Feedback Problems

[jazzfreak]

Since I've started using an extension cab with my combo, I've been fighting feedback significantly. Any advice would be appreciated.

Equipment:
15 inch archtop with a floating pickup
Strings are .13 Jazz Swing TI's
Henriksen 110 with all EQ settings at 3:00
Ear Candy Jazz Bell extension cab

Before obtaining the extension cab, I would occasionally fight a little feedback particular on the A string, especially when holding a note. Then, I typically had the combo on a tilting stand. Now, since I have the units stacked, the extension cab is sitting directly on the floor.

Short of plugging the f-holes, would any of the following help?

Sitting the units side-by-side, both on tilting stands
Placing the stacked units on a carpet square
Turning down any of the EQ settings
Stuffing a cloth under the floating pickup

Any suggestions would be very much appreciated. I do have the unit behind the neck vs the body of the guitar.

Thanks,
Ed

[wintermoon]

position your body to shield the guitar from the amp

[Stringswinger]

Try turning down the bass EQ on the amp. I bet that having the bass at 9 o-clock will remove the 5th string feedback altogether.

[vernon]

These are helpful suggestions. I've found that using a parametric eq pedal such as an Empress ParaEQ to notch out or minimize the hot resonant frequency. My Heritage Eagle with floater sounds gorgeous, but those "hot notes" can start making you crazy after a while. Try different approaches until you find something that works but still preserves the essential voice of the guitar.

[Donnie]

Raised it off the floor? Tilt it back? Sometimes just the physical position is the answer; also does your amp have a "notch" setting?

[Jabberwocky]

The trouble with speakers is this: we place them where we can hear them best; where we can hear them best is where the guitar can hear them best, too.

So, short of having our pinnae surgically repositioned backwards we have to get used to not hearing our speakers directly in order not to induce feedback. In-ear monitors go a long way towards hearing a canned version of your amped set-up.

Sitting off to the side of the speaker stack helps. Having a thick Sonex tiled short wall between player-guitar and speaker stack helps a little better.

(You see these RPG sound diffusors and Sonex tiles to break up or absorb reflective sound waves in a properly treated sound room.)

Filling up the cavity of your archtop with carded sheep's wool or synthetic fibre works well but is a little messy. You lose the acoustic vibe of your archtop though. It sounds muffled. Amplified, it makes little difference. Wedging felt underneath the pickup does not hurt it.

If you have ever blown across the mouth of a bottle, well, that is what happens in the cavity of an archtop essentially: standing waves. Filling the bottle up with loose fibre eliminates the standing waves entirely. Does the same in an archtop.

A semi-hollow thinline is always the alternative.

This the section to plug the Made in the USA Doug's Plugs or my Made in China version, Wang's Bungs.

[andyb]

Jabberwocky has it right, sound waves reacting with the archtop.

I asked a friend who runs a recording studio about it, I had an Eastman archtop and a Roland cube at the time, it was a feedback monster. He invited me to call in to work out a fix, I also had bought an EQ pedal thinking that would fix things, he said it was useless to fix feed back.

This is what we did, and it worked.
I set up as usual me sitting down to play, with the amp on the floor behind me about 4ft to my left, my body between the guitar and amp. There was a bass player and drummer practicing and we were playing loud in a small space. The feedback was awful.
He then started moving the amp around, trying to find a spot where the problem frequency was no longer causing feedback. It was on the E or A string probably both.
The feedback stopped when the amp was right behind me and raised up, almost next to my ear, head height when sitting. He explained in this position I was sitting inside the sound wave for those low frequencies. He recommended an amp stand or putting the amp on a table.

You could give that a try.

[Burrellesque]

A single black party balloon lightly inflated inside the guitar always solves any feedback issues in my archtops.
Easy to install and remove (untie or pop).

I also find that moving the balloon around a little inside the guitar offers subtle tone shaping too.

I'm convinced that I get closer to a lot of the recorded jazz guitar tones I like with a balloon in the guitar too. All those gigging greats probably had all kinds of stuff in their guitars if they were on the bandstand every night.

[rob taft]

A single black party balloon lightly inflated inside the guitar always solves any feedback issues in my archtops.

I don't play any longer in situations that require any volume but this is what I have used. Cheap and as the OP says easy to remove. I tried the cotton, cloth, foam, tape over the holes but the balloon is much easier to remove.

[jazzfreak]

Thanks. Sorry to sound naïve, but how do you keep the balloon from falling to the bottom of the guitar, or will it just stay in place without having to secure it in some fashion?

[rob taft]

I put it in the f-hole uninflated, blow it up tie a knot in the end and tuck that part under the top. Mine don't move until they lose pressure like all balloons will do over time. I was too cheap to buy Doug's plugs which also work well and I had more than one archtop with different sized holes which would require a different set of plugs, therefore the balloon idea.

[jazzfreak]

Thanks again. BTW, I left off one important piece of information. I can set-up in my home in a very small room and be facing the amp, literally two feet away and experience no feedback whatsoever! Yet, in the club I can be 8-10 ft away from the amp which is positioned on the neck side of the instrument and still fighting feedback

[Runepune]

It's all about those (lower frequency) waves hitting your guitar and setting it in motion. Your hollow guitar has resonant frequencies that are the most easily triggered ones. Depending on where you are in relation to the source (cab) and where the cab is placed in the room (walls, floor), you may be standing in hot spots or not.

Using a ballon or any other party trick to dampen resonance in the guitar will obviously help

Use as little bottom end as you're comfortable with. Having the cab on the floor or near a wall will give you a considerable bass boost. Get it off the floor or dial bass down on the amp.

Move yourself and/or the cab around. It's hard to tell exactly where it works best as it also depends on the room.

Is it possible to set the cabs beside each other? Even with a little distance between them? In that case you may be able to cancel out an offending frequency hitting you (One cab needs to be half a wavelength of a troublesome frequency further from you than the other cab...E.g. one cab being one meter further from you than the other will cancel out around 170 Hz.) Might not be very practical though Although I've used it as a stunt solution on an occasion.

I use a Kemper myself, so I can easily notch out offending frequencies. Not sure if there are eq stomps with narrow enough filters to be useable for notching out such problems, but it would surely be handy for the archtop crowd Your best bet is probably the Empress ParaEq.

[pingu]

I put foam in mine through the holes
Both sides ...
Worked great and dulled the sound of
the box , which was too bright anyway (for my taste)
Then relented and removed the foam from
The lower half of the guitar (as you sit with it)
Happy now , and no feedback ....

Careful with the electronics if you do it
Maybe just stuff the top half like me

[jazzfreak]

Thank you! Still curious I can literally be "right on top" of the unit while playing at home with no feedback whatsoever.

[rpjazzguitar]

I used upholstery foam to solve the problem on one guitar. Probably overkill. I didn't know about the balloon trick, which makes more sense.

[wintermoon]

I've said it in many threads, Doug's Plugs are the bomb.
been using them for over 10 yrs, best $50 I ever spent on a guitar accessory.

[Runepune]

Still curious I can literally be "right on top" of the unit while playing at home with no feedback whatsoever.

You may very well be in a spot where frequencies that excite the guitar cancel out.

[Burrellesque]

I tried foam plugs. They deadened the tone of the guitar too much for my liking. Also... they don't do much for the aesthetics of a nice looking instrument.

[vernon]

I was intrigued by the black balloon idea, so I tried it with my Heritage Eagle. It helped very little in my case... a few db notched out at the offending frequency worked significantly better. I was hoping it might be the magic cure, but - alas - no.

[rpjazzguitar]

I was intrigued by the black balloon idea, so I tried it with my Heritage Eagle. It helped very little in my case... a few db notched out at the offending frequency worked significantly better. I was hoping it might be the magic cure, but - alas - no.

I know that a lot of pro players use unmodified archtops and, somehow, don't have the feedback issue. Wes comes to mind. From what I've read, he used a stock L5 and a pretty powerful amp. When he did his live albums, it certainly sounds like he was playing loud enough for the guitar to feedback.

That said, I was never able to control feedback reliably using amp positioning alone. Not that it couldn't work in the right setting, I suppose. But, at my mostly low rent gigs, I don't always have much choice about where to the put the amp. Sometimes, 4 feet behind me to my left is outside the building, or inside the piano.

I was ready to smash my Godin just before I stuffed it with foam -- which muffled the acoustic sound horribly, but wasn't really noticeable when amplified.

Anyway, for the most part, I've played solidbody guitars. An archtop may sound better than a solidbody, but any solidbody sounds better than feedback.

[Jonathan0996]

I put foam in mine through the holes
Both sides ...

I'll second that recommendation. It's the best solution I've found. It takes a bit of patience to stuff the foam in there, but it's much better than messing up your sound by EQing the guitar to suppress the feedback. EQ isn't a good way to carve out feedback frequencies; it's for making the guitar sound good.

You might need a couple blocks of foam to block the F-holes completely. You don't need to fill the whole guitar with foam; just use enough to block the F-holes. I don't think it really changes the electric sound of the guitar, but for me it made playing gigs much easier. Fighting feedback all night is a drag.

Of course, if maintaining the acoustical properties of the instrument for home use or recording is important to you, foam isn't a good solution. But if for a gigging guitar, I think it's a great solution.

[Jonathan0996]

Thank you! Still curious I can literally be "right on top" of the unit while playing at home with no feedback whatsoever.

It's easy to underestimate how much difference in volume there is between playing at home and playing on the gig. Gigs are a whole 'nother world.

[Marty Grass]

I saw an Ibanez ad that says that their top tends to decrease feedback, but the pickup is a floater. That puzzled me.

I get that feedback involves the amplified frequencies coming from the speaker and hitting the guitar or pickup in phase to create a very high output in just certain frequencies in which are in phase with the speaker output.

Archtops tend to have lower tone feedback from the top vibrations. Strats and LPs tend to have higher frequency feedback.

My assumption with a floater that doesn't rest on the top is that feedback occurs because the pickup structure is resonating. If so, the body or top construction would have no direct effect on feedback. I can imagine an indirect effect from the speaker vibrations moving the top and that the top vibrations create movement in the floater.

Anyway, I'm curious about the physics of this.

[TH]

Strings initiate vibration. It's where the energy that moves the top comes from. The pickup hears the string, or in a piezo, the pickup hears the top that's moved by the string.
When things are loud enough so a sympathetic vibration occurs, something "hears" the signal from the amp, and that vibration gives signal back to the string, the string signal will become stronger through the vibrations that came from the amp. That loop of string-pickup-amp-air-string is your feedback loop.
In an acoustic guitar with a magnetic pickup, the top will also move air, and it will also "hear" the vibrations and feed that signal back to the string.

Anytime output is strong enough that it becomes input into a string, you'll get feedback.
Sometimes certain frequencies will be stronger: the resonance of a body in an acoustic archtop, or wood also has its own resonance, and these will recognize certain frequencies and "sing along" as a sympathetic feedback loop. This vibrates back into the string through the bridge and you'll get a lower frequency howl at those frequencies.

That's the signal chain. You can break it at any point (move the guitar so the air doesn't vibrate the string, make the top thicker to discourage top vibration, separate a pickup from the wood of the top and make the top less resonant, use an EQ to notch or attenuate a vulnerable frequency) and you'll reduce your chance at feedback.

That's kinda how it works.

David