Puzzled re adding mass etc…

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davidafterwork
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Puzzled re adding mass etc…

Post by davidafterwork » Sat Oct 16, 2021 2:23 am

Hello
Just wondering if someone could have a look at these figures from my 00 size guitar I just finished and comment on my query. This is my first time to try adding side mass
Resonant frequencies with neck and bridge on are
105 (target 95)
178 (target 180)
219 (target 226)
My query is re adding mass… the design book in 2.29 says 430 grams moved the frequency by 6hz
I have 2 pieces of 25x6 steel plate which weighs 112 grams
If I am to drop from 178 to say 170 I would need even more than 430grams which sounds like a serious size piece if steel to bolt on… am I wrong in saying that and should I be trying to bring my 178 up to 180 instead??
Any help re how to proceed would be appreciated
Cheers

johnparchem
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Re: Puzzled re adding mass etc…

Post by johnparchem » Sat Oct 16, 2021 3:26 am

Personally I would not do anything until it was strung up at tension and then measured. I would also evaluate how the guitar sounds. My guess is after being strung up the top will drop a bit (2-5 Hz). Then you may be able to use side mass to get close to 170 Hz if you think you need to lower it.

If those were my strung up numbers, and I was using Trevor's live back bracing pattern and I had scooped out the center of the lower bout brace I would consider filling in that brace and retuning the back. If you raised the back resonance to target, the top would be really close to 180 Hz

davidafterwork
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Re: Puzzled re adding mass etc…

Post by davidafterwork » Sat Oct 16, 2021 10:16 pm

John
Thanks a lot for the reply. I will take your advice and check when strung up. I thought it was to be tested without strings on but as I said it’s my first time to try side mass so I will wait. Can I assume with those figures that you would be trying to get the 178 down to 170??
Dave

johnparchem
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Re: Puzzled re adding mass etc…

Post by johnparchem » Sun Oct 17, 2021 1:43 am

davidafterwork wrote:
Sat Oct 16, 2021 10:16 pm
John
Thanks a lot for the reply. I will take your advice and check when strung up. I thought it was to be tested without strings on but as I said it’s my first time to try side mass so I will wait. Can I assume with those figures that you would be trying to get the 178 down to 170??
Dave
It depends where the top ended up. If it was are around 174-175 Hz I would add mass to move it toward 170 Hz at least enough to get it off of F. I happily live with a 178 or a 172 Hz if it sounds good.

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Steve.Toscano
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Re: Puzzled re adding mass etc…

Post by Steve.Toscano » Tue Oct 26, 2021 8:57 pm

Firstly.
How does the guitar sound? Is there something wrong (acoustically) with it? Why do you want to move the top freq?
If you havent strung up, do that first.

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kiwigeo
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Re: Puzzled re adding mass etc…

Post by kiwigeo » Sun Nov 07, 2021 6:09 pm

What Steve says..string it up and let it sing before playing around with the top frequency.
Martin

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