Mike's Oud Forums

AIR/BODY RESONANCE TONES

Edward Powell - 6-22-2010 at 04:59 AM

WHAT MAKES THE AIRSPACE/BODY RESONANCE TONE?

...you know, that strong tone you get when you sing into the soundhole? Kind of a WHOOF that shakes the whole instrument when you 'hit' it.


What causes it?
-volume of air?
-resonance of back material?
-general resonance of all materials combined?
-LENGTH of the air space?


Here is a collection of my instruments which I checked for air resonance tones:

From left to right, I will give the AIR/BODY RESONANCE TONES, that I found for each- from left to right each instrument has a progressively LOWER air/body peak tone.



1 (far left)- ragmakamtar #6 - F# (4th fret on the D string of a guitar) is the air peak tone. strange because the actual air space is pretty big with a body depth of about 16cm. However, the body is not SO long (not so short either), but the instrument all in all is under tremendous tension from 31 strings. Also having the 3 necks might be stifling resonance? The back is made of papier mache and a bit of bondo and is NOT very resonant. It also has very big neck and back blocks and 4 suspended braces inside. The air tone is F# but is is not very powerful.

2 - Arabic oud- C# (but with strings OFF the air tone goes DOWN TO B!!!!

3 - extremely cheap total crap guitar (extremely heavy wood and bracing!) - B (no strings). Is this not STRANGE? The body is SOOOOOOO thick that it can not be resonating, but still it has an air tone the same as the oud! The body is much more shallow than the oud's but the air space is a bit LONGER (and MORE of the air space has that long length - THIS IS THE ONLY THING I CAN SEE THAT WOULD EXPLAIN THIS SURPRISINGLY LOW AIR TONE ON SUCH AN UNRESONANT INSTRUMENT!). ---but it has a small sound hole and I heard that this creates more bass.

4 - "the insect" (original instrument with body a bit like a "sape". Air tone = A (with strings on!)... so this is a very very low air resonance for a very very thin and shallow instrument - BUT THE AIR SPACE HAS A LOT OF LENGTH!

5 - "the sartar" (another original instrument) G (no strings) so this has an air tone very similar to "the insect" even though it has MUCH more air volume --- BUT THE LENGTH IS VERY SIMILAR!

6 - "gambri" - G... similar air volume and length as the "sartar + insect" both

7- "BIG GAMBRI" (afrobass) low D (like drop D on guitar E string). This has the longest airspace.

- - -

I would think that taking the strings OFF the oud made it's AIR TONE go down by a whole tone, would prove that the general resonance of the body (with strings off the body is undo no tension and is therefore suddenly much more resonant) contributes greatly to the air-tone.

BUT then how can we explain such a deep low air resonance with this thick plywood guitar which has the resonance of a concrete slab???

I'm confused.

fernandraynaud - 6-22-2010 at 05:15 AM

"I'm confused."

Of course. You have too many instruments, and in addition you are trying to make ouds grow sarod necks.

Edward Powell - 6-22-2010 at 05:22 AM

No, I am trying to make sarods protrude oud bellies! :))

Manil - 6-22-2010 at 05:52 AM

Hey you play guembri too, I have one a small one called Aouicha, I like this instrument a lot, to repond to your question, I have no clue :)

ALAMI - 6-22-2010 at 06:48 AM

Hi Ed :
Quick and incomplete answer: check Helmholtz resonance principle.
Some infos are also somewhere right on these forums.

rojaros - 6-22-2010 at 08:34 AM

Hi, it's Helmholtz resonance.
But: the body and the top of course act as a filter, and depending on many interdependent factors they

1. make the resonance sharper or wider (Q-factor)

2. By possibly having some resonances near to the Helmholtz frequency or its multiples the can add some sum or difference tones that also could be audible or influence the resulting pitch of the resonance. It's a highly coupled system of many parts that are capapble of vibrations!

Best wishes

Robert

Edward Powell - 6-23-2010 at 12:15 AM

Helmholtz yes... but how does this explain that the oud's resonance dropped one whole tone simply by taking the strings off? Would not THIS indicate that there is a strong WOOD resonance here, because removing the tension on the body will surely increase resonance which will make the peak tone drop!? So for me this proves it is not ONLY an air resonance.

Having said this - then how can it be explained that the CHEAP GUITAR and the SMALL GAMBRI have such low air resonance - since both do not have expremely large air spaces, and BOTH HAVE EXTREMELY STIFF, THICK, NON-RESONANT BODIES..... this observation tends to support the theory that the LENGTH of th air space is what makes the most difference.

And lastly, how can it be explained that the ragmakamtar which has a very large AIR VOLUME, actually has a pretty high (F#) air resonance???? One theory I might offer is this--- maybe the F# I am picking up on the ragmakamtar is actually an F# lower than I am registering (which makes it close to the SMALL GAMBRI). And maybe the fact the RAGMAKAMTAR is so big, and has such an unresponsive back - maybe this is causing a general unresponsiveness in the instrument - - - - someone on the luthiers' forum suggested that a very large instrument can lose it's responsiveness (like trying to blow a tune on a COKE BOTTLE when the opening would be 3X larger.

rojaros - 6-23-2010 at 11:05 PM

Quote: Originally posted by Edward Powell  
Helmholtz yes... .


This all points to my 2d point - there are many couplings of different modes of vibrations, and certainly there are some standing wave modes that are interacting with the 'helmholtz' mode (which Helmholtz studied on spherical cavities with stiff walls and relatively small openings, so that there were not so many coupled modes).

As for the tension release of the top: certainly the fundamental top mode frequency goesn down when the strings are loose, because the the top is then working with smaller Young modulus.

Maybe the released top of your oud has an fundamental eigenfrequency that is lower than the air resonance.

best wishes
Robert

Edward Powell - 6-24-2010 at 12:04 AM

Hi Robert
I am not sure I completely understand your last point unfortunately.

But I think you nailed it when you say that the oud's air resonance is a combination. I feel that the back and the airspace are peaking at the same pitch. This is also true of good guitars. Therefore we get a resonance that really helps the guitar/oud's tone.

rojaros - 6-24-2010 at 07:36 AM

Hi Edward,
I'm also only guessing from my general physical knowledge. Beeing around with accoustic instruments for most part of my life I have learned to know that we don't know much how they really work - one can be sure they are very complex in their mutual interactions and interdependencies. And the better an instrument is, the more complex it is.

I have had many many discussions on these issues with my good friend and accomplished guitar maker Sebastian Stenzel, and, though I have a long standing acquaitance with classical guitars, I'm sometimes surprized by his foundings, which I at first glance find counterintuitive, but which work obviously very well, as his masterly made guitars prove aboundantly.

As to the last point: Wood certainly has a variable elasticity coefficient; which means, when it is relaxed, it's lower, and when you bend it (which mean, if you apply tension), it becomes stiffer, the closer you come to the point where it would just break. That's also why every top of a guitar (or oud for that matter) has a certain optimum working point, and if you put on strings of a too low or a too high tension, it's pushed outside of the optimum working.

Now, when you relax all strings, the tension on the top gets much lower, so it's having a much softer elasticity, which means that the fundamental top mode frequency is also much lower. If it's energy is transferred more efficiently than that of the air resonance, then this is what you hear, because there is the masking effect of the softer source by the louder source ... That's the effect I'd suspect - but of course I might be wrong.

best wishes
Robert

PS See Sebastian Stenzel with some very interesting articles on different aspects of guitar making for download

rojaros - 6-24-2010 at 07:42 AM

PS For his first Oud see also Stenzel Oud

best wishes

Robert

Edward Powell - 6-24-2010 at 11:27 AM

...yes, less tension on wood means more flexibility which means lower resonance.
So if my oud's "air" resonance goes down when the string tension if off, this means that we are NOT so much hearing an "air" resonance, but rather a wood resonance that is being affected by the string tension. I probably means the soundboard - - - BUT the string tension is putting stress on the entire body including the back (and even the necks). So still theoretically it might be a back resonance also we are hearing. (?)

rojaros - 6-24-2010 at 08:31 PM

I don't think there is much back resonance in oud anyway. Being bend it's quite a stif structure, and it's modes, I suppose, are much higher in frequency.

You could find out about that when the oud is without strings, by tapping softly against top, body and neck and see what you get. Maybe you find the spot where you can triger the same note...

Best wishes
Robert

Aymara - 6-24-2010 at 10:45 PM

Quote: Originally posted by Edward Powell  
So still theoretically it might be a back resonance also we are hearing. (?)


I'm not an expert, but to my understanding there are mainly 3 factors, that influence the sound of acoustic stringed instruments besides the string choice:

1. the soundboard (incl. bracing and soundhole size and placement)
2. the body (air capacity and shape)
3. the neck

And we also know, that the choice of woods is important. If you have two ouds for example, that have the same body design, a rosewood bowl would have a deeper bass than walnut.

So I guess, that besides Robert's explanations about soundboards ... we shouldn't forget the bracings by the way ... every of the three main parts have their own eigenfrequency, which in sum produce the resonance frequency of the whole instrument.

Or am I wrong?

Regarding the Ragmakamtar ... don't overlook, that though it's body has a high air volume, the body is relatively flat, which in my opinion is the main reason for it's high resonance frequency. Do a bit of research about acoustic bass guitars and you'll find out, that you need a deep body to achieve a deep bass ... do you remember this mexican bass guitars? ;)

PS: The average acoustic bass guitar lacks deep frequencies and sounds only a bit deeper that a western guitar, because it responds mainly in the lower mid range. There's only one acoustic bass guitar on the market, that is different: the Stoll, which sounds nearly like a contrabass, though less loud ... look HERE.

Edward Powell - 6-25-2010 at 12:25 AM

Actually, the ragmakamtar version I am talking about (version6) has a back depth of 18cm which is pretty deep I would say. I made it this way to "get" that deep air resonance, but it didn't work so well, although it was an improvement over all the previous ragmakamtars.

I have a feeling that what is more important than the width and depth of the air space is the LENGTH. I have a hunch that increasing the length of the airspace will give more bass the quickest.

Back to the ragmakamtar; I am not sure where the current problem is --- but I have a few guesses:
- back is made from heavy papier mache and not at all resonant
- it has 3 necks which add a lot of extra weight - further dampening resonance
- air space is pretty wide and thick but not long - not a focused shape like a bottle or a pipe, perhaps this air shape is more difficult to "excite" being big and round rather than long and tight?

Edward Powell - 6-25-2010 at 12:28 AM

Quote: Originally posted by rojaros  
I don't think there is much back resonance in oud anyway. Being bend it's quite a stif structure, and it's modes, I suppose, are much higher in frequency.

You could find out about that when the oud is without strings, by tapping softly against top, body and neck and see what you get. Maybe you find the spot where you can triger the same note...

Best wishes
Robert


I made the ragmakamtar version 6 back from papier mache which is thick, heavy and really non-resonant - because of the theory that the back does not influence the sound. But the result is that I have not much and not very deep air resonance, even though the soundboard is very large and very lightly braced.

Anyhow, at the moment I am building a new ragmakamtar with a very light and resonant thiin wood back, so it will be interesting to hear the difference.

rojaros - 6-25-2010 at 11:54 AM

Well, by stating that there is not much back resonance in oud I didn't mean at all that it doesn't play an important rôle in forming the sonic characteristic of the oud; quite on the contrary: the body and the neck and the peg box all function as frequency selective filters and they give coulour to the sound, also they certainly influence the attack and the sustain of the oud.

But these things do not concern the deepest frequencies; I don't think the bowl is radiating any significant amount of energy by itself thereby contributing to te level of fundamental frequency of the oud. (What I feel with my stomac are certain resonances quite a way up over the basses).

As I cannot become tired of emphasizing: any accoustical instrument, especially anything made of different woods and with a quite complex geometry is an intricate system of coupled vibrations and any attempt to isolate one factor over the others has only a limited value.

Interestingly enough an experienced luthier kind of intuits (I could say as well: knows on a pre-intellectual level) what has to be done in order to achieve a certain overall character of the instrument.

As Sebastian Stenzel stated immediately after I played his first oud for the first time: "The sound doesn't come as a surprise to me; it is exactly as I have envisioned and intended it, and the extent to which this is the case, that is the surprize!" (maybe not the exact wording).

And I knew intuitively he is fully capable of doing that; otherwise I would't have ordered an oud from a luthier who yet hasn't built any.
Today, after three days of intensive playing, the oud already is in a shape I wouldn't even dream of it's possible!

Why I'm writing this? Because it points to the limitations of our explanations of the accoustical behaviour of complex instruments - without a lot of experience we allways will be doing more or less educated guess work ...

best wishes
Robert

Edward Powell - 6-25-2010 at 02:35 PM

Hi Robert - thanks again for your amazing insight.
Here is my current thinking:

In my attempt to solve the "ragmakamtar riddle"... and a lot of brainstorming later, I can say that my current thinking can be summarized as follows:

- the back of an oud is not so much responsible for the bass range. However a "good" back will "help" the instrument's volume, sustain, and attack since it is resonant and encourages vibrational flows. Therefore the ragmakamtar's non-resonant papier mache back is probably one reason for the instrument's lack of volume and attack.

- I feel now that the air-peak tone (what we get when we sing into the hole), is NOT coming from the back, and in fact also NOT coming from the Helmholtz, but it is mostly coming from the soundboard. Perhaps a coupling of the soundboard and the air resonance - but I feel it is mostly from the soundboard --- otherwise why would it be that when I took off the string tension on my oud, the air-peak tone dropped a whole tone? Furthermore, obviously the soundboard has a lower resonance than the back...

- I had previously thought that the ragmakamtar's air tone was F#... the F# (4th fret of D string on a guitar) because this the only peak tone I could find, and it was pretty weak (which I attributed to the papier mache back). BUT(!) and further thinking, observation, and analysis I think I have realised a very very important mistake in my assumptions... First is following with the idea that the air-peak tone is primarily coming from the soundboard - - and second is that when I play the lower F# on my ragmakamtar (like 2nd fret of E string on guitar), then this low F# is actually very loud and fat!!! The F# an octave above is NOT very punchy at all - certainly not a full fleged "peak tone" --- again I was blaming this on the paper back. . . but I have finally opened my eyes to the fact that what I have done with the design of ragmakamtar version 6 is to OVER COMPENSATE and in fact make the body, soundboard so large, and the bracing so light - that the result is a general soundboard resonance tone MUCH lower than an oud's!

I think I just almost didnt want to SEE this because I was so sure that this would not even be possible - but yes, I am pretty sure that in my long struggle to get a deeper oud sound I finally overdid it and put the resonance SO LOW that it is out of range, and therefore is missed in the instrument's normal playing area.

- So probably the reasons that the ragmakamtar's oud sounds very thin are:
1) upper register - low high range (2nd nylon string) is thin probably because the BACK is not contributing any resonance
2) the mid register (3rd string) is thin because the soundboard is resonating TOO LOW, and therefore not "grabbing" the mids.
3) I think/feel that the fact that there are 3 bridges and 3 necks on this instrument is causing some disturbances in the normally free flowing of vibrational energy.

- - - -

How to solve these problems?

1) problem one can be helped simply by making a light wood back
2) problem three can be helped by improving the design layout, and getting the bridges more "out eachothers way", and also making the necks and heads much shorter and lighter.
3) PROBLEM #2: the soundboard's overly LOW resonance (due to it's very large size, and very light bracing...) this is the stickler! However logic tells me that perhaps this can be solved actually by making the bracing more heavy! On the surface, this would seem very irrational - to try to increase resonance, volume, and attack by bracing MORE HEAVILY!!! but on the otherhand, with a soundboard which is SOOOOO big and wide, it is also obvious that this huge plate is going to have a very low/deep resonance... and the only way to make a plate resonate higher is to add more bracing.

You might just say - "well, why not just make the body and the soundboard smaller?" - but the reason why this can not be done is because when you have two bridges, they MUST be very far apart from eachother otherwise they intercept and disturb eachothers resonance (what I mean is that the bridge itself is very chunky, then there is all the string tension - so the result is an area which is VERY VERY STIFF... but a bridge "likes" a pretty loose area 15cm away from it - not a stiff area like another bridge). So each bridge can NOT be crowded. Therefore that necessitates a very large soundboard - but then a huge soundboard, WHEN ACTING AS A "WHOLE OBJECT" (as it obviously will do!) will surely have a very low resonance.

I think that the most difficult to question to answer is this:
Bracing a huge soundboard will raise it's general peak tone up to the range of a normal oud -BUT will this "extra bracing" in some way immobilize the soundboard in critical areas which are necessary for transmitting vibration from one of the bridges to the proper areas of the soundboard?

---the only way to find out is to test it.

rojaros - 6-25-2010 at 04:30 PM

Hello Edward,

my new oud has very thin grenadill ribs interspaced with very thin pear ribs: grenadill is very 'glassy' and has strong resonances, pear is also quite hard but has higher damping. This help to make the resonance peakes a little more broader.

The necks should be stiff but light (guitar makers use cederella odorata for this purpose; maple is also nice).

A consistent way to find out the real helmholtz frequency (and this allways exist in a cavity, though it might be masked ar so low that you cant excite it with singing) would be to use a sine tone generator and a loudspeaker, and then slowly sweep the frequency and measure the output energy or trust your ears.

In guitar construction the air frequency mostly hovers somwhere around F# - G#, so it's slightly higher than E, the lowest regularly played note. That is certainly for a good purpose. If you put the air frequency lower than that, you might completely loose focus of the bass range.

The top shouldn't be too stiff, but even worse is to flabby. Beeing on the slightly stiff side and then let the time soften it up a bit is probabely right. That way your trebles will also be better focussed and projecting.

Huge soundboards also seem to be a problem. Often smaller tops sound better than large ones.

Energy transfer through the bridge is quite complex. The torsion is quite an important factor in traditional oud. If you put a great tension on your top, some doming or concave form (like with turkish ouds) might help to get the working point of the top right.

I don't have a big experience with bracing at all, but you must consider that the static effectivity of making the bars wider is proprtional, whereas, if I remember right, to make them higher, proportional to the third power. So the way to go is to make them narrow but high; that way you spare mass without loosing strength. But if you make them to narrow, you'll have some selective resonances, because the bracing acts as a filter suppressing wavelengths that fall within the width of the bars.

Just again some educated guessing, as I have never build any instrument by myself ...

best wishes
Robert

Aymara - 6-25-2010 at 09:38 PM

Hi again!
Quote: Originally posted by rojaros  

In guitar construction the air frequency mostly hovers somwhere around F# - G#, so it's slightly higher than E, the lowest regularly played note. That is certainly for a good purpose.


That leads me to the question: Should the eigenfrequency of the instrument be dependent of the desired tuning? And wouldn't in the case of the guitar standard tuning the best eigenfrequency be E, the deepest available note? If not, why?

Edward Powell - 6-25-2010 at 11:43 PM

Quote: Originally posted by rojaros  
Hello Edward,

my new oud has very thin grenadill ribs interspaced with very thin pear ribs: grenadill is very 'glassy' and has strong resonances, pear is also quite hard but has higher damping. This help to make the resonance peakes a little more broader.

The necks should be stiff but light (guitar makers use cederella odorata for this purpose; maple is also nice).

A consistent way to find out the real helmholtz frequency (and this allways exist in a cavity, though it might be masked ar so low that you cant excite it with singing) would be to use a sine tone generator and a loudspeaker, and then slowly sweep the frequency and measure the output energy or trust your ears.

In guitar construction the air frequency mostly hovers somwhere around F# - G#, so it's slightly higher than E, the lowest regularly played note. That is certainly for a good purpose. If you put the air frequency lower than that, you might completely loose focus of the bass range.

The top shouldn't be too stiff, but even worse is to flabby. Beeing on the slightly stiff side and then let the time soften it up a bit is probabely right. That way your trebles will also be better focussed and projecting.

Huge soundboards also seem to be a problem. Often smaller tops sound better than large ones.

Energy transfer through the bridge is quite complex. The torsion is quite an important factor in traditional oud. If you put a great tension on your top, some doming or concave form (like with turkish ouds) might help to get the working point of the top right.

I don't have a big experience with bracing at all, but you must consider that the static effectivity of making the bars wider is proprtional, whereas, if I remember right, to make them higher, proportional to the third power. So the way to go is to make them narrow but high; that way you spare mass without loosing strength. But if you make them to narrow, you'll have some selective resonances, because the bracing acts as a filter suppressing wavelengths that fall within the width of the bars.

Just again some educated guessing, as I have never build any instrument by myself ...

best wishes
Robert


HI Robert
I think you need to start building! My educated guess it that your instruments will sound GREAT! :)

Thanks for your feedback, it is helping me to hopefully solve this riddle. . . .

I think the two main problems with the ragmakamtar are:
1) huge soundboard- BAD (but bridges far apart - GOOD)
2) normal size soundboard - GOOD (but bridges too close - BAD)

How to solve this riddle????
-maybe making ALL strings from both necks coming out of just one bridge??

Edward Powell - 6-25-2010 at 11:56 PM

Quote: Originally posted by Aymara  


That leads me to the question: Should the eigenfrequency of the instrument be dependent of the desired tuning? And wouldn't in the case of the guitar standard tuning the best eigenfrequency be E, the deepest available note? If not, why?


Yes, the peak-note is completely connected with the tuning you want to use. Having the peak-note for a guitar be bottom E is not ideal because remember that the peak-note is FATTENING a whole RANGE of notes both above and below it. Therefore if the peak-note is E, then you are wasting the fattening potential coming from this peak-note on the notes below E. BUT if you really like a drop D tuning, then having the peak-note at E or F would be great because the low D will also sound rich.

Now, relating what you mention to my own experience with the ragmakamtar, and also remember what Fernando said about the instrument play US rather than the other way around. So, in support of my realisation that the ragmakamtar (because of it's huge soundboard and very light bracing, has a VERY VERY VERY deep resonance. I have the lowest string now tuned to A (that is the same as an open A on a contrabass!), and I find that I am always playing around in THIS lowest octave!! And it sounds great! I can hardly pull myself out of it.

Now, thinking further, if I will adjust this instrument's design and bring the resonance UP to the range of a normal oud, then the higher and mid notes will finally sound full BUT, that deep deep octave that NOW sounds good, will surely suddenly NOT sound as good as it does now.

So therefore, with this new design I probably ought to think seriously about how I want the instrument to be tuned.

Yes, I agree with Robert that I will make the new bracing still narrow, but much much higher - like 20mm as opposed to the 12mm generall in there now. The current ragmakamtar soundboard is pretty tight around the bridges but very very flexible and bouncy in the other parts.... I have always had this flexibility as a goal, but finally I realised I took it too far! Or at least, I now know that a floppy soundboard on a huge soundboard is NOT a great combination!

rojaros - 6-26-2010 at 01:00 AM

Hi Edward, I'm affraid, I have two left hands, as far as woodworking goes - though I love to watch a skilled master.

As to the issue of air resonace frequency: I don't think it should be at the lowest pitch you are aiming at. I think it has a very good reason that since more than hundred years for guitars it is above the lowest pitch.

People have tried all sorts of body construstions and sizes; but what was laid out by Torres seems more or less to be holding true.
But this of course has something to do with the guitar sound vision: it should have a strong but focused bass capable of projection. And above all guitar is a polyphonic instrument, which is not the case basically with the oud (apart from the mauro-andalusian music).

Now, let's adress the riddle you formulated:

big top - far spaced bridges versus smaller top, close standing bridges.
First of all: you could have the construction done in a way that the top almost acts as two tops by having an inner wall - if necessary with some ports to eneable the body to act as a big cavity.

The issue than would be than to shape the top itself (thicknesses - bracings) in a way that it really can act as if it were two tops. That should be feasible.

Secondly: you also could have a smaller top and bridges standing closer together by reconsidering their construction: make them lighter, make them arched (not having full contact with the top), using lighter wood, etc. etc. That should be possible because you use floating bridges, as I can see.
You also could reconsider and use traditional bridges. They function quite differently from floating bridges and have their own merits. They let the body vibrate more freely when made to proper proportions with a lighter but stronger wood (pear eg.)

One little remark to the issue of the top size: In my discussions with Sebastian Stenzel he often mentions 'larger top', 'smaller top' in relation to guitars where I barely can see a difference. It seems that every milimeter counts.

Also if the coupling of the top to the sides is stiffer, it makes effectively for a smaller top. So there are some ideas how one could reduce the effective vibrating area of the top without sacrificing the body size, if the latter has a good reason. But it seems that body size often is overestimated, it's only one of a few of important factors for how the bass actually works. See all the old Torres guitars; they are pretty small and have beautifull focused bass.

I enjoy very much our exchange

best wishes
Robert

rojaros - 6-26-2010 at 01:08 AM

Quote: Originally posted by Aymara  
Hi again!

Quote: Originally posted by rojaros  

In guitar construction the air frequency mostly hovers somwhere around F# - G#, so it's slightly higher than E, the lowest regularly played note. That is certainly for a good purpose.


That leads me to the question: Should the eigenfrequency of the instrument be dependent of the desired tuning? And wouldn't in the case of the guitar standard tuning the best eigenfrequency be E, the deepest available note? If not, why?


Hi Chris, I don't think that is true and it's not very practical, too. You want to have a good instrument that is able to take a dropped tuning.

I have a Hanika guitar that has an air frequency somwhere around G# which in the usual range, even rather on the high side.

But this guitar is unbeatable in dropped tunings. I go as far as tuning it to a cello tuning(!) starting with C (major third lower than the usual E!!!) and it's just there (if the strings are chosen accordingly).

As I write again and again, there are many interdependent factors that make for a good and flexible instrument and fixating one's gaze on only some of them would quite likely lead to a construction that is out of balance.

best wishes

Robert

Aymara - 6-26-2010 at 01:16 AM

Quote: Originally posted by rojaros  
you could have the construction done in a way that the top almost acts as two tops by having an inner wall...


Mmh, interesting idea, because that reminds me of the two chamber bodies of Godin and Rob Allen. So who knows, maybe a four chamber body would be even better for the Ragmakamtar?

BTW ... if you do a research, you can find photos of the inner body design of the Godin two chamber guitars.

Just a thought ...

Edward Powell - 6-26-2010 at 01:36 AM

yes!

this is the plan of my new ragmakamtar design - originally I planned to make the lower fingerboard hang OVER the soundboard like a cello's, the idea being that it would leave a larger area available to resonance in the soundbaord - but now I am realising that the soundboard is really too big, so I have decided to let this lower fingerboard attach directly to the soundboard and it will function to actually KILL this area of the soundboard, bringing the soundboard's resonant area more into the size range of an oud.

rojaros - 6-26-2010 at 02:04 AM

Do I see it right that you're using traditional bridges now? Very good idea I think.

In guitar construction you would underpin the fingerboard through a wood block under the top, so that the neck is being stabilzed. That kills that part of the top anyway.

I think also the neck angle is an important issue for the sound (and not only for playability as is often believed). Because when you have a neck that is slightly back tilted, this by itself gives more tension force orthogonal to the top!

And then reconsider the holes! They function as openings for the helmholtz resonator, so for that matter their only count as total open area. But spreading that area over few holes has the disdvantage of killing whole regions of the top for lower frequency modes. It also could be holes in the region where the neck is coming in (this has been succsessfully used in guitar construction, though it didn't convince too man players).

Best wishes
Robert

Edward Powell - 6-26-2010 at 02:32 AM

yes, good thinking!
I could use those areas of the top that I am planing to KILL, as areas to put the soundholes.
However, I am still not totally sure if the soundhole (in traditional area) is actually stealing area from bass production. But maybe yes.... I have seen both cases - 3 soundholes and great bass, one soundhole and bass bass, no soundholes are great bass. . . . . :shrug:

I was thinking to play it safe this time and try to replicate an oud's bracing and layout - but as you say, maybe better to think twice about this.

I now plan to go for a normal oud fixed bridge, but a floating bridge for the sarod.

Yes, a block UNDER the fingerboard overhang would be good too.

Hey, have a look at this interesting vid:
http://www.youtube.com/watch?v=fAEQKmyB5Nk&feature=related

rojaros - 6-28-2010 at 06:56 AM

Hello Edward,
first of all I don't think you want to KILL any of the soundboard, you'd rater want to controll the different regions in a way as to make them work for the purpose they are suitable for. The big areas have more ability to have large modes and are so naturally suitable for bass - but if you make them to loose, they loose their other purposes.

If you would divide the body internally through a wall still allowing the air inside to communicate, you would additional stability, coud do the bracing more pliant and the coupling to the sides softer, thus maybe having a better focussed bass at the end. This would also allow for each part of the body having its smaller sound hole.

Again, just ideas

best wishes
Robert

Edward Powell - 6-28-2010 at 11:25 AM

Thanks Robert, I have some thoughts on what you say - - -
...but for the moment, here is a clip of a concert we played last night. You can hear the low register of the "oud".

I am very happy with all the strings except the dugah and neva strings. If I can just get these two strings stronger, and keep the rest just as good, then I will be pretty satisfied. . .

http://www.youtube.com/watch?v=CWpTLP_oKa4

Edward Powell - 6-28-2010 at 11:29 AM

this gives an idea of the "sarod" part.... I am experimenting with a VERY buzzing lowest string. Maybe this is over-doing it, but I actually like the incredible sustain the open jawari gives. . .

http://www.youtube.com/watch?v=7jn92rR1MbE

rojaros - 6-29-2010 at 01:33 AM

Quote: Originally posted by Edward Powell  
Thanks Robert, I have some thoughts on what you say - - -
...but for the moment, here is a clip of a concert we played last night. You can hear the low register of the "oud".

I am very happy with all the strings except the dugah and neva strings. If I can just get these two strings stronger, and keep the rest just as good, then I will be pretty satisfied. . .



Hello Edward, I'm not so familiar with indian terms; what are dugah and neva strings?

Edward Powell - 6-29-2010 at 02:01 AM

Dugah and Neva are the Turkish names of strings.
Dugah = the 3rd string (the thinnest wound string)
Neva = the 2nd string (the thickest nylon)

these strings represent the mid-range of the instrument, and on every single ragmakamtar (6 now) I have build these two strings have always been the problem. The highs have always been good (probably because the areas around the bridges have always been nicely tight), and the lows have always been good (probably because of the instruments large size)....

but the mids have always been weak (probably because there is something going on there which is acting like a mid-range filter/block. Probably several things- - - - high on my list of possible culprits are:

1- close proximity of the bridges to eachother
2- non-resonance papier mache back
3- previous wood backs too heavily braced
4- too much tension around bridges (good for highs but killing mids?)
5- bridges not being in the center of the soundboard
6- necks totaling too much extra weight
7- air resonance not coordinated with other resonances

Anyway, I am trying to identify as many possible causes as I can, and then working on these.

rojaros - 6-29-2010 at 05:22 AM

Hello Edward,

again guessing, but if I think of guitars, the g is always the weekst point, in terms of presence and volume. That is partly because the string is too thick and so too stiff.

Did you try fluorocarbon for neva? Or even plastic wound flamenco strings (Savarez has some different ones)? A hard tension plastic wound guitar g (as some flamenco player use it) could be also good for the dugha (it would be probabely on the low tension side, but never mind, sometimes this is the best for oud...

Too heavy bridge could also kill the midrange - that would be easy to check on your free floating versions; just make them of a different material or thinner or a combination of both.

Also too stiff top can be a problem.

Another issue with guitars is, what could be called 'the working point' of the top. Some guitars require a higher tension string set, some lower tension, depending on the way how the top and its bracing is laid out.

Generally the quality of the guitar is best if you hit the right tension, and diminishes, if you miss it, this or that way.

This is not only true for string sets, buth within that, each string has its particularily suitable tension. They are not necesserily the same!

I'm sure you did already a lot of experimentations with strings, but maybe not systematically enough.

As I gather, you play for your living, so it pays of to be totally confident of your instrument! Why don't you get yourself few rolls of SEGUAR FLUOROCARBON Premium leader (the best string material I've ever encountered) in as close spaced thicknesses as possible and to some experimentation (maybe also using the String Calculator String Calculator). You might be surprised, how much is changed with the proper tension.

Of course, if you know all of that, than just trash it...

best wishes
Robert

Edward Powell - 6-29-2010 at 06:23 AM

...but interesting that on Turkish fretless guitar, they play MOSTLY on the G string!

You mean PVF strings? I MUST use a PFV 2nd nylon because the normal nylon sounds absurd. But normal nylon works great on the 1st nylon.

Yes, on the floating bridge there is ALOT of room to tweek (but also alot of room to mess it up - - I still have not decided what kind of bridge for the new instrument... I guess fixed bridge is more safe).

Yes, when I changed the neck angles, the bridges neede to be raised majorly - then the mids suffered a bit. Beccause of the increased tension due to raising the bridges I lowered to tuning from B to A... maybe to suffering mids are because the bridge is now heavier due to being taller?? but they are of light material and extremely thin now.... but this is a very good point.

Yes, absolutely further experimentation with strings is crutial. I still don't have a good source for PVF unfortunately.

It is amazing how many factors can have an enormous influence on sound - right down to the kind of pick you use!


rojaros - 6-30-2010 at 12:03 PM

Maybe you can find a store in the USA or Canada having Seaguar Fluorocarbon Premium Leader.

This is really an excellent string material, having all the good characteristics of fluorocarbon without the bad ones ...

best wishes
Robert

Aymara - 6-30-2010 at 12:52 PM

Quote: Originally posted by rojaros  
This is really an excellent string material, ...


Many nylon guitar players like it. It has been discussed before here in the forums some time ago.

rojaros - 7-3-2010 at 02:31 AM

Hello, Melton Tackles in California has a special offer of Seaguar Fuorocarbon premier Leaders, just google it, it's a good offer, it seems

best wishes
Robert

BTW Edward, are going to have some concerts in southern Germany?

Aymara - 7-3-2010 at 03:56 AM

Quote: Originally posted by rojaros  
BTW Edward, are going to have some concerts in southern Germany?


Germany might be an interesting place for Edward. Here are many medieval markets and festivals and the oud would fit nicely in there.

rootsguitar - 1-14-2013 at 09:01 AM

I started out by searching: " sape " and found this thread...I have to admit I tend to oversimplify things in my mind though find all of this really interesting.


I can't resist wondering how relevant these ideas stayed in creating that great tone of the latest Ragmakamtar...

does the tone radically change if one of the neck's is unstrung?





Edward Powell - 1-14-2013 at 10:44 AM

Hi Roots...

I forgot all that was written on this thread... but I recall it being very enlightening. Regarding the AIR RES., I know for a fact that once I learned how to control and place the air res., suddenly my instruments started sounding much much better!

Now, to answer your question... yes, if I have only the oud neck strung up and the sarod strings off, the oud will sound a little sweeter than when the sarod strings are on. The is because the sarod strings add more tension to the soundboard, thereby making it less able to respond optimally to the light energy of the nylon strings. So with both necks strung up the oud is a tad more "tight" sounding. But luckily the difference is very small.

I would say that for the sarod there is not much improvement if the oud strings are not on. Actually the sarod really likes having the oud strings on because they resonate like sympathetic strings, giving an Indian effect.

Regarding performing in South Germany, I would love to, and I live quite near in fact. However I don't currently have contact there unfortunately. I will be going soon for some gigs in Hungary and Serbia with this bassist and an Indian percussionist... have a look at this vid if you are interested in Ragmakamtar + Double Bass, playing in 7.5 beats.
https://www.youtube.com/watch?v=opSiIbqQoGQ

rootsguitar - 1-15-2013 at 10:48 AM

Bueno Edward! Cool clip, I enjoy that fretless dialogue with the bass---I'll bet that's great music to travel with. Striving for originality within a tradition is real medicine---creative path!

The ideas in this thread are really useful to my practice hours too, they make me listen to the instruments more and remind me of all the persistence/real time skills that went into creating them.

It must be that the spirit of "thinking outside the box" fueled these stringed-ideas as they traveled across oceans.

Keeps me searching for a tone when my ideas start to slow ( lol).

-------Best