F holes in archtop guitars

[Fra88]

Hi everybody,

i wanna ask you a technical question.
Do you think it's better to cover f-holes in archtop guitars(i have an ibanez Geroge Benson), to prevent any possible feedbacks while you're playing?

Has anyone of you already tested some of that?

Thank you for your possible reply.

[Jimmy blue note]

If you experience feedback, it could be the result of a number of things. Each of them can be addressed (or suppressed) in a different way. Often the most vulnerable system to feedback will be through the strings hearing the amplifier and giving the signal back to the top. That's why Hendrix could get a solid piece of wood to howl. Suppressing the strings is difficult because it's where you create the fundamental vibration.
The next system to "hear" a vibration and amplify it is the acoustic system. That involves the air inside the guitar, or the air resonance. One of the significant contributors to the acoustic guitar system is the internal air resonance, related to the helmholtz resonance. These waves connect or couple the top and the back and they contribute to the overall character of the acoustic sound especially in the lower frequencies. Once an air resonance is excited, it'll couple with the top and create a feedback system. The aperture, or opening, will act as a port to change the frequency of the internal resonance...so changing the size and shape and amounts of 'ports' will effect the air resonance. If you cut or block the F hole, you can change the amount that the internal standing waves can move the top. That's the idea.

In a GB10, they designed it so the top itself is more resistant to feedback by adding mass and stiffness to that element. It cuts the ability of the top to vibrate, which is why it doesn't "sing" the way a less massive top will. There are separate curves for air resonances and top resonances but any suppression in either or both systems will cut down on feedback. However, if the acoustic input (volume of the air out of the amp or PA) is great enough, it can overwhelm any system, even a Stratocaster in front of a stack of Marshall amps.

That, in short is what you're dealing with. Put the amp on the opposite side of your body and in small volumes, you can block the guitar from 'hearing'.
Try it out without blocking the holes first. You might find that with that guitar, it's resistant on its own design merits. YOu can also get an equalizer, and if you can isolate the resonant frequency that the guitar "sings with", you can notch out that one peak and keep it from howling.

That's the first line of defense. There are other systems of acoustical chaos, but start there.
Good luck.

It should be noted that contrary to the popular misconception, most of the sound doesn't come "out of the F holes" but rather from the top itself, but the top can be driven by the internal air modes. If you think of a speaker, the cone drives the air, not the port. Visualizing a guitar this way can help you understand the physics of your guitar.

[sgosnell]

The 'obvious solution' is to just don't play so loud. Lower volumes cause less feedback. But a guitarist can't always control the stage volume, and feedback can be caused by other instruments, not just the guitar. The bass especially can cause a guitar to feed back, as can horns and even other guitars. If putting the amp on your left side doesn't help, covering the f holes might, but there is no guarantee. A very responsive carved top archtop guitar can feed back very easily. Thus the 'obvious solution' becomes "don't use an archtop guitar for that situation". If it's that loud, you may need a semi-solid body or even a solid body. Tone doesn't matter a whole lot in those situations, so use whatever works. I just don't play in loud groups any more, because it's not worth the pain to me. YMMV.

[nevershouldhavesoldit]

Tone doesn't matter a whole lot in those situations

I respectfully disagree, as I think Jon Herrington, Jerry Cortez and others who tour with loud groups like ToP and Steely Dan would. It’s true that the contribution of guitar construction to tone is less important in loud settings. But no matter how you get it or what you do with it, tone matters a lot. Metheny played his 175 with some very loud groups but always sounds like Pat Metheny. I can’t imagine how bad it would have been if Robben Ford sounded like Hendrix when backing Joni at the huge venues in which Miles of Aisles tracks were recorded.

[Marinero]

So, a question to Jimmy Blue Note:
What do you believe is the sound difference between F-holes and a traditional sound hole a la Gibson Howard Roberts?
Marinero

[mickmac]

My GB has a polyester finish Tape over the F holes with vinyl tape problem solved mickmac

[sgosnell]

If you're getting feedback, your tone has gone to hell in a handbasket. Any nuances from a carved top are lost then. Better tone will be possible from a semi at that point. Use the proper tool for the job. At least that's my opinion.

[Woody Sound]

If you're getting feedback, your tone has gone to hell in a handbasket. Any nuances from a carved top are lost then. Better tone will be possible from a semi at that point. Use the proper tool for the job. At least that's my opinion.

I don't think an Ibanez GB has a carved top. ICBW.

[nevershouldhavesoldit]

If you're getting feedback, your tone has gone to hell in a handbasket. Any nuances from a carved top are lost then. Better tone will be possible from a semi at that point. Use the proper tool for the job. At least that's my opinion.

Lest we forget, there have been many great blues, rock, and funk guitarists who played big boxes and got great tone with hair! Here's just one example: Robben Ford with Jimmy Witherspoon -



And as for tone, whether loud or soft he sounded just like Robben Ford! Jump to 3:05 in the first one to head straight for the cream - maybe taking off the 'guard enhanced the tone by opening up the treble f-hole

PS: Does anybody have any idea what was under the treble foot of the bridge on that sharpie 400 in the first video??

[pingu]

Lest we forget, there have been many great blues, rock, and funk guitarists who played big boxes and got great tone with hair! Here's just one example: Robben Ford with Jimmy Witherspoon -



And as for tone, whether loud or soft he sounded just like Robben Ford! Jump to 3:05 in the first one to head straight for the cream - maybe taking off the 'guard enhanced the tone by opening up the treble f-hole

PS: Does anybody have any idea what was under the treble foot of the bridge on that sharpie 400 in the first video??

Thanks for posting these , they’re great !

in the second vid , it looks like masking tape
for holding the bridge feet in place
(although in the first vid it does look like
some tape is under the treble bridge foot
.... probably a work in progress i guess)

the S400 sounds incredible ....
he appears to play rhythm on both pickups and
switches to the neck pu for the solo in the first vid
the S400 sounds fabulous

[burchyk]

Should be able to get really loud before feedback on the laminate as long as the amp does not compress too much. Solid state is great for this. Keeping the bass low also helps.

[Cunamara]

In that first picture of Robben Ford with the L5, it looks like the guitar is stuffed a la Pat Martino; that was Martino's solution for eliminating feedback with a hollowbody guitar in an organ trio. He stuffed it full of yards of upholstery material til it was essentially a solidbody. Or perhaps taped with the tape on the inside of the F-holes.

In the videos, however, the guitar (S400?) is clearly not stuffed. It looks like electrical tape holding down the bridge base so that it wouldn't move out of intonation while being played.

And those videos are perhaps proof that what guitar you play doesn't really make that much difference when it comes to electrified sound, something George Van Eps reported having tested in the early days of electric guitars. Robben Ford sounds like Robben Ford no matter what instrument and amp he's using.

Johnny Smith was of the opinion that bass frequencies are the culprit in driving feedback in hollowbody guitars. He did not like the Fender-type tone stack with its accentuated bass/treble and scooped mids; he wanted an amp with a flat tonal response across the spectrum and had one made by Gibson and then by EMRAD in Colorado, although they didn't really catch on in the marketplace (Johnny thought there weren't enough knobs for the rock 'n' rollers).

[rpjazzguitar]

Some players seem to do just fine with full size archtops. Wes comes to mind as an example.

But, I always got feedback when I tried it so I stopped playing archtops. Too bad, too, because I think they can sound great. I tried to control it with positioning but could not. Stuffing the body with foam deadened the acoustic sound on one guitar and didn't affect the amplified tone tht much. But, it seems like a waste to buy an acoustic and then stuff it.

And, the cheapest solid body sounds better than an archtop which is feeding back at the time.

[Jimmy blue note]

PS: Does anybody have any idea what was under the treble foot of the bridge on that sharpie 400 in the first video??

When you're on the road, quick string set changes are a part of life. On an archtop with a floating bridge, securing the foot of the bridge in the right location keeps the guitar in tune-the intonation true-while you slap on fresh strings.

[nevershouldhavesoldit]

When you're on the road, quick string set changes are a part of life. On an archtop with a floating bridge, securing the foot of the bridge in the right location keeps the guitar in tune-the intonation true-while you slap on fresh strings.

I just change 3 at a time. If I needed to remove all of them at once, I put a piece of low tack masking tape over each end of the bridge to hold it. And that tape strip (or whatever it is) on RF’s S400 looks to me like it’s under the bridge foot.

[JohanAbrandt]

I just change 3 at a time. If I needed to remove all of them at once, I put a piece of low tack masking tape over each end of the bridge to hold it. And that tape strip (or whatever it is) on RF’s S400 looks to me like it’s under the bridge foot.

I change 1 at a time, is there any benefit in changing more at a time?

[lammie200]

I have a pedal that dials out any feedback without affecting the frequencies that don't cause it. I forget what it's called but there are several on the market to choose from. It works for me.

[sgosnell]

I change 1 at a time, is there any benefit in changing more at a time?

I occasionally remove all the strings at once, in order to clean the fretboard or do other work. Sometimes the board and the frets need cleaning and buffing. I use low-tack tape parallel to and up against the bridge to mark the position, and then remove the bridge. I don't want it in place for lots of things, and for several reasons. I just take it off. Replacing one string at a time is perfectly acceptable, and I do it often, but sometimes I want all the strings off.

[Gregc57]

Ted Nugent always used a big box guitar ('62 Byrdland?'), no?; and no one plays louder than Ted!
Ted Nugent’s 1962 Gibson Byrdland | Vintage Guitar® magazine

[icr]

When I read 'loud archtop' I think Eric Gale (not Gales!). Tasteful overdriven L5.

[rpjazzguitar]

Ted Nugent always used a big box guitar ('62 Byrdland?'), no?; and no one plays louder than Ted!
Ted Nugent’s 1962 Gibson Byrdland | Vintage Guitar® magazine

Ted used the feedback as part of his music. I read that he had the stage mapped out in his mind, so he knew where to stand to get the feedback he wanted.

[tbeltrans]

I have a pedal that dials out any feedback without affecting the frequencies that don't cause it. I forget what it's called but there are several on the market to choose from. It works for me.

Mine is the Empress Para-EQ, but I am not sure if these are made anymore.

Tony

[tbeltrans]

I would be afraid to put any kind of tape on the F holes on my Gibson Citation, but I seem to remember years ago there was a guy around here who made some kind of rubbery thing custom for your F holes that just plugged into them. As I recall, you sent him an outline of your F holes and then he sent you the pieces. Maybe somebody still does that?

Tony

[nevershouldhavesoldit]

I would be afraid to put any kind of tape on the F holes on my Gibson Citation, but I seem to remember years ago there was a guy around here who made some kind of rubbery thing custom for your F holes that just plugged into them. As I recall, you sent him an outline of your F holes and then he sent you the pieces. Maybe somebody still does that?

Tony

"Doug's Plugs", which are sadly no longer available. Here's the most recent thread.

[tbeltrans]

"Doug's Plugs", which are sadly no longer available. Here's the most recent thread.

Yes! That was it. Thanks for remembering.

Tony