The cause of the feedback is from high SPL (Sound Pressure Level) entering the
guitar body. The sound vibration not only causes the top to vibrate WITH
the surrounding air, but the SPL also enters the guitar body and bounces around
inside, causing more vibration to the top (i.e. the guitar bridge and ultimately
the strings). This causes the string or strings to vibrate more, causing
more sound out the amp. My Doug’s Plugs seal up the f-hole and stops the
SPL from affecting the air inside the instrument.
In
effect, the SPL bounces off the top the same as a solid body. Since the
top is free floating, however, some feedback is still possible but the overall
reduction is dramatic. If you want to try an experiment, get some masking
tape (either the tan stuff or the blue - the blue has less adhesive). Tape
up both of the f-holes so they are sealed up. Use two or three layers of
tape to thicken it up so they are more like my plugs. Then play your
guitar like you would during rehearsal or a gig. If you notice a decrease
in feedback, then my plugs will work for you and actually work better.
(Some people still use clear packing tape to cover the holes but this gums up
the finish, and to me looks very unprofessional.)
The plugs I make are made of very light weight high density foam, the same stuff
sometimes used to make flip-flops. The main plug fits into the sound hole
and a slightly larger top flap, made of the same material, keeps the plug from
falling inside, and seals up the hole. The plugs will have a very slight
dampening effect on the vibration of the top since they are not glued, screwed,
or permanently attached to the top - much like a shock absorber. I have
not noticed any effect on the sound on my guitar, nor have any of my customers.
In fact, since the feedback is eliminated, you can actually add back some of the
EQ you had to take out to eliminate the feedback, giving you the rich sound you
have at lower volumes. Some purists may say that it affects the sound, but
they don't buy my product because they either don't ever get that loud, or still
prefer to use clear packing tape, or use balloons, which can still dampen the
soundboard.
I would definitely say that my Doug's Plugs will greatly reduce the feedback you
have as long as it's not microphonic feedback (high frequency feedback that
squeals like a microphone). That type of feedback is caused by pickups
that are not potted with wax or epoxy. The type of feedback most commonly
experienced by owners of archtops is where one note in a chord will vibrate out
of control, overshadowing the rest of the chord, or one note in a melody line
runs out of control. In some styles of music like Blues or Rock, a small
amount of feedback is probably ok, like the kind of feedback experienced by a
solid body Les Paul - more of an effect rather than a hindrance.
Also, please understand there are always circumstances, such as room shape,
overall SPL from PA systems, bass amps, drums, as well as use of effects pedals,
which can contribute to feedback. I don't guarantee that it will totally
eliminate feedback given the above conditions, but I do honestly state that the
feedback will be significantly reduced if not totally eliminated. After
all, even a solid body guitar will feed back if the volume is high enough.
In
effect, the SPL bounces off the top the same as a solid body. Since the
top is free floating, however, some feedback is still possible but the overall
reduction is dramatic. If you want to try an experiment, get some masking
tape (either the tan stuff or the blue - the blue has less adhesive). Tape
up both of the f-holes so they are sealed up. Use two or three layers of
tape to thicken it up so they are more like my plugs. Then play your
guitar like you would during rehearsal or a gig. If you notice a decrease
in feedback, then my plugs will work for you and actually work better.
(Some people still use clear packing tape to cover the holes but this gums up
the finish, and to me looks very unprofessional.)