I know that it won't reinforce that pure 100 Hz tone and make my equal-tempered G and G# notes sound sour? Or maybe it would just boost the fundamental timbre of my guitar and improve the general tone, and it wouldn't interfere that much with the equal-tempered note series.

Someone should run some careful double-blind listening tests and try it.

But not me. I already like the sound of my guitar, and I don't want to mess with it.

[TonyP]

Years ago when a friend was trying to build a mando, he bought a kit, and the Siminoff book. One of the things he told me about the process was the top and the back were supposed to be "tuned". So, it makes sense a mando would want to "sing back" at a certain frequency.

I think Roger Siminoff's "dedamping" process has and element of that to it. I'd have to read the website again, but I thought I remembered something about scanning for resonant freqs.

Personally, I don't think you would want to just concentrate on the few freqs that the mando really wants to resonate at. I notice when my mando is warmed up, it seems that everything is more resonant, not just one string course or one spot on the fretboard. For that matter, why not suspend it in a soundproof cabinet, and bombard it with pink noise?? That would be all the frequencies, the same volume, at the same time....

Dr. Dave Cohen has written a lot about resonance and "nodes" and I find his posts to be very enlightening. He mostly posts in the builders section. I don't know if I've run across any reply's by him about de damping. Would be interesting.

And for the record, I am one of those woo woo's who believes in mando's breaking in, opening up, being "awake" and a sleep. Not scientific I suppose.

[sunburst]

There are many resonances in a mandolin. The one that "sings back to you" is the main air resonance, commonly called the "Helmholtz" resonance. It can, in fact be adjusted somewhat by different amounts of sound hole area (larger or smaller) but not shape.
Blasting that frequency at a mandolin would probably do as much to "wake it up" or "break it in" as any other frequency, but not as much as playing the dickens out of the thing.

[Ivan Kelsall]

I tend to come down on the side of John Hamlett in this. Un-strung,the Mandolin tself will have it's own resonant frequency.With strings on,it becomes a much more complex array of tones, overtones & resonant frequencies.I think that it would be difficult to pin down one frequency which would excite all the resonant frequencies equally at one time. Playing the Mandolin has to be (IMHO),the very best way of making the instrument vibrate in all it's resonant frequencies.The sheer multiplicity of 'notes played' in even a simple tune must excite hundreds if not thousands of 'sympathetic vibrations' in the instrument ie.if you play the open G,the instrument will vibrate in a certain manner,if you play the open G along with the open D,it will vibrate in another manner & so on.So many combinations !. I also agree with TonyP's observation that a 'warm' Mandolin (physically warm that is), really does come alive. Very often when i get chance to practice in my living room,the only room i keep heated during the day,i'll have both Mandolins out. I'll play one & then the other.During periods like this,the instruments are getting warmed up - literally - & i've noticed that at a particular point they just loosen up & it's as though a veil has been lifted from the tones i'm getting. It's an ear opening experience,believe me,to suddenly hear one of your instruments produce such wonderful tones & volume - a bit un-nerving really,makes you wonder if the darned things don't have a life of their own !!,
Saska

[Fretbear]

There is no question that the break-in phenomenon is real, it is just that it is not fully understood. When I finished building my mandolin and began to play it almost constantly, it literally went through "birth-throes" (as opposed to death throes) where notes could actually be heard changing their pitch and timbre in real time, almost like screaming sometimes. The sound of the instrument changed after 2 months, 6 months, 1 year and 2 years and was constantly improving, mellowing in tone and increasing in volume.

Waking up and going to sleep is also a very real phenomenon for some instruments. If I leave my mandolin in it's case for longer than a week and then go and try to play some good music on it, either jamming or recording, it will almost be as if in a bad mood. Difficult to tune, and even when tuned, not really resonating well or easily giving out music. After several hours, my friends will look over at me as the instrument's volume begins to crest and it becomes extremely loud when played hard. These are real happenings, and other people will concur. I am convinced it relates more to archtop instruments, as my flattop guitar, while it's sound has improved as it has aged, does not go to sleep if I don't play it. As far as breaking the instrument in, is it not one of the few genuine joys left in this bloodless electronic world, where your skill gets kindled along with the instrument's capability and you merge together to create heart music.
The best things take time and don't need to be rushed.

[Ivan Kelsall]

Quote :- "Waking up and going to sleep is also a very real phenomenon for some instruments".
That's something else i've found to be true.When i recently got my Lebeda,because it hasn't been
played very much,despite being 8 - 9 years old,i didn't play my Weber for over a week as i tried to 'play in' the Lebeda to a degree. When i did get my Weber out,it sounded as though it hadn't been played in months,let alone days,& it was only after a couple of days playing that it 'came back to life'. I also agree re.the 'archtop theory'. My Guitar,even after weeks of 'sleeping' in it's case,is always in tune & doesn't need 'waking up'. Maybe it's just the way the stresses change in archtop instruments as agains a more stable 'flat top'. Interesting to hear any comments from 'flat top' Mandolin owners on this. You raised a couple of good points there Fretbear,
Saska

[Ravenwood]

My experience has been that all wooden instruments open up over time to varying degrees. I have both arch top and flat top guitars that I acquired in the 1970's, and both carved top and flat top mandolins. I also have a fiddle that was made in the 1960's. All of them have opened up to varying degrees. The arched top/carved instruments seem to open up more than the flat tops, but even my inexpensive TC OM has improved over time. Interestingly, I have a Gold Tone mandolin (I think a GM30) that has a laminate top which has also opened up over a year of playing. Not nearly as much as my Eastman, but its sound has definitely improved. I've also noticed that the older instruments no longer "go to sleep" as Fretbear mentioned. They did years ago, but in more recent years its doesn't seem to matter how much or little they are played. Has anyone else noticed this in older instruments?

Interesting comments about resonance. When the kids left home I converted a small bedroom into a music room. All of the stringed instruments are hung on the walls. When I play anything, the other instruments sing back. My granddaughter is quite entertained by the phenomenon.

[farmerjones]

just as well add my two bits. I'll state this like i know, but i don't.
When a mandolin is strung and brought up to pitch and the strings are settled, it acts as one, as apposed to a bunch of bits. A sonic pump. Made to be stimulated/drove in one spot: where you typically pick. So other than just playing the daylights out of it, one could rig up something like a the cylinderical bow found on a hurdi-gurdi, to drive the open courses for an extended period of time. I don't think i'd drive more than two courses at once. This is an open invitation to build such a thing. Even if didn't work, somebody would buy it.
OTOH if it took between one and two thousand hours to open an instrument up just playing. Imagine the relationship that you would build with an instrument if you spent that time thus.

[MikeEdgerton]

Here is every thread with the search term "resonant frequency" in it for anyone interested in past discussions.

[SternART]

Siminoff measures the resonant frequencies of the cavity, top, back, & tone bars......part of his dedamping process is then frequency specific........for long periods of time.

[farhights]

Concerning the "opening up" phenomenon, does it peak? I mean, is there a point beyond which the tone cannot improve any more, or do you all think the process continues indefinitely, no matter what the age of the instrument?
Anne

[sunburst]

If you use a FFT application (measures resonances) and so much as "bonk" on a mandolin, anywhere on the mandolin, the FFT will detect all the resonances in the mandolin; top, back, air, body, all of them from one "bonk". What that means is; the frequency you blast at the mandolin will excite all of the resonances in the mandolin no matter what frequency you blast. That's why I said that blasting the frequency of the Helmholtz resonance will likely do about as much good as any other frequency toward "opening up", "waking up", or "breaking in" the mandolin.

Anne, there is a little bit of evidence that violins (in particular) do increase in amplitude and perhaps other aspects of sound through playing, so we can't really say that there is nothing to the idea of mandolins waking up or opening up, but there is certainly no agreement that they definitely do open up, and certainly no agreement as to how much.
It is observably and pretty much undeniable that a brand new mandolin's sound changes significantly in the first hours after it is strung up, but beyond that it gets harder to be sure there is much change going on.
Personally, my observations lead me to believe that a couple of years of playing improves the sound of a mandolin, but beyond that any change is hard to detect.

[TonyP]

I've had my Newson F5 for 23yrs. For 21 of those years it was my only mandolin. I also got it 4yrs after I started playing. So I feel like I know this mandolin intimately. When I started playing there were no other mandolin players around I could "compare notes with". I learned mostly from books and a little from listening to records(yeah, it was that long ago), and except from an occasional Mandolin World News was isolated so to speak from "mando lore".

All my discoveries about like the back having so much difference in the sound if it was away from me. And that when I went to the coast it got louder and better sounding, leading me to humidify the instrument. And that when I was playing all the time, I got used to that sound. But if for some reason I'd not pick it up, leaving it in it's case, it would sound different. It would sound "tight" and quieter than usual. And the amount of playing time it would take to get that "sound" was seemingly proportionate to the amount of time I'd not played it.

I had a 4yr stint that I only played it like once or twice a month, if that. When I came back to playing again it seemed like it took over a month of every night to get it back, to where it was. So, even though the mando is 24yrs old, it still goes to sleep if I don't attend to it, both with proper humidity and a certain amount of aggressive playing.

So when I came upon the net and mando lore, first through CoMando, then the Cafe, I was surprised to see so many experience the same things independently. And just as surprised to see how vehemently these experiences were seen as unsubstantiated and ignorant.

[DerTiefster]

Maybe folks only believe what they personally experience (or are told by authorities in whom they believe....) and so don't believe you if your experience is different from theirs. It is easy to think that so complex a material as wood might have some secrets, and that different people might really be experiencing differences in its behavior.