Archtop vs Steel String Acoustic Sound

[pmatolcsy]

Hi,
I'm designing my second archtop guitar. Every archtop I've ever played sounds different and to my ear at least, not as desirable as a traditional steel string acoustic.
I've read Benedetto on Archtops and Somogyi on the resposive guitar.
So here's my question. Assuming Strictly Acoustic (no pickups), Identical Acoustic Strings, woods , body volume , port areas , neck construction and joining stiffness,
what contributes most and in which order to the difference in sound? Identified differences which I am aware of are as follows:
Top thickness and or Thickness Gradient
Top shape(independent of body volume)
Port shape and position
Bracing Differences(Please consider X braced archtops only. I prefer the sound)
Bridge/Tailpiece Design and subsequent loading of the plate.

I have my theories but I'm looking for others opinions.
Well Educated, Not so well educated (that's me) ,wild and drunken(not too often) guesses accepted

[pmatolcsy]

Add grain runout to the list

[lamanoditrento]

I would have thought the biggest difference first and foremost would be scale length

[Dekka]

I'm definitely in the less-educated category.... but I think if you go back to the original instruments, Archtops were large-bodied instruments that needed to be heard acoustically in an orchestra. Those instruments would have had a lot of punch but not so much sustain. Flat tops were comparatively small-bodied but, over time, have evolved into larger/louder instruments and based on numbers alone, would appear to be more popular in general.
But I think, mechanically, the biggest difference would the relationship between the strings and the top, i.e, the strings on an archtop exert downward pressure to the top via a starkly different bridge.
Your talking about two completely different guitars that have tops designed to react in completely different ways. A bit like comparing a gong with a wobble-board.
Also, I'm not understanding "...independent of body volume" re: Top Shape????

[pmatolcsy]

What I mean is total body volume. like if you filled the two guitars with water and poured it out they would measure at the same amount. that and the port size determine the helmholtz resonance, what you get when you hum in the sound hole.

[jeffhigh]

I'm not an archtop builder, But I'd basically agree with Dekka.

Originally archtops were intended as orchestra instruments to be strummed hard and compete with banjos etc.
The floating bridge and rigid plate centre with flexible edge (and the f holes) gives a big monopole response but not the complexity of a fixed bridge acoustic.
Cut and volume were the aims

What we think of today as the Jazz archtop sound, mellow chords and melody, only became possible with the magnetic pickup and rolling the tone control down.

[Dekka]

What I mean is total body volume. like if you filled the two guitars with water and poured it out they would measure at the same amount. that and the port size determine the helmholtz resonance, what you get when you hum in the sound hole.

I get what "volume" is ... but am struggling with the "independent" bit. The sound is dependent upon the relationship of the two, isn't it?

[pmatolcsy]

Yes I'm comparing an arch top and a flattop with the same body volume.What I meant was when you alter the shape of the top it alters the body volume.Since it does that, in order to be comparing the same two guitars you would have to alter the height of the sides to compensate. Thats what I meant by Independant of Volume. Do different shapes (flatter arch, higher arch, rapid change in height ,slower change in height) affect the volume and tone.

[rocket]

In a word,,, yes!!