Dealing with archtop feedback

[jzucker]

Minutes before I would have smashed my Godin Multiac Nylon (which was acoustically about as loud as many full bodies) I bought upholstery foam. Well, it was foam sold by an upholstery shop -- I can't identify it beyond that.

I stuffed the body of the guitar to the gills with it.

Acoustically, it became dull and muted. Electrically, it wasn't much different than before. Feedback was absolutely gone.

Guitar was noticeably heavier. This Godin has only a few small circular openings (near the electronics). I had already taped them with no noticeable effect.

I'd try the Doug's Plugs type solution first. Or the one about blowing up ordinary party balloons inside the guitar (anybody tried that?).

Where / how did you stuff it?

[Spook410]

This is an everyday problem in the world of flat top guitars. The solution is simple and universal: a notch filter to dial out the resonant frequency.

[Oscar67]

This is an everyday problem in the world of flat top guitars. The solution is simple and universal: a notch filter to dial out the resonant frequency.

I’ve seen Tommy Emmanuel do a show at close to 100dB. He was ridiculously loud. Never went to see him again after that. Anyway, in addition to notch filters, acoustic players like Tommy tend to combine an internal condenser mic with a piezo bridge pickup and a sound-hole plug. Not common in jazz.

In a jazz environment, I’ve seen Martijn van Iterson tilt his Fender Hotrod combo all the way back to an angle of about 30 degrees to the floor, sitting on a barstool right in front of it and turning it way up to be heard over the din of an 18-piece bigband. No feedback from his old 125, not even when soloing (and he was really loud then). Yet I’ve seen others struggle with feedback at levels that were a mere fraction of the volume Martijn plays at. Feedback is an elusive beast. I think it a lot has to do with with the EQ settings on the amp, the settings of the guitar’s volume and tone controls and how the resulting sound from the amp correlates to the frequencies at which a certain guitar feeds back. Perhaps I can put it in simpler terms: a different player might twiddle knobs to get his/her preferred sound from the same guitar and amp and might not get feedback. If you can’t get your sound at the required volume without feedback, then short of stuffing your guitar or turning down, a parametric EQ is pretty much the only way to go.

[rpjazzguitar]

Where / how did you stuff it?

The Godin has two access panels on the back. A small one for the electronics and a bigger one accessing the body. I can't recall if I bothered stuffing the smaller one -- I might have been reluctant out of concern that I might damage the electronics. But, I stuffed the larger one to the brim. Probably overkill.

[jzucker]

I’ve seen Tommy Emmanuel do a show at close to 100dB. He was ridiculously loud. Never went to see him again after that. Anyway, in addition to notch filters, acoustic players like Tommy tend to combine an internal condenser mic with a piezo bridge pickup and a sound-hole plug. Not common in jazz.

In a jazz environment, I’ve seen Martijn van Iterson tilt his Fender Hotrod combo all the way back to an angle of about 30 degrees to the floor, sitting on a barstool right in front of it and turning it way up to be heard over the din of an 18-piece bigband. No feedback from his old 125, not even when soloing (and he was really loud then). Yet I’ve seen others struggle with feedback at levels that were a mere fraction of the volume Martijn plays at. Feedback is an elusive beast. I think it a lot has to do with with the EQ settings on the amp, the settings of the guitar’s volume and tone controls and how the resulting sound from the amp correlates to the frequencies at which a certain guitar feeds back. Perhaps I can put it in simpler terms: a different player might twiddle knobs to get his/her preferred sound from the same guitar and amp and might not get feedback. If you can’t get your sound at the required volume without feedback, then short of stuffing your guitar or turning down, a parametric EQ is pretty much the only way to go.

It's often other instruments generating sound waves that cause the top of the guitar to vibrate. This is why putting the amp behind you and to your left is not a complete solution.

[AllanAllen]

I didn't reply to your previous (similar) comment here but I'm EXTREMELY proficient at muting strings. I mute strings with the left hand and I rest the heel of my right hand - just-north - of the bridge because I like the percussive quality it lends to the tone. My muting technique is such that I often employ a little trick where I strum single notes with the right hand and mute all but 1 note in the left hand, hitting 4-6 strings and only the single note I am not muting comes through. This is similar to what freddie green did and also what funk/R&B guitarists do with left hand muting...

When playing loud, that does NOT inhibit the feedback. I can have all 6 strings totally muted but if the drummer (or keyboard, monitors, etc) are loud, the sound-waves vibrate the top of the guitar and that induces feedback. The entire top of the guitar essentially becomes a microphone.

Pat Martino didn't casually make the decision to put 5lbs of upholstery cotton into his L5. He certainly knew how to mute strings. So does george benson who uses packing tape.

Feedback is not just from open strings either. Many instruments have sympathetic vibration from resonant frequencies and if you sustain a chord or certain notes, they will feedback. I don't want to mute the strings of a note I'm trying to sustain.

Tape, cotton, plugs all work very well but have varying degrees of effect on the tone of the instrument.

Luckily it works for me. But I'm now willing to accept it's a problem for some people. I didn't mean to put you down, or imply I didn't believe you.

[sgosnell]

Every guitar has a different resonant frequency. One might howl uncontrollably in a given situation, while another doesn't feed back much at all. Changing guitars isn't the most inviting solution, but it can sometimes work.

[wintermoon]

Luckily it works for me. But I'm now willing to accept it's a problem for some people. I didn't mean to put you down, or imply I didn't believe you.

you're probably not playing in that high a volume situation. think loud. really loud. I've seen a couple of your videos w/ a trumpet, bassist and drummer. try playing w/ a hard hitting drummer and a cranked Hammond B-3 w/ a Leslie next to you on a cramped stage.
w/out some kind of equalizer it's pretty much impossible and like Jack I've pretty much mastered the art of palming fwiw, but it just won't work all the time.

[AllanAllen]

you're probably not playing in that high a volume situation. think loud. really loud. I've seen a couple of your videos w/ a trumpet, bassist and drummer. try playing w/ a hard hitting drummer and a cranked Hammond B-3 w/ a Leslie next to you on a cramped stage.
w/out some kind of equalizer it's pretty much impossible and like Jack I've pretty much mastered the art of palming fwiw, but it just won't work all the time.

I used archtops in garage rock bands way before I thought of playing jazz. 2 guitars, drums, bass, Rhodes doing Who covers. It’s why I’m so adamant you can use your hand.

[Alter]

I have an L5 copy by Carl Mesrobian, in which I had a single soundpost installed, a single straw of wood somewhere towards the middle of the guitar connecting and muting the top and back. It made the sound a lot more percussive and middy, less open, but improved feedback handling a lot.

After many years and both failures and successes of using archtops at gigs, I tend to favor laminate and smaller ones. Gibson archtops are one class higher than anyone else at fighting feedback, but still..

[SierraTango]

I have an L5 copy by Carl Mesrobian, in which I had a single soundpost installed, a single straw of wood somewhere towards the middle of the guitar connecting and muting the top and back. It made the sound a lot more percussive and middy, less open, but improved feedback handling a lot.

After many years and both failures and successes of using archtops at gigs, I tend to favor laminate and smaller ones. Gibson archtops are one class higher than anyone else at fighting feedback, but still..

Back on post #14 of this thread, I noted the soundpost idea, and it didn't seem to get much traction. Everybody would rather stuff foam in the guitar or plug up the soundholes with flip flop material.
Call me crazy, however it seemed to work for Mundell Lowe, who was a notorious tinkerer. I played his Mapson at Jim's shop through a Twin at
at loud levels with no feedback-a 17' all carved archtop. It was almost totally dead acoustically though.
Plus, it's a reversible mod.

[Jim Soloway]

I used archtops in garage rock bands way before I thought of playing jazz. 2 guitars, drums, bass, Rhodes doing Who covers. It’s why I’m so adamant you can use your hand.

I think you probably can if you're willing to work hard at it but you are then letting the threat of feedback determine your playing style. Just my opinion. but that's not a trade off I'd be willing to accept.

[jzucker]

Back on post #14 of this thread, I noted the soundpost idea, and it didn't seem to get much traction. Everybody would rather stuff foam in the guitar or plug up the soundholes with flip flop material.
Call me crazy, however it seemed to work for Mundell Lowe, who was a notorious tinkerer. I played his Mapson at Jim's shop through a Twin at
at loud levels with no feedback-a 17' all carved archtop. It was almost totally dead acoustically though.
Plus, it's a reversible mod.

that's because the sound post changes the tone more than tape or f hole plugs. And it's not easy to get in and out without damaging and potentially cracking the top. I've used a sound post before and it worked well but it not only changed the tone, but to wedge it in there so it doesn't slip, it pushes the top near the bridge enough that you end up lifting the top of the guitar slightly, evidenced by having to lower the bridge screws to get the action down!

[Jim Soloway]

that's because the sound post changes the tone more than tape or f hole plugs. And it's not easy to get in and out without damaging and potentially cracking the top. I've used a sound post before and it worked well but it not only changed the tone, but to wedge it in there so it doesn't slip, it pushes the top near the bridge enough that you end up lifting the top of the guitar slightly, evidenced by having to lower the bridge screws to get the action down!

I keep coming back to idea of a notch filter. Acoustic guitarists seem to get a lot of mileage out of the concept with flat tops so my head keeps say that if it works with flat tops why wouldn't it work with archtops?

[SierraTango]

that's because the sound post changes the tone more than tape or f hole plugs. And it's not easy to get in and out without damaging and potentially cracking the top. I've used a sound post before and it worked well but it not only changed the tone, but to wedge it in there so it doesn't slip, it pushes the top near the bridge enough that you end up lifting the top of the guitar slightly, evidenced by having to lower the bridge screws to get the action down!

I get your experience and concerns, perhaps that is why Mundell had the builder of the instrument do the soundpost mod. IIRC, Jim used a special tool similar to the one used on Cellos to place the soundpost in the optimal spot.

[sgosnell]

I've used a sound post before and it worked well but it not only changed the tone, but to wedge it in there so it doesn't slip, it pushes the top near the bridge enough that you end up lifting the top of the guitar slightly, evidenced by having to lower the bridge screws to get the action down!

Those are symptoms of a poorly installed soundpost. The soundpost has to be properly sized, and placed in the perfect location.

[jzucker]

I keep coming back to idea of a notch filter. Acoustic guitarists seem to get a lot of mileage out of the concept with flat tops so my head keeps say that if it works with flat tops why wouldn't it work with archtops?

I think there's a disconnect here. The notch filter will absolutely work for 1 or 2 notes that resonate sympathetically and cause feedback on the guitar. In some ways, the muting technique works here too - or just letting go of the sustained note.

Where both of those approaches fail miserably is what (IMO) is the real problem with feedback on a jazz gig. You're playing a tiny club with electric piano, organ, a loud drummer, a PA system and lots of sonic reflections. In many of those cases, the ambient sound waves cause the top of the guitar to vibrate which then causes feedback of its own. In that case, the notch filter and muting do not work. In the cases of folks on a big stage, the acoustic guitars are most often out front and able to be isolated from the big waves of pressurized sound. When I'm playing in a small corner of a small club, I have no control over any isolation. Often, I don't even have the choice about putting my amp behind me and to the left. But when a big drum-kit, electric bass and electric piano start pounding out loud notes, those filters and muting don't stand a chance.

that's why you need things like soundposts, f-hole covers, etc. Because those impediments to top vibration help immunize the top from the microphonics of the sound pressure.

[jzucker]

Those are symptoms of a poorly installed soundpost. The soundpost has to be properly sized, and placed in the perfect location.

The guy who installed my soundpost was a former luthier of the gibson and fender custom shop and worked on many of gibson's custom shop archtops. I absolutely trust him to know how to install a soundpost.

Anyway, unsubscribing. Feel free to carry on.

[rpjazzguitar]

Does a high end carved archtop with Doug's Plugs sound better than a cheaper build that isn't as sensitive to feedback?

I've always wondered how it makes sense to spend extra money on a high end archtop guitar which sounds fantastic acoustically -- and then dampen the top.

What am I missing?

[AllanAllen]

Back on post #14 of this thread, I noted the soundpost idea, and it didn't seem to get much traction. Everybody would rather stuff foam in the guitar or plug up the soundholes with flip flop material.
Call me crazy, however it seemed to work for Mundell Lowe, who was a notorious tinkerer. I played his Mapson at Jim's shop through a Twin at
at loud levels with no feedback-a 17' all carved archtop. It was almost totally dead acoustically though.
Plus, it's a reversible mod.

I wonder what made it acoustically dead. If the violin family all have sound posts I can’t see that they’d make the instruments dead.

[Gitterbug]

Is this a cultural problem? USA: V-8 roar. Europe: in-line 4 hum. I pity all who have to find ways to prevent their archtops from howling. A minority, I hope. There are other guitar types at ease with those volumes. Does an archtop even sound good on the brink of feeding back? My only serious feedback situation, long ago, was when I was squeezed to play a Godin 5th Ave right next to a 15" Fender Excelsior.

[Spook410]

I think there's a disconnect here. The notch filter will absolutely work for 1 or 2 notes that resonate sympathetically and cause feedback on the guitar.

It's not 1 or 2 notes. It's a range based on the frequency and Q. And you can cut the frequencies in that range completely or not completely. And you can adjust more than one frequency range though I've not heard of that being necessary.

Usually based on the individual guitar. If flat top players can manage their guitars in loud settings using notch filters, will work on archtop guitar as well.

If you are in a setting where a notch filter will no longer manage feedback (though that brings Tommy Emmanuel with his flat top at silly volumes to mind using a notch filter to manage it) then I would think an archtop is not the best choice as you're not going to hear the nuance anyway.

[SierraTango]

I wonder what made it acoustically dead. If the violin family all have sound posts I can’t see that they’d make the instruments dead.

I was probably a bit harsh saying it was "acoustically dead". During my time with the builder Jim Mapson, he had two other guitars in the shop with pretty much the same specs as Mundell's with no soundposts. Playing them back to back unplugged, the Mundell guitar was just muted and softer sounding.
I recall the conversation going in the direction of "a guitar is not a violin, air works better than coupling the top and back plates" There are several discussions on this forum regarding players installing soundposts with various results.

[sgosnell]

Guitars and violins are driven differently. A bow and a pluck don't work the same. A violin has very little volume when plucked, but can be loud when bowed. Guitars are not played with bows.

[Lionelsax]

If you are right-handed put your amp on your left, if you are left-handed put it on your right.
They say it works, it works for me.