Ported upper bout....?

[jaymarsch]

I posted earlier in this thread and have enjoyed following the discussion. I have little knowledge about all of the science behind sound ports but know that I love the most recent guitar that I received with one. This port is about an inch by about three inches and it is Sparky Kramer's standard port design.



I really appreciate the discourse here as it is fascinating how tone can be shaped and shifted by each luthier for a desired affect.

Best,
Jayne

[surveyor]

I'm a "hobby shop" builder and though I've not studied Helmholtz frequencies and resonance physics, I just like the way they look and being older, I appreciate being able to hear myself playing for a change.

<a href="https://imgur.com/xPoT7le"><img src="https://i.imgur.com/xPoT7le.jpg" title="source: imgur.com" /></a>

[surveyor]

I was trying to include a pic, must have copied the wrong code

[Guitars44me]

This has been a very informative thread. Three cheers for the Custom Shop crowd!!!

I have some midrange loss in my left ear from my years as a drummer. (But from the guitar amps placed adjacent my hi-hat, NOT the drums)

The best place for my side ports has been on the upper shoulder where it is close to my left ear. My right ear is obviously closer to the main portion of the top, so it needs no help. (I hope).

I am contemplating removing the ES 1.3 from my custom RT2c, and perhaps enlarging the three knob holes a tad. I prefer my K&Ks in all my other guitars and don't want to mess with the batteries any more...

Not to hi jack but anyone have experience with something like this?

And Todd, do you add any side wall reinforcement before the ports go in?

Cheers and play pretty

Paul

[jaymarsch]

Originally Posted by surveyor

I was trying to include a pic, must have copied the wrong code

Nice. If you build a third with the port in the shape of Arkansas, you'll have the Texarkana Trio! I completely agree about the benefits of ports and aging ears!

Best,
Jayne

[fitness1]

Originally Posted by Guitars44me

And Todd, do you add any side wall reinforcement before the ports go in?

No sir - the only power tool I use for the small ports is the tiny Dremel bit for a starter hole - everything else is carefully done with a reamer or sanding. If the guitar is Nitro, it can chip easily with the reamer so you have to be extra careful!

[Alan Carruth]

My first 'port' experiment, the 'corker', used 5/8" holes, iirc, in pairs, and there were ten pairs along the entire bass side of the box. I got lots of data about what happened when you removed the corks from any pair of holes. I had that guitar at H-burg, but don't remember which one (it was at the Santa Rosa Civic Center, if that helps).

The main difference out in front when you open up a port is the change in the pitch of the main air resonance: it rises. The effect actually encompasses the whole 'bass reflex' range of the guitar, all the way up through the 'main top' resonance an octave higher and a bit more. It's as if the whole spectrum was tilted a bit to the left: the 'main air' peak gets relatively a lot higher, and the main top peak also gets a bit taller. The larger the port, and the further it is from the main hole, the greater the effect. A port of a given size in either end block does a lot more than one at the waist, and the tail block one more than the neck end. You don't often see ports at the tail end because they make lousy monitors, but they can change the sound out in front a lot.

If you sum over the power in the whole spectrum it does not appear that opening a port makes any difference. That increase in the low range seems to be balanced off by a small shift downward at higher frequencies. OTOH, a port can also 'listen to' internal resonances in the box that don't normally produce sound, and thus create peaks in the high frequency output where there were none, or even dips, before. In other words, opening a port doesn't necessarily make the guitar more efficient, it just makes it sound different, or project that sound in a different way.

Guitars are complex beasties.

[jaymarsch]

Originally Posted by Alan Carruth

Guitars are complex beasties.

This, alone, should be a sticky!

Best,
Jayne

[Tim McKnight]

Originally Posted by runamuck

I don't know this from my own experience but have read that, as a general rule and to some extent, reducing the soundhole diameter increases low frequency response.

If that's true, does adding a sound port decrease bass response?
If not, why?

That is exactly why I reduce the main sound hole diameter when installing a side sound port, to negate the loss to of bass response. Although there are other ways to bolster lost bass response, during the build process.

[Guitars44me]

Originally Posted by Tim McKnight

That is exactly why I reduce the main sound hole diameter when installing a side sound port, to negate the loss to of bass response. Although there are other ways to bolster lost bass response, during the build process.

I am not sure what John Kinnaird has been doing on my Customs but there is PLENTY OF BASS, although well balanced, even tuned down, and sizable ports in the upper shoulders.

Cheers

Paul

[Nama Ensou]

Originally Posted by fitness1

No sir - the only power tool I use for the small ports is the tiny Dremel bit for a starter hole - everything else is carefully done with a reamer or sanding. If the guitar is Nitro, it can chip easily with the reamer so you have to be extra careful!

Really feeling tempted to do this!

[fetellier]

I do ports on most of my guitars, at first I did it basically free hand with dremel and round sanding sticks but now use this routing jig. The photo shows a dremel but now I use a palm router and a small pattern bit I purchased from stewmac.




URL=https://s190.photobucket.com/user/fetellier/media/Fan%20fret%202018/IMG_2007.jpg.html][/URL]



Fred

[jaymarsch]

Originally Posted by Guitars44me

I am not sure what John Kinnaird has been doing on my Customs but there is PLENTY OF BASS, although well balanced, even tuned down, and sizable ports in the upper shoulders.

Cheers

Paul

My Kramer has plenty of bass and balance as well. I imagine that each luthier who build in sound ports to their regular designs have figured out how to balance yet another set of variables to get the result that they are seeking, depending on the customer.

Best,
Jayne

[iim7V7IM7]

As Tim mentioned, the sound hole is in many cases reduced in size to compensate for the additional surface area provided by the sound port to avoid altering the helmholz resonance of the body. Additionally, aside from being functional, they can be artistic accents as well...

Here are some examples from some of my instruments: Gypsy Grand Bouche by Bernie Lehmann (top left); 000/OM by Howard Klepper (top right); Classical with two sound ports by Peter Oberg (middle right); 0-12 by Bruce Sexauer (bottom left) and Nylon Hybrid by John Buscarino (bottom right).

[redir]

Originally Posted by Alan Carruth

My first 'port' experiment, the 'corker', used 5/8" holes, iirc, in pairs, and there were ten pairs along the entire bass side of the box. I got lots of data about what happened when you removed the corks from any pair of holes. I had that guitar at H-burg, but don't remember which one (it was at the Santa Rosa Civic Center, if that helps).

The main difference out in front when you open up a port is the change in the pitch of the main air resonance: it rises. The effect actually encompasses the whole 'bass reflex' range of the guitar, all the way up through the 'main top' resonance an octave higher and a bit more. It's as if the whole spectrum was tilted a bit to the left: the 'main air' peak gets relatively a lot higher, and the main top peak also gets a bit taller. The larger the port, and the further it is from the main hole, the greater the effect. A port of a given size in either end block does a lot more than one at the waist, and the tail block one more than the neck end. You don't often see ports at the tail end because they make lousy monitors, but they can change the sound out in front a lot.

If you sum over the power in the whole spectrum it does not appear that opening a port makes any difference. That increase in the low range seems to be balanced off by a small shift downward at higher frequencies. OTOH, a port can also 'listen to' internal resonances in the box that don't normally produce sound, and thus create peaks in the high frequency output where there were none, or even dips, before. In other words, opening a port doesn't necessarily make the guitar more efficient, it just makes it sound different, or project that sound in a different way.

Guitars are complex beasties.

Does the audience hear that or just the player?