Double back ukulele

ktuurna

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German master luthier Tom Ziegenspeck has developed interesting construction.

"This ukulele has a double back, which creates a tonal advantage.
As a master plucking instrument maker, I can confirm that, especially with ukuleles, the back is an area which very little, if not at all, resonates. This is because when playing, the instrument is held completely against the body and the back of the instrument is thus dampened. However, if you install a soundboard in the interior of the instrument that cannot be dampened, you get an instrument that is significantly louder."


I have noticed when I play ukulele and if I don't hold it so that it is not against my body sound is better and louder. I think that Ziegenspeck's construction could work. What do you think? I have met him and tryed his ukuleles (not double top) and they are very well made and sound good. I think I will try that. Then I know.
 

greenscoe

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If you go to Tom's site there are 2 examples of double back ukes with a description and photos and Tom playing these instruments. If you use Google translate to read the German text, he explains that he's found that a spruce inner back works best. We don't see a photo of a spruce inner back so don't know how this is braced or exactly how he configures the linings. I suspect it will be lightly braced, if at all, as the outer back is the one that needs to be strong.

Anyone who went to MUMF in 2018 or 2019 will have met Tom and seen or played his instruments. I don't think he's the sort of guy interested in gimmicks so if he's doing this he must think there's some merit in it. Like ktuurna, I suspect I'll have to give this a try.

https://www.ziegenspeck-ukulele.de/
 

Kelali Kev

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I was studying some of his photos. It looks like the inner back was braced the same as a regular back with the two cross braces beneath the sound hole, and a centerline patch. There is kerfing around the edge holding it in place with the smooth side of the kerfing facing the center of the instrument and the kerfed side glued to the side. More importantly, he has a series of holes in the sides between the 2 backs which will allow the inner soundboard to vibrate independently of the outer back without there being a vacuum created in that space which would dampen the inner soundboard. I like the idea.
 

printer2

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Tim McKnight

"TT - Thanks for that. But you also build double backs right?

TM- I do build double backs which I call "Hollow Backs". They are not double backs in the sense like double tops are. The construction is very different and proprietary. I don't have too many secrets but this invention is mine. In the simplest terms there are two backs, an inner and outer back and both are independent of each other separated by an air space. Therefore if the outer back is dampened by the player's body the inner back is still free to vibrate. This design has a tremendous amount of forward projection more so than any guitar that I have experienced or heard to date.

Playing a Hollow Backed guitar sounds very much like a conventional guitar from the player's perspective. However, if someone stands across the room from the guitar they get a tremendous amount of sound blasted at them. The inner back almost acts like a trampoline for the sound produced by the top.

Imagine that the sound that the guitar produced was in the form of a tennis ball. Throw that ball at brick wall (a conventional back design) the sound or tennis ball would travel a given distance. Now throw the tennis ball at a trampoline and the sound (tennis ball) rockets off traveling a far greater distance."

http://www.guitarbench.com/2009/10/21/mcknight-guitars-luthier-interview/
 

Timbuck

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Really it’s a double top so it needs a sound hole to stop the vacuum effect ..maybe a violin style sound post under the bridge would be worth a try as well to transmit vibes.
A drum Tom Tom does have more depth and sustain with a bottom head fitted but the volume is just as loud with just only the top skin fitted as per Concert Toms...just a few thoughts. :)
 

Tukanu

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I have built several doubleback dulcimers. The principle is the same where the back of the dulcimer is dampened by holding it on the lap. It does help with both tone and volume. Also I have been considering a doubleback mandolin. A builder in Quebec and another in Israel have been quite successful. Note the air space around the inner back and the lack of bracing.
doubleback 008.jpg
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12694829_600047930149412_7229759245799083139_o.jpg
 
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Jardin

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I think it is great to be building these features into a build. However, for those who want something for an existing instrument there are options.

If dampening from being held against the body is the issue there are these:
https://www.tone-gard.com/

(No affiliation by the way)

My uncle plays mando and when I last saw him several years ago he had one of these and it made a noticeable difference for sure.

Same thing can be made for a Ukulele apparently :
https://forum.ukuleleunderground.com/showthread.php?32693-ToneGard-for-Ukulele
 

Uke-alot

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It seems like an instrument with a double back would have a greater chance of unwanted resonances (which could unnaturally emphasize certain notes) between the front and floating back than a conventional instrument. Or at least, with a conventional instrument, an unwanted resonance of the back would be somewhat damped by the player's body.
 

printer2

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It seems like an instrument with a double back would have a greater chance of unwanted resonances (which could unnaturally emphasize certain notes) between the front and floating back than a conventional instrument. Or at least, with a conventional instrument, an unwanted resonance of the back would be somewhat damped by the player's body.

But resonances are what gives the instruments their character. Otherwise acoustic guitars will sound like electric ones, as an example.
 

ktuurna

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Tim McKnight

Tim,
I read your interview that you linked. Not much about your Hollow Backs, but very interesting interview anyway, especially what you told about using domestic wood to guitars. You might be interested in a project that was done a few years ago.
"The Leonardo Guitar Research Project (LGRP) is a Europe based independent non-profit organization that was funded by the European commission (Leonardo-Da-Vinci and Erasmus+ ) from 2011 till 2017.
The main goal of LGRP is to study, demonstrate and communicate the possibilities of building acoustic and classical guitars from non-tropical woods
Together with partners from different fields we aim to develop a cooperative knowledge platform concerning the use of alternative non-tropical wood species in guitar making".

Our school (Ikaalinen School of Arts, Crafts and Design, Guitar making deparment) was partner of that projects and we got much interesting knowledge about that.
There was funny things too. When players blindtested guitars, they found difference when they play same guitar etc. And they are A good example of psycho-acustics. You can't trust your ears always. If you think brasilian rosewood is best and you think you play guitar made from that, it sounds better to your ears. And the players who test guitars were experienced top guitarists.
Attitudes are deep within us and we don’t even know it ourselves.
There was an article about that that project in American Lutherie #124 / Winter 2015. If you don't have it, you can read it from here
https://sites.google.com/site/leonardoguitarresearch/LGRP-in-American-Lutherie
I like to use northern wood in my instruments. Flamed arctic birch is my favorite because of its beauty and acoustic properties, but it is sometimes little tricky to handle and stability is challenging, but we have find the way to do that.
 

Uke-alot

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But resonances are what gives the instruments their character. Otherwise acoustic guitars will sound like electric ones, as an example.

Well....The problem I'm bringing up is when both the front and back both exhibit a resonant peak on the same note, and that note (or chord) booms much louder than any other note. Or when the front and back have resonant peaks that are close, but not quite the same, and the note corresponding to that frequency sounds sour. This a very important consideration with instruments that are played with bows (wolf notes), but can be an issue with other instruments as well.
 

Michael N.

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The double top (actually a double back) is an old concept. It dates back to the early part of the 19th century and then seems to resurface again in the early part of the 20 th century. I think one of the well known Spanish guitar makers started offering a version in the 70's. It's an idea that's never really gone away yet never quite made it into widespread use.
 

printer2

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Well....The problem I'm bringing up is when both the front and back both exhibit a resonant peak on the same note, and that note (or chord) booms much louder than any other note. Or when the front and back have resonant peaks that are close, but not quite the same, and the note corresponding to that frequency sounds sour. This a very important consideration with instruments that are played with bows (wolf notes), but can be an issue with other instruments as well.


And that is why the maker adjusts the resonances so they do not fall on the same frequency or multiples as well as keeping them off the note centers.
 

ksquine

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I just like the term "master plucking instrument maker" ;)

Internal sound chambers and double backs have been around for a while. Selmer guitars had an internal sound chamber, Gibson tried the Virzi tone producers in mandolins, etc.
I'm sure they all "work" at some level but never seem to catch on.
 

Pete Howlett

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When Tom worked with me I shared this idea which I covered in 1976 in my Bachelor's thesis on the history and development of the classical guitar having met Peter Sensier who made guitars with a double back...