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| Acoustic soundholes in rim http://mowrystrings.luthiersforum.com/forum/viewtopic.php?f=10101&t=53972 |
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| Author: | jimbag [ Mon Feb 22, 2021 10:51 am ] |
| Post subject: | Acoustic soundholes in rim |
I want to add 1 or 2 soundholes in the rim of my current guitar build (steel string Grand Auditorium). I have read in quite a few discussions that it's a great feature that once tried, you will always want them. My question is what diameter, and should I do 1 or 2 of them. One guy wrote that he always puts one in the upper, and one in the lower bout, with a diameter of no greater 3/4". That sounded small, but he insisted it should not be larger. I kind of like the idea that they are small, for aesthetic reasons, but I have no experience with them. Anyone heard or tried of using 2 side soundholes? Any other input using 1. Thanks PS I have a 4" hole in the top. |
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| Author: | SteveSmith [ Mon Feb 22, 2021 10:57 am ] |
| Post subject: | Re: Acoustic soundholes in rim |
I do 4 holes cause I like the way it looks and sounds. Doesn't seem to affect the forward projection. I've seen single holes in the upper rim as large a 1 1/4", didn't seem to cause any trouble. Attachment: IMG_0893.JPG
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| Author: | Bryan Bear [ Mon Feb 22, 2021 11:01 am ] |
| Post subject: | Re: Acoustic soundholes in rim |
I use 1 hole about 1.25 in diameter depending on binding. I haven’t decided if I like it better on the apex of the upper bout curve or in the flatter area closer to the waist. I won’t speak too much as to the whys since I’m not sure I fully understand them. From posts I have read (many from Allan Carruth), the impressions I got (right of wrong) was that the hole doesn’t need to be very large, the closer it is to the players ear the more effective it is, and that the closer it is to the soundhole, the less impact it will have on the sound that the rest of the room hears. Take that all with a grain of salt: there could very well be posts coming up that contradict or clarify what I just said. I’m not sure I have all that right. |
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| Author: | Alan Carruth [ Mon Feb 22, 2021 11:23 am ] |
| Post subject: | Re: Acoustic soundholes in rim |
I have a .pdf on 'Ports' on my web site, talking about some of the experiments I've done on that. I spent 'way more time than I expected to; it's a more complicated subject in some ways than you might think. But the basics are pretty simple. Opening a 'port' will raise the pitch and output of the 'main air' resonance. This is the lowest pitched resonance that can produce useful sound, and has a lot of bearing on the low-end sound. Just what the effect will be in a given case can be hard to say: as often happens on the guitar, it's a matter of balance. More power in the low end implies a 'bassier' sound, while a higher resonant pitch favors a more 'open' or 'treble balanced' tone, so you've got opposite effects from the same action. The further the port is from the main sound hole, and the larger it is, the greater the effect. A 2" hole just below the wide part of the upper bout may not change the sound as much as a 1" hole at the base of the neck, or an even smaller one in the tail block. Most of whatever effect there is on the sound out in front seems to be related to the pitch change in the 'air' mode, rather than the added power output. It takes a pretty big change in power to sound even noticeably louder, but a pitch change that shifts a resonance onto or off of a played pitch can alter the sound of that note a fair amount. The main use of a 'port' is as a monitor. The lowest notes on a guitar have wave lengths in the air that are much longer than the box, so they put those sounds out as a 'point source', about equally in all directions. As you go up in pitch the sound becomes more directional, so that the high frequencies are going out of the hole and off the top toward the audience. The player hears the low notes about as well as anybody in the room, but can only hear the higher frequencies if they're reflected back. In a big, dead, or noisy room the player doesn't have much feedback, and the effect can be pretty disconcerting. Pun intended: I've been there. There is a fair level of high frequency sound rolling around in the box, and a port that you can see into as you play will direct some of that toward you. Again, the closer the port is to the main hole location the more the sound it puts out will be like what's coming out of the main sound hole. As with the 'main air' resonance, opening up a port alters the pitch and power of any internal resonance it hears, so different locations will produce different results. I like to use a fairly small port, around 1" diameter more or less, just below the wide part of the upper bout on the bass side. This is large enough to be a useful monitor in most circumstances, and small enough to leave the balance pretty much where you want it. I normally cut down the size of the main hole when I'm going to put in a port, but it's a bit hard to say how much of that to do. Making it 1/4" smaller in diameter might be a good place to start. Since you already have a 'normal' size sound hole, I'd say keep the port small. I'll note that, in the early days of using ports, some folks said they were practically 'magic', and would 'improve every instrument'. I don't believe anything is always an improvement: I like ketchup on hamburgers, and sometimes on eggs, but not on ice cream, although such things are a matter of taste. Opening a port does what it does, and it always does the same thing. That's what I spent all the time figuring out. They're useful if you play a lot of big, dead, noisy rooms ('restaurant gigs'), and folks with hearing loss seem to like them, but they're not magic. It being the 'net and all, those early posts are still out there; take them with a grain of salt. |
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| Author: | jfmckenna [ Mon Feb 22, 2021 1:57 pm ] |
| Post subject: | Re: Acoustic soundholes in rim |
Be careful of what you wish for too. I built myself an 000 that I really loved till I put a sound port in it. I thought I would like the idea of a monitor on the side especially since I was using the guitar more with my band. I don't exactly hate it now but it changed the sound way more then I thought and went from a guitar that I really liked to one I begrudgingly pick up to play now. |
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| Author: | Barry Daniels [ Mon Feb 22, 2021 2:08 pm ] |
| Post subject: | Re: Acoustic soundholes in rim |
Make a plug for it. |
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| Author: | jfmckenna [ Mon Feb 22, 2021 2:11 pm ] |
| Post subject: | Re: Acoustic soundholes in rim |
Yeah I have that on my agenda for some day when I get around to it. I was thinking like a sliding door. Could be the reason why I don't like it is becasue it's too big. Especially after hearing Alan say he goes for about 1in. This one is oval but larger then that. |
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| Author: | Alan Carruth [ Wed Feb 24, 2021 3:42 pm ] |
| Post subject: | Re: Acoustic soundholes in rim |
You could also restrict the main sound hole some. One way that is nicely 'stealthy' is to make a sleeve of some sort that goes into the hole, making it into a longer 'neck' for the 'bottle'. This will drop the pitch of the 'main air' mode, and it's usually easy to get it back into the range you want. It's easy to experiment with strips of card stock taped in place. When you find the size that suits you can make up something nicer. If it's black, and particularly if it's set back just a little from the edge of the hole, most folks won't notice it. You can also make it from clear plastic, which is even less visible. A similar sleeve on the port will also make that work more like a smaller hole. |
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