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#1
10-07-2020, 08:20 PM
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Adding sound port
I have a solid s/RW Tacoma Orpheum auditorium size guitar that I keep wanting to add a sound port. My luthier is not really keen on the idea “ if it ain’t broke don’t fix it”.
It was made in the early 2000s in Indonesia before Tacoma went under. It is worth $500 at most, but I would not do it if it might ruin it. I put a sound port in a junk guitar once and liked it. I would just go with a grouping of 5/8” holes. Is it less safe to put sound hole in a solid side than a laminate? Would you guys recommend against doing it? I would have the luthier do it. Thanks Whvick 
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#2
10-08-2020, 06:19 AM
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Slightly less safe yes. For a solid wood guitar you probably should install some thin ply's of some sort of wood then drill through that. It's a bit tricky to do that properly. There is a product, I forgot now what it's called, but it's basically liek small plastic pellets that you soak in water to soften up and it molds to the shape of anything you press it up against. So what I do is use that stuff and press it up against the side of the guitar where you what the port on a sheet of wax paper then when that is solid I drill a hole through it. Drill a small hole through the center of the sound port area trough your ply'a (or even a single sheet) then using a bolt through the whole thing with a wing nut clamp it all in place with glue.
Then I use a hole saw and drill out the sound port.
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#3
10-08-2020, 08:08 AM
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That's 'Friendly plastic'. One of my students gave me some; I don't remember where he got it. It's normally cloudy and turns transparent when it softens.
Even a fairly small port up near the wide part of the upper bout on the bass side will confer most of the advantages, without altering the sound very much. I'd use the Friendly plastic on the inside and the outside to make a pair of shaped cauls. find a hobby shop that caters to model airplane makers, and get some thin polar ply: they make it down to 1/32" or less. Glue a piece of that on the inside with the face grain across the grain of the side wood. Then you can drill your hole; I'd go for one about 1" in diameter or a bit bigger, but not as large as 2". On my first port experiment, the notorious 'corker', I used cloth side tapes, since I had to reinforce the whole side to drill tend pairs of 5/8" holes. Although I was not worried about longevity it has held up quite well, with no side cracks in the solid IRW in seventeen years (!). The cotton-polyester tapes are between the holes: I did not drill through the tapes.
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#6
10-08-2020, 02:42 PM
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Talldad wrote:
"Sounds ports are fun, useless, but fun." I beg to differ. A friend of mine borrowed the corker to do some blind playing tests, and determined that the ports didn't help. On reading his write-up I thought he had missed something; all of his tests were done in quiet reflective rooms, such as workshops, and practice rooms and a small stage at a music school. Also, a student of mine, who's into statistics, pointed out that his sample was very small. The problem with the rooms is that guitars are highly directional in the way they put out sound. The fundamentals of the lowest notes have wave lengths that are much longer than the box, so they're emitted more or less omnidirectionally, as from a 'point source'. The player hears those sounds as well as anybody in the room. As you go up in pitch and the wave lengths become shorter the guitar becomes more directional; above a certain point the sound is coming off the top and out of the hole toward the audience. The player only hears that from room reflections, and if the room in large or dead, or there's background noise, you won't get it. I can tell you from experience that this can be very disconcerting, if you'll pardon the pun. A port that the player can look into as they play could tap into high frequency sounds in the box that are not normally audible directly. To test this I made another test mule with a port in the usual location that could be easily blocked with a magnetic cover. I practiced removing and replacing it silently, and took it to the last two Montreal guitar festivals, a GAL convention, and a local folk festival. Tests were run in the venues; large rooms with some sound deadening, and background noise at a fairly constant level. Players were asked to seat themselves and put on a blindfold. I flipped a coin to determine whether the port would be 'open' or 'closed', and handed them the guitar to play for a short time while I flipped the coin again. Then I took the guitar back without any comment, and handed it back with the port in whichever state the coin had determined: about half the time it was the same, and half the time it was different. After they'd played it again I asked them if it had been changed or not. When it had not been changed players said it had been half the time; they were guessing. When it had been changed they got it right virtually every time. I got over a hundred of these tests. When I handed the data to my statistics guru he said there was no need to run the numbers; the result was perfectly clear: players can hear a difference in a large, dead, or noisy room (a 'restaurant gig') when it has a port they can see into. Customers who have hearing loss also report them as useful. Gotta go.
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#7
10-08-2020, 05:24 PM
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They are definitely NOT useless if by useless you mean they don't do anything?
FWIW I had an OM that I built for myself many years ago that I loved. When all this sound port business came out I decided to put one in... Bad move. I have not liked the guitar since. So while they definitely DO something they may not do what you want too. In all fairness I still play the guitar and the port provides an audible difference when seated playing as I can hear better but it did something to the tone of a guitar that I was used to and liked, it changed it. But it is kind of cool to have that personal monitor. Another port story I have is a guy who owned a music store I did repairs for and who was a musician who started losing hearing as he aged. He had an old Takimine guitar with barn door electronics that went bad so he pulled the electronics out and by accident discovered sound ports. So he had me drill out ports in every guitar he owns and now a guy who was hard of hearing can enjoy playing the guitar again. So yeah, they do something.
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#8
10-08-2020, 09:09 PM
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Adding sound port
I have a slight hearing loss. I’m the guy who makes Mickey Mouse ears to hear you in a crowded restaurant .
The sound port in the junk guitar really helped me hear it better. But I gave it to a kid that needed a guitar. I hate to ruin a good guitar. I wish I could get to a store somewhere that carries guitars with sound ports, but none of the major brands do so. Mostly custom guitars I assume. Thanks Guys
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#9
10-09-2020, 01:25 AM
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Sorry about the 'useless' comment. Had already provided a much greater explanation of the why but a glitch prevented this from being posted, subsequently all I had left was 'useless'
When you include a sound port on your build you make it easier for the guitar to breathe in and out in response to the myriad of vibrations the soundboard is experiencing. This fundamentally changes the frequency response of the guitar. Imagine a glass bottle quarter full of water that you blow across, make the bottle aperture bigger, the frequency will drop. A sound port has the same effect and move the response by about 1 Hz. By using an app called FFT by Studio Six you can measure the frequency responses from tapping, its Sonic Signature if you will. The graph has two curves of the same guitar, one with sound port open and one with it covered with light-weight plastic and tape, as you can see they are not identical by about 1Hz. Luthiers know that the difference between a good guitar and a great guitar is in the width of an Angel's Hair. By adding a sound port you make have taken a good guitar and made it very responsive indeed, the reverse can also be true, you could also have moved it from one Meh to a different Meh. But one thing is true, you no longer have the same instrument, you only have a similar one. The idea that a 1 inch hole can gather up all of the complex frequencies that an audience hears and present it to the player as perfect representation of the sound is fanciful at best. You may get a greater abundance of frequencies at around 90Hz, the resonant frequency of the chamber, this may even be pleasing (lots of bass), but it won't be representative of the guitar and the price paid will be changing the sound of the entire instrument for better or worse. The idea that a sound port will change a guitar's tone is rooted in glass bottles, just physics. My two best ever builds have sound ports, I quite like them, they're fun but they are not a panacea from making all guitars great. Alan, I loved reading your post, thank you. PS Can't upload a picture, sorry.
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#10
10-09-2020, 02:23 AM
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#11
10-09-2020, 04:48 AM
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#12
10-09-2020, 05:29 AM
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Quote:
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#13
10-09-2020, 11:10 AM
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Talldad wrote:
"..make the bottle aperture bigger, the frequency will drop." I'm assuming that was a typo? Actually, the pitch of the 'air' mode rises when you add a port, the same as it does when you enlarge the sound hole. One problem is that the closer the port is to the main sound hole, the less the pitch rise for a given size of port. A port next to the neck raises the pitch a lot more than one down on the wide part of the upper bout, and one in the tail block has an even greater effect. If you're trying to get your 'main air' pitch in between played notes as an aid to controlling a wolf it's hard to know how big to make it.
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#14
10-09-2020, 04:33 PM
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Quote:
I'm helping a long-time friend and customer build a classical guitar. He is building one, I'm building another. They are "identical" but for the position of the port. On my guitar, with the port open, the pitch is about 20 Hz higher than when the port is sealed. Mine has the port located at about the widest point in the upper bout. His guitar has the same pitch as mine, when the port is sealed. When his port is open, his is 20 Hz higher than mine, 40 Hz higher than the sealed-port frequency. His port is located in the lower bout between the waist and the maximum width of the lower bout. This is exactly in line with your comment, above.
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#15
10-09-2020, 07:48 PM
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Quote:
Use a router, go down slowly   Steve
__________________
Cole Clark Fat Lady Gretsch Electromatic Martin CEO7 Maton Messiah Taylor 814CE
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