Official Luthiers Forum!

Good day all! I've been building Jumbos lately and enjoyed some early success. I've been able to build back-to-back with nearly identical sound, and I attribute a good bit of those results to the Gore/Gilet approach to matching resonant frequencies from guitar to guitar. FWIW, my primary body frequency target is 77 which puts it just outside the lowest note on the guitar, avoiding conflicts with certain notes while adding a lot of nice low-end to open chords.

Now, I'm doing research on a Parlor. I've noticed a lot of posts regarding the Antes plans (from LMI?) so I'm leaning that direction. I will certainly read through those threads for advice as well.

My question is about target resonant frequencies on a guitar that small. Obviously I won't be able to hit anything as low as the Jumbo's, so where do you all target your main, top and back frequencies on a body that size?

Also, any other tips on smaller instruments would be welcome. Hoping to use Koa with an Englemann top and the plans mentioned above.

Thanks in advance!

I've built two from that plan. The only difference was in bracing size. First was following the plan, the second had thinner braces, 1/4" if I recall. It sounded much better, not as "tight".
Can't give any opinion about body frequencies.

I have built three from the Antes plans. The plans are generally considered over braced, I lightened the braces in mine quite a bit. The plans are also drawn as tho you had X ray vision and were looking thru the top - it is possible to put the tone bar on backwards.

My guitars were built out of rosewood - EIR, Mad and Braz. Two of them have Lutz tops, the other sitka. I used 24.5 scales. The guitars will fit in commercially available TKL cases (which is a good thing)

I frankly can't tell a difference between the guitars. They are somewhat boxy sounding, biased to the mids and trebles as you would suspect, but still enough bass for old timey and bluesy fingerstyle. They are amazingly loud - one of them was played at a GAL Steel String listening session and someone commented on how well it projected to the back of the hall.

I didn't or don't do any fancy analysis of the guitar as its was being built - I mostly followed the plans and lightened the braces to try to match the tops. I flex and tap and shave, but its mostly blind stupid luck that my guitars sound as good as they do. I can't give any advice on voicing.

Thanks much. Those look like they turned out very nice indeed. Lot of work on that inlay...

I asked Trevor for advice about a target for body frequency for an Antes Parlour build and he said he had no idea, he's never built anything that small, just go for the top and back frequency difference and let the body fall where it may.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Do you mean your body cavity Helmholtz resonance on the Jumbo's are77Hz? That's really low. the Helmholtz resonance is usually near or a little below the frequency of the second lowest string, around G-A on a guitar. I made one Dred that resonates right on E and I liked it so much I left it that way. But my small parlor guitars are usually around A and I attempt to make them Ab-ish.

Thanks for the tip. My Jumbo Helmoholtz is just below a D#... and yea that's lower than what I've read or heard from others, but when people hit an open E chord there eyes get real big... I think (know?) based on voicing these before finishing them with Wavepad, that thinning the edges of the top around the lower bought nearly 40% drops that frequency significantly. Partly, this is due to my x-bracing being very thin the last few inches before it hits the edge of the lower bought, and because none of my other braces even come close to the rim (except the transverse). BTW I take credit for none of this. All from Gore/Gilet and Somogyi.

To be fair, I was trying to build a guitar for the biggest, broadest strumming sound I could get. Designed for big moment worship leading, not for intricate finger picking or soloing. It also has an Adi top that's a hair thick in the middle. It gives a lot of headroom. I had a client in last week to play his before the finish went on, and he said his and the demo he played seem to beg to be played louder and louder.

Ironically, the extra low end makes for a really nice evenness across the spectrum even when playing softly. Well, when a good player plays softly . I'm a saxophone player, and a guitar hack. But, whenever someone demo's this thing I'm in heaven listening to it.

Sorry for the detour... we are talking about Parlor's here!

I have built a bunch from those plans. 1/4” bracing, tops in the 0.100-105 range. Body depth same as an OM so extra depth and x splayed a little more combined with an elongated bridge at about 6.7” to catch the edges of the X. Bridge plate around 0.090”.


I would say the best have been double side Mahogany with Lutz tops and BZ rectangular bridges. A Brazilian bodied one was a great guitar too.

Here is a link to my site with some pics and a cell phone video of Michael Johnson playing one.

http://www.kennedyguitars.com/size-2/

I love these little guys and they have been popular. They are a speciality guitar and have some limitations but they sound absolutely great plugged in with a K&K pickup.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

One problem I ran into was that my hand is too big to fit in the soundhole of the Antes plan. So no brace trimming after the body was closed up and I had to make pinless bridges. The clamping was hard to figure out, hope they hold. The were gifted to grandkids so I'll probably get them back if they don't.

"that thinning the edges of the top around the lower bought nearly 40% drops that frequency significantly."

That's a lot, typical I only thin my lower bout perimeters around 12 -14%, but then I'm not building Jumbos, mostly OMs for pickers.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Well, that's a wild guess. I didn't get my calipers out. I use a sharp block plane and work around until I hit the target frequency. Honestly, because I flush trim before thinning, I don't know how I'd get an accurate measurement without some fancy tools. Maybe 30% is more accurate? I just know I can tell where I've thinned without squinting.

Does sound nice and open, with more fullness in the E and A than I might expect from a lower bought that size. Body about 4" then? Do you taper the back much?

Also, what scale did you use? The Plans, or longer?

Thx.

No need for fancy tools, I just use scratch blocks to see/control how much is to be removed, 0.15m and 0.3mm in this case.
Ends up being slightly more after sanding, so about 0.35 to 0.40mm in this case

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

I didn't think about Helmholtz when I made my archtop. i checked and it is around b. B, Bb, Ab all rattle it blowing in the f holes. Now I know why it sounds so good around the open b! Also around e and f aren't too.bad.
Does anybody plan the breathing mode in from the start?
The "parlor one" I'm working on is a small baroque in A? with a 540 scale. Should be comfy.

Colin, that marker is.seriously cool.

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Why be normal?

Mine are 4" at the heel and 3 1/4" at the head block. 24.9 scale.

On thinning the edges, I do it on all flattops. I had a kid spent a summer with me back in 2005 who completed the Red Wing MN Lutherie school and they had Dana Bourgeois come and talk about voicing and he taught me what he learned. It involved sanding the edges of the lower bout while tapping the top and listening for a tone difference and feeling the vibration at the bridge. Sounds a little voodoo but you can hear it open up and feel a change in vibration and I eventually developed a feel for it.

I have come to rely on the technique a lot as the final voicing processes after the box is closed. I do it before the binding is place so I can (kind of) measure the thickness of the edges with a caliper. I would say with an OM top of say 0.116 the edges usually wind up in maybe the .096-.100 area when it sounds about right.

I avoid wide purfling with this technique for fear of weakening the top attachment. Usually just one 0.060 bwb.

As far as cases I was unable to find a stock case that fit perfectly, at least to the point that I was willing to use it for a client. I had Cedar Creek do a custom a number of years ago and it is a beautiful case and fits perfectly. They have the specs under my name and I think other folks on this forum have ordered them in the past. Not sure what the current price is as I have not had to order one for a year or so.

Hope this helps. As always a million other ways I am sure that one can approach it and that work well in the hands of those that use them.

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It's not what you don't know that hurts you, it's what you do know that's wrong.

"I avoid wide purfling with this technique for fear of weakening the top attachment. Usually just one 0.060 bwb"
Question.
With wider bindings, as long as the purfling depth is less than the thickness (say 2/3rds) of the top, does that not help prevent weakening the soundboard attachment?
The top is then still glued to the linings for the maximum possible width (after binding)

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

Cool! I've never done it like that before. I like to thin the lower bout braces to zero at the linings but have never cut them short like that.

Anyway it sounds like you are marching to the beat of your own drum and I say march on!

Guitars are complicated. I have a series of parlor guitars that I make that are based off a guitar built in about 1895 or so by the then C. Bruno and Sons company (based off of Antes plans). Everyone always comments on how surprised they are at the bass response of these instruments. And the lower X-Brace is tucked into the linings at about 3/16th in... Go figure?

I am not sure Colin. I am doing mostly double sides these days and they usually wind up around .100-.110 after sanding flat. My bindings are .060 and combined with .060 wide purfling that is about half as thick as the top it leaves a lot of spruce still glued to the lining. That was my thinking.

I like the scratch blocks. Great idea!

_________________
It's not what you don't know that hurts you, it's what you do know that's wrong.

Not my idea, got it from Ervin Somogy.

_________________
The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

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John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

This is a picture of 2 parlors I made some time ago.


And the bracing (Dimensions are in mm).


The frequencies are:



These were my first parlors, so I cannot comment on the sound much. But I like how they sound.
Braces Width: UFB = 8 mm
X = 7 mm
others = 6 mm
You can get the height from the picture.

Hope this help.

Slight detour to mention that I really like Alain's spectrum analysis software (screenshots shown above). It gives me what I need, and it is all right there, without having to do any special tweaking. It is pre-tweaked for just this purpose.

Just a satisfied customer.

Excellent info, thanks a bunch! What woods did you use on those?

African mahogany (Kahya) for neck and body. 24 " scale length.
One had a lutz top the other an Engelman spruce.
The Engelman (right one) was french polish top and body which explain the darker color.
The Lutz was varnished with a waterbase.
The Engelman went to a customer, I kept the Lutz. This was in 2016, no sign of problem so far.
The A brace is missing in the first photos.
Here is the complete bracing

Thank you Don!

For those interested you can get a copy at:

https://drive.google.com/open?id=1X4FSJ ... uAeHgzvdnP