F holes, again

[Fernando Esteves]

Hello guys, sorry for the lot of posts lately...
I saw one post about F Holes and had some info there that even suggested to me try the Ken Parker upper bout hole or the D'Aquisto round hole, problem is I think them damn ugly...

For a non cutaway, I would try a round hole like flat-tops or other shape on that position, but for a cutaway, I may stick to F Holes (unless I discover a new kind that I don't know).

So, I've the Benedetto book and he has some instructions about size and placement of the holes, do you all agree or does it differently?
And size and shape? What is your idea?
thanks a lot,
Cheers

[Fernando Esteves]

These are the designs I've made that most like at the moment

[Alan Carruth]

Round hole archtops sound different from f-hole ones. Some measurements I've made suggest that the 'normal' round sound hole placement, just above a pronounced waist which is a little higher than halfway up the length of the box, acts to produce a more complex timbre, contributing to 'tone color'. F-holes don't do this in the same way, and also 'hear' different internal air resonances, and all of that tends to produce a different character of sound.

I read some place years ago that a long slot has an effective area equal to a circular hole with a diameter 1/3 the length of the slot. I'm not sure if that's entirely true, but even fairly narrow long f-holes do seem to act like round holes a lot larger. Most 'recent' archtops I've seen have had holes with a lot of area in any case, and that shifts the 'main air' resonance up quite a lot in pitch. This does a lot to produce the 'open' or 'forward' sound that is characteristic of modern archtops. My most recent archtop used holes that are pretty similar to your smaller ones, and very much in the range of the holes on the Loar L-5 I was trying to emulate. This gave an 'air' resonant pitch at 115 Hz(just below A#). The ''air' mode on my 'Winter' archtop, which has holes more in line with the later D-Aquisto designs, is at about 135 Hz (between C and C#). Most flat tops have an 'air' pitch between G and A, although some go as low as F, particularly on Classicals. The two most recent arch classicals I made, both on the 16" 'Small Jumbo' platform, with round holes, had the 'air' resonance just below 100 Hz (between G and G#), and a timbre that is more 'classical', and somewhat 'lute-like'.

A side 'port' raises the 'air' pitch. Combined with even a small F-hole I think it would probably shift it too high for my taste.

[Freeman Keller]

A couple of comments on what Alan just said. I am currently in the process of building a 16 inch archtop somewhat following the L5 model. I have been tapping the top thru all of the carving phase and monitoring the changes using Alan Lambert's wonderful spectrum analyzing software. The thing that was very dramatic to me was the resonance at 117 hz that suddenly appeared when the box was closed. That corresponds perfectly with what Alan was saying about the main air resonance.

My guitar has f-holes patterned off of old Gibson design (they were actually taken from an ES335 but I think they are pretty similar to what Gibson used on other guitars). I have bound the holes which does make the area a little smaller, I have no way of calculating the area (and wouldn't know what to do with the information if I did).

A couple of things for Fernando to think about. I know that one function of the f-hole is to somewhat weaken the top next to the side letting the center section move more freely. I have no idea what moving the hole to the upper bout does to change this. If he intends to bind the hole it is worth while thinking about the shape - I have used both wood and plastic binding with this Gibson style and binding can be bent to fit all the little points and miters, I have seen f-hole shapes that I wouldn't even try to bind.

There was a panel discussion by modern archtop builders at the 2008 GAL conference that was written up in the Summer 2009 issue of American Lutherie. They do discuss a lot of the subjects that Fernando has been asking about - sound hole shape, size and location, sound ports, bracing.

[Darrel Friesen]

I've only built two archtops with an oval hole and six with f holes. One of the oval hole ones was a bass. No real discernible, at least to me, difference in sound with the other bass I built with conventional f holes. The six string definitely sounds different although still very pleasing and with a little more bass than the ones with f holes. It also has a side soundport. I don't worry much about the sound differences as they are small with similar bracing, top and back thickness, recurve etc. still sound like a guitar!

[Fernando Esteves]

Thanks for the answers, guys.

My understand is that the bigger the F Hole, the more open or "brighter" the tone of the guitar will be, right?
Then I need to start think about, because it's Adirondack top, parallel bracings and I don't know how much will be enough in the search for a more open and "direct" tone... The round or oval hole I think only works visually with non-cutaway and I probably will do the guitar with cutaway.

[Patrick Hanna]

I think you can make f-holes in a variety of shapes and sizes that can look and sound very nice. I can't comment on whether the size of the hole will affect brightness or darkness of the tone. Many factors working together will affect those sound qualities. Wood choices, grain spacing, bracing, top and back thickness, depth of recurve, etc., etc., etc., but you already know all that. I encourage you to experiment with designs that you draw on paper and move around on your plan diagram until you find a combination that pleases your eye and does not compromise bracing. I'm a big believer than if it looks right, it will probably be right. I know some others will disagree.

[Fernando Esteves]

Thanks