flat VS radiused

mertz · #1 03-07-2007, 06:04 PM

So I'm slowly gearing up for my first full acoustic build. I'm designing this one from scratch and was hoping some of you folks could chime in on the pros/cons of a flat vs radiused top. I understand the theoretical advantage to having a radius, but was wondering what your thoughts are on how it actually affects tone. Thanks for any advice!

-Luke

Antz_Marchin · #2 03-07-2007, 06:56 PM

Quote:

Originally Posted by mertz

So I'm slowly gearing up for my first full acoustic build. I'm designing this one from scratch and was hoping some of you folks could chime in on the pros/cons of a flat vs radiused top. I understand the theoretical advantage to having a radius, but was wondering what your thoughts are on how it actually affects tone. Thanks for any advice!

-Luke

Alright after learning about this for a few weeks I'm giving some information as an amateur +1, but no means expertly. I'm in the same boat as you, just getting ready to go. From what I've read/learned, as your radius grows (guitar gets flatter) you will tend to increase your bass response at the slight expense of treble and sustain. This can be heard as you are toning the soundboard. Tap, and flex and you will hear a higher tap pitch as you flex the top (analogous to bending a string I guess). This is why larger Dreds, Jumbos, etc have a flatter back than an OM, OOO (20', 25' versus 15') to bring out that "rumbly" D-28esque bass response. When you get to something as small as a Baby Taylor, I think that really small back radius is there to increase the volume (LxWxH) of the sound chamber a bit. When you say you know the theoretical reason, I guess that means the strength point so I'll just leave that. Good Luck with the guitar, I sure know that I'm gonna need it.

SteveS · #3 03-07-2007, 07:19 PM

Luke,
Just another opinion for you. You know what they say about opinions.

The radius on the top has little to no effect on tone. It is done to add strength. Just like an egg shell is strong because it is curved, a guitar top is stronger when curved.

Tim McKnight · #4 03-07-2007, 07:58 PM

And... another opinon - In my hands radius does indeed impact tone and sustain. More radius = higher overall pitch and more sustain. Less radius (flatter) less sustain and lower overall pitch.

Think of the top of the guitar acting like a timpani drum head or a bowed steel saw. As you increase the tension or radius or bow = higher the pitch and longer the sustain and vice versa.

mertz · #5 03-07-2007, 10:20 PM

Both my Larrivees (OM-02 L-02) and my Taylor 314kce seem to have flat tops. Is this the case or is it just a very large radius so it appears flat? I know some R. Taylors come with a flat top... if the top is going to be flat should the bracing compensate?

-Luke

scub73 · #6 03-07-2007, 10:44 PM

Quote:

Originally Posted by mertz

Both my Larrivees (OM-02 L-02) and my Taylor 314kce seem to have flat tops. Is this the case or is it just a very large radius so it appears flat? I know some R. Taylors come with a flat top... if the top is going to be flat should the bracing compensate?

-Luke

Regarding an ealier post- I disagree and feel radius or flat tops will definitely impact tone.

R. Taylors come with either radius or flat tops, no difference in price, your choice of either. I ordered a flat top on my R. Taylor because of what one of the Luthiers there spoke to me about.
I understood that radius tops will make the guitar sound a little more broken in than a flat top will when new. They like to do radius tops on their Cedar and Redwood tops to add strength to the softer woods along with giving it more of a "punch" in volume. He told me that over time, when the flat top breaks in, the flat top will sound better (his opinion). With the spruces, you don't need the extra strength or punch because they are already harder, stiffer and louder playing woods.
All just my opinion and what I am hearing.. Others may disagree..

gregg · #7 03-08-2007, 07:48 AM

And another opinion, well at least something else to consider.....the dome in the top and back also gives your guitar a bit of insurance relative to humidity changes...specifically the wood has more room to shrink, where a flat top has less room for shrinkage before potentially cracking/splitting etc... Of course if the guitar is properly humidified it shouldn't really matter. Relative to tone, I think what Tim says is more in line with conventional wisdom, I know a builder who has experimented with this exact consideration and he prefers the tone of his flat top guitars....says they are not as strident, they're warmer, bigger bass. Oh yeah, another consideration is that a domed top seems to help prevent the bridge from distorting the top under string tension....it's stronger when arched. FWIW, I prefer a domed top for structural and tonal reasons.

Cheers,
Greg

scub73 · #8 03-08-2007, 10:25 AM

Quote:

Originally Posted by gregg

And another opinion, well at least something else to consider.....the dome in the top and back also gives your guitar a bit of insurance relative to humidity changes...specifically the wood has more room to shrink, where a flat top has less room for shrinkage before potentially cracking/splitting etc... Of course if the guitar is properly humidified it shouldn't really matter. Relative to tone, I think what Tim says is more in line with conventional wisdom, I know a builder who has experimented with this exact consideration and he prefers the tone of his flat top guitars....says they are not as strident, they're warmer, bigger bass. Oh yeah, another consideration is that a domed top seems to help prevent the bridge from distorting the top under string tension....it's stronger when arched. FWIW, I prefer a domed top for structural and tonal reasons.

Cheers,
Greg

I agree with much of what you say, but I disagree about the radius'd top being insurance against shrinkage etc.. I believe they would be just as suceptible to cracking, splitting etc due to poor hydration. Radius tops would lend overall strength (with possibly some loss of tone?), but I think it would be braced just as tightly as a flat top so I don't think the effects of low humidity would be less on one than the other.

Just my opinion..

#9 03-08-2007, 10:43 AM

OK Tim McKnight, Gregg, and SteveS: You've all taken Somogyi's soundboard tuning class so why are the opinions varied on the tonal impact of a radiused top? Just curious.

El Conquistador · #10 03-08-2007, 10:48 AM

Quote:

Originally Posted by saffron_boots

OK Tim McKnight, Gregg, and SteveS: You've all taken Somogyi's soundboard tuning class so why are the opinions varied on the tonal impact of a radiused top? Just curious.

I was wondering the very same thing. Is this topic not covered in the Somogyi class?

Antz_Marchin · #11 03-08-2007, 10:51 AM

Quote:

Originally Posted by scub73

I agree with much of what you say, but I disagree about the radius'd top being insurance against shrinkage etc.. I believe they would be just as suceptible to cracking, splitting etc due to poor hydration. Radius tops would lend overall strength (with possibly some loss of tone?), but I think it would be braced just as tightly as a flat top so I don't think the effects of low humidity would be less on one than the other.

Just my opinion..

Firstly, I wouldn't say that a Radiused top exchanges strength for a loss of tone. Maybe a slight decrease in bass response but an actual increase in overall balance and sustain. As far as the strength of the bracing of flat vs. radius, I don't believe that this comes into play when talking about low humidity and cracking. From the way I see it you can brace a guitar twice as strongly as a standard guitar and it will still crack when you dry it out, maybe even crack easier since the stronger the bracing the less freedom the top has to contract/expand. I could be wrong here, but this is how I see it.

gregg · #12 03-08-2007, 11:25 AM

Yes it's covered in the class...I thought I agreed with Tim? I'll let Steve speak for himself. I also believe that you will find that most builders will agree that a domed top acts as a bit of insurance against shrinking/splitting/cracking tops under extreme humidity changes....not to say that they wouldn't have issues as well, it just might give you a bit of room to spare comparatively speaking.

Cheers,
Greg

Tim McKnight · #13 03-08-2007, 11:35 AM

Yes, it is covered in Ervin's class but I am speaking more from experience than from actual theory. What works for me may not work for Steve or Greg or others. I used to use a 25' radius in my tops (which is a higher arch) and my long distance mentor (John Greven) encouraged me to flatten them out and listen to the changes. I followed John's advice and noticed a dramatic change in tone.

scub73 · #14 03-08-2007, 11:50 AM

Quote:

Originally Posted by gregg

Yes it's covered in the class...I thought I agreed with Tim? I'll let Steve speak for himself. I also believe that you will find that most builders will agree that a domed top acts as a bit of insurance against shrinking/splitting/cracking tops under extreme humidity changes....not to say that they wouldn't have issues as well, it just might give you a bit of room to spare comparatively speaking.

Cheers,
Greg

I'm sorry, I don't know about this class you are all talking about?? I have not taken any "class" about radius or flat tops...

SteveS · #15 03-08-2007, 11:58 AM

Quote:

Originally Posted by saffron_boots

OK Tim McKnight, Gregg, and SteveS: .....why are the opinions varied on the tonal impact of a radiused top?

Probably because it is just one of many factors.
I will build with a dome, and never flat.
There are successful builders that build flat - I think Ryan and Olson build flat.
There are many ways to make a great sounding guitar. There is no one right way.
That's a beautiful thing.