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Hello everyone. I am building my second guitar, a classical. I have the sides glued to the top and head block. I am getting ready to glue the back on. Before I do so, I am interested in a sound port. Is it too late to install one? If not, what is the process for creating a hole. What size should I go with?

Again, the EIR sides are bent and installed to the top and head block.

Thanks,

Doug

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Guitars...One's too many...Twenty is not enough.

Doug,

I have installed sound ports on a couple of classicals. The first one had already been completed, and I just drilled a hole in almost at the top of the upper bout. It was a spur-of-the-moment kind of thing. The port was probably bigger than most folks do -- about 1.5" in diameter, but the difference in sound was remarkable. It's like having my own personal monitor when I play that guitar.

The second guitar I ported, I followed Robert Ruck's guidelines more or less. I cut a port on both the treble and bass sides, each one 3.5" from the heel centerline, 7/8" in diameter. I cut these ports before I installed the back. To give them a bit of visual interest, I glued down alternating pieces of white and black veneer to the inside of the sides before drilling the ports (I used a 7/8" Forstner bit). Not only do the veneers give the ports a bit of visual interest, but the layers help reinforce the sides somewhat.

Best,

Michael

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Live to Play, Play to Live

Yup....its not too late!
you could reinforce the side with any kind of hard wood or veneers like Michael said and you should be fine.

Robbie O'brien has made many classicals with soundports.

Maybe he'll chime in!

_________________
Peter M.
Cornerstone Guitars
http://www.cornerstoneukes.com

I spent some time a few years ago experimenting with port locations. I built a classical guitar with 20 holes all down the right side, and plugged them with corks. Then I took it to H'burg so folks could try it out, and measured the tonal changes after I got home. I've built several 'real' guitars with ports since, too.

IMO, the main benefit of the port is as a monitor. It helps direct some high frequency sound toward the player, depending on where it is. It also changes the timbre of the guitar, and the bigger it is and the further from the 'normal' soundhole, the greater the change. Thus, for my own guitars, I make a 1" diameter hole just above the wide part of the upper bout on the right side. This is big enough to make a useful monitor, and small enough and close enough to the main hole that it doesn't have too big an effect on the tone. It will raise the pitch of the 'main air' resonance, which gives you a lot of your low-end 'fullness', so you probably should reduce the diameter of the 'main' hole a bit to compensate: say by about 8-10 mm. If you're unsure, make the main hole small and leave a wide margin between it and the rosette. That way you can trim it a little bigger if you want.

You might want to make a backing caul to use when drilling the port to avoid splintering

Alan,
Would you happen to have any pictures of your ported guitar?

Well, that's the thing Alan, most people who do these ports do it because they want it to affect the sound. I, like many builders, use a bigger port then that, do not reduce the size of our soundholes, and people prefer the sound with the port, both from the playing and listening position. Naturally, tastes will vary.

There are some pics on my web site; under 'New Work', although they are not all that new. I just put out a ported guitar with a much nicer surround to the port, but the customer whisked it off before I could get a god picture.

Changing the sound is certainly a valid reason to put in a port, and a big one, if that's what you like. I may use 'radical' means, but the ends for me are generally pretty traditional. One of the nice things about the guitar world is that there's so much room for different tastes and methods.

With all of this talk of "changing of the sound", I am hesitant of putting a port in at all. How drastic is the change and in what way?

_________________
Guitars...One's too many...Twenty is not enough.

Doug,

I would say "Let not your heart be troubled." I was very happy with the change in sound on the first guitar I ported, and as I mentioned above, I pretty much just punched the hole in an already finished instrument -- used a 1-1/2" hole saw, in fact. Didn't even get any chip-out, surprisingly enough. The guitar was one of my prototypes, so I didn't much care how the sound was affected. I just wanted to see for myself what happened.

I haven't finished the other guitar I've ported (real soon now), but I look forward to the volume and tone difference between the two porting styles, especially after reading all the comments here.

Best,

Michael

_________________
Live to Play, Play to Live

Ok. My first is a proto type also, or was it "Can I really build a guitar out of the spare wood I have lying around"?

I'll port that one to get an idea of what the effect is.

Thanks

_________________
Guitars...One's too many...Twenty is not enough.

The nature of the change will depend a lot on where you put the port and how big it is, so it's hard to give a precise answer. In general thuogh, the port does three things:

1 - It raises the pitch of the 'main air' resonance from what it would have been in the same guitar without the port, assuming you don't change the main soundhole size. This resonance gives you a lot of the low-end sound, since it's fairly powerful and usually comes in around G on the low E string. Raising it by very much can make thelowest notes sound 'nasal' or lacking in 'fullness'. The further from the 'main' hole you put the port, the greater the pitch change for a given port size. The larger the port the greater the change.

2 - It actually seems to _reduce_ the overall output of the guitar very slightly over the band of frequencies below about 1000 Hz. This is tied in with the effect it has on the 'main air' mode, and the way that couples with the top. However.

3 - There will usually be a large increase in output at one or more _specific_ frequencies, depending on which interior air resonance[s] the port can 'hear'. Most of these occur at mid- to high frequencies, and they are generally not very effective at being heard through the 'normal' hole. Again, the larger the port, and the further from the 'main' hole, the greater this effect will tend to be.

The way it all adds up is the putting a 'reasonable' sized port in a guitar gives a slight increase in the output; perhaps 1-2%. The narrow band increase just beats out the broad band drop when you average it out over all the frequecies. Interestingly enough, the size and location of the port don't seem to effect this at all: you get about the same overall power from a big port as a small one. However, the big port will most likely give much more power at high frequencies, where youre hearing is most sensitive, while most of the drop will be in the low range. Thus the port tends to _sound_ louder, but less 'balanced'. Definitely a case of 'no free lunch'.

But the reality is, if you take a bunch of ported guitars, play them, cover the port, and play them again, they sound louder, better, more open. Again, and again, and again.

Alan, I don't know why, but I know it is true. Perhaps your measurements are accurate, and it's a perceived change. In which case, that's what matters, not the "objective" numbers. Or perhaps you are suffering from an experiment with a sample size of 1.

I certainly haven't heard a ported guitar that sounded nasal, or was trending in that direction. Or less full. Or quieter. Or unbalanced. This is based on playing at least a dozen of them, and testing by closing and opening the port.

rlabbe wrote:
" Perhaps your measurements are accurate, and it's a perceived change. In which case, that's what matters, not the "objective" numbers. Or perhaps you are suffering from an experiment with a sample size of 1. "

Certainly there is a great difference between the sound we percieve and what our instruments can measure. A lot of effort has gone into trying to devise ways to convert from one to the other; to predict what something will 'sound like' from measurements, and none of them work very well.

I'm not questioning _your_ perception of the guitars you've played, that would simply be folly. I have heard and played a number of other 'ported' guitars besides my own, and have formed my own opinions. The data I got from my experiment generally backs them up. Some ported guitars do sound 'nasal' or lacking in bass fundamental to me.

One issue here is well-known in the acoustic community: there is an almost total lack of commonality in terms. We all use the same words to talk about things, but we use them differently, so it's hard to communicate. My 'nasal' might be your 'clear'.

As for a 'sample size of one', that's another problem in guitar acoustics research. It's _very_ difficult to make 'identical' guitars: I know; I've tried. The best way to test something like the influence of ports really seems to be to do as I've done; build a guitar with ports you can open and close simply, and try it in different configurations. Sure there are potential problems with this: there is no 'perfect' experimental protocol. However, I've observed other similar experiments on other instruments, read of more, and my findings tally well with the few results I've seen published in juried journals of similar experiments. I'm reasonably confidant that my 'small sample' has given me some insight into how these things work. Obviously, if you want to repeat my experiment, or do another in a different way, and you get different results, I'll listen, but don't be surprised if I raise objections too.

:)

[QUOTE=rlabbe] But the reality is, if you take a bunch of ported guitars, play them, cover the port, and play them again, they sound louder, better, more open. Again, and again, and again.
[/QUOTE]

Some months back I read an article on the 'net that was an interview with Robert Ruck, who I suppose was one of the first to start doing this. I've searched for the article again, and have been unable to locate it, so I'll have to paraphrase a couple of his comments from memory.

Ruck believes that the volume increase is not just due to the ports themselves being additional areas that sound can escape the box. He says that he thinks the ports act as a vacuum relief. Recall that soundwaves are alternating areas of compression and rarifaction of the air and that the waves are being pumped, so to speak, out of the soundhole. Well, he thinks that the ports are reducing the work needed to pump the air out of the box through that single soundhole.

Ruck also commented that he measured the volume levels of one of his unported guitars compared to one of the ported ones. I don't recall the specific numbers anymore, but he said that there was a slight, but noticeable increase in volume both to the player and the listener. So it seems his first point is borne out by the data he collected.

If I run across that article again, I'll post it here.

Best,

Michael

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Live to Play, Play to Live

I only build classical and flamenco guitars and respect Robert Ruck's skill and the sound of his guitars so I tried building in ports into my guitars.

I do not put them in as a standard feature and offer as I would any other addition to a base model. I have stayed to the size and relative position of Ruck's ports.

In general while I like the ability to hear more clearly the sound coming from the guitar, my conclusions pretty much match up with Alan's.

It is not a magic bullet and if the change in overall tone and volume is something that you like than that is fine. It is very subjective...I have had customers that even when they liked the sound of a guitar with sound ports that they played ended up ordering one without as they did not want the look of a classical with sound ports...

[QUOTE=Shawn]
I have had customers that even when they liked the sound of a guitar with sound ports that they played ended up ordering one without as they did not want the look of a classical with sound ports...
[/QUOTE]

Yup, that's classical players for you. Most are deeply conservative, not only in their views of what a classical should sound like, but especially what it should look like.

Oh well . . .

Best,

Michael

_________________
Live to Play, Play to Live

[QUOTE=Alan Carruth]One issue here is well-known in the acoustic community: there is an almost total lack of commonality in terms. We all use the same words to talk about things, but we use them differently, so it's hard to communicate. My 'nasal' might be your 'clear'. [/QUOTE] That's an extremely good point. Hope I didn't come across at too petulant yesterday. I know I was feeling petulant, but do to unrelated stuff in my life.

[QUOTE=Michael McBroom]Yup, that's classical players for you. Most are deeply conservative...[/QUOTE]
I think the real problem is that concert guitar playing is very competitive, and it's difficult to gain respect from audiences and peers. Players are really concerned with what others will think of their choice in instruments. The big boys and girls seem more willing to consider cutting edge guitars.

Hmmm . . . maybe nowadays that might be true, but it didn't used to be. The reason why the modern classical looks the way it does is not because of Antonio De Torres, but because of Andres Segovia. Prior to Segovia, the Viennese school was alive, well, and robust. Prior to Segovia, multi-stringed guitars were quite common. He was adamant about what "The Guitar" should look like, how many strings it should have, and what it should sound like, and because of his stature and influence, the classical world conformed to his views and wishes. The Viennese school (and others of non-Spanish tradition) was no longer in fashion, and multi-strings faded into obscurity.

The momentum that Segovia fostered continues, and only in recent years seems to be disappating somewhat. I'm all in favor of his influence going away, btw, cuz I believe the instrument will only benefit from innovation.

But there is still rather strong bias out there. For example, recently, I mentioned to Janet Marlow, who plays the 10-string, that I had taken a master class from Pepe Romero back in the 70s. She told me she had too, and that when he saw her pull out her 10-string, he asked her, "Why do you want to play one of those? People will think you're a freak." Pretty strong and traditional views from a fellow who is one of the "big boys" by most anyone's measure.

I have not just run into resistance from players over sound ports, but even over wood selection. A fellow local to me that owns a "guitar salon" is interested in carrying my guitars, but only my 6-strings (no 10-strings), and only spruce and cedar topped ones. No redwood tops, and no non-traditional back/side material. Hey, it's his loss, and his clientele's.

Best,

Michael


Best,

Michael

_________________
Live to Play, Play to Live

rlabbe wrote:
"Hope I didn't come across at too petulant yesterday. "

I was thinking the same of my post, which is why I put in the 'smiley'.

Lots of smart folks have been making guitars for a long time, and trying out all sorts of 'improvements'. Some work and some don't. The ones that work get picked up on pretty quickly, and become part of the 'standard'. If ports are as good as all that they'll be 'standard' on most guitars within a few years, and nothing we say one way or the other will change that. Patience, folks....

Michael,

Yeah, we've gotta give Segovia his propers for rescuing the guitar as a viable concert instrument, but he was a mixed blessing. The Romeros were just too close to Segovia and his era (and his Spanishness) to make a leap into the avant garde. Same with the USA's first virtuoso, Christopher Parkening.

There always have been people willing to take chances with both music and instruments, though. Bream and Williams come to mind. Today, there are players like David Russell, David Starobin, and, yes, Janet Marlow who are willing to take a different path.

You're certainly right about continuing bias, though. Richard Schneider is a prime example of innovators who suffered because of it.

Keep pushin' the limits, my friend. You'll find your path. CarltonM38928.9676736111