Mono mobility (Martin and my TG style) results

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davidafterwork
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Mono mobility (Martin and my TG style) results

Post by davidafterwork » Sat Feb 27, 2021 7:02 pm

Hello all
I have done my tests ( pic attached) on my 1st TG style guitar and my Martin OM 28. As I said I really love the Martin guitar sound ( bought new this year) and wanted to see if I could measure my results against it and learn something. The pic showing all my results is below. I’m afraid it doesn’t really help me as it sounds so much better than mine and yet the numbers SEEM to be similar.
I didn’t do the bridge rotation test because I tried it with the mobile phone and just didn’t trust that method so will make the frame Trevor uses and then do it.
I am going to look at the section “Adjusting the top main resonance” in book 2 and see if I can learn something about what I might be doing wrong.
I would really love to get some input from you guys as to how I might improve the sound I am getting as I am struggling now to locate the issue although I do note a big difference between the target of 226 for the back and Martin’s 259 so is there something here to note?? I realise sound is a bit subjective when playing guitar but still feel there are improvements I could make but not sure how to proceed.
Thanks in advance again!
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Re: Mono mobility (Martin and my TG style) results

Post by Semmens Guitars » Sat Feb 27, 2021 8:58 pm

Hi,

You might try to install weights to bring the Top Main Resonance down from 177 to 170, It will Improve the over all sound giving you more volume and a wider bass response.

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kiwigeo
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Re: Mono mobility (Martin and my TG style) results

Post by kiwigeo » Sun Feb 28, 2021 2:35 pm

Is the back on The Martin coupling with the top? I think this needs to be established before comparing back frequencies for the two instruments. Are those frequencies gathered while tapping the back or top of the instruments?
Martin

davidafterwork
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Re: Mono mobility (Martin and my TG style) results

Post by davidafterwork » Mon Mar 01, 2021 1:20 am

Thanks for the response
My question now is according to 22.3 in Book 2 the "...main cavity resonance and the main top resonance must not be exactly an octave apart.."
1 My main body is 97 so am i right in saying it should be 95 ( between 2 semi tones)??
2 My top is 177 so should come down to 170 (between 165 and 175) as its easier to bring down than bring up ???
3 My back should be 4 semitones above 170 so how do i calculate that figure?? Is it 210? Is there a quick calulator for that or is ok to use 10Hz per semitone here as a rule of thumb???
I really appreciate the feedback as I think I am nearly there in my understanding and this is the last piece of the puzzle for me!
I will then have a look at HOW I go about doing these 4 things!!

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Re: Mono mobility (Martin and my TG style) results

Post by Dave M » Mon Mar 01, 2021 3:14 am

For your last question you simply need a table of note frequencies - many available on the web.

F3 is around 174 Hz, G3# is around 207. I don't think we need to be too exact about this gap.
------------------
Dave

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Re: Mono mobility (Martin and my TG style) results

Post by Semmens Guitars » Mon Mar 01, 2021 8:56 am

1. 95 would be better - 97 is close to the note G. I find that when I get this frequency I can get some nasty sounding G chords/notes
2. It is always wiser to bring the top down with side mass as it dose not effect other frequencies much. It's very hard to stiffen a top after it is built to make it go up.
3. 3-4 semitones is ideal but I have found as long as it is not closer than this it usually dosen't cause a problem.

2 ways to move your main body...carve your back braces down. It will shift everything down as everything couples. You can open your sound hole which will raise the frequency along with all the others too. You'd have to remove a bit of timber off the back braces to move it from 235 to 227 but your main cavity resonance will drop with it and could get down to 95.

Have you thinned the edge of the guitar? Thinning the edge will also move your frequencies down as you are reducing mass of the top and reducing stiffness. It improves the sound of your guitar....until you go too far and then it has the opposite effect!!

The Frequency Chart is at the back of book 1

hope this helps.

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kiwigeo
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Re: Mono mobility (Martin and my TG style) results

Post by kiwigeo » Mon Mar 01, 2021 4:05 pm

Is your bridge on yet? You need to allow for the effect the bridge mass will have on main top frequency (it will bring it down).
Martin

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Re: Mono mobility (Martin and my TG style) results

Post by Semmens Guitars » Mon Mar 01, 2021 4:22 pm

kiwigeo wrote:
Mon Mar 01, 2021 4:05 pm
Is your bridge on yet? You need to allow for the effect the bridge mass will have on main top frequency (it will bring it down).
Yes your right - I was assuming the bridge was on.

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Re: Mono mobility (Martin and my TG style) results

Post by davidafterwork » Tue Mar 02, 2021 3:11 am

Thanks again
Can I confirm a few things before I take to the tools again...
1 All test were done with guitar finished ( lacquered/bridge/ strings on as in TG Video)
2 To bring 97 down to 95 you say weights but I haven’t put in side mass blocks into the guitar so will reducing the back brace do that instead?
3 Shave back brace to get down from 235 to 226?
4 Bring top down from 177 to 170 by reducing x brace at the joint area?
Sorry for all the questions but as I said I believe I am nearly there and looking forward to doing the next one now with my up and running Excel sheet!
Ps do you put in side mass blocks as standard knowing that you may or may not use them? Obviously I should have in this case but is reducing the braces on the back a viable alternative for me?? ( question 2 again..)
Thanks again to all for the valuable input
Dave

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Re: Mono mobility (Martin and my TG style) results

Post by Jim watts » Wed Mar 03, 2021 10:35 am

I find this to be a very interesting and appreciate your posting it here. While I don’t have the answers your looking for I would like say that even if you matched the numbers for these modes, you guitar would still sound different. I also think that this is a fairly obvious statement so I apologize for that. But sometimes I think I fall into that trap. There are many higher order modes that contribute to the guitars sound that we really don’t get much or any control over. It’s just that these low order modes such as T1,1 and such, we do get some control of and they obviously influence the sound. So I think that even if these match you Martin, there’s a chance you still may not be happy.
I don’t know I’m just thinking out loud.
Please keep us posted, this is good stuff!

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kiwigeo
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Re: Mono mobility (Martin and my TG style) results

Post by kiwigeo » Thu Mar 04, 2021 3:19 pm

davidafterwork wrote:
Tue Mar 02, 2021 3:11 am

Ps do you put in side mass blocks as standard knowing that you may or may not use them? Obviously I should have in this case but is reducing the braces on the back a viable alternative for me?? ( question 2 again..)
Thanks again to all for the valuable input
Dave
You put in an extra wide side splint on each side with a T nut. Pieces of metal are screwed into the T nuts with a hex head allen bolt if you find you need to trim your main top frequency. Can you retrofit same?.....it'd be tricky but not impossible.
Martin

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Re: Mono mobility (Martin and my TG style) results

Post by Semmens Guitars » Fri Mar 05, 2021 2:29 am

I have retro fitted the Mass Support blocks a few times its not hard to do you just have to make sure they fit perfectly. I have used 5 minute epoxy to get them to stick. Just make sure you wear a glove!!!

I would do this before touching any braces.

Yes...I put the support blocks in as a back up plan. I rarely use them but I have had to shift a few problem notes from time to time.

Question 2 - Adding side mass will not drop the Air frequency down from 97 to 95.
Question 3 - Shaving the back braces will drop the back frequency - and all others will drop with it which in your case is a good thing as the air freq may move down from 97 which is what you want and the top will move down a little too -
Question 4 - don't touch your x brace - after you have your back frequency right (hoping that the air freq has moved down a little as you only have to move it 1-2 hertz) add you mass support blocks and drop the main top frequency down to 170.

Depending on the thickness of your back you may have to remove a bit of brace material. I attack the lower bout brace first as this has the biggest effect and then the middle brace if it hasn't moved far enough. Test often as you go though as I have had it not move much and then BAM! a few strokes of the plane and it drops.

Hope this helps.
Matt

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Re: Mono mobility (Martin and my TG style update) results

Post by davidafterwork » Sat Mar 13, 2021 3:28 am

Hello all
I had my TG style at
104
188
236
I tried shaving the back brace to bring the numbers down but didn’t seem to be having much effect...
Just for fun I put 30g of blu in 2 pieces ON the top and below the bridge as TG did on the video and look at the numbers now...
103
179
224
Guitar even sounds better but now I see the benefit of side mass blocks as shaving braces is very slow and tricky.
I have now moved the blu tac inside the guitar to underside of top.
Any ideas on why the first number 104 only dropped by 1 while the other 2 dropped significantly with 30g mass???
Also it is not easy to read the Spectogram except for the T1 number so any ideas there??? I feel like I could be cheating by picking the peak with the nearest number to 226 !!
Thanks for all the help guys

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Re: Mono mobility (Martin and my TG style) results

Post by Semmens Guitars » Sat Mar 13, 2021 4:40 pm

I have found the air frequency (104) doesn't seem to drop much when adding side mass or mass to the bridge like you have done.

If you turn the guitar around and only tap the back it will highlight the back frequency for you.

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Re: Mono mobility (Martin and my TG style) results

Post by davidafterwork » Sat Mar 13, 2021 6:47 pm

Thanks for that but how then do you get just the 104 main air to drop when the other 2 numbers are right now???
Also I only tried the blu tac to see what would happen As I wasn’t getting anywhere with shaving the braces.
I was amazed at the drop in the other 2 numbers with just 30g of blu tac!!
Dave

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Re: Mono mobility (Martin and my TG style) results

Post by Bruce McC » Sat Mar 13, 2021 7:03 pm

To drop the main air frequency you can reduce the diameter of the sound hole with a ring of purfling/binding or
add a tornavoz. The deeper the tornavoz the more the the main air will drop.
Bruce Mc.

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Re: Mono mobility (Martin and my TG style) results

Post by kiwigeo » Sat Mar 13, 2021 9:02 pm

I use 20cent pieces stuck on with bluetack....you end up using less bluetack :)
davidafterwork wrote:
Sat Mar 13, 2021 6:47 pm
I was amazed at the drop in the other 2 numbers with just 30g of blu tac!!
Dave
Martin

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