Banjozilla Sound Clip
Here's the story of this fearsome monster:
In 1990, I had started really getting into bluegrass music, jamming with some friends of mine. I mostly played a Carvin fretless 5-string electric bass back then. That group eventually evolved into the All Digital String Band, which is still going strong today. Steve Frankenberger, our original banjo player, had made up a funny Bass Banjo contraption to mess around with. It was a 20" bass drum with a simple maple neck attached to it, some strings and a bridge. It didn't work very well, but it got me thinking about the whole idea of an upright Bass Banjo......Was it possible to make it into a serious, useable instrument?
I was just getting my musical instrument company started as a sideline hobby/business and I decided to take on the challenge as a project for myself. I did some research and found that Gibson had made a few giant Bass Banjos back in the 1920's. They only made about 10 of them, and only one or two still exist today. Does anyone know more? They were very large, about 6'5" tall with about a 32" diameter rim and four strings. Other than Gibson, I haven't heard of any instrument companies producing an upright Bass Banjo. Deering and a few other companies have made horizontal Bass Banjos, which are just a little larger than a conventional banjo. Note: Just in the last five years, at least one other independent Luthier was building and selling an upright Bass Banjo, but I don't know if he's still doing it.
My idea for my Bass Banjo was to make it comfortable to play and similar in feel to an upright bass. I wanted the tone to be warm and deep, with some banjo twang, but not too much. I wanted it to sound more like an old time open back banjo, down lower. For styling, I wanted to give it a 1920's look, with old wood and brass decoration. I made layouts using different sizes for the rim and head, and settled on a 24" rim, 8" deep. This would give it enough low frequency and acoustic power capability, while being reasonable to get my arms around. For asthetics, I went with a very large, flat, tilt back headstock with ornate edges. I wanted it to really look like a banjo.
Well, it turned out to be a substantial engineering project! Almost everything on it required large special fixtures and a lot of experimenting. I didn't complete it until late 1992.
I originally designed and built it as a 34" scale 6-string bass, tuned BEADGC, with a fretted fingerboard and roundwound strings. At the time, I thought that would be the best combination of range and tone. I played it that way for many years, but it wasn't good enough. The electric bass sized roundwounds just didn't have enough power and the tone was too twangy. I thought about building another whole instrument, but eventually decided to rework the original.
In 2005, I finally did a major rebuild on Banjozilla, converting it to a 40" scale 4-string fretless, much more like a conventional upright bass. It's the same neck, narrowed down, and with a new fingerboard. The fingerboard is an ebony upright bass replacement, trimmed down a bit, which now overhangs the head. To get the longer scale length, I moved the bridge down below the center of the rim. I added a very strong assembly of brass plates to the tailstock as the anchor for the strings. The internal spring system (more on that below) stayed the same, but was relocated. The strings are Super-Sensitive brand stainless steel core flatwounds, in upright bass length.
The new configuration works very well. It's much more comfortable to play, better looking, and is about twice as loud. The tone is just what I wanted. It's definitely a different sound than an upright bass, but it's still warm and subtle and fits well into the background. It's first public outing in the new configuration was the 2005 Topanga festival, and it's been there almost every year since then. These days, Banjozilla is usually parked in the office of my shop. I polish it up thoroughly once a year, and only take it out for special events.
Over the years, I've refined the design in my head, and someday I'd like to develop it into a production instrument. I also have a lot of new ideas on how to build the structure, to make it lighter and more resonant, and more repeatable for production. This one is built like a tank, and is much too heavy! I'd also make the neck removeable, similar to the Baby Bass, so it's easier to adjust and can be taken apart for shipping. The plan would be to keep the features and finish simple, and aim for a selling price under $2500.
I can't take orders for Banjozillas at this time. I'm much too busy with my Scroll Basses and other work for many clients. And, no, I'll never sell the original one. I have too many happy memories with it.
Overall height: 6'5"
Diameter of rim: 25 1/2"
Depth of rim: 8"
Head: 24" Remo Ambassador Clear
Strings: 4, tuned EADG; steel core flatwounds
Scale length: 40"
Weight: 25 lbs
The Spring System:
One of the first things I found out in designing this instrument is that you can't just scale up a banjo! There's no way that a mylar head of that diameter could support the downforce of the bass strings. So, on the back side of the head is an adjustable spring system which supports a floating shoe that's directly under the bridge. The spring system is set up to counteract the download of the strings, and its characteristics are the primary resonance and damping effect on the strings. The head is sandwiched between the shoe and the bridge, and goes along for the ride, like a giant speaker cone.
Much of the development time of this instrument was in this spring system, because it's the real heart of the tone. I went through at least seven iterations of the design, including some complex combinations of maple leaf springs, brass bars, etc. What I finally ended up with was surprisingly simple. I got the best overall sound out of steel coil springs, and a very light weight alder shoe.
The brass knob on the inside adjusts the load that the springs apply to the back side of the bridge. I found that the best setup is where the spring/string balance is pushing the head slightly convex. I don't understand why, but this produces better tone and volume than when the head is dead flat.
The rim is built up out of layers of arc-shaped segments of maple and walnut, sort of like building a round block wall. It's beautiful looking, but it was a pain getting all the segments to fit together correctly. I don't think I'll do that again! The circumference of the rim under the head has an 1/8" wide brass ring inset into it, to give the head a really solid, precise edge. That was also a lot of work, and I'm not sure if it was worth it. I made up the brass pull rods which tension the head. They fit down into the maple flange around the back of the rim, and are tightened by socket head machine screws from the back.
I experimented with several different heads, and ended up using a Remo Ambassador, which is one of their heaviest gauge mylar heads. The head is cranked up very tight, much tighter than you'd typically run a bass drum. If you look close, you'll see that the brass pull rods are pulling directly on the aluminum ring of the head, with no seperate retainer ring. I'm amazed that the bond between the mylar and the ring hasn't failed! But that same head has been on there under tension for fifteen years, and has survived many all day festivals. Remo makes a good product.
This monster is actually through-neck style construction! The center maple slab of the neck is one piece from the tip of the headstock down into the tailstock, about 5 1/2 feet long. The side laminations are walnut and maple, and carbon fiber is inset into the center slab. The neck is glued into the rim, and I built a special 6 foot long fixture that holds the entire instrument while I did the fingerboard, fretting, etc. Like the rest of this project, this construction was design overkill.
A Resonator Back?:
Some of you may ask: Why not try a resonator back? Right after I initially got Banjozilla together, around 1993, I built an experimental resonator back for it. I didn't like it at all. It added bulk and weight, and mostly just took away the bottom end of the tone. It didn't add any noticeable volume level and made it harder to hear myself playing. Maybe with some development I could have improved it, but it didn't seem to be worth the trouble.
A Pickup System?:
Yes, I originally had a pickup in Banjozilla when it was a 6-string. It was a surprisingly difficult technical problem. It should have been obvious, but mechanically coupling a 24" diaphragm to the strings creates, effectively, a giant microphone. It was a nightmare to amplify. Whatever method is used to pick up the sound, whether a microphone, a magnetic pickup, piezos, etc., as soon as the sound is in the air, the head picks it back up and feeds it back into the strings. I remember some experiments where it was so sensitive that, with a little amp 6' away, as soon as it was turned up enough that you could barely hear it, it was already feeding back! I tried a lot of different things, but the heart of the problem is the giant diaphragm. Sure, I could put on a magnetic pickup and completely dampen the head, but then it would lose the characteristic banjo sound.
I eventually found a partial solution. I mounted a pair of Fishman disk piezo pickups vertically on the back face of the bridge. This way, they were mostly picking up the fore-back motion of the bridge, which wasn't so directly coupled to the motion of the head. This worked okay for an indoor acoustic band environment, but it was still far too feedback prone to be used in a loud club. It's a tough problem, with no good solution. I used the Banjozilla in a studio recording at Disney with my bluegrass band in '93, and it sounded great on tape. If I remember right, the engineer used both a condenser mike out front and the feed from the pickup. The acoustic sound from the mike was much better, and was all we used in the final mix. When I did the conversion to 4-string in 2005, I just left the pickup system out. When I've played it on stage recently, we've put a single mike out about 4 feet in front of it, in line with the center. I stay well back from any front stage monitors, and we only feed the bass signal into the side fill monitors. It still would be very difficult to play in a loud nightclub. But why would I want to anyway?