Welcome to one of the most active flamenco sites on the Internet. Guests can read most posts but if you want to participate click here to register.
This site is dedicated to the memory of Paco de Lucía, Ron Mitchell, Guy Williams, Linda Elvira, Philip John Lee, Craig Eros, Ben Woods, David Serva and Tom Blackshear who went ahead of us.
We receive 12,200 visitors a month from 200 countries and 1.7 million page impressions a year. To advertise on this site please contact us.
|
|
RE: flamenco body styles and bracing-where to start
|
You are logged in as Guest
|
Users viewing this topic: none
|
|
Login | |
|
Andy Culpepper
Posts: 3023
Joined: Mar. 30 2009
From: NY, USA
|
RE: flamenco body styles and bracing... (in reply to Tom Blackshear)
|
|
|
Of course a guitar pumps both air, and vibrations that travel through the air. I suppose having a soundhole means that the top is actually freer to move because it can get the air inside the guitar out of the way when it wants to move in, and suck air back in when it's pushing out. So I guess all the "air pumping" is happening in the immediate vicinity of the guitar itself. I guess the main thing I'm still wondering about is how you can separate "air movement" from "vibrations" and how the two interact with each other. Inside the soundbox it seems like they are basically the same thing. When you tap on a guitar top, there is definitely air being pushed out of the soundhole, which to me is also accompanied by sound. As you're tapping, you will hear the sound louder and fuller the closer your ear is to the soundhole as opposed to somewhere else on the top, and as I mentioned you can smell the air coming out. Granted this may not qualify the guitar as an "air pump" in the literal sense of the word. This is somewhat unrelated but anyone who has messed around with doing Chladni patterns on an assembled guitar will know that certain resonances can only be stimulated by putting the driver (speaker) over the soundhole, such as the "main air mode" or Helmoholtz resonance. Also the main top resonance is much easier to drive from the soundhole. So at least the lower frequencies are more responsive to vibrating the air inside the guitar than to vibrating the top itself. The higher modes of the top are almost always impossible to drive from the soundhole but work by holding the speaker over the guitar top at certain spots. Thinking about all this reminds me of how incredibly complex a system the guitar is... but I definitely gain something from these little luthier chats, even if it is accompanied by a headache
_____________________________
Andy Culpepper, luthier http://www.andyculpepper.com
|
|
|
REPORT THIS POST AS INAPPROPRIATE |
Date Jun. 27 2011 0:31:03
|
|
Andy Culpepper
Posts: 3023
Joined: Mar. 30 2009
From: NY, USA
|
RE: flamenco body styles and bracing... (in reply to estebanana)
|
|
|
quote:
the guitar is working as a movable diaphragm to make pressure waves which _move through_ the medium of air. Can't argue with that and I don't think anybody was. But as usual there are other interesting facets to the discussion. When I tap on a guitar top I can literally feel air blowing on my face out of the soundhole. To me this constituted "pumping" in the bicycle pump sense but on a small scale, even if it is just pumping back and forth... but I can easily abandon that particular word as it seems to have offended certain people (?). I think it's pretty obvious to anybody that no liquids are being pumped, and that air is not literally hitting you in the face in a way that you can feel when you listen to a guitar. But there is definitely air movement in and around the guitar which seems inseparable from vibrations, although it may be a secondary factor. The thing about removing the back of the banjo is interesting, I've wondered what would happen if you were able to do that with a guitar. Exactly what the back is "doing" is definitely up for debate. Here's an interesting point from Canadian luthier John Park's site: "If you had taken the 12″ speaker from a guitar amp and eliminated the cabinet, you would find that no sound below about 500 Hz [cycles per second] would come out. The reason is that any sound wave coming forward from the cone would be sucked into the vacuum created on the back side – unless the cone reverses direction before it can get there. Thus, without some sort of baffle to isolate the pressures, the air around the speaker just churns about inaudibly under about 500 Hz ." So do "sound waves" have the same property as the air they travel through in that they move at the same speed and can be sucked back/canceled out? I guess the analogy to waves moving through water is a good one. When you drop a rock into the water, there is a lot of water churning around immediately near the rock, but it sends out ripples that don't really *move* the water they're passing through very much. Still the amount of water that's moved initially determines the amount of ripple that results.
_____________________________
Andy Culpepper, luthier http://www.andyculpepper.com
|
|
|
REPORT THIS POST AS INAPPROPRIATE |
Date Jun. 27 2011 22:19:09
|
|
New Messages |
No New Messages |
Hot Topic w/ New Messages |
Hot Topic w/o New Messages |
Locked w/ New Messages |
Locked w/o New Messages |
|
Post New Thread
Reply to Message
Post New Poll
Submit Vote
Delete My Own Post
Delete My Own Thread
Rate Posts
|
|
|
Forum Software powered by ASP Playground Advanced Edition 2.0.5
Copyright © 2000 - 2003 ASPPlayground.NET |
0.140625 secs.
|