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Does a port as shown in the photo allow the guitarist to hear the music better?
Does the sound port change the sound for those who are out in front of the guitar?
Thank you.
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03-14-2021 11:10 PM
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Good topic; I've been wondering about this as well. I think this is more an acoustic thing; when playing electric, pointing the cab upwards makes a big difference - for the player, the band and the audience.
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It does really help the player hear the acoustic sound of the instrument much more. It's also a good place to use a small condenser mic as it gives a nice overall sample of the sound. It doesn't seem to effect the amplitude of the sound projected forward, which means strangely enough, anyone out front can't tell.
When these first appeared, I was incredulous, but after making a lot of subjective listening and objective tests on SPLs and glitter chladni pattern frequency spectral analysis it does turn out that the guitar really doesn't change in any perceptible way. Even the helmholtz air resonance, which changes a lot with the aperture of any soundholes in the top plate, doesn't seem to change with the introduction of side ports.
Carleen Hutchens was a violin builder who devoted her life to lutherie and acoustical research did a notable experiment with a violin she'd built for this purpose. A violin was built with ribs (sides) riddled with holes of different sizes in different locations. Matching each hole was a small cork that effectively sealed the air.
Corks were removed and replaced in all combinations with no discernible effect in sound or loudness. Except for a change in the very top and bottom (neck block and end block) where the long horizontal standing "bathtub mode" is most effected, it really didn't effect the vibration of the top, back or amount of air that those plates moved.
So, in my opinion, no, it doesn't effect the guitar in a detrimental way, but it does let the player hear the guitar much better.
My two cents.
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Just some quotes from Alan Carruth (found here and there, and on my waste- and notebooks). Btw., long-time fan here of Alan's deep acoustic knowledge and generous sharing ...
- Opening a port causes the 'main air' pitch to rise, and the overall output at the 'main air' frequency to increase. [...]
Overall, then, it seems that a side port does change the sound of the guitar in a way that's far more useful to the player than the listener. I tend to feel that it would be most useful for somebody who plays a lot of 'restaurant gigs': more or less large and 'dead' spaces where there is some background noise, where you're not likely to get high frequency feedback from room reflections. If you mostly play in livelier or smaller spaces, a port may not be as much help.
- I do make guitars with ports, by the way. They have their uses, and can be worthwhile. I just don't think they're miraculous.
- Microsoft Word - sidePorts.doc (alcarruthluthier.com)
- Do you like side sound port on your guitar(s)? Wow - I played a Tim Mcknight guitar! - The Acoustic Guitar Forum
- Which tones do you hear from your soundport?? - The Acoustic Guitar Forum
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I worked with Al, he's a good friend and one of the greatest resources of acoustical knowledge that ever lived. We had many discussions on side ports and he'd had several intriguing experiments he was working on concerning upper bout ports, his shop was as much an experimental lab as well as a place where amazing instruments came into being.
Originally Posted by Ol' Fret
It was always fun. I went to MIT, studied acoustics and each time we'd come up with some speculative question about why something works a certain way, we'd get into lively conjectures. Then the next time I saw him he'd have unbelievable test results and instruments he'd built in part or in total to prove or disprove a theory. He's a gifted engineer and a wizard of a luthier.
And yes, he was the one who had that violin, and a guitar with various ported variable aperture openings in the sides which he built so he could have an authoritative opinion. Then if he was lucky he'd put his findings into a paper he'd submit to the GAL or CAS or some other journaled publication.
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I have sound ports installed in three of my acoustic guitars. I noticed no difference when sitting in front of the guitar when someone else played them. However, as a player I do notice the difference and others who have stood behind me or played the guitars also noticed a difference. I did notice that in spaces where there is a lot of reflective surfaces the port is not has effective or noticeable. I attribute that to the reflection of sound coming back to the player and washing out the small volume from the sound port. In a dead area or larger space the improvement to the player is noticeable. IMO, the audience couldn't tell or wouldn't care about the difference.
That said, if I was to have another guitar built, I would have a sound port installed. Mind you the port should be sized to work in harmony with the other openings in the body.
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And how about once plugged in? Does it basically become Moot?
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Yes. Once the sound from the amp approaches the volume I hear, I don't hear the port anymore. My mind just kind of makes it invisible, or inaudible. Originally Posted by jads57
There are some guitars that are built with a sliding door to adjust the aperture. I haven't done nor tried this but it seems a cool idea.
The pickup knows nothing of what's going on with the port so the signal going to the amp is as if there were no port. Business as usual.
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I think they are very helpful for an acoustic archtop, and have put them in a dozen guitars. Alan is a great source of knowledge about guitars, and once built a guitar with dozens of ports plugged with wine corks. He opened them up one at a time to try to measure the difference.
I asked him what his ultimate takeaway was. He said a relatively small port (<2” diameter) really didn’t affect the tone much but gave the player something of a monitor effect. This is especially helpful for archtops that are more unidirectional than flat tops. I’ve added a 1.5”x2” oval port in my acoustic archtop builds ever since.
Sent from my iPhone using Tapatalk Pro
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So, the OP's question could be answered - with considerable restrictions:
1. Yes, at least with certain guitars.
2. Very likely: no. It could even be that the overall projection of a guitar with additional side sound port(s) towards the audience in front of the guitar would be decreased.
Of course, all of this is a bit moot, since the vast majority of us will play amplified.
It must be great to learn directly from Alan Carruth - wish he would be making (and selling) more archtop guitars!
My own experiences are absolutely modest and anecdotal. 500 years of violin or cello making, and purely acoustic performance practice, saw no advantage in adding a sound port. If you wanted the 'main air' pitch to rise, you chose a slightly smaller body (such as Guarneri), or larger sound holes, etc.
Of course, the archtop guitar is a completely independent instrument, but general acoustic considerations can be transferred from violin making experience.
To support the answers, again some notes from Alan Carruth:
- The effect of the port will vary depending on what the guitar sounds like in the first place. [...] Whether the change is an improvement is another matter. If the guitar starts out with a 'main air' resonance that's a bit on the low pitched and weak side then opening a port will almost certainly help. If the 'air' pitch is high, it could be a detriment.
[Well, in most cases the 'main air' resonance of archtop guitars is higher anyway than of comparably sized flat-tops, so opening a hole could be needless.]
- Blind listening tests of player response have come up with mixed results. R.M. Motolla did a small study, using my first port 'test mule', and found that players could not hear the difference. However, his tests were done in quiet, reverberent spaces, where you might expect room reflections to provide good feedback. I did a rather larger study at the last two Montreal shows, a folk festival and a GAL convention, to see whether the port made a difference in a noisy room. The spaces ranged from the usual 'dead' hotel ballroom to more 'live', but in every case there was about 72 dB-A of background noise, which proved to be 'white' noise. Basically, in those circumstances, when the port was not changed the players were guessing as to whether it had been or not, but when it was changed they got it right almost every time. Listeners in front seldom seem to hear the effect.
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I think it depends on the guitar and how you're using it. I had a laminated Holst with a port, but it was mainly an electric guitar that I always played plugged in. The difference was minimal, although it was useful for spurring conversation. I think on a solid wood guitar with more of an acoustical voice it would probably make some difference to the player when not plugged in. I doubt there's much difference to the listener.
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I bought a "Raines" with the upper sound hole, the effect was stunning. Alas the seller did not reveal the many top, side and back cracks that were "stabilized" and I returned it. Since then I've looked for others but they are few and far between... no luck so far.
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Of the three guitars I mentioned above, all are flattops and of the three two are nylon strings. As far as an amplified archtop goes, I would not bother with a sound port. I don't play any of my archtops as a pure acoustic. In my unscientific test I asked my 93 year old (at the time) Mom to stand directly behind me with her back to me while I played my Flamenco with the port closed and open. She noticed the change every time but we were in my great room which is pretty dead sound wise. I took the same guitar into my bathroom which is fairly large as far as bathrooms go with tile floors, glass, stone countertops etc and I/we couldn't hear really any difference between the open and closed port.
Of course this topic gets a lot of discussion on the acoustic forums. A large majority of the folks opposed to a port generally never owned a guitar with one or played one for any length of time. But on that forum, they argue incessantly about cutaways, multiscales, Martin vs Taylor etc.
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With acoustic archtop guitars, a side soundhole port makes a huge difference to what the player hears.
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I agree! Great improvement from the player’s perspective. It’s not a subtle difference.
Last edited by Gilpy; 03-16-2021 at 03:46 PM.
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Absolutely and positively. Originally Posted by Hammertone
Almost all of my archtops are carved acoustics. Almost all have sound ports. When you cover the port with your hand it's like someone suddenly turned down the volume and turned the EQ off. Don't know how much difference it makes on a laminate. But even primarily electric archtops get played acoustically fairly often.
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As usual I've received detailed answers from you all, an I thank you all for them!
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I think I've played that exact guitar! The sound port definitely helped combat some of the NAMM floor cacophony....
PK
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My Bill Comins hollow laminate archtop (with no f-holes) has a sound port which makes a huge difference to the overall acoustic response for the player ...
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Originally Posted by mrichman
My Bill Comins hollow laminate archtop (with no f-holes) has a sound port which makes a huge difference to the overall acoustic response for the player ...
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Beautiful ! Originally Posted by mrichman
My Bill Comins hollow laminate archtop (with no f-holes) has a sound port which makes a huge difference to the overall acoustic response for the player ...
I`m curious because I have a 15" Koll carved archtop with no f-holes.
The advantage is to reduce feedback. Do you think the port re introduces feedback into the box (as compored to a sealed box)?
I wonder what qualities the side port vs the top f-holes present in terms pf feedback rejection. Thoughts? thanks
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I don't think the side port adds to the possibilities of more feedback than without, especilly on a laminate. I can turn this Comins up as loud as I want and there is no hint of feedback at all. Maybe a deeper body would be different, but this guitar is only 2" deep.
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Top feedback is not because of the F holes as much as it is the top moving in sympathy with the sound projected from the amp. Common misconception is that sound is made through music escaping out the sound holes. It's actually the top, like a speaker diaphram that you're hearing. Originally Posted by WahmBomAh
In your case, the F hole-less top doesn't hear any interaction with the resonant air modes so it does attenuate the feedback signal. But what the air "hears" through a side port is a VERY small contribution.
It's about where the moving air is coming from and what hears it:
Top vibrates. It moves air. You hear it. Acoustic sound.
Pickup hears a string. Amp hears an electronic signal. It moves a speaker. You hear it. Electric sound.
Pickup hears a string. Amp hears the signal and moves a speaker. The TOP hears it and the pickup hears the top moving. Feedback loop.
The sound port is on a relatively rigid portion of the guitar, the ribs. There's not much that moves there. And there's not much connection to the vibrations of the top, and in fact it anchors the top where the top moves against the non moving ribs.
The air modes don't effect the sides. You hear the air but the sides don't move. Negligible contribution to the feedback loop.
If you're concerned about feedback, the amp amplitude would have to be pretty high to initiate that, much higher than the signal coming from a port. If you're high enough to even hint at feedback, you're certainly way above what's coming out of the port. A port covering, sliding door, foam plug, duct tape (non residual painter's tape) or a piece of Post-It even, would make the port irrelevant. But honestly, unless you're doing a Jimi in front of a stack of Marshalls, my opinion is it's not going to be an issue.
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The slim hollow Comins is very beautiful! Thanks for exhibiting it! I'm learning useful details from your posts friends!
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Thanks so much....A pleasure to benefit from this breakdown. You`ve obviously put a lot of thought and time into this while I`m here scratching my head. Originally Posted by Jimmy blue note
A follow up if I may.
Understood on your explication thanks ..SO ... About what the pickups hears from the box;
Do you think the end product in the chain would be affected by the side port?
I mean ... Given we start with the same guitar with and without the side port...
Will the harmonic structure be changed in the electronic chain ...or would it be only in an unplugged setting that we hear the side port?
I would go with the assumption that whatever comes out of the box ...ends up amplified at the end but I`m curious as to what you think.
When commissioning my Koll,I spoke to Saul about a possible side port. Do you think my guitar would sound more "open" ..less "nasal" through the amp if there was a side port in there?
thanks !
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