Reso's: Soundwell vs Open Body

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Reso's: Soundwell vs Open Body

Postby crowduck » Sat May 13, 2006 2:49 am

A comment by Ricochet on another thread got me to thinking about how different reso's sound. I've noticed the sound difference between a spider bridge reso, and biscuit bridge reso, but until that comment hadn't thought about the fact that most 'production' spider bridge's are made with a 'soundwell', except for tricones. There are a number of independent makers persueing 'tonering/sounpost' designs, and some install custom baffles. I believe that most biscuit bridge reso's are made 'open body' with no controlling soundring or baffles.

The difference that I notice is that the 'spider/soundwell's' sound 'tight and focused', whereas the 'biscuit/openbody's' while loud, sound sort of 'broad, fat, and scattered'.

I'm not an acoustic engineer, but I'm considering doing some experiments with my open body reso's. I'm thinking of taking some pieces of stiff breathable foam, cutting them into those trapazoid or rhombazoid shapes seen on walls of sound studios. Then sticking them inside the reso body to the rim in varying places around the upper and lower bout. I'm wondering if that would 'refine' that open body sound by deflecting or canceling some of those sound waves bouncing around inside that body cavity?

Any thoughts, opinions, or criticism.

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RE: Reso's: Soundwell vs Open Body

Postby ricochet » Sat May 13, 2006 3:15 am

I'm thinking foam's not the way to go. That will increase the apparent volume of the cavity, and broaden the resonances, but greatly decrease their peaks. It'll be a very different sort of effect from a soundwell made of relatively nonabsorbent material that divides up the cavity into smaller, connected sections.

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RE: Reso's: Soundwell vs Open Body

Postby crowduck » Sat May 13, 2006 3:45 am

>I'm thinking foam's not the way to go. That will increase
>the apparent volume of the cavity, and broaden the
>resonances, but greatly decrease their peaks. It'll be a
>very different sort of effect from a soundwell made of
>relatively nonabsorbent material that divides up the cavity
>into smaller, connected sections.
>
>"A cheerful heart is good medicine."

Rico,

I was sure I could count on you, but I'm confused by your comment, "increase the apparent volume of the cavity". Wouldn't 'any material' added to the the sides/rims actually 'reduce' the cavities volume? Is there some principal of physics or acoustics that I'm missing? I admit to not being expert in those subjects, my engr background is in semiconductor electronics and such.
Thanks for your help and wisdom.

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RE: Reso's: Soundwell vs Open Body

Postby bignick » Sat May 13, 2006 4:12 am

[updated:LAST EDITED ON May-13-06 AT 00:13 AM (EST)]I would think stuffing the body of an acoustic instrument with anything is going to deaden the sound substantially.

I agree that a spider bridge sounds more focused and I think that you can hear the actual cone a lot better.

There are players that prefer their reso/dobro to sound more like an acoustic with a fat round tone, and others who like to hear more of the wood.

In any either case, you are not going to want to kill that natural reverb and ambience of the body by stuffing it. IMO it makes sense to have enough open space to allow the cone to do a bit of vibrating and reflect sound throughout the inside of the guitar. Without that breathing room it seems that you would greatly reduce sustain.

Players that want a more focused metallic sound should should try picking closer to the bridge and try finger and thumbpicks. This isn't always easy on a reso because of the cover plate. Someone needs to design a plate that accomodates for pickers that like to get nearer to the bridge without sacrificing the muting capabilities of their palm or leaving the saddles unprotected.
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RE: Reso's: Soundwell vs Open Body

Postby richard » Sat May 13, 2006 4:20 am

a while ago i widened the soundwell holes in my samick reso, because i wanted to see if the jumbo body size would allow the sound to increase in volume and 'open up' a bit more. The holes were really quite small.

It was a bugger of a job, but when i finished i noticed a difference in the sound. There was a bit more volume, but i had lost some of the midrange sound that i had come to associate with my resonator. Trebles and basses seemed to be pretty strong, but i can only describe the sound as getting a bit closer to a regular acoustic.

At the time someone suggested experimenting with plastic discs or something to cover up the holes and find a sound i liked with varying sizes. I'm pretty sure it would have been someone on this board.

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RE: Reso's: Soundwell vs Open Body

Postby crowduck » Sat May 13, 2006 5:35 am

>I would think stuffing the body of an acoustic instrument
>with anything is going to deaden the sound substantially.
>
>I agree that a spider bridge sounds more focused and I think
>that you can hear the actual cone a lot better.
>

>In any either case, you are not going to want to kill that
>natural reverb and ambience of the body by stuffing it. IMO
>it makes sense to have enough open space to allow the cone
>to do a bit of vibrating and reflect sound throughout the
>inside of the guitar. Without that breathing room it seems
>that you would greatly reduce sustain.
>
>Someone needs to design a plate that
>accomodates for pickers that like to get nearer to the
>bridge without sacrificing the muting capabilities of their
>palm or leaving the saddles unprotected.

Nick,

I'm not proposing "stuffing the body". I was thinking of using some kind of material like hard breathable foam small pieces about 1/2" thick, and cutting the surface in a geometrical shape/pattern to control those sound reflections.

I agree about the bridge plate/palm rest problem. I've got a cover plate that I'm removing the big palm rest, and replacing with something smaller, a thin metal drawer handle positioned just to the rear of the saddle, allowing for palm damping, while still protecting.

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RE: Reso's: Soundwell vs Open Body

Postby louisianagrey » Sat May 13, 2006 7:33 am

[updated:LAST EDITED ON May-13-06 AT 04:58 AM (EST)]The people who experiment with sound shaping inside open dobro bodies usually use either plywood or acryylic baffles in various positions. I'm not convinced that foam is the way to go.

Regal are now making one model with a more open body inside. I suspect the reason for the predominance of soundwells is historic - the Koreans copied old dobros and the Chinese just copied the Koreans.

I can't remember wheher you had fitted a Quarterman cone, Richard. I find it's much easier to get the characteristic dobro honk with one of those, although the body shape also helps and in that respect I don't really like those Samicks.

I don't really see the problem with picking near the bridge. Watch Rob Ickes and see how close he can get, it's really only a matter of practice. The palm rest on a dobro is usually narrower than the rest on a biscuit bridge guitar in any case.

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RE: Reso's: Soundwell vs Open Body

Postby crowduck » Sat May 13, 2006 8:11 am

This is something like what I had in mind:

http://www.controlnoise.com/wed.jpg

Here's what is said about it:

"A convoluted surface pattern, cut into the face of the material, is designed to maximize the acoustic absorption qualities of the foam. The open cell structure dissipates noise energy to control harsh reflected noise and reverberations in a variety of applications."

"Note that foam DOES NOT block sound from transmitting. These Wedges will instead absorb echo bouncing to control reverberation."

I think it might be 'echo bouncing' in open bodies that I'm trying to 'tame'.

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RE: Reso's: Soundwell vs Open Body

Postby louisianagrey » Sat May 13, 2006 9:04 am

The only way to find out if anything works is for some pioneer to have the will to try it, which the rest of us probably wouldn't do because we've already decided it won't work. No-one is infallible and you may well prove us wrong, so let us know how you get on.
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RE: Reso's: Soundwell vs Open Body

Postby bignick » Sat May 13, 2006 1:15 pm

I need to get a Rob Ickes video.

You have nothing to lose by trying it Crowduck. I also have enlarged the soundwell holes in my Johnson and it definitely increased volume. I agree that the more open a reso-body is, the more acoustic-like it is going to become.

I believe (I might be mistaken) that the sound chamber theory came about to increase the strength and durability of the instrument. I'm not sure if it was advertised to alter the sound of the guitar at all. I read that in a Tim Scheerhorn interview on Vintage Guitar. He mentions it.

His theory was to remove the soundwells all together because he believes that resos weren't meant to be durable enough to stand on. Only durable enough to play. He makes some good points in the article.
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RE: Reso's: Soundwell vs Open Body

Postby ricochet » Sat May 13, 2006 3:25 pm

Yeah, adding absorptive material like foam to a speaker cabinet does increase its apparent volume, along with decreasing the peaks of its resonances and broadening its resonant response. You're designing a speaker cabinet, so looking at sites on cabinet design will help you.

In electronic terms, you're adding resistance to a resonant circuit, decreasing its Q. It's not an exact analogy, at least for a simple LC tank circuit, but it's pretty close.

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RE: Reso's: Soundwell vs Open Body

Postby louisianagrey » Sat May 13, 2006 4:41 pm

You can see some of Rob's playing at http://www.youtube.com/watch?v=NAQNz92QY1w&search=dobro

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