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Thread: Lloyd Loar F5 soundhole aperture area

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    Registered User j. condino's Avatar
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    Default Lloyd Loar F5 soundhole aperture area

    Has anyone calculated the the total surface area of the aperture for a Loar era F5 soundhole? I know there was a slight range, so if I had to chose, make it the 1st choice John Reischman's and the Griffith A5 second.

    'Doing a little experimenting back at the skunkworks...

    Thx,

    j.

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    wood butcher Spruce's Avatar
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    Default Re: Lloyd Loar F5 soundhole aperture area

    Quote Originally Posted by grandcanyonminstrel View Post
    Has anyone calculated the the total surface area of the aperture for a Loar era F5 soundhole? I know there was a slight range, so if I had to chose, make it the 1st choice John Reischman's and the Griffith A5 second.
    Quite a difference between the two...
    I'm sure you've seen this wonderful Darryl pic comparing an F5 with the A5:



    This should be an interesting discussion...

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    Default Re: Lloyd Loar F5 soundhole aperture area

    I don't have any measurements on a Loar F5 but I do have the following measurements. I assume the size of the f-holes are important in the tuning of the air chamber as referenced on the Loar labels.

    1924 Gibson H5 Mandola, Loar signed (combined area of soundholes = 3.03 sq inches)
    1939 Gibson F7 (combined area of soundholes = 3.19 sq inches)
    1941 Gibson F5 (combined area of soundholes = 3.5 sq inches)
    1960 Gibson F5 (combined area of soundholes = 4.19 sq inches)


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    Registered User amowry's Avatar
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    Default Re: Lloyd Loar F5 soundhole aperture area

    Approximately 1.7 square inches for Loars, taken from Adrian's drawing of a typical Loar soundhole. The "unusually large" soundhole on his drawing is about 2.1 square inches.

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    Adrian Minarovic
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    Default Re: Lloyd Loar F5 soundhole aperture area

    1175.61mm2 for typical f hole projected on flat surface (like on drawings).
    1190.89mm2 projected on arching (curved surface)
    That is 1.822, resp 1.846 square inches.
    Generated by 3D CAD SW
    Adrian

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    Default Re: Lloyd Loar F5 soundhole aperture area

    Were the f holes cut using a template or was it more freestyle?

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    Adrian Minarovic
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    Default Re: Lloyd Loar F5 soundhole aperture area

    Quote Originally Posted by George R. Lane View Post
    Were the f holes cut using a template or was it more freestyle?
    On Loars definitely template cut. Any differences are either due to slight chamfer on upper edge or some work after cutting if tear-out occured.
    Adrian

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    Registered User j. condino's Avatar
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    Default Re: Lloyd Loar F5 soundhole aperture area

    Perfect. Thx.

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    Registered User j. condino's Avatar
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    Default Re: Lloyd Loar F5 soundhole aperture area

    Quote Originally Posted by Spruce View Post
    Quite a difference between the two...
    I'm sure you've seen this wonderful Darryl pic comparing an F5 with the A5:



    This should be an interesting discussion...
    Thanks Bruce; I've had the Griffith A5 in my hands for an uninterrupted afternoon of luthier nerdery and playing.....

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    wood butcher Spruce's Avatar
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    Default Re: Lloyd Loar F5 soundhole aperture area

    Quote Originally Posted by grandcanyonminstrel View Post
    Thanks Bruce; I've had the Griffith A5 in my hands for an uninterrupted afternoon of luthier nerdery and playing.....
    Isn't it wonderful?

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    Registered User gweetarpicker's Avatar
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    Default Re: Lloyd Loar F5 soundhole aperture area

    Quote Originally Posted by HoGo View Post
    On Loars definitely template cut. Any differences are either due to slight chamfer on upper edge or some work after cutting if tear-out occured.
    I'm not a builder, but I was under the impression that altering the soundhole is the final opportunity to tune the air chamber of a mandolin after all the sanding and shaping is done. I was wondering if some of the difference in soundhole shape/size may have been deliberate for voicing the instrument, a departure from the starting point template if you will? Just a thought.

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    Default Re: Lloyd Loar F5 soundhole aperture area

    Charlie Derrington (Mandozine interview, Question 8 [Q8]):

    Question: "... main factors in adjusting the bass frequencies when building a mandolin ..."

    "Build it like a Loar. Adjustments were made on the Loars by adjusting the treble f-hole size."
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    Default Re: Lloyd Loar F5 soundhole aperture area

    Quote Originally Posted by dhergert View Post
    Charlie Derrington (Mandozine interview, Question 8 [Q8]):

    Question: "... main factors in adjusting the bass frequencies when building a mandolin ..."

    "Build it like a Loar. Adjustments were made on the Loars by adjusting the treble f-hole size."
    Well, I would tend to question the extent to which this was actually known to Charlie Derrington, or whether it was perhaps a product of a bit of speculation on his part, or on the part of his associates. I also believe that he might have been propagating something of a myth, here, or at least trying to preserve a "mystique." The mystique of the Loar is worth something to Gibson, let's not forget.

    Having reviewed the pictures on the Mandolin Archive, I can confirm that there is simply not that much variation in the f-hole sizes of the existing Loar-signed F5's. They seem to have nearly all been copied from some fixed template, in fact. Besides, to increase bass frequencies, you need to reduce the hole size, which is not really possible after the hole is cut -- unless the holes were cut undersized in the first place, which I seriously tend to doubt. Yes, changing the hole size CAN be used to voice the instrument, in principle, but frankly, there isn't a whole lot of tonal latitude doing it this way, as tiny changes in the aperture size really don't make all that much of a difference to the tone. Changing the top thickness or bracing, on the other hand, can exert a much more dramatic effect! I remain skeptical that hole size was ever used much to voice mandolins. Most of the voicing came from adjustments to the carving (esp. top thickness) and the bracing.

    A soundhole might indeed have been enlarged slightly, from time to time, to hide small amounts of tear-out in the cutting process. But remember that a larger hole reduces, not enhances, the bass response.

    Anyway, Loars tend to show significantly more variation, from one to the next, the carving of their tops than in the sizes of their f-holes. I think that tells you something, right there!
    Last edited by sblock; Oct-27-2017 at 8:38pm.

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    Registered User gweetarpicker's Avatar
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    Default Re: Lloyd Loar F5 soundhole aperture area

    I'm guessing the top graduation and bracing are the first thing to get right and do make the most difference, but I wouldn't overly discount the effect of small changes in the soundhole size. A larger soundhole does raise the frequency of the lowest air resonance of the mandolin which could have a negative or positive effect on the perceived bass response. The body and soundholes need to be right-sized to emphasize the notes you want. A small change in the size of the f-holes, say from a combined area of 3.2 sq inches to 3.5 sq inches would probably raise the lowest air resonance a few Hertz (maybe 10 Hz on an F5 where the lowest air resonance is typically somewhere around 300 Hz). That's close to a quarter step which might make a perceivable tonal difference especially if there is some coupling of the air resonance with the top and back wood resonances.

    Anyway, I don't know how much, if at all, Gibson worried about soundhole size. I just wanted to throw some love at the soundhole size as an important tonal ingredient!

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    Default Re: Lloyd Loar F5 soundhole aperture area

    Quote Originally Posted by sblock View Post
    Well, I would tend to question the extent to which this was actually known to Charlie Derrington, or whether it was perhaps a product of a bit of speculation on his part, or on the part of his associates. I also believe that he might have been propagating something of a myth, here, or at least trying to preserve a "mystique." The mystique of the Loar is worth something to Gibson, let's not forget.
    I just thought the quote was interesting and pertinent to the discussion. I'm by no means an expert, I'm just an interested student. And i didn't know Charlie, although I wish I had. I'm not too much a mistique conspiracy theorist either, and since Charlie had his hands working on more modern Gibson F and signed Loar mandolins than probably anyone else in the world during the period that he worked at Gibson, I'd tend to believe he knew what he was talking about. As a student I'd be more likely to listen to someone who had their hands in the wood rather than to worry about the theoretical.

    If people read the quoted and linked interview, there's also plenty of discussion about shaping tone bars and tops, but the topic was sound hole aperture area, so that's what I quoted.
    -- Don

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    Ursus Mandolinus Fretbear's Avatar
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    Default Re: Lloyd Loar F5 soundhole aperture area

    I have always found it interesting that the Loar-signed mandolas had such delicate F-holes, smaller than the mandolins, especially considering that everything else on the mandolas was "just a little bit bigger."
    I have always found the standard Loar F hole size to be slightly excessive, at least from an aesthetic point of view. The very earliest examples from '22, strangely enough, were on the smaller side. I have only built a couple of mandolins, but the F-holes on my personal F5 were cut slightly smaller just because I thought it would be easier to expand them than to decrease them later on. I ended up leaving them that way and combined with a slightly heavier neck (more like an F4) that instrument has a strong bass and midrange response.
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    Default Re: Lloyd Loar F5 soundhole aperture area

    I wonder how a builder would know when the tone bars were correct for the sound he was after, did they remove the back each time they wanted to reshape them also the same for the carving of the tops, like how much to take off after they were put together....I also read that C. Derrington said that tonal qualities could be adjusted by changing the shape of the FF sound holes and after reading that I enlarged the sound holes on an F-12 that I had, to be honest I couldn`t tell any difference...

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    Adrian Minarovic
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    Default Re: Lloyd Loar F5 soundhole aperture area

    Even Charlie D was humean and I believe he would probably change some of his opinions over time, but since he is not with us, many folks take all his posts as gospel. When I look at my early posts I see that I saw many things differently ten years ago. These days, with huge amount of new information available everywhere we can give more reliable hypotheses han few years back.
    When we look at Gibson as factory and put together all information from brochures and compare them to the final product we can say that Loars were made to specs that they got from most succesful prototypes. The very early Loars have different tonebar shapes and positions, slightly smaler f-holes, fingerboards, even the pickguard bracket on prototype was different from the later Loars...
    They mention tuning of free plates, tonebars attached to top, and then whole instruments in the white. My guess would be they tried all this on the prototypes and when succesful model was found they just measured the specs and made the rest to numbers (there is some variability that is rather random - result of hand work more than intentional "tuning"), the final tweaking in the white was likely still done on the later Loars - easy way to balance the bass/treble.
    It would be interesting to compare the A hole with the early Loar f hole, perhaps they re-used old template they no longer used for F-5's....
    Adrian

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    Registered User sunburst's Avatar
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    Default Re: Lloyd Loar F5 soundhole aperture area

    I wish I was the mathematical type so that I even cared to remember the mathematical relationship between aperture size and Helmholtz frequency. I believe it is a logarithmic progression or something vaguely similar, but what it means to me is this:
    All else being equal, it takes a huge difference in aperture size to make a small difference in Helmholtz resonance frequency. That means a little bit of enlarging of f-holes in a completed mandolin just doesn't make much difference. I don't see it as a useful method of adjusting the sound of a completed mandolin.
    Also, I agree with Hogo. Charlie Derrington was nothing more than a human being and as such was subject to being wrong about thing just like the rest of us. He was very opinionated, and I also have it on fairly good authority that he could be prone to speculation and exaggeration at times.

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    Registered User Hendrik Ahrend's Avatar
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    Default Re: Lloyd Loar F5 soundhole aperture area

    If I'm not mistaken, the myth of tuning the sound chamber by opening/adjusting the sound holes was first promoted by Roger Siminoff, at least way before Charlie Derrington mentioned it in public.

    https://www.mandolincafe.com/news/pu...s_001217.shtml

    The F5L-ad from the early '80s already mentions the tuned f-holes - in reference to the Loar F5. Roger's book on mandolin making was first published in 1973. I don't have it at hand, but I wouldn't be surprised, if the sound hole myth was born right there.

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    Default Re: Lloyd Loar F5 soundhole aperture area

    The shape and size of the soundholes and the air volume of the body are the biggest factors determining the prominent, lowest air resonance peak (A0) of a mandolin's frequency response graph. This peak only approximates the mathematically calculated Helmholtz frequency since the formula assumes a non-vibrating box. I did a little experiment with a 1941 F5 mandolin where I measured the A0 at 333Hz with a combined area of the two f-holes at 3.5 sq inches. When I covered one half of one of the soundholes, the combined area of the soundholes dropped to 2.6 sq inches and the A0 dropped to 303 Hz, nearly a whole step. Covering one half of one soundhole is a drastic change I know, but it does illustrate the potential for changing one of the prominent frequency response peaks. Also I have seen the lowest wood resonance of an f-hole mandolin top (0,0) reported in 240 Hz to 320 Hz range. Altering the soundhole size has the potential to affect the tone especially if the alteration influences the coupling between the A0 and the (0,0) resonance.

    Again I don't know what Gibson did on their mandolins, but I would hesitate to discount the significance of soundhole size.

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    Registered User sunburst's Avatar
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    Default Re: Lloyd Loar F5 soundhole aperture area

    Quote Originally Posted by gweetarpicker View Post
    ...I measured the A0 at 333Hz with a combined area of the two f-holes at 3.5 sq inches. When I covered one half of one of the soundholes, the combined area of the soundholes dropped to 2.6 sq inches and the A0 dropped to 303 Hz, nearly a whole step...
    If my quick mental calculations are correct, reducing the aperture area by around 26% reduced the Helmholtz by around 9% in that exercise.

  28. #23

    Default Re: Lloyd Loar F5 soundhole aperture area

    Quote Originally Posted by gweetarpicker View Post
    The shape and size of the soundholes and the air volume of the body are the biggest factors determining the prominent, lowest air resonance peak (A0) of a mandolin's frequency response graph. This peak only approximates the mathematically calculated Helmholtz frequency since the formula assumes a non-vibrating box. I did a little experiment with a 1941 F5 mandolin where I measured the A0 at 333Hz with a combined area of the two f-holes at 3.5 sq inches. When I covered one half of one of the soundholes, the combined area of the soundholes dropped to 2.6 sq inches and the A0 dropped to 303 Hz, nearly a whole step. Covering one half of one soundhole is a drastic change I know, but it does illustrate the potential for changing one of the prominent frequency response peaks. Also I have seen the lowest wood resonance of an f-hole mandolin top (0,0) reported in 240 Hz to 320 Hz range. Altering the soundhole size has the potential to affect the tone especially if the alteration influences the coupling between the A0 and the (0,0) resonance.
    In my experience, reducing the AO by nearly a whole step will produce a significant and noticeable difference in the overall bass/treble balance. Increasing bass response while diminishing the high frequency response. Even a half step will cause noticeable changes in the balance of the mandolin. Changes less than one half step will generally have little or no noticeable change. Certainly not significant. This is why I consider the notion that Lloyd Loar or anyone else at the Gibson company tweaked the size of the treble F-hole to achieve some kind of magical tuning is fanciful at best. Anyone who has actually done meaningful, practical experimentation with aperture size knows this. You would not get a significant degree of change in the voicing by this method unless you were willing to put up with F-holes that were very different in size from bass side to treble side. Besides that, this method would only allow you to increase the AO frequency when most people would prefer a move in the other direction when it comes to Loars.

    That said, a significant and noticeable difference in sound can be achieved by reducing/increasing the total area of the apertures. This can be done by changing the width and/or length of the F-holes. In gweetarpicker's example, The total area was reduced by 25% so a similar result could be achieved by a 12.5% reduction of each F-hole. Sure, you can only get about one whole step worth of change (without changing air cavity volume ie. side height) but that's plenty enough to be noticeable.

    This thread made me think of a quote that I think I recently read on this forum. It went something like, "the difference between theory and practice is much less in theory than in practice."
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    Registered User gweetarpicker's Avatar
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    Default Re: Lloyd Loar F5 soundhole aperture area

    Yeah I'm thinking that enlarging the soundhole is more of a fine tuning thing, not a dramatic change. After all if you play an instrument with part of the soundhole covered, you typically hear only a subtle difference. On an earlier post, someone mentioned 1.7 sq inch f-holes versus unusually large 2.1 sq inch f-holes. I'm guessing that much difference would produce at least a perceptible change in tone.

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    Registered User gweetarpicker's Avatar
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    Default Re: Lloyd Loar F5 soundhole aperture area

    Quote Originally Posted by Oliver A. View Post
    Anyone who has actually done meaningful, practical experimentation with aperture size knows this. You would not get a significant degree of change in the voicing by this method unless you were willing to put up with F-holes that were very different in size from bass side to treble side. )
    Sounds like you're making a great point from practical experience! I certainly defer to your building experience on this discussion. I was just trying to see if anyone thought that the differences in Loar soundholes might have been a deliberate attempt at voicing. From what your saying, any change in tone would be minimal anyway since the soundhole shape and sizes between examples are not that different (so why bother?).

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