Official Luthiers Forum!

[QUOTE=Rick Turner] Careful, Lance...
You'll get the same reputation I'm building here!

Don't forget, folks, that air is a compressible medium. It acts as a spring and thus the volume itself has a resonant frequency. In the classic Helmholz resonator, you're not dealing with the surface of the enclosure moving, too. It's not coupled.   In a guitar body you've got coupled resonances making things weird.

You know why I put side ports in guitars and now in some ukes? Because I like them, and more importantly, my customers really like them. My customers like paying me to cut holes in the sides of the guitars we build for them. I like getting that little bit more sound in my face, and I like getting that little bit more money that lets my customers get a little bit more sound in their faces, too. I like side ports because it's win, win, win all the way to the bank.[/QUOTE]

Rick that's a great post start to finish...when it comes down to it, all that matters is customers like them, and are willing to pay more to get them.

My wife wants me to build her a guitar with a bunch of ports along the side...shaped like cat's paws walking up the side. Go figure. Hey, if she's willing to pay for it...

_________________
"I want to know what kind of pickups Vince Gill uses in his Tele, because if I had those, as good of a player as I am, I'm sure I could make it sound like that.
Only badly."

Any thoughts on the affect of two holes in the upper but instead of a traditional center hole, on sound?

_________________
A higher purpose for wood.
Rich Smith
Issaquah, WA

Hesh-"Rich I took Lance's comment to mean that even if you are a very experienced builder the theory here, regarding this subject, changes frequently and is difficult even for pros to keep up with. I saw no put down to any one here, just that we all have an equal opportunity to pull our hair out understanding this topic........"

I didn't see a put down either(which I would overlook either way). What you say though, we all have an equal oportunity to pull out our hair. Doesn't seem to be what he is saying. I can see how he would be saying that it is confusing to even very experienced builders, so you are better off focusing your efforts elsewhere. He said this,
"Ok, how many of you discussing this thread have built more than 50 guitars? If so it really doesn't matter! Believe me it changes! ".

On a side note, and regarding the wants of paying customers being a reason for me to build a certain way(good, bad, or indifferent). I am not building for paying customers. Although I do want people to enjoy what I build. So to that extent I am motivated to build to suit their needs.

My chosen career suits me and my need for income. Instrument building has and will be my hobby. Issues that relate to making guitars faster, building to the will of the market, or speed and value of my work are not things that I want as a part of my hobby(i actually want to seperate those things from my hobby). Repeatability, accuracy, understanding, control, and trying things that are new(to me at least). Are all things that add interested to the hobby. I also get a great deal of gratification when people enjoy using what I have built.

My professional life is driven by many demands, and I look to avoid those demands in my hobby. I understand why these are important to a person that strives to make a living(or has been able to for decades- which is an amazing accomplishment ) making guitars, they are of less importance to me. Just FWIW.

Peace,Rich

[QUOTE=Dave White] [QUOTE=Pwoolson] Is it possible for a person's brain to bleed? 'cause I'm pretty sure I've got a pretty good size hemorage going right about now. [/QUOTE]

Paul,

You'll be OK, just put a couple of postits over your ears [/QUOTE]
I tried that and they are fluttering like crazy. I can't tell if they are in phase or not but lots of air is rushing from the "ports".

[QUOTE=Pwoolson] [QUOTE=Dave White] [QUOTE=Pwoolson] Is it possible for a person's brain to bleed? 'cause I'm pretty sure I've got a pretty good size hemorage going right about now. [/QUOTE]

Paul,

You'll be OK, just put a couple of postits over your ears [/QUOTE]
I tried that and they are fluttering like crazy. I can't tell if they are in phase or not but lots of air is rushing from the "ports".[/QUOTE]

Maybe you need a couple of postits on your nostrils as well

_________________
Dave White
De Faoite Stringed Instruments
". . . the one thing a machine just can't do is give you character and personalities and sometimes that comes with flaws, but it always comes with humanity" Monty Don talking about hand weaving, "Mastercrafts", Weaving, BBC March 2010

Pretty soon I'll have to start figuring out the Hemholz of my head and tune the ports, blah, blah, blah.
Then my brain will start bleeding again from trying to figure out why it's bleeding.
It's madness I tell you, madness!

Lance,
   I've built 470 or so acoustic guitars under the name of Omega Guitars
and a good number more with my signature on them prior to that and the
most interesting thing about that number, as I'm sure you'll agree with
the total of guitars that you've built, is that I've enjoyed 470 or so very
unique and and challenging tonal environments as I have built them.

   I've heard guitars from guys who have built only ten that sounded
better than those coming out of shops of guys who have built
thousands....or claim to have and some of those guys who have built so
many more try to come across as the "end all" in guitar builders. They've
simply chosen a design and direction and have never really tried to
understand what makes it work or what could make it better, but just put
them together and send them out the door.

   The application of Helmholtz resonance propertires to guitars is a
stretch at best since the resonance and its reciprocation are determined
by the relationship between the activated air inside of the body cavity
which becomes what is being referred to as the Helmholtz chamber and
the static ambient air pressure outside of it. It's impressive technology to
try to apply and to talk about, but the unplugged, unresisted soundhole
and airflow through it creates a completely different and separate set of
tonal, resonant and flow dynamics from those of true Helmholtz
technology applications.

     I'd say that the guitar body provides a variable of some Helmholtz
principles, but since there is no constant and predetermined resistance to
provide a consistent environment for accurate documentation, Helmholtz
technology being applied to guitar research is more of a tangent of the
technology itself.

    The best and most commonly recognized example of a true Helmholtz
resonant situation is an Acoustic Suspension speaker enclosure. In these
enclosures, there are no ports or open passageways for air to use to
escape unresisted, but the known air resonance of the actual cone of the
speaker and its ability to utilize the air inside as a spring to create the
"Helmholtz" characteristic resonance puts it in that category of
enclosures. The speaker's ability to provide peak efficiency while doing so
is obviously provided and determined by a combination of the air
resonance of the speaker cone itself, the physical area of its surface and
the length of the speaker coil's throw which will all contribute to the
"compressibility" of the container's or enclosure's contents and its ability
to provide the necessary return to be efficient. It relies on the
combination of both proactive and reactive cycles to create its resonance.

     Since the body of a guitar is open and the air can escape quickly and
with little resistence, the hole in it needs to be "tuned" to determine the
amount of that slight resistence. The tone differences between the woods
that we use for backs and sides are simple and obvious indicators of this
principle. A Mahogany guitar sounds completely different from a
Rosewood guitar for any of several reasons (that we all have our own
opinions on because of our own experience and choices), but the ability
of the air to activate it into offering its tonal contribution to the sound is
of paramount importance to the overall resonance and achievement of a
desired result.

    It's been mentioned here and is fairly common knowledge that a
smaller soundhole will reduce the precerved frequency of the tone as the
body is tapped and that is precicely the intention of Acoustic Suspension
technology and Helmholtz resonance. A properly designed and calculated
speaker enclosure not much bigger in volume than a guitar body can
generate clean, powerful and usable sound all the way down to 25 or 30
Hz because the air is completely contained and restricted and can be
activated to create a resonance of the cabinet enclosing it.

    A guitar body isn't able to reproduce those results....and no...not even
those from the greatest builders in the world whether touted as such by
the latest issue of our ad revenue hungry publications or by the builders
themselves. The guitar can produce those frequencies, but not with the
level of efficiency of a closed system.

    The air inside of a guitar can do the same in creating a thorough
resonance of the woods that make up the cabinet that it is enclosed by,
though. The longer it is held inside after being activated by the player's
attack, the more efficiently it is able to resonant the woods around it. The
problem is that if it is held in too long, the system will lose it ability to
work efficiently and harmonics to the desired tone will become dominant
and the guitar will lose its clarity and separation....and obviously, volume
will suffer. I've played guitars that were a mess simply because the body
dimensions just didn;t work together to produce a good tone.
Harmonically dominant and muddy, they may have looked played great,
but were difficult to get a good sound from. The most common move to
these characteristically bad tones in recent years has been to deepening
of the body...especially on smaller bodied guitar models. A deeper body
doesn't always mean a bigger, better sound, but can create and
uncontrollable resonance mistake.

   This is interesting stuff to throw around and talk about with other
builders. I've had lots of fun learning it over the years and have spent
time with acoustic engineers and resonance specialists at Lehigh
University and at a few industry specific companies to talk about it and to
pick their brains. I even taught a guitar building class to a graduate of the
Advanced Institute of Science and Technology in Japan a few years ago
and he had brought along a few pieces of equipment for to record and
dicument alot of what happened with the woods, both as individual
components and as parts of the assembly. We had a great time, even
though we spent alot of it translating things to one another, and I was
able to glean alot of practical knowledge from him.

    I've read some great books...and some not so great books...on the
subject and have found that alot of it is subjective and that alot of the
people who claim to be the authorities on it just like to hear themselves
talk as long as there's an audience.

    I have several expensive and technical software packages that were
recommended by acoustic engineers and have used them on every one of
my past 150 guitars or so to try to nail down something consisten to offer
and use as I build, but the variables are so many and so common that all
of the results are better for reference than for anything else. They prove
what they prove for that particular guitar and it certainly has its value for
doing so.

    I've come to the conclusion that, at least for me, it's best to listen to
each piece of wood that is being considered for any particular guitar's
construction, match it to the other pieces that will become part of the
guitar according to resonance, weight and strength and then coax them,
as individuals and as a tone creating system into the most efficient
marriage of pieces possible. That's why i keep all of my tops, back/side
sets, bracing, necks and even my binding woods separated according to
their fundamental resonant frequencies to be able to choose woods that
will compliment one another as they are joined into the tone creating
system that each guitar is. A cryptic practice? Maybe, but it's become
part of what I do.

   One of the most overlooked luxuries that we enjoy as small shops or
solo luthiers is the ability to take the few minutes necessary to carefuly
select each component. If you've been to the big houses, you've seen
quckly that it's all about the numbers and the assembly personel just
grab whatever piece is next on the stack or on top in the box of pieces at
their bench side. They rely more on the deeply established designs for the
consistency in tone that they achieve than on this kind of care in selection
of parts and materials.

    There's no substitute for the "good 'ol" luthier's ear in my opinion. I've
played and heard your guitars and it's obvious to me that you understand
that because the tonal, volume and response results you've achieved just
don't come from formulas and technology, but from experience and
paying close attention to even the smallest and seemingly "unimportant"
details..

    I've also played and heard guitars from a few of the "authorities" on it
that have all the answers....at least on paper...and it has been obvious
just as quickly that they're spending too much time trying to impress
people with their knowledge instead of with the tone of their instruments.
I hate to say it, but they may want to skip a show or two and being in the
limelight as a critique of the work of other builders or a featured speaker
and focus on listening a little more closely to woods they're working with
and the way that they're assembling them.

    Lots of cooks in the kitchen when it comes to our business and the
stew can get muddy real quick. It's a fascinating craft and it contunually
amazes me how it can surprize me every time I walk up to one of my
benches to meet a new set of wood.

Sorry for the long post, but this thread sparked alot of thoughts for me.

Thanks for your patience,
Kevin Gallagher/Omega Guitars

"The most common move to these characteristically bad tones in recent years has been to deepening of the body...especially on smaller bodied guitar models. A deeper body doesn't always mean a bigger, better sound, but can create and uncontrollable resonance mistake."

Good points Kevin. I, for one, have gravitated towards deeper bodies in my smaller guitars. Your points above are well taken but I also believe that adding a sound port to a deeper body changes the entire dynamics of the sound box. With a properly sized [tuned and located] hole in the side, the deeper box takes on a whole new set of characteristics that differ from a one hole box, at least in my hands and to my ears.

_________________
tim...
http://www.mcknightguitars.com

Hmmmm. I think that calling an "acoustic suspension" loudspeaker a Helmholz resonator is a bit off.   A bass reflex cabinet is a Helmholz resonator, to be sure, with the port which is often ducted these days, but acoustic suspension loudspeakers are basically small infinite baffles (aka. sealed enclosures) that use the compression of the air as part of the suspension of the speaker cone. In fact they are generally stuffed with damping material to eliminate as much resonance as possible.

Another point...there have been a couple of references to the efficiency of an acoustic suspension speaker cabinet...in fact they are the least efficient of any loudspeaker enclosures precisely because they do not couple to a Helmholz resonator. The chief advantage to such speakers is that they do not allow the back wave of the cone to interfere with the front wave, and so the phase response is quite good.   Also by making the suspension very floppy and designed for long excursion, speakers and the cabinets can be made quite small and yet still have considerable low end response when driven with sufficient power.

Also, though speaker cones are certainly coupled to the air, the primary restorative force acting on the cone is electromechanical.   

The other similarity between acoustic guitars and bass reflex cabinets is that the back wave of the top/cone is added acoustically to the front wave. The phase relationships are considerably more complicated with guitars as the nodal and anti-nodal response of the tops is more complex than with most loudspeakers not driven into distortion.

I got pretty heavy into loudspeaker enclosure design theory in the early 1970s as part of the team that engineered the Grateful Dead's Wall of Sound. Those cabinets were all sealed boxes, and I developed the dimensions using wavelengths 1/3 octave apart for width, height, and depth. You can read more about what we did on that in the Blair Jackson book, "Grateful Dead Gear."

Since then I've been more attracted to transmission line speakers which may be an interesting direction in which to take guitar design someday...

Tim,
   I know many builders have moved toward larger depth dimensions on
their smaller bodied guitars, but the ones that seem to have shown tonal
problems are those with excessive depth.

   I can see the addition of 1/4" pr 3/8" of depth to a body with little
negative effect. I have actually seen more depth added than that which
can present the physical volume of a Dreadnaught with the body profile
of an OM and these are typically boomy and muddels in their articulation,
punch and note separation.

    I also agree that the addition of a sound port does eliminate some of
the muddiness and lack of separation.

   I have several guitars of different models in the shop right now with
soundports on them and look forward to watching and hearing them
come out.

   I certainly wasn't implying that the work of any particular builders had
suffered in quality of tone, but just that I'd heard the effects of the trend
to excessively deep bodies in some guitars that I've played in recent
years. I'd played guitars of more typical depths in the same models from
those builders that sounded so much better and had more power, volume
and separation of notes.

    I also know that you're an avid researcher and ducmenter of your
results and wouldn't make a move toward deeper bodies unless you had
allowed the change to prove itself to you as being a good one.


All the best,
Kevin Gallagher/Omega Guitars

[QUOTE=Pwoolson]Both pieces of paper (port and soundhole) pretty much fluttered a little and then sat there.
Conclusive evidence that I'm right and everyone else in the world is wrong![/QUOTE]

That makes perfect sense to me.

Essentially sound is a disturbance in a medium, in this case the bridge is excited by the strings, moves the top, disturbs the air both inside and outside the box (kind of like dropping a stone in a pond, and all the energy radiates outward from the spot the stone hits). So from that analogy you would think that the air moving through the sound hole and port would be in phase.

_________________
Brock Poling
Columbus, Ohio
http://www.polingguitars.com

[QUOTE=Rick Turner]Careful, Lance...
You'll get the same reputation I'm building here!

Don't forget, folks, that air is a compressible medium. It acts as a spring and thus the volume itself has a resonant frequency. In the classic Helmholz resonator, you're not dealing with the surface of the enclosure moving, too. It's not coupled.   In a guitar body you've got coupled resonances making things weird.

You know why I put side ports in guitars and now in some ukes? Because I like them, and more importantly, my customers really like them. My customers like paying me to cut holes in the sides of the guitars we build for them. I like getting that little bit more sound in my face, and I like getting that little bit more money that lets my customers get a little bit more sound in their faces, too. I like side ports because it's win, win, win all the way to the bank.[/QUOTE]

hey rick, im seriouslly thinking about trying this sound port idea, is there a percentage that this port should be as compared to the soundhole, same size??

as far as, reputation, well i been doing this long enough to learn, that some people are just better at this than others. its a fact of life, and sometimes, people have a hard time accepting that.

Mark

The back wave from a vibrating diaphragm is out of phase from the front wave by definition.   The only way to put it in phase is to delay it by a half cycle (plus anywhere from zero to several or even many full cycles). It all gets tricky because it's frequency dependent, too, and because of the compressible nature of air, there are frequency and more subtle phase shifts as well. What you really get is that the air flow will be in phase at some frequencies and out of phase at others and you'll also have many degrees of phase shift all over the frequency spectrum.

All of that is some of why we went to Digital Signal Processing to do the Mama Bear modeler project. We could capture the phase shifts which very much establish the signature sound of any particular guitar and make approximate algorithms from all that info.

Kevin Gallagher wrote:
"When I hear these guys, my mind wanders to the many people who have found the secret to miracle of the quality of Stradivari's violins...the finish...the treatment of the wood....whatever. I tend to like to give a little more credit to the skill of the builder and his willingness to be flexible enough to address each set of components that landed on his bench to
be fashioned and assembled into one of his instruments as a unique platform from which to work."

Yup, the 'secret' of Stradivari: he knew more about making good violins that we did. Of course, it helped that he was working in a living tradition, so he could change things.

I think there are two extremes to avoid here: an over reliance on mathematical proceedures, and a totally Luddite rejection of all technology. I think these things are 'way too compluicated, and our level of understanding 'way too poor, to be able to reduce them to formulas. OTOH, why would you NOT want to gain at least some level of rational understanding of the way these boxes work? Sure, each set of wood will be different, but knowing in general how the soundhole size or location, or the presence of a port, effects the tone of a guitar will generally be helpful in trying to get the tone you want from _this_ set of wood. Of course, you can simply build a few hundred guitars until you get the 'feel' of it, and that's a great way to go. But a little bit of physics can make a neat short cut.

It would be nice if you could predict the pitch of the 'main air' resonance from knowing the body size and shape, and the soundhole size and location, but it doesn't work like that. As Rick pointed out, the 'main air' resonance is not the same thing as the ideal 'Helmholtz' resonance: the 'main air' is the result of the interaction between the 'real' Helmholtz mode and the wood of the box.

Think about it this way: if the walls of the box were rigid there would be a 'real' Helmholtz resonance, with a certain pitch. OTOH, if you had a box with a big enough part of the back cut out so that there was no Helmholtz resonance, then the top would move freely, with no pressure changes to effect it, and you could call that motion the 'real' main top mode.

When you put the box together the two have to work together; there's no way around it. When they do they effect each other: the presence of the top kicks the 'real' Helmholtz resonance down in pitch a bit, and we call that the 'main air' resonance. Similarly, the air working on the top kicks the 'real' main top mode up in pitch some, and we lamely stil call it the 'main top' mode because we haven't the discipline to agree on some other name. Just to make it a little more complicared, the 'main air' and 'main top' pitches are also effected by the back and sides.

That's why there is no real way to predict the pitches of any of these things in advance. You can get close, but it's still likely to fool you.

Fred Dickens (who worked in Bell Labs and built on the side) once made a classical guitar 6" deep, and cut it down inch by inch until it was only half that or less. The 'main air' pich went up by 7%: much less than you'd predict for a real Helmholtz resonance. (find the 'blow tone' on an empty soda bottle, then fill it halfway up; that's what he was expecting)

As the body got more shallow the coupling between the top, back, and air got stronger, and this kicked the air mode further down, even as the shallower body gave a higher pitched 'real' Helmholtz mode. In other words, the increase in coupling cancelled out most of the drop in the Helmholtz mode. I've seen the same thing on one or two I've cut down for other reasons: the 'main air' mode pitch hardly changes, but the 'main top' pitch can rise, even though I didn't make any changes in the top. Without some qualitative understanding of the physics this would make no sense, and if you made that mod expecting the 'main air' pitch to rise, you might be dissappointed.

Al,
   It's funny to see you mention Fred Dickens. Being born and raised in
northern New Jersey found me crossing paths with several guys from Bell
Labs in the 80s and Fred was one of them. His passion for building
instruments made a lasting impression on many of the people he worked
with there in Whippany.

   Fred was kind enough to meet me several times at my shop in Paterson,
New Jersey where I operated Kevin Gallagher Guitarworks making mostly
Strat and Tele necks from much more exotic woods than Fender was. I
was building acoustic guitars on a limited basis at that time in a small
section of the shop, but was leaning toward a full time move to them
more and more.

   Fred and I met several times at a machine shop where I did some work
as journeyman machinist and toolmaker in Hackettstown, NJ about 25
miles from where he worked to throw some ideas around and to cut up
some Brazilian rosewood that I'd stumbled on in a barn. He was an
incredibly intelligent and insightful guy who could see things clearly and
quickly that seemed to be draped in mystery for the rest of us. His
edication certainly payed a part in his ability to do so, but he had a gift...a
sort of discernment for the behavior of wood parts assembled together to
form any of a list of instruments.

    During one of our visits with one another, we met at the shop of a
friend of mine in Morristown, NJ where Fred showed me an interesting
little thing he was starting to mess with concerning the "Helmholtz"
techonolgy that he so regularly used in his design and building efforts. He
was suspending a guitar body on four small pillars that were capped with
rubber tips cut to a taper to provide as small of a contact area with the
back as possible. They looked sort of like the pointers that teachers used
to use in classrooms.

   He would lay the body on these small pillars that would barely touch the
back at points as close to the perimeter as possible and then place a plug
of a predetermined weight over the soundhole. The plugs were made out
of light woods or of cork so that air could escape from the body through
the covered soundhole when it was activated, but with the resistence
presented by the plug's weight.

   It created a "real" Helmholtz environment in which the air could lift the
plug to allow release or exhaust, but the weight of the plug could also
provide the reactive closing of the hole to allow for the consistent volume
of the cavity to be maintained without the piston or displacement area of
the chamber being able to change.

   The damping of the back by the supporting pillars was minimal, but the
closing of the soundhole presented drastically different resonant
characteristics in both the main air mode and main top pitch.

    It always amazed me when Fred would begin to make mention of the
projects that he had on one burner or another. I still can't figure out how
he could have possibly fit all of it into a 24 hour day or 7 day week, but
he did. He was brillient, motivated and had an old fashioned work ethic
so the amount work he could do in any given time frame would embarras
most people. So few people...even in the world of lutherie...know of his
incredible work and findings that it is a shame. If I were to name one
person and their work as being the best kept secret in the history of
lutherie, it would have to be Fred Dickens.

    I wish that we had become better friends at the time, but he was very
busy and so was I so we fit our meetings in between other things. We just
had similar interests and curiosities and had tried and found some of the
same things out prior to our first meeting. We actually met through a
mutual friend who was interested in instrument building and had picked
my brain and Fred's spearately for years and finally arranged a meeting.
I'd like to say meeting two great minds, but I'd never have the audacity to
include myself in the same echelon of operation and understanding that
he walked so effortlessly and regularly.

    My background was different than Fred's, but I ws always happy to
have him ask me what I thought or what I had found after we'd agreed to
collaborate on a search for answers. Even though Fred could offer mind
numbing technicality and science to back his findings, he was very
humble and said to me on more than one occasion, "It seems so simple
that we should know it, but I guess we weren't meant to."

    Findings in these areas can be disappointing and surprizing and will
likely be confusing to many and frustrating to others and the two
extremes can be experienced and applied by all at one time or other.
Sometimes, there's just no solid explanation or answer, but good results
fall at the mercy of intuition and the unexplainable things we feel and
hear as we work that are arrived at through our unique experiences and
nothing more.

    It's important to have some practical understanding of the technology
involved in discovering and applying the principles we're talking about for
documentation and product development's sake, but it's just as important
to, sometimes, just throw your hands up and do it because it works...even
though it goes against everything you think or the numbers seem to
indicate.

Thanks for sparking some great memories,
Kevin Gallagher/Omega Guitars

I think having an understanding of why these things are not as simple as they may appear at the surface. Is a very good thing. Just knowing that there is not going to be a magic bullet formula that allows you to use an element as a simple design tool will help me avoid jumping to conclusions, or assumptions. Sometimes accepting that lack of clear predictability also makes you pay closer attension to your observations in a more unbiased way. Often times you can blind yourself by focusing so much on proof that your theory worked the way you thought it should(clear observation is a challenge for just about anyone I would imagine).

Peace, and thanks for your thoughts.

All this fuss about sound ports - and here I thought they just looked cool, (especially Zimmermans's ). This may be an ignorant question but who first put a sound port in an acoustic guitar? What did they hope to accomplish by doing so? Just curious to see where the idea came from if anyone out there knows.

[QUOTE=lex_luthier] [QUOTE=McCollum] But if the ambient air pressure is different from one day to the next, how will this affect the way the guitars push air?
The same way they dial carbs in with racing, would you need to change the size of the ports?
Lance [/QUOTE]

Or how about if you tuned a guitar's air resonance below sea level in New Orleans and took it to a gig in Denver? It would certainly push more of the lighter air in Denver, so the resonant frequency would rise. Enough to make a significant difference in tone? I surely don't know.
[/QUOTE]

Don't know about that, but you could kick longer field goals...just ask the Denver Bronco's FG kicker! OR...maybe your notes would go farther.
Actually, I think you need to build them with adjustable aperatures (f stops?) so you could adjust for any air pressure, humidity(density), or field goal situation.

_________________
Hank Mauel

Kahle, I first saw pictures of soundports in a coffee table guitar book (can't remember the name of it). They were used way back in turn of the century guitars so they have been around for at least 100 years.

Hank, Maybe we should try using "Jets" instead of ports. We could tune the pilot jet to control the low speed errr low frequency bass circuit, use an adjustable needle to control the mids and then a main jet to control that almighty ham fisted flat picker.    I just can't figure out where to put that darn air screw.

_________________
tim...
http://www.mcknightguitars.com

[QUOTE=Tim McKnight] Kahle, I first saw pictures of soundports in a coffee table guitar book (can't remember the name of it). They were used way back in turn of the century guitars so they have been around for at least 100 years.
QUOTE]

Yep - just about everything we're enamored with trying to reinvent the crudely underengineered simpleton guitar are things that can be discovered in the old Spanish guitars of the 1800s.

_________________
Instagram: @jfrenchluthier
Web: https://www.jfrenchguitars.com/

Kevin:
I agree that Fred's work is one of the best kept secrets in guitar acoustics. It's realy too bad.

Tom Knatt and I used to go visit him when we were down at Carleen's for classes. There was always something new to discuss, and more to learn. Fred was better than anybody I know at seeing the weak point in your argument or understanding. Usually he'd play along, asking questions and feeding you line, until he'd lead you into a paradox. Then he'd point out the problem, reel you in, and sit back to watch you flop around like a catfish on a dock. There was never any malice in it; he was always ready to tell a story on himself, and never made fun of others, although he sure had some opinions. Did you ever see the picture Pauline took of him on the sidewalk in front of the Ramirez shop?

Somebody wrote (I should have written the name down first!):
"Yep - just about everything we're enamored with trying to reinvent the crudely underengineered simpleton guitar are things that can be discovered in the old Spanish guitars of the 1800s. "

The guitar as we have it is the product of a long line of cultural selection. All of the obvious stuff has been tried, much of it many times. If it works, it's most likely in there already. That's why it's so hard to make big improvements without going to some new technology.

I do balk at the words 'crude', 'simpleton', and 'underengineered'. The guitar has been pretty well optimised, but 'optimum' doesn't mean 'perfect', or even 'good'. It's just 'as good as you can expect under the circumstances'. I have to wonder how far the auto makers would have got if they'd been stuck with steel that varied in strength by as much as 30% plus or minus from one batch to the next? That's what we deal with in top woods, even in the same species, and back woods are much more variable!

I'm a mechanical engineer by education and training. I'm not the best engineer in the world. I do work at a large company and I can hold my own with anyone that I work with. I've done well, have a few patents, yadi yadi ya......
I say that to let you know that I'm not at all afraid of the technical aspects of building and analysis. I just don't want to be bothered with anything but the most basic and obvious, like strength to weight ratio, stiffness, adhesives, etc. I can do computer analysis all I want at work. I get tired of that.
I build about 4 guitars a year and do it as a release from all that, to have fun and be creative.
If anyone wants to try to reduce guitar making to numbers and formulas, go ahead, but count me out. The last guitar I've built sounds better to me than than almost anything I've played, and I've played acoustic guitar for 30+ years. No formula did that. I did make use of engineering principles and deflection testing, but that just got me in the ballpark. Carving the braces to a tap tone that was pleasing to me, not a strobe tuner, got me the rest of the way, and I think was at least equally if not more important.
I'm not interested in taking this art and moving it into science. If you are, that's great and I hope it works out for you.
My suspicion is that a skilled builder using his hands and his ears will always be able to make a better sounding guitar than someone that relies on anything with a chip in it to make his decisions. YMMV

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.

A Lucchi tester has a chip in it. It can tell you about stiffness to weight and you can then relate that to density.   That can guide decisions and get you there quicker than deflection testing of raw wood. I don't have one, but I'd use it if I did and it would only help, not determine.   

I think the best we can do is to combine the art with some reasonable science. There's only a lot to be gained by balancing what are often presented as polar and diametrically opposed approaches. What's wrong with doing both?

[QUOTE=Rick Turner]...... What's wrong with doing both? [/QUOTE]
Nothing at all. I use some science.
Isn't this one of those things that is best left up to the individual? I don't think anyone should follow my lead, that's just for me.
Going technical is probably not an option for some, in terms of cost and/or understanding.
I had a conversation at lunch with an engineer about my latest build. He wants to put accelerometers on it right away. That's great for him and I wouldn't mind letting him do it.

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"An adventure is only an inconvenience rightly considered. An inconvenience is an adventure wrongly considered." G. K. Chesterton.