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How are you doing sound ports? And are you making your soundhole smaller to compensate for the port? How large of an area are you using? I've read the past stuff that I could find but would like to see if there is something more that those of you have learned about them.

For what it's worth, here's mine. I would guess it is between 2 and 4 sq. in. overall. Based on advice from folks here and at the MIMF I didn't change the size of the soundhole. Hasn't been strung up yet and I've never played one with a port but I'm looking forward to it.

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Steve Smith
"Music is what feelings sound like"

I keep mine small, about 1 sq in. It changes the main air resonance about 1/4 step on an OM, so I don't bother with any soundhole changes.

Pat

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formerly known around here as burbank
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http://www.patfosterguitars.com

Adding a side port raises the pitch of the 'Helmholtz' air resonance, and thus raises the 'main air' mode frequency (which is a somewhat different thing). Basically, the further the port is from the 'main' hole location the greater the pitch rise for a given size port. A small port by the tail block riases the 'main air' pitch a lot more than a large port just below the shoulder. Also, the larger the port in a given location, the greater the 'main air' pitch rise.

If you like the results you're getting now, with the 'main air' pitch where it usually comes out on your instruments, and you want to preserve that, then you will want to make your main soundhole a little smaller. I generally use a port about 1" in diameter, and reduce the main soundhole diameter by about 1/4" to 3/8".

Leaving the main hole the same size and adding a port will most likely give a more 'open' or 'forward' sound, with the possibility that the lowest bass notes will be a bit less 'full'. It's hard to say, though. We can measure what happens when you open a port, in terms of sound output and frequency response, for example, but it's hard to say what that 'sounds like'. Aside from all the problems of putting values on various subjective terms like 'tone', a port changes a lot of other things besides the 'main air' pitch, and you hear the result of al of them. We're still sorting this stuff out.

One of my students made a reso with the soundhole as part of an elaborate decorative scheme. I thought it might be to small, but he couldn't enlarge it without messing up the design. Sure enough, when he got it together, it was 'choked'. After a few experiments to figure out the best course of action, he ended up making a port in the upper bout, just above the wid part of the shoulder. He reinforced the inside, and cut the port with a handshaft, grinding away at it with the strings on the instrument. He kept enlarging it until it stoped sounding better and started to sound worse. Then he neatened up the hole a bity, and made up an insert to dress it up, and make it a little smaller. The end result sounded good, and looked as though he meant it.

I added sound ports on my 4th and 5th builds and love the sound, it is interesting to block and uncover the port thwhile someone is playing the difference in sound is quite noticable. The 1st one was just a round hole that I think I will retro fit to an oval shape, the round hole looks like a bird house entrance and I keep thinking it needs a little perch added so the bird can land before entering. I did an oval shape on the 2nd one and it looks much better.
I get a 3 Hz increase in the resonance frequency with the port open as compared to blocking it with masking tape.

Fred

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Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

Fred, when you say there is a noticeable sound difference are you referring just to the player or also the listener?

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Steve Smith
"Music is what feelings sound like"

People out front also hear the difference, it seems to me to be a brighter fuller tone, but my ears may be tricking me. To me it sounds better when it is open and everyone that has played it agrees. Seems to be worth the extra effort to add it.

By the way Steve I will be down your way in late August, maybe can get together an talk guitars.

Fred

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Fred Tellier
http://www.fetellierguitars.com
Facebook page http://www.facebook.com/pages/FE-Tellier-Guitars/163451547003866

To me as for playing it or to the lothers or to both. Are you saying that you hear the same change no matter if you are playing it or listening? I only played one with a port. And my first reaction was ," Wow, this sounds pretty loud.' And then I noticed it had a port and thought, "Oh that's why ."

That would be good. I should have this one strung up by then. I did the port because I remember how I used to like to play with my ear on the side of the upper bout sometimes just cause it sounded so good. I think something would break if I got into that position now

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Steve Smith
"Music is what feelings sound like"