f-holes

[chris clay]

i am building myself a double bass and am now looking into what considerations need to be taken into account when i draw up the shape and location of the f-holes.

i appreciate that, once in place, they are used to locate the bridge; and i presume that they must have a very relevant function in letting the sound resonate out of the body of the bass.

how do i arrive at the optimum shape, size and placement for these openings?...and out of interest does anyone know why and when this particular shape was chosen...and if other shapes work just as efficiently

[KSB - Ken Smith]

Originally Posted by chris clay

how do i arrive at the optimum shape, size and placement for these openings?...

After over 400 years, they are still searching for that perfect F and where to put it.

The basic key is not to put them in the wrong place!

String length is important as the FFs set where the Bridge is to be.

I have played many great Basses that I thought the FFs were either too low, too big or too small. Still, they were some of the better Basses I have seen.

Learn a little more about why FFs are placed where they are and about the sound coming out of them before deciding on a design or placement. Don't rush this step. It will be permanent.

[Carl Johnson]

google images of "f holes" you'd be suprized by the variaty and amount of information on just that subject.

[chris clay]

Originally Posted by KSB - Ken Smith

Learn a little more about why FFs are placed where they are and about the sound coming out of them before deciding on a design or placement. Don't rush this step. It will be permanent.

Ken, I have it in my head that my decision on the placement of the f-holes must follow a sequence that goes along these lines
(1) edge profile(ie the shape) of top plate is already established
(2) string length set which establishes bridge position
(3) bass bar alignment decided upon
(4)..and then the f-holes fitted into this configuration

although i've a sneaky suspicion that perhaps (1) should have been deferred until (2) (3) and (4) were sorted...ah well...

[chris clay]

Originally Posted by Carl Johnson

google images of "f holes" you'd be suprized by the variaty and amount of information on just that subject.

thanks for the suggestion Carl....although there could be some interesting links given the search title !!

[Caoimhín]

I've seen pictues of 'C' holes on some really old bass. Can't remember where though but they were pointing out - like following the shape of the C bout ya know

[Silversorcerer]

I like the serpentine ones, sometimes called tears. Historically there are many shapes. The "f" is just a "c" with an inward turned top and notches. From a purely acoustic standpoint, the size of the holes along with the size of the body determine the instrument's Helmholtz resonance frequency. The body size is primary, the f-hole size is a way to make a minor (permanent) adjustment. Whether or not luthiers use this in practice is beyond me, but given the mathematics, it is plausible that some might.

While it would seem intuitive that sound comes out the hole, mostly just air comes out, and goes in as well. Sound seems to come off of the top and back primarily.

Henry Strobel has some great books on violin family instrument design and construction and there are some rules of thumb for f-hole placement, which are indirectly related to bridge placement. One thing I remember (but I don't know where I read it) is that when viewed from the side (full profile view), the f's should appear to line up longitudinally with the top and not slant toward the top or toward the ribs. I don't know if that is functional or aesthetic.