carved or flat top octave mandolin

[Bob Schmidt]

For my next build I am thinking of building a guitar bodied octave mandolin, and am trying to decide on a flat top guitar or arch top carved guitar body for it. I would be inter4ested i any thoughts of the difference since I have not been able to find a lot on you tube for comparison.

[Rodney Riley]

Haven’t played any octaves yet. But pictures of carved tops I’ve seen....beautiful.

[foldedpath]

What do you want it to sound like? My personal take on octave mandolins is that I want it to sound like a big mandolin, not a 12-string guitar. Tastes vary on that, it's just my personal preference, so take the following with a grain of salt.

The furthest you can get from a 12-string guitar timbre is with a carved archtop OM build along the "Gibson mandolin on steroids" line, like my Weber Yellowstone OM. It has a slightly smaller body and internal resonant air mass than a guitar-based OM (GBOM), so it emphasizes the midrange more than the bass. It's "punchy" and sounds like a big mandolin.

An archtop GBOM (guitar-based OM body) gets you a little closer to the guitar timbre with that larger body volume, while still sounding somewhat like a mandolin to my ears. The design typically has a slightly stronger bass than big mandolin-body OMs like my Weber.

A flat top GBOM will get you closer still to the 12-string guitar timbre. At that point, the only real difference is the tuning in 5ths and fewer strings. Personally, I don't see much point in this design, although it's easier to build.

If you're going for a flat top OM, I think you might get a more useful and interesting sound if you build a smaller volume teardrop shape, instead of a full guitar body. Like what some people call a "Celtic" OM or bouzouki, or the Big Muddy mandolas and OMs. This will shift the emphasis away from the boomy guitar body bass, and more into the jangly bouzouki zone, which can be nice for cutting through a group of fiddles in an OldTime jam or Irish session.

Anyway, just some thoughts on the subject. Good luck with whatever you end up with!

[Chuck Leyda]

A lot to consider...I agree with Foldedpath for the most part but I would say bridge also plays a part. You can find OMs with mandolin or guitar style pin bridges. Mando bridge might inch the sound a bit towards mandolin.

I had a flat top, onion shaped, mando bridged Petersen Octave mandolin and I don't think it sounded like a guitar. Same for my flat top A style oval hole Gernandt.

So how much like a guitar do you want it to sound? A lot?
Guitar bodied, Pin Bridge, Round Sound Hole, Flat Top.

More like a mando?
Onion (A) body, mando bridge, F hole, arched top.

In between?
Mix and match!

[Bob Schmidt]

I just finished a build of a carved top bouzouki the end of last year and love the sound compared to my trinity college bouzouki. They are both long scale length (660mm). My thoughts for the OM (short scale length) would be to tune it GDAE and play more melody on it, but still have the strong accompaniment capability. I was thinking guitar body to extend the bass a bit.
I agree with the 12 string analogy; I have herd people bring them to a session and they just don't seem to fit well. Perhaps if they were tuned more to an open tuning they would work better, but it is not the sound I would be looking for.
I currently switch between the mandolin for melody, and the bouzouki primarily for singing accompaniment, and thought that an OM would fill a gap between the two.
Thanks for causing me to look at the end product more. I was mostly thinking about the build aspects, and a flat top would be easier, but perhaps not what I would want in the end.

[fox]

You could go with an induced, curved top and floating bridge, if you want to be different!

[peter.coombe]

I have just finished my first OM. I went with the teardrop shape, flattop with induced arch, floating bridge, 21 inch scale length. Is X braced with carbon fibre reinforcement. Very pleased with the sound with D'Addario EFT46 strings, and I can play it, the scale length is not impossible for a mandolin player. I was going to make an archtop using the same mould, but the sound of this thing is so good and it's also really loud, it makes me wonder if I should go archtop. It is heaps of fun to play, and I will be very surprised if it is not sold and out the door fairly quickly. An archtop is lots more work, and the wood is more expensive so maybe not worth the extra trouble.

[Bob Schmidt]

Peter,
What was the arch radius you used? I agree the arch top is a lot more work. If I go that direction I will probably use a small guitar design with a pin bridge just because it would be a new learning experience to build one. I like the idea of using the same mold so maybe I will go with an induced top, and think of an arch top for the following build. Thanks for the input.

[Bob Schmidt]

I might be showing my ignorance here. Is it possible to use a pin bridge on an induced arch?

[fox]

There is a complete and detailed build thread on here somewhere that show how Nigel Forster builds his induced tops.
Edit.. I found it.... https://www.mandolincafe.com/forum/t...d-Thread/page4

[Bob Schmidt]

Thanks for the link. It is a good pointer to another resource for those of us new to the craft. This forum has proven quite helpful in getting me through my first build. It amazes me that so many builders are willing to share their expertise so freely.

[fox]

Have you looked at the “speaker box design “?
I have built several tenor guitars lately, using just this concept .... basically... a rigid dense body, rigid central bracing and a flexible lip on the soundboard.... just like a speaker box!
No doubt the design produces a very interesting effect but of course everything is subjective.

[kurth83]

I prefer mando (floating) bridges regardless of other factors, because I can adjust intonation for different string weights without having to go see a luthier to move the bridge. For that reason I avoid GBOMs. My trinity College (flat-top tear-drop) can be strung to produce a variety of sounds, not all the way to GBOM level, but I can get pretty close if I want.

Having tried it both as an 8 string and a 4 string instrument, I found that the mandolin-esque tone was more a factor of the dual string courses and string type than the body shape. Admittedly this is with a sample size of one.

The TC's smaller body with 4 strings sounds like a parlor guitar. String it with 8 and it sounds like a mandolin. I imagine a GBOM strung with 4 strings would approach a larger-bodied guitar sound.

[peter.coombe]

The induced arch for the top and back is 15 ft. I used the same template that I use for my guitar backs. The mould was a big mandola mould from a mandola I made almost 20 years ago, but the sides are 65mm wide instead of 50mm. I have moulds everywhere so many there is no more room, so I did not want to make another one. I have made a couple of flattop mandolas using the same construction only smaller and they sound very nice too. Different sound from the archtop mandolas, but very close in terms of quality of sound.