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Reso cone warning!

I just did my first build using a lightning reso cone from Gitty and at the end found I had a problem with intonation. I laid everything out first as I always do, used a 24" scale. I was very careful to measure twice and cut once for the hole to hold the cone. All done and string it up and something is not right, intonation is off. I used a medium action since I wanted to do both slide and finger notes, it is fully fretted. I know it will go a bit sharp if the action is too high. So , to get the intonation to be correct , I had to slide the discuit/ saddle back by a bit over 1/4", so now the biscuit is not centered on the cone "nipple" like it should be but teetering on the edge. I think I will make a new biscuit/saddle on an oval shape (maybe rectangle) and screw it to the cone so it does not tip off the edge of the "nipple". I've done resonators before but never one where moving the biscuit causes a problem. I guess the moral of the story is I needed to figure in some "compensation" in my calculation of where to mount the cone on the box for my scale length.

Anyone else run into this??

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Permalink Reply by ChickenboneJohn on November 14, 2017 at 9:18pm

You do need to add some compensation to the theoretical scale length, and with a reso, you need to set the centre of the reso cone and biscuit back so that the leading edge of the saddle, not the centre of the cone is on the compensated scale length. There's about a 1/4 inch error for you right off the bat if you didn't take into account both those factors. Also, how high is the action at the nut and 12th fret? If it is more than about 1mm at the nut and 3mm at the 12th fret you'll be pulling the notes sharp.

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Permalink Reply by Bluesheart on November 16, 2017 at 4:29am

Yep, thanks! I knew that of course but did not think about at the right time! Next one will have that added. I will prob lower the action a bit too which will help also. I just got caught up with the beauty of that copper cone and did not think about having really very little area on the cone top to move the bridge around on.

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Permalink Reply by Taffy Evans on November 15, 2017 at 6:27pm

Hi John, that's what I would do. then you have the full contact of the biscuit on the top of the cone for better transmission of sound.

Regarding moving the whole cone back, you mentioned that it would leave old holes exposed. What I would do is make a thin wooden cover the outside diameter of the cone, that is wide enough to cover the old screw holes.

Cheers Taff

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Permalink Reply by Bluesheart on November 16, 2017 at 4:08am

Yep, that looks like the best solution. Simple wins most of the time. Thanks!

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Permalink Reply by JL on November 16, 2017 at 2:21am

I've not built a resonator yet, but have 'compensated' enough bridges that when I do, it will be based on another regular build with the same strings & scale & action and using the compensated bridge position as a guide so that I can plan the cone's location.

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Permalink Reply by Bluesheart on November 16, 2017 at 4:10am

Yep, great idea and kind of why I put this out there, so maybe others don't fall into the same trap. If only I had done this, would not have an issue now. Thanks!

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Permalink Reply by Richard Dean on November 16, 2017 at 6:02am

Thanks Blues, when I get back to finishing mine I'll have to take all this into consideration when I make my replacement neck.

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Permalink Reply by jawbone on November 18, 2017 at 3:24am

This a question prompted by Chickenbone Johns post... I'm trying to figure out "the compensation" - I'm afraid I may have missed something. Why the compensation and is it only for reso cones??

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Permalink Reply by Richard Dean on November 18, 2017 at 3:57am

The original poster was trying to set up intonation, and couldn't because of the inability to move the biscuit(bridge) very much before loosing it's surface area, it rest on. The "Compensation CB is talking about, is merely allowing for the 1/8 to 1/4" usually needed to move the bridge in order for everything to be in pitch all the way to the 12th fret and on. Stewmac's website that has the fret calculator, also gives you some of that information below the fret calculations to get your bridge position close. In most of our non-resonator builds, the issue is usually moot as for the most part there is usually enough space on our soundboards to move the bridge wherever we need it to be.

So, he was saying he compensates for that in his builds.

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Permalink Reply by ChickenboneJohn on November 18, 2017 at 5:46am

"Compensation" is needed for all fretted insturments. As you press the strings down to the frngerboard it will tend to pull the strings sharp, so you need to set the bridge back a little from the theoretical scale length, which helps to the flatten the note to nearer how it should sound.

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Permalink Reply by jawbone on November 18, 2017 at 6:21am

OK - Thanx - got it now!! I was afraid there was some magic about reso's that I didn't know about !!! ;-) Luckily I play so badly intonation is the least of my problems!!!!

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Permalink Reply by Taffy Evans on November 18, 2017 at 9:04am

And....as strings have different thicknesses they require different amounts of compensation. Don't forget ( I've mentioned this before) the way one pushes down on strings whilst playing also sharpens or flatens the notes even though the intonation is correct.
Taff