The effect and importance of body depth?

**RJVB** · 01-31-2023, 07:58 PM

I saw the general build specs of Daniel Slaman's The Dome nylon-string archtops today. I had of course noticed that these are full-depth, but according to what I saw they're only 7cm at the deepest point of their belly.

I quite like their acoustic sound on the recordings I've heard, but recordings are notoriously bad at assessing how full or loud an instrument can really sound.

What's the effect of body depth on the acoustic voice of an archtop?

**Jimmy blue note** · 01-31-2023, 08:41 PM

Body depth is but one factour in the overall sound of an instrument. It speaks to and for a volume of air moved and as a general rule, the deeper a body is, the lower the resonant air mode is. This is also dependent on sound holes, size of the F holes, the "tuning" or matching of vibrational modes in the top and back and how well they are coupled by the air inside.
I've built instruments that were well matched in top and back modes and the thin body created a strong coupling between the two so there was a strong bass. But if the top and back plates aren't tuned in phase with one another, there won't be that kind of frequency enforcement and a deeper body with a lower frequency air resonance, a deeper body is one way to get a stronger bass response.

There are lots of factours, thickness of the plates, bracing and the interaction of the bound plates, but yeah, a deeper body can very well increase a bass response all other things being equal.

**sgosnell** · 01-31-2023, 10:15 PM

Yeah, I think speaking very broad generalities, deeper bodies have more bass response. I think there is somewhat less correlation between acoustic volume and body depth. One of the loudest archtops I've played acousically was only 1.75" at the rims. Not a lot of bass, but a lot of volume. Not a really pleasing tone, but it was loud. I sold it, and I regret it. I think I'm probably done selling guitars. I do hold the possibility of buying another(s), but I don't plan to sell.

**mr. beaumont** · 01-31-2023, 10:59 PM

7mm?

**nevershouldhavesoldit** · 01-31-2023, 11:12 PM

Originally Posted by mr. beaumont

7mm?

Either he meant 7 cm or he can slice cheese with it

**sgosnell** · 02-01-2023, 12:02 AM

7mm is a reasonable thickness for a guitar top (not a Gibson). I had assumed that's what the OP meant, not the full thickness of the entire body.

**RJVB** · 02-01-2023, 07:49 AM

OOOps, yes, I meant 7cm.

A 7mm top won't be driven by nylon strings, which is what these guitars are for

Interestingly the last few of Daniel's nylon string archtops (around 2019 as judged from serial numbers and YouTube dates) appear to have full-size rims, as compared to this one from about 10y ago:

(nut width is 48mm on these so a max depth of 7cm seems plausible)