Building the Double Top Mandolin in the Israeli Style

Attachment 196178

What is a double top mandolin? Not to be confused with a construction method of laminating two tops together as an alternate to conventional top-bracing.
Quite simply, it is a deep body mandolin with an additional sound board placed in the chamber of the mandolin. The idea is that the inner top acts to reflect and refract the sound waves to alter the sound of the mandolin. Some feel it “cleans” the tone of harsh overtones adding more balance in the highs and lows. I’m sure there is no shortage of opinions (pro and con) for adding the interior top, and its effect on tone and volume.

The Design: Attachment 196179Attachment 196180
The first hurdle is the lack of information to guide the builder. It is a process of trial and error spread over several instruments to arrive at a satisfactory balance. After searching the web for clues as to construction, I came away with only a handful for photos. Thanks to Tom Gibson in Australia, Yaron Naor of Israel, and Richard-Depault of Canada for sharing photos on the web and in some cases, building details. The design is attributed to Kerman, however I wasn’t able to find any details of his construction methods to guide me.

The overall size I chose for this mandolin: 9 ½”x12” body, 2 1/4” deep, 13 7/8” scale. The shape is based on the medieval lute. The round bottom has a 4 ¼” radius and it flairs out with a 9 ½” radius up to the neck joint. This a pretty simple design, but I think it works well on this style of mandolin.
I decided to place the inner top about half way between the sound board and the back as a good starting point and it is based on various photos found on the web.
There are two schools of thought for securing the inner top to the sides. Either you can anchor the entire perimeter of the inner top to the sides, or you can leave the lower end unanchored to allow it to vibrate more freely. I decided on the latter.
In either case, you will need to add a pair of “false sides”. These perform a number of functions. They form anchor points for the forward section of the inner top. They extend all the way up to the sound board and offer some support for the top. Lastly, they create a secondary chamber of sorts. They are curved away from the actual sides to allow air (and sound) from the bottom chamber to pass up and out through the sound hole.

The overall size I chose for this mandolin: 9 ½”x12” body, 2 1/4” deep, 13 7/8” scale. The shape is based on the medieval lute. The round bottom has a 4 ¼” radius and it flairs out with a 9 ½” radius up to the neck joint. This a pretty simple design, but I think it works well on this style of mandolin.
I decided to place the inner top about half way between the sound board and the back as a good starting point and it is based on various photos found on the web.
There are two schools of thought for securing the inner top to the sides. Either you can anchor the entire perimeter of the inner top to the sides, or you can leave the lower end unanchored to allow it to vibrate more freely. I decided on the latter.
In either case, you will need to add a pair of “false sides”. These perform a number of functions. They form anchor points for the forward section of the inner top. They extend all the way up to the sound board and offer some support for the top. Lastly, they create a secondary chamber of sorts. They are curved away from the actual sides to allow air (and sound) from the bottom chamber to pass up and out through the sound hole.

“False Sides”
After the neck and tail blocks were glued in, the false sides were bent so that they could be to the neck block and blend into the sides. They are taller than the sides so that they could be shaped to match the crown of the soundboard.
Attachment 196183

Glue linings were installed next, along with some strips to support the inner top:Attachment 196184

The inner top was then installed from the underside:Attachment 196185

Note that the inner top is free-floating beyond the false sides. It is spaced about 1/8” away from the sides and the tail block. A sound hole was cut before the inner top was glued in place.

The rest of the construction was straight forward:
Attachment 196186Attachment 196187

Thank you, that is very interesting!

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Originally Posted by Graham McDonald

Thank you, that is very interesting!

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Yes, I am curious as to how it sounds. It looks Great.

I cant post a sound file, but I can send you an attachment to your private email.

Yes, please. PMed to you.

Cheers

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Originally Posted by Tukanu

I cant post a sound file, but I can send you an attachment to your private email.

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Sorry, messed up my question!

Quote:

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Originally Posted by Tukanu

I cant post a sound file, but I can send you an attachment to your private email.

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Sent you a PM, thank you.

Tukanu, it sounds good, I think better that the Flatiron, and they get a lot of praise around here. Thanks for the sound file.