Search found 573 matches

by peter.coombe
Fri Apr 19, 2019 6:47 pm
Forum: Instrument Builders Forum
Topic: More mandolin thoughts
Replies: 12
Views: 1832

Re: More mandolin thoughts

Do you think the shape of the soundhole (oval vs round) has much effect on the resonant freq? No, the surface area of the soundhole, the volume of air in the soundbox, and the stiffness of the top, back and sides determines the main air mode frequency. The shape does not matter. In terms of the oth...
by peter.coombe
Thu Apr 18, 2019 8:59 am
Forum: Instrument Builders Forum
Topic: Wood identification
Replies: 5
Views: 1237

Re: Wood identification

Looks like meranti to me. I don't think it is red cedar.
by peter.coombe
Mon Apr 15, 2019 11:06 am
Forum: Instrument Builders Forum
Topic: More mandolin thoughts
Replies: 12
Views: 1832

Re: More mandolin thoughts

Has been some more progress on this. I have some more data from new mandolins, and I have managed to borrow a couple of instruments from a local customer to measure. Ideally I really need a research grant to make 20 identical mandolins or guitars and vary the tunings. I am suffering from a lock of q...
by peter.coombe
Fri Apr 12, 2019 9:48 am
Forum: Instrument Builders Forum
Topic: Acoustical effect of back woods
Replies: 25
Views: 2970

Re: Acoustical effect of back woods

Thanks Peter, On your first post I had trouble imagining what the control would be. I appreciate your detailed explanations. My understanding from your comments is that without the control, testing with instruments that clearly sound different, we have to assume or be convinced that their methodolo...
by peter.coombe
Wed Apr 10, 2019 8:50 pm
Forum: Instrument Builders Forum
Topic: Acoustical effect of back woods
Replies: 25
Views: 2970

Re: Acoustical effect of back woods

So it’s a bit like saying, in order to see if you can tell the difference between Granny Smiths and red delicious (blindfolded perhaps), then first let’s make sure you can tell the difference between apples and bananas? Yep, something like that. Negative results in science can be tricky. If you rep...
by peter.coombe
Wed Apr 10, 2019 10:15 am
Forum: Instrument Builders Forum
Topic: Acoustical effect of back woods
Replies: 25
Views: 2970

Re: Acoustical effect of back woods

Scientific hat on. When doing scientific experiments there are two questions you need to ask and answer (1) Is what has been observed in the experiment real and not an artefact of the methodology (2) Is it repeatable. A control is used to answer (1), and you repeat the experiment a number of times a...
by peter.coombe
Tue Apr 09, 2019 9:46 am
Forum: Instrument Builders Forum
Topic: Acoustical effect of back woods
Replies: 25
Views: 2970

Re: Acoustical effect of back woods

Yep, Nigel you are right. Rosewood guitars sell, other woods are harder to sell. Hopefully this study and the publicity it has received might start to shift that, but it is like shifting the Titanic with a tinny. I have not had the same problem with mandolins. Australian natives sell just as well as...
by peter.coombe
Sat Apr 06, 2019 9:24 am
Forum: Instrument Builders Forum
Topic: Acoustical effect of back woods
Replies: 25
Views: 2970

Re: Acoustical effect of back woods

Interesting observation. If the guitars did not have active backs then maybe there is little or no difference in sound, as you would expect. However, confining my criticisms to the rating test, which is the main part of the paper, I still believe it to be fundamentally flawed. They get a negative re...
by peter.coombe
Fri Apr 05, 2019 10:27 am
Forum: Instrument Builders Forum
Topic: Acoustical effect of back woods
Replies: 25
Views: 2970

Re: Acoustical effect of back woods

Thanks Trevor. This is the first time I have seen the original article, and a quick read of it has not changed what I have said about the summaries of the paper elsewhere. I still think their methodology is fundamentally flawed. Using a rating system for 6 guitars that sound more or less similar and...
by peter.coombe
Fri Mar 15, 2019 8:59 pm
Forum: Instrument Builders Forum
Topic: More mandolin thoughts
Replies: 12
Views: 1832

Re: More mandolin thoughts

One thought that has occurred to me since the first post - the Lyon and Healy type mandolins that I made have a different bridge from the more recent mandolin of my own design. The bridge is quite a bit lighter. That could explain why the difference is consistently 3.5 semitones rather than 4 semito...
by peter.coombe
Tue Mar 12, 2019 3:00 pm
Forum: Instrument Builders Forum
Topic: More mandolin thoughts
Replies: 12
Views: 1832

Re: More mandolin thoughts

I am happy to have a chat with you at the NFF.
by peter.coombe
Sun Mar 10, 2019 7:35 pm
Forum: Instrument Builders Forum
Topic: More mandolin thoughts
Replies: 12
Views: 1832

Re: More mandolin thoughts

Thank you Graham. I was beginning to wonder if anyone would take any notice, but you did and you nailed it. When I have more data I will write it up properly and submit to the GAL for publication because it is an important finding if correct. That is assuming the new data continues to support my hyp...
by peter.coombe
Thu Mar 07, 2019 9:59 am
Forum: The Gallery
Topic: First Classical
Replies: 8
Views: 1200

Re: First Classical

Thanks, that is good information. In Port Fairy at the moment, and don't have my records, but from memory I think the main air mode came in at between F# and G, and 2.5 semitones between the main top and main back mode. When tapping the bridge before the stings went on there was a really big woof ou...
by peter.coombe
Tue Mar 05, 2019 11:07 pm
Forum: The Gallery
Topic: First Classical
Replies: 8
Views: 1200

Re: First Classical

So kpart, how do you get the weight down on the bridges? Can't remember if I made the top thinner than the plan, half way to Port Fairy at the moment so can't check, but I think I did, the Swiss Spruce was quite stiff along the grain. What I do remember is that the fan braces were really small. What...
by peter.coombe
Tue Mar 05, 2019 10:49 pm
Forum: Instrument Builders Forum
Topic: Port Fairy Folk Festival
Replies: 5
Views: 1094

Re: Port Fairy Folk Festival

Yep, halfway there already.
by peter.coombe
Tue Mar 05, 2019 10:47 pm
Forum: Instrument Builders Forum
Topic: Tapping boards!
Replies: 14
Views: 1494

Re: Tapping boards!

Any music instrument with a wooden box and strings follows the same physical principles. Those principles are outlined in the books. The frequencies will be different for different types of music instruments, but the principles remain the same. Apply the principles and you will most likely end up ma...
by peter.coombe
Mon Mar 04, 2019 5:24 pm
Forum: Instrument Builders Forum
Topic: Tapping boards!
Replies: 14
Views: 1494

Re: Tapping boards!

Read the Gore/Gilet books. All is explained there.
by peter.coombe
Mon Mar 04, 2019 1:34 pm
Forum: The Gallery
Topic: First Classical
Replies: 8
Views: 1200

First Classical

This is my first classical guitar. It has taken around 3 years, rumbling along slowly in the background. Made the big effort to finish it for Port Fairy. Glad I did, I like it, and so far it has kicked the behind of every other classical guitar I have had access to. A customer told me he had a "wond...
by peter.coombe
Mon Mar 04, 2019 1:06 pm
Forum: The Gallery
Topic: Tenor guitar
Replies: 3
Views: 745

Re: Tenor guitar

Case arrived today at the last minute, so if you are going to Port Fairy I will have it there.
by peter.coombe
Mon Mar 04, 2019 1:04 pm
Forum: Instrument Builders Forum
Topic: Acoustic cases
Replies: 5
Views: 883

Re: Acoustic cases

Hiscox for OM guitars. I used Presto for custom cases for odd instruments, but they have closed down "temporarily".
by peter.coombe
Mon Mar 04, 2019 8:40 am
Forum: Instrument Builders Forum
Topic: More mandolin thoughts
Replies: 12
Views: 1832

Re: More mandolin thoughts

Here is a picture of the main top mode on the latest mandolin. You can see the fingerboard extension over the sound hole. Without it the main air mode was bang on G#, the fingerboard extension lowered it about 1/2 semitone. Mandolins are a bit more complicated than guitars because there is a tailpie...
by peter.coombe
Sun Mar 03, 2019 11:22 pm
Forum: Instrument Builders Forum
Topic: More mandolin thoughts
Replies: 12
Views: 1832

Re: More mandolin thoughts

Forgot to mention that the last mandolin I measured with the interval of 4 semitones, recently finished, sounds devine. About as close to the perfect sounding mandolin I have ever had the pleasure of playing. I went through a similar process as in the book i.e. what is the perfect mandolin, and rede...
by peter.coombe
Sun Mar 03, 2019 11:16 pm
Forum: Instrument Builders Forum
Topic: More mandolin thoughts
Replies: 12
Views: 1832

More mandolin thoughts

Following on from the other mandolin thoughts thread which referred to my flat top mandolins, I have been measuring some arch top mandolins. The results have been very interesting. Firstly some background. Many years ago I began measuring free plate modes in archtop mandolins after reading up on som...
by peter.coombe
Sun Mar 03, 2019 12:17 pm
Forum: The Gallery
Topic: Tenor guitar
Replies: 3
Views: 745

Tenor guitar

I am calling this tenor guitar the Gillian Alcock special in memory of my great friend and colleague Gillian Alcock who passed away in November last year. The top is made from King Billy Pine from Gillian's last King Billy plank from our tree we purchased in 1997. If she had not been forced to retir...