So I went ahead and made a set of f-hole covers. The outers are the rubber souls (sic) of $1 flip-flops. The foam is 2" upholstery foam from walmart. Started with the pencil rubbings, cut the outers slightly oversized compared to the hole, cut the foam slightly oversized compared to the outers. Epoxied the foam to the outers being careful to not epoxy them at the edges, making sort of a slot that the top of the bass fits in. Worked the foam carefully inside and positioned them in the openings. So the foam is on the back side, the flip-flop on the outside, sandwiching the top of the bass and holding in place that way. I made one and fitted it before I made the second. I didn't do any feedback checks until the second one. I'm not sure I notice a difference, but maybe--or maybe the first one knocks it down quite a bit by itself. I want to think it is better. I'll gig with it tonight and see. The quality of the sound was still good. I noticed a little breakup in the lower ranges, but maybe I was just loud. I'll tweak on it. I think I would give it a 7 out of ten as far as construction. It is a little rough. The foam is light green. I colored the top black with a marker, but it shows through in a couple spots--just barely. The edges of the rubber are a little rough--maybe a drum sander could be used on this material? Not sure. I used a reciprocating scroll saw to cut both, so it was really easy. I would like them less obvious, so if they work I'll make some out of thinner material with a flat surface. Total time spent was about two to three hours. I never play without an amp, so I'm not even sure how to judge how much they cut down the unamplified sound. It doesn't seem to be a lot. They would need to be modified a bit to make them more remove/replaceable. As they are I would expect to need to re-epoxy the foam a bit after taking them out. I'll just leave them in all the time if they work. We'll see. Cost online: $90. Cost to me: $7. But I could make three sets for $10. {}
I use four black cotton dress socks (two per F hole). Inexpensive, durable, readily available (look in the sock drawer), and they're even concert black!
And I bet they don't look any less cool than these! How effective are they? I'm gonna investigate Betty Boop stickers for mine.
I don't know how effective they would be in the high volume world to avoid feedback; I use them in conjunction with the enormous rubber mute for quieter practice at home.
I used them at a gig Saturday. I didn't necessarily think I could get louder--but maybe. It is definitely not night and day as of yet. I do think they have cut the highs somewhat, so maybe with some additional tweaking the overall sound may improve. This gig was a lower volume, small room, Rumble 200 amplification-only event. I have played there before with no issues. I had noticed a the last gig I was having trouble getting the volume up as much as I had before. I believe I may have cut the EQ quite a bit over time. I need to re-center everything and start over me-thinks. Before any final judgement is made.
So one more quick follow-up then I'll yield the floor. . . For Saturday's gig I spent a bit of time tweaking the settings. Got what I felt was some good volume out of it, For the second set I was asked to turn up a bit, and did so with no issues. I feel like I need to be a bit louder, so I'll probably tweak on it just a little bit more next time. The setting was a medium sized club with a small PA, bass not ran through the PA. PA is a set of 15" main speakers and powered 18" subs. About 3k watts, I think--total. In the future I'll be asking to be ran through the PA whenever we bring the subs. Seems a little silly to basically just have the kick drum coming through them, and me having to push my stage volume more. In summary, I think the f-hole covers are worth having. If one is concerned about looks the $90 retail ones are probably worth the cost. Otherwise, if you have a good method to cut out the rubber and foam, just roll your own!
I once talked to the bassist in a loud trio lead by a Rhodes player. I asked him about feedback issues and he confided he had taken a cheap laminate bass, had the top removed, the entire body filled with foam and the top put back on. Sure enough, foam was visible through the f-holes.
The bassist for Mark Collie did that exact same thing. I assume without removing the top. The foam expanded out through the f-holes and was proud by about an inch or maybe a little more. Seemed to work for him. I considered doing that, but I would rather work with a luthier or setup person on that.
I’ll resurrect the dead here; feed back elimination is all in your eq, and gain staging. Get those two things dialed in and feed back becomes a non issue.
I'd observe that on many if not most acoustic stringed instruments, sound holes are really superfluous. ~75% to ~90% of the volume is produced by the soundboard vibration and literally emanates from the top. Sound holes help add depth and tone from the inside of the instrument, but add relatively little volume. On my Alcoa, the previous owner coated the inside-back of the instrument with textured acoustic paint to help reduce the metallic tone when the instrument is played acoustically, and it worked, but I suspect at a cost of somewhat muting the instrument. That's ok for me, it's loud enough acoustically for my small 4-piece band, and for louder musical groups I like to amp anyway. My DB has a trap door hinged over a 7"x7" hole centered inside the driver side C, which was put there for repair access. That's a pretty big hole for a sound hole; by itself it's more of an opening than both of the F holes combined. When playing acoustically I typically open that trap door up (I keep it open with velcro tape). It might add enough volume to notice it, maybe up to 10%. But more, it adds a whole lot of bass tone to the instrument, sort of like a one-knob EQ. I think I'd agree mostly with DonaldFraser that EQ and gain settings alone might actually be a better feedback solution than covering the F-holes. I guess an easily reversible way to test that is to simply duct tape over the F-holes (but don't press the tape down hard) and try some high volume amplification, compared with EQ / gain setting changes. That said, filling a DB with Styrofoam should mute it for sure. But then, why not just use a stick bass?
Sad but true in 90% of the “billy” bands here in SoCal. Instead of focusing on being solid players with something unique to offer, many guys fancy up poopie basses, that they really can’t play.
Hey--I resemble that remark! lol But seriously, whatever it takes to light the fire. The key is to keep improving, I suppose. It's just a little more costly with the DB, so that tends to turn people off from trying to get better. Maybe. Fortunately nobody of consequence has looked behind my curtain--yet. But it's just a matter of time. I tend to play just the EB at festival-type shows where we just do one set. So I haven't had to follow/open for any real DB players and get shown up!!
Nobody is going to show you up. Most bass players are nice people who will gladly show you a thing or two if you ask. Rockabilly as a sub culture doesn't necessarily reward musical proficiency, but 1000$ in lessons will get you further than a flame job... Besides, we should improve because we want to.
Seems to me like if you're playing so loud you have to fill the bass with foam to stop it feeding back, you should just declare defeat and play a Fender bass.
For a bar band playing loud honky tonk music I think feedback abatement is a necessary evil. My biggest problem is the acoustic guitar player wanting his guitar cranked in the monitors, and not having a separate send/wedge so I can kill it. That really makes the old bass tingle. And that's nothing the bass pre-amp can really handle. Using a pickup, even a piezo, would seem to lessen the need to have a pristine acoustic tone, anyway. Plus Johnnie Drunkie doesn't care how authentic you sound. He does like a flashy flame job (easily done with automotive decals!) Right now the best thing I can provide on the DB is a good, loud thump. Slapping is secondary, but to me, If You Ain't Slappin, You Ain't Happenin' (TM). So what I think I'll do is set up one bass for volume, one for tone. Assuming I can get 2 of them set up to be playable. Until now my main bass has been a CCB that's just about a half step above a barn find as far as quality/play-ability. Let me get some time playing an actual instrument before putting too much into my thoughts on the subject.
FWIW I could play just as loud with piezo pickups as I could with my mag set up zero feedback issues. It’s all about gain staging and frequency control via negative eq-ing.
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