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Post by cb1974 on Jan 10, 2020 19:42:30 GMT
I am looking to build my second acoustic. Had a thought about that the back board function could be affected if held against the body when playing. Could this effectively dampen the sound?
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Post by Onechordtrick on Jan 10, 2020 19:56:42 GMT
I am looking to build my second acoustic. Had a thought about that the back board function could be affected if held against the body when playing. Could this effectively dampen the sound? Some mandolin players have a device that holds the instrument away from the body to minimise any potential damping. Try playing your guitar held away from you and held close and see if it makes any difference? |
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Post by cb1974 on Jan 10, 2020 20:18:31 GMT
I will try that, cheers.
The reason is that if it does, then I was thinking of a back board, Lets say 6mm thick then routing out 80% on the outside about 4mm leaving a 2mm face allowing it to resonate regardless if its pressed against you or not. Any thoughts?
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Post by cb1974 on Jan 10, 2020 21:19:16 GMT
Probably didnt explain properly. Not to route out a full area but to take out linear sections with original thickness between to enable the body/player to press against and allow 2mm sections vibrate regardless?
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Post by Onechordtrick on Jan 10, 2020 22:22:52 GMT
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Post by cb1974 on Jan 10, 2020 22:54:49 GMT
Spot on. Thanks. Idea!
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colins
Luthier / Guitar Maker
Posts: 2,397 
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Post by colins on Jan 11, 2020 10:00:01 GMT
cb1974 There are two types of back on a guitar, passive and active. The vast majority of steel string guitars have passive backs that are simple reflectors, as steel strings are often played standing up or, when sitting, with the back against the stomach any active back would be damped. It's far more common to have an active back, that also vibrates to a minor extent, on a classical guitar, these are always played sitting and with the guitar held in such a way that the back is not damped against the stomach. Even here some makers are building stiff, double layered backs on their classicals. My advice to you would be to forget about trying to make the back active, concentrate on getting the top to be as 'musical' as possible with a good clean tap. Feel free to ask as many questions as you need. Colin
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Post by cb1974 on Jan 11, 2020 13:49:12 GMT
Thanks for the advice Colin.
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Post by Alan J on Jan 14, 2020 13:11:33 GMT
One of the difficulties of making an active back, apart from it being suppressed by the player, is dealing with its resonant frequency. The top resonates, the chamber resonates and the back resonates regardless of how well it is built. The skill is in making guitars is getting them resonate at the right frequencies for the sound that you want. Those that have reached Jedi status can create instruments where the back frequencies complements the others rather than clashes with it. Trevor Gore (Aus) has done some fascinating work on the subject.
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Post by cb1974 on Jan 15, 2020 21:17:52 GMT
Thanks for the heads up on Trevor Gore. He IS a Jedi.
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Jo whoever he is.
