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Hey I am new here and am just starting my first build! So, I am excited to get to know you all!

I do have a question though, I have been contemplating this for some time and the other threads I looked at didn't give a clear answer. I am working on my first Dreadnought guitar and I plan on using a top that is radiused to 50' and a back that is radiused to 15'.
First I know that I want a strong bass response reminiscent of an HD-28 but I also want slightly more balanced mids and I know that a radiused top, since it makes the wood stiffer, can sacrifice some bass response. I also understand that a radiused top is more stable hence the 50' radius. So to accomplish getting a strong bass response but also slightly more balanced mids would thinning the top slightly and lightening the bracing (in comparison the a Martin HD-28) give me the stronger mids without sacrificing the presence of the bass?

My other question is; it was alluded in an earlier thread that you can get the same TONAL results building a flat top as a radiused top by varying your methods of construction. I assume what they mean by this is changing bracing patterns, weight, material, thinning tops etc.

Any opinions?

I think a flat top should be slightly stronger, especially behind the bridge to counteract the string tension. I have fixed an older 12 string and 6 strings (all steel by the way) with a completely FLAT top and ladder braced too... they sound fantastic but I can't say if its the top radius or other factors...

I want to go with flat top on my next/future build because I don't have money for 10 different dishes... they are expensive and more expensive to ship.

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I actually found a pretty ingenious way to make your own! Here is a link to it.
http://acousticblog.mokkou.jp/?p=44

alluded to 'here' or 'there'?...your post is verbatim in both places

as best I can tell domed tops were implemented for structural integrity in a mass production environment.

in said environment (where in a specific model all tops are of the same thickness, all braces are made the same EXCEPT THEY ARE DIFFERENT PIECES OF WOOD) 'tonal results' would be different between flat and domed...adjustments in design would be required to achieve the same/similar 'tonal results'.

in an environment where the craftsman has the desire to tweak things (deflection tests, Chlandli patterns, use of one's innate senses) a whole new ball game is opened up and it essentially comes down to the ability of the luthier.

in a nutshell, in a production setting sweeping statements about woods used, radius of dome, etc., do have some relevant meanings...in a craftsman's shop these many times mean about squat as most things fall under the control of said artisan...

Charlie Hoffman and Jim Olson have done OK with flat tops.

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Hey Jacob,

There are tonal reasons for radiusing a top, but I think you will find that most builders do a radiused top for structural reasons. As you mentioned at the top of your first post, there are so many factors that contribute to the tone. A radiused top alone won't give you, or not give you the sound you are looking for. Experimenting while building future instruments will help you understand how all the different factors you mentioned control the sound.

Some builders use a variety of different top and back radiuses depending on the model. For me I have used 15' for the backs and 28' for the tops on everything I have built in the last 10 years. It has worked well for me. A set of radius dishes are a good investment if you plan to build a lot of instruments.

Josh

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Thanks everyone for the advice so far! I do understand that a radiused top is primarily for structural integrity but the side effect from what I have read is a decrease in bass response. This is what I want to avoid!

The reduced bass response is dependent on the radius, and it's not necessarily bass, but lower midrange. Old Martins had an effective 50' radius whereas currently they're built on a 36' radius (see John Greven's article on voicing). Tops with flatter radii and rounder braces tend to have a woodier presentation, but this is not always the case. Taylor's are built fairly flat, but they've always been bright in their presentation and their standard bracing for years was 3/8 x 5/8 rough stock and scalloped -- so mass and scalloping and radii are not necessarily governing principles, but rather part of the equation you create in the choices made in the course of building that determine what your instrument sounds like. You then, having a data point, need to decide what you want more/less of and make small adjustments until you get what you want.

I think that if you took a flat top and introduced a radius without changing anything else, then your statement might be true. However, that is not the way things are done. The radius provides more bending stiffness to stand up to the string forces, which allows the luthier to use a thinner/lighter braced top. So the overall stiffness may be the same, may be more, or may be less than the original hypothetical flat top.

The point is a better way to say it would be that a stiffer top will have decreased bass response. The radius (or lack of) is one knob that can be turned to adjust the stiffness, but there are others as well (wood properties, top thickness, bracing pattern, bracing height, etc). And these knobs are often turned in concert to achieve the desired results. So it is not a very good statement to say "a radiused top will be stiffer and have a decreased bass response". Without any other information, no one can say whether a given radiused top will be stiffer or more flexible than any given flat top.

It's your first build, so why not keep it as simple as possible? Flat top. Easier geometry, easier assembly, and lotsa bass.

Steve

Is there a greater risk of a flat top cracking from low humidity than a radiused top?

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David, could you describe what you mean by rounder braces?

Yes, absolutely, and I know this from firsthand experience! I would only consider a flat top if it was braced at the lowest humidity the guitar is likely to see in its environment.

It's not like a 50' radius or a 25' radius is going to stay that way. These have to be considered highly nominal. Every time the humidity changes, so will the top arch.

James, more parabolic than pyramidal. -- db

I used to build with a radius, tried all kinds, but now I build dead flat. They just sound better to me. I build smaller guitars for the most part and I do believe it brings out more low range. But you could build with a very shallow radius like a 60' for example if you are worried about strength. Depending on your methods you don't necessarily need a radius dish to build. I never used one. You can arch braces in a few minutes with a plane and then just glue them to the top using a flexible caul for clamping pressure.

Thanks, Dave.

A 60' radius is actually what I planned on using. I actually just finished making my own radius dish too. I made a small one in the shape of a guitar though and plan on just using clamps to glue the braces on. I don't have enough works pace for a go bar so this will work for now and I know several other luthiers that use this method.

That will work just fine. That's how I do it when I build flat. IT's a traditional classical guitar building method, the solera is the dished out work board.

I'd like to build a flat top for this reason, but I'm worried about the cracking issue. Have you had any problems with yours?

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"I am always doing that which I cannot do, in order that I may learn how to do it."
Pablo Picasso

https://www.facebook.com/FenskeGuitars

Every guitar I've built (11 to date) have true flat tops, none have crack issues. Build to a lower humidity versus where the guitar will live, ensure the guitar stays hydrated and it will be happy!!!

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I've only built 3 so far. I own two of those and one is out in the wild. One was my prototype and came out real well so I like to keep it around as a demo, the other was that little parlor that I built for the challenge and I think I've played that guitar every day since I built it I like it so much. So far so good. 'Course mine stay in my shop under very controlled conditions so I am not worried about them.