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Resonator Bridge Mass

Posted by Jason G on January 18, 2017 at 1:40pm in Building Secrets, Tips, Advice, Discussion

Hi All,

I'm building a six string resonator using the 7" thunder spun aluminum cone.  The cone has a 1.25 wide flat spot in the center for mounting a biscuit bridge.

Problem is, on this particular build, my cone will be inset into the box around 3 inches.  I'll basically need a ~3 inch tall extension on the bridge to bring it to the proper level near the top of the box.

I've read various comments around minimizing the mass of the bridge to improve sound.  Initially, I thought I'd basically run a 3 inch tall hardwood dowel of the appropriate width between the cone and bridge, but that's alot of mass.  Alternatively, I've been noodling using a thin wall aluminum tube, hoping I could affix it (JB Weld?) to the cone, and not affect tone too much.  What about a hardwood dowel, drilled out as much as I can?

Any thoughts on bridge mass for resonators, and ideas on essentially making a three inch tall biscuit bridge?

Thanks!

Jason

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Replies

  • Jason G January 19, 2017 at 2:13pm

    Thanks again all for the suggestions and info... very helpful!

    Taff - good call on the string angles...  was going to try to maximize to put more downward pressure on the cone, but hadn't thought about keeping them equal.

    Darryl - almost exactly what I was thinking about doing, other than slapping a standard biscuit bridge on the top of the cone.  Any reason for going with copper over aluminum?  I'm surprised of the sound improvement by reducing contact points between the tube and bowl...  think that was a function of reduced contact service, or maybe even just reduced bridge mass?  

    • darryl kernaghan > Jason G January 19, 2017 at 4:05pm

      copper was what i had on hand, and experience has led me to think that thick aluminium "swallows" sound or absorbs it a fair bit, the reduction in contact surface area, i think, had 2 effects,1 being less mass, but, as you can see in my pic, it is hard to see the contact of bridge and bowl, and i'd guess the less contact area made for a more uniform contact if the bridge/ bowl connection was not exactly square and contacting the full 360 degrees of the tube, it did brighten the sound a lot 

  • Moritz Voegeli January 19, 2017 at 4:45am

    My brother experimented a lot optimizing a gretsch honeydipper resonator guitar: he ended up replacing the original maple biscuit with a big but thin washer with the outer diameter of the biscuit and a stag horn bridge: he thinks replacing the washer with a similar item from carbon fiber with less mass could sound even better. Maybe mass is one criterion for biscuits, the other possibly stiffness.

    Looking always for an even better biscuit, so when he slaughters his young bulls he is looking for an apt piece of bone to shape biscuit and bridge from one piece of bone, to give this option a try, but till now without success...

  • darryl kernaghan January 19, 2017 at 3:58am

    I've actually done this, but i used copper tube,,[1 1/2" diameter] and about 4 inches long, i placed a 1/8" stainless rod sleeved in 4mm copper tube as the saddle, at first it was not very effective, so i cut semi circles in the bottom edge where it sat on the bowl, and that reduced the contact area on the bowl by more than 50%, and it was pretty good after that

    res paul

  • Taffy Evans January 19, 2017 at 12:23am
    Hi, I'm thinking that that is a long way for the strings to Send vibrations to the cone, I wonder if you might lose some of the cone effect if using timber? Using an aluminium tube might be the go to help maintain the desired tone, with a regular biscuit bridge on top. Would be advisable to have the angle of the strings off of the saddle close to the same angle on both sides, so as not to have one side pushing the bridge over. These angles are important on orchestral instruments with their high bridges. Just some thoughts.
    Cheers Taff
  • Jason G January 18, 2017 at 6:23pm

    Thanks both for the thoughts.  I'll see if I can snap a pic when I get home so you can see what I'm working with.  

    It's inset because I'm using the tail light housing from a sixties Ford Galaxie as the cone "bowl".  The 7" cone, with a tiny bit of grinding, actually sits perfect in the bottom of the housing.  It's an oil can guitar - going for an automotive / jet-age look.  As it sits, the cone and housing look (or will look) like a turbine.  Certainly more for aesthetics than sound, but I still want to make it sound as good as I can... 

  • Bluesheart January 18, 2017 at 4:50pm

    Would it be possible to instead raise the cone closer to the top?

  • Bluesheart January 18, 2017 at 4:35pm

    The aluminum tube idea sounds interesting but I'm not sure you can keep it upright. I'd sure try it w/o the glue first.

  • Tom T January 18, 2017 at 3:14pm

    Wish I had a photo of this build. Hard to understand why the cone has to be recessed so much.

    Anyway, a 3' tall biscuit might be a bit unstable under string tension. Don't know if anyone has ever tried this or not.

    Now, another approach might work for you. A cello, for example, has a wooden bridge that (at least on mine) is over 4" tall. It seems stable under the strings and works well. What if you used a normal ( i.e. 1/4" tall) slotted biscuit and made a 3" tall hard maple bridge? You could drill holes in it to reduce mass as is done on both cello and violin bridges. With some scroll work, it could look pretty cool.

    That's all i got............

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