View Full Version : Two Cohen demos

Dave Cohen
Mar-05-2009, 1:45pm
Here are a couple of demos just completed. The blond instrument is one of my "classical A" short (13.1") scale mandolins with a slotted headstock. Woods are Engelmann spruce top, Euro maple back/sides/neck, Macassar ebony headplate/pickguard/trim. The sunburst instrument is a 13.875" scale A mandolin with Engelmann spruce top plate, Euro maple back/sides/neck, and ebony headplate/pickguard/trim. I know, I know, I need a polarizing filter.


Mar-05-2009, 1:47pm
Those look wonderful. I espescially like the classical one.


Woody Turner
Mar-05-2009, 2:07pm
Beautiful work and woods! Is the soundhole unusually large on the blond one?

man dough nollij
Mar-05-2009, 2:12pm

What is the purpose of the short scale? Does it affect playability or sound at all?

Mark Walker
Mar-05-2009, 2:54pm
Dave - fine work! I like that classic look of oval holes!

Keep it up! :)

Dave Cohen
Mar-05-2009, 3:47pm
The short scale is approximately the same length as that on a Neapolitan mandolin. I built the first of those for Mike Schroeder back in 2002. His main mandolin at the time was a Calace Neapolitan, so I made the scale length close to that of the Calace. The motivation was playability, though scale length does have its own impact on sound. My classical A is also similar in concept to the short scale L&H A. This one is the first one I have done with a slotted headstock, and I like what I am seeing and hearing.

My oval soundholes are slightly larger than typical (e.g., Gibson, L&H,...) oval hole mandolins. The old Gibsons have a soundhole area of about 2.7 sq. in. The total area of two ff-holes on a typical ff-hole mandolin with the same body size is about 4.0 sq. in. That gives the old oval hole mandolins a Helmholtz resonance frequency of about 210 Hz. By comparison, the Helmholtz resonance frequency of an ff-hole mandolin is usually around 280-300 Hz. I have aimed for a little more projection by making the soundholes larger in an attempt to raise the Helmholtz resonance frequency a bit. Not sure if that is all that there is to it. My oval hole mandolins still sound like oval hole mandolins, though they have a recognizable Cohen sonic stamp.


Mar-05-2009, 4:06pm
Wow, that classical A is spectacular!!! I can only imagine the sound it has.

man dough nollij
Mar-05-2009, 4:09pm
What is the reasoning behind the "teardrop" shaped bridge base? It sort of makes sense that the bass side would need more surface area, but I'm not sure what theory backs that up. Or is it just about having more mass on the bass side?

Mar-05-2009, 4:13pm
I need to visit, you know - a test drive. Real nice work Dave!


Bernie Daniel
Mar-05-2009, 5:15pm
man dough nollij: What is the reasoning behind the "teardrop" shaped bridge base?

Yes I was wondering about that too. I noticed some years ago Gibson started doing something very similar with the new wave MK-72 guitars they started making around 1978 to 1980.

These guitars were very edgy and represented "all that Gibson knew about acoustic guitars" (their claim) at the time.

What is the reasoning behind this bridge?

Beautiful mandolins -- love that classical I hope you can post a sound clip.

Dave Cohen
Mar-05-2009, 5:35pm
There is no reasoning behind the bridge foot shape, or at least there isn't any now. I started doing that way back when, with the thought that if there is was anything to Kasha's reasoning, I would be covered. Tons of physics later, I am pretty sure that there is nothing to Kasha's reasoning. But since I started doing it that way, and it can look good if done well, I have continued to make them that way. I don't think that there are any sonic advantages to that bridge foot shape, but there are a couple of advantages to my bridges. One is that I carve them to lower mass than conventional bridges. I have measured the mass of conventional bridges at anywhere from 13 to over 18 grams. Depending on the material, mine weigh anywhere from 5.6 grams to slightly less than 10 grams. Bridges from some of the densest samples of Macassar ebony have been about 10 grams, while some smallish rosewood bridges for the classical A mandolins in this batch were about 6 grams. Another advantage to my bridges is that because of the width of the bridge foot on the 4th string side, there is no tendency for the bridge to tip over.


Mar-05-2009, 6:02pm
Lovely Dave! OOOHHHH, slot heads! :)

Mar-05-2009, 6:54pm
I wouldn't mind having to break those in; love the slottie, especially!