Adding sound port

[Talldad]

Originally Posted by Alan Carruth

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.

That’s interesting. Indeed I meant rise, but I had no idea that the location of the port was also a factor, fascinating. I

[Talldad]

Originally Posted by Alan Carruth

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.

That’s interesting. Indeed I meant rise, but I had no idea that the location of the port was also a factor, fascinating, why do you suppose it behaves that way.

I’ve often wondered about building a guitar that has no sound hole but a series of sound ports built all around the guitar’s sides that have a slightly bigger cross sectional area than the original hole. Once you’ve dealt with the structural problems of the reduced mass from the sides and structural integrity, would you not have a guitar with a much bigger vibrating plate and potentially much more complexity in its sound?
How on earth would you brace such a plate?
Would the plate get away with being thinner?
This is why I’ve never built one I guess, so many fundamental changes would make it pure fluke to built a ‘great’ guitar on a first attempt.

[Alan Carruth]

Designer and craftsman David Pye wrote:
"Where the problem is old, the old solutions will nearly always be best (unless some new technique has been introduced) because it is inconceivable that all of the designers of ten or twenty generations will have been fools".

If you look through the history of the guitar you'll find that most, if not all, of the 'new' ideas have been tried, and usually more than once. Some of them become fads for a time, but they're usually not the majority of the better instruments being made, and generally speaking the guitar goes back to more or less the same layout in a short time. There are reasons behind the traditions.

Of course, the guitar is a very complicated beast in the way it works, and there's a lot we don't know about that. The 'normal' sound hole location is a good example. Some folks have put a large port in the side, just above the waist, with the same area as a normal hole, in the expectation it will work the same way, and free up area on the top. It doesn't seem to. For one thing the high frequencies that are normally going out the hole toward the audience are now blasting the player, who doesn't need nearly as much of that. Not being centered on the top the hole also 'hears' things it normally would not, and may not 'hear' some things that it should. The upshot is that you end up with something that doesn't sound like a guitar usually does. You may or may not like that sound, but it's less likely to fit into the standard repertoire. There are also reasons to think that it's likely to be less 'interesting' than the standard layout.

It turns out to be very difficult to make changes in the guitar as we know it that will be broadly accepted as 'improvements'. This is not to say we should not try, or to automatically reject such changes. What it does is to point out that a certain amount of familiarity with what has gone before can be useful in informing such efforts: there's no sense in re-inventing the Edsel, or closer to home, the Gibson 'Mark' series. The traditional designs are well optimized, and we should not find that surprising. What would be surprising would be a radical new design that took over the world in a short time. I've seen enough promises along that line that I'm skeptical. It was claims like that that got me started looking into ports, and it didn't take long to come down to earth on them. They are not 'magic'; they do what they do, but they won't, as some maintained, 'make every guitar better'.

[whvick]

Does overall size of sound port matter?
I just want to hear the guitar better
Would two small 5/8 or 3/4” holes do me just as good as a larger port and maybe not negatively affect the guitar as much?

[fitness1]

Originally Posted by whvick

Does overall size of sound port matter?
I just want to hear the guitar better
Would two small 5/8 or 3/4” holes do me just as good as a larger port and maybe not negatively affect the guitar as much?

As Allan has stated, not every guitar will benefit the same from port installation. To your question though, I've found smaller ports to be best for my ear and what I'm trying to accomplish.

My Cordoba Solista was a VERY good sounding guitar before installation.....I put the dual/dual ports in (very small as you can see) and it made it an outstanding instrument.

Two well known builders were pretty shocked when we did the A/B test with the ports plugged and opened.

In the end, I made them ever so slightly larger than pictured.

I'm on the verge of porting my Webber dread in a similar fashion.

[whvick]

Originally Posted by fitness1

As Allan has stated, not every guitar will benefit the same from port installation. To your question though, I've found smaller ports to be best for my ear and what I'm trying to accomplish.



My Cordoba Solista was a VERY good sounding guitar before installation.....I put the dual/dual ports in (very small as you can see) and it made it an outstanding instrument.



Two well known builders were pretty shocked when we did the A/B test with the ports plugged and opened.



In the end, I made them ever so slightly larger than pictured.



I'm on the verge of porting my Webber dread in a similar fashion.

What diameter holes did you finally have ?

[fitness1]

Originally Posted by whvick

What diameter holes did you finally have ?

Hard to measure precisely as they are slightly beveled - but they appear to be 17/32 "internal" and 5/8 "external"

[Alan Carruth]

The 'corker' used pairs of 5/8" holes, since that's the size of cork I could get at the hardware store. That would be about the same area as one 3/4" hole, and it's enough to have a useful 'monitor' effect if you can see into the hole. The larger the port the greater the effects are, both good and bad. I don't see any particular benefit to a port larger than about 2", but that's my opinion.

One of my students made a resophonic guitar with a small sound hole in the upper bout of the face that was part of an overall artistic motif. I thought when he showed me the drawing that it would be to small, and it was; the sound was 'choked', but there was no way to enlarge it without ruining the art work. Instead he made a port in the side. He reinforced the area with a cross grain wood patch and then used a burr on a hand shaft to cut a hole. Since he didn't have to remove the strings to do it he was able to enlarge the hole in steps, playing it in between. As he went on the sound got better for a while, then plateaued, and finally started to get worse. At that point he cleaned up the edges and made it nice and round, and fitted in a decorative insert to give a finished edge and reduce the area to the correct size. I'll note that this was the only sound hole, but I see no reason why you could not do something like that with any port.

[cugir321]

Originally Posted by redir

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.

Make a cover for it....a piece of tape works fine....I've experimented with covers...cover the hole and your back to normal. I have 3 guitars with sound ports....two had fishman preamps which I removed.....It works fine as a soundport hole. I love it on my Bedell BDD-18-M...cheap little 100.00 guitar which now sounds like a vintage D-18 since it aged....at least to my ear because the bass come straight up...and yes most of the sound change is increased bass...it sounds very vintage from the top hole but the sound hole makes it sound like a monster at my ear level....love it.

[cugir321]

I saw a luthier who did some with ports....he said puting a hole near front edge of the top side increases the volumn and bass to the listener.....putting a hole in the back curve of the side changes the tone....he used a slider to adjust the tone.

I love how removing a fishman 301 made my Bedell louder and bassier to my ear....changed it slightly to the listener coming from the sound hole.

I have another of the same guitar that I'm about to put one in the front side...facing up to my face....I may do a second further back....

I haven't tested this but I bet it would make a huge difference if the vocal mic could pick up some sound.....or you mic'd it from the top. Maybe use a small goose neck mic over the sound port...and a magnetic in the sound hole. mix 'em...I'm going to search youtube to see if anyone has done this with a sound port....especially the goose neck mic.

[nikpearson]

In my experience sound ports located in the topside upper bout significantly alter the instrument’s sound from the player’s point, usually giving more warmth and bass, and possibly a better representation of the instrument’s sound for the audience.

Any additional hole will raise the Helmholtz main body air resonance which can sometimes change the instrument’s overall sound considerably. Many of the best guitars I’ve played have had a relatively low body resonance; notably Julian Bream’s main Hauser which had a resonance slightly below F# - I should add this wasn’t one of the guitars I’ve played but it’s safe to say that it was a very good instrument!

Alan’s information about the siting of the port is fascinating. I hadn’t realised this was the case. I conducted some experiments of my own using both classical and steel-string instruments and inserts to reduce the sound hole diameter. It was possible to drop the main air resonance very significantly but slow a certain level the sound output was pretty horrible!

I’ve been working on a steel-string guitar with interchangeable rosettes to allow tuning of the air resonance without a port. None of the adjustable sound port designs appealed to me. At some point I’ll get it finished.

[redir]

I've sold that guitar that I was talking about before. But since then I added a port in one of my classical guitars. I had a nice doubletop guitar in for repair a few years back that had two ports on each side of the heel about 3 inches or so from the heel. I put one in at about the same location on the upper or bass side of the guitar and I love it. So it goes.

[Okotok]

I don't give it a lot of thought. I put oval shaped holes in the upper bout of all of my guitars these days and don't know if there is minutiae effects. They seem to work great and look cool too!

[RogerHaggstrom]

>It turns out to be very difficult to make changes in the guitar as we
>know it that will be broadly accepted as 'improvements'.

Even when it works. A correct nut intonation and my own invention, the segmented saddle, always make the guitar sound better. But they are time-consuming to make, and few people know what they are missing out on.