Adding a sound port to an acoustic guitar

[fitness1]

Originally Posted by RJVB

That's how I interpreted the suggestions above for using a CO2 canister or vacuumcleaner tube with sand paper on it. Drill a starter hole, and then work the make-shift tool held parallel to the side wall (at the point of the hole) and to the guitar's centre line. That would grow the drill hole to something oval.
Glad I asked

So those make-shift tools are used in the beveling step?

It all depends on your method, which is sometimes dictated by placement, the finish on the guitar and availability of tools, etc.

Larry said 'you don't sand through' but you certainly can. I've ported a couple dozen guitars now and the only power tool I used was the dremel for a starter hole, and even that isn't required if you use the tube method for a single port in the upper bout.

The reamer/C02 cartridge method comes into play when you are making small holes.

[RJVB]

Thanks. I had not realised that Tim is a professional builder and that might have taken down the instructions deliberately.

My remarks remains valid but not any more than his decision about sharing or not.

I guess this can be shared though:
http://www.mcknightguitars.com/sound-ports/

There's some data on that page showing how overal the sound volume increases (though apparently hardly if at all at a longer distance).
I guess this shows that "there's more sound in the box" than can come out of the front sound hole, and that the additional sound from the sound ports benefits not only the player but everyone close by.

[Birdbrain]

Originally Posted by Willie_D

I think I'll leave mine as is.

Funny, because I was about to do this to my cheapest Seagull, using a circle saw. If it'll drill a doorknob through a door, it out to work on a about. I've seen a UTube video endorsing this tool. But I won't use a concrete bit.

[Dr Tone Control]

Originally Posted by Alan Carruth

Dr Tone Control:
There's a .pdf on my web site, on the 'Acoustics' page, on side ports. It's old (as is everything on the site!) but has a lot of the data.

hi Alan the pdf is fascinating

A quick question: I tried a small guitar today with a port, and for my playing, the port added too much of the frequencies around the 6th and 7th fret on the middle 2 strings. How can that sort of thing be prevented from happening?

Cheers
Tone

[Alan Carruth]

There are two ways to alter the sound balance coming out of the port; change the size and change the location.

There are a lot of different internal air resonances that the port can 'hear', and project sound from, and they tend to be more active in different spots. The exact pitches will vary from one guitar to the next, and opening a port changes the pitches: in short, there's no way I can say just what's going on in your guitar via e-mail. Enlarging the port might help, or it might not.

It might have worked out better if the port had been in a different place, but once you've drilled a hole in the side you're stuck with that. Basically, again, the closer the port is to the main hole, and the smaller it is, the more the sound coming out of it will be like the sound coming out of the main hole. You might still not like that if it's too much in your face, though.

One of my students decided he needed a port on the reso he'd made. He used a burr on a hand shaft ( you could do he same with a Dremel) to cut a small hole where it seemed that it might work, and got an improvement. He kept enlarging the hole until the sound started to get worse, and then made a decorative rim for it. This reduced the size just enough to get it back into the 'sweet spot'.

Not everybody likes the way a ported guitar sounds; you may be one of the ones who doesn't.

[Neil K Walk]

I'm on my way out the door so I've got to follow up on the links, but Tim inspired me to try building and I often afflict my flawed imitations to his craft upon him every June at the McJam. I just closed the box on a build and intend to put a soundport on it. I think I'll save Tim the headache and do it myself lol!

That being said, I glued a veneer inside the upper bout where I want to put it. I don't want there to be any chance of creating a key crack. Other than that, I was thinking that I would use a drill with a 1/4" brad bit and then flesh it out with a Dremel.

[RJVB]

Originally Posted by Alan Carruth

One of my students decided he needed a port on the reso he'd made. He used a burr on a hand shaft ( you could do he same with a Dremel) to cut a small hole where it seemed that it might work, and got an improvement. He kept enlarging the hole until the sound started to get worse, and then made a decorative rim for it. This reduced the size just enough to get it back into the 'sweet spot'.

Seems like the clever way to go about it. I've never seen a soundport on a reso though; if mine is any indication I can imagine they'd quickly become too loud.

[Alan Carruth]

The problem on that reso was that it was 'choked' to begin with. The builder had incorporated an elaborate inlay as part of the design, and the area he'd left for the sound hole was very small. I had told him when he began that I thought it would be inadequate, and it was. Since he could not enlarge the hole without compromising his design he opted for a port. In the end it worked out well.

[RJVB]

I'm guessing then that it was not a spider bridge design? From what I understand those send most of their sound straight out. Even the other types must output a considerable amount via the cover plate (I did always wonder how sonically transparent a thin aluminium cone is).

Unless it was a design akin to this exotic beauty?

(Paul Beard custom A-model)

[redir]

I put a port in one of my personal steel string guitars and it made the guitar worse. So I guess I'm one of those that don't like it. having said that, I put them in classical guitars and I think they make a much improved difference there.

Also, FWIW I wanted to try just to see so I used a regular old 1.5in hole saw. The kind that you chuck up in a drill and it worked like a charm. I'm not saying you should do that, but I am saying that it works.