Some notes and observations made while building a fEARful bass cabinet. The opinions expressed are my own; use at your own risk.
Please do not copy and repost these photographs or link directly to them from my server.

Some time ago I bought a Line 6 LowDown® Studio 110 to use with my bass as a practice amp. It wasn't a bad move - I've ended up playing much more than before I owned it - but recently I've become dissatisfied with a few aspects of it: 1. The hiss from the headphone output is annoyingly loud. 2. There are only two usable sounds from its bass amp models IMHO. 3. The 10" speaker in a sealed cabinet struggles to produce the lowest notes of the bass. It was only ever meant to be a practice amp, but an upgrade looked inevitable.

Having built some bass cabinets before, including a stupid refrigerator-sized monolith with a McCauley driver, I decided that there had to be something out there that someone more knowledgable had already designed. Not long after I found the Greenboy fEARful and knew I would have to build one.

Early on I had decided to use box joints on the corners primarily for appearance sake. The Duratex finish used on most fEARful boxes is nearly twice the price in Australia and it seemed a little steep for something that will probably spend most of its time sitting in one place. Shipping from the US was similarly expensive for a single container.

The first jig I made used a router to cut the fingers of the joint. With ordinary plywood the tear-out was unpredictable and often destroyed both the leading and trailing edges of the cut. I've seen router jigs that used bits with a spiral pattern; perhaps this would have solved the problem but I was unwilling to spend the time and money to obtain a new bit.

Instead I built another jig using a dado blade (seen in the background of the photo above), an old table saw crosscut jig and a piece of 3/4" baltic birch plywood I had lying around. The result - tested here on the 12mm Malaysian ply I'm using for the fEARful box - was much better.

Keeping the damaged sides toward the inside of each corner hides the flaws caused by the dado blade tear out.

A dry fit to make sure things are on track...

While the top, bottom and side panels were cut to the overall dimensions per the fEARful plans, the box joints themselves were cut slightly deeper to compensate for the thickness of the plywood material. Though the label on the plywood panel suggested the board was 12mm thick (which is, after all, less than the 1/2" used by the official fEARful build) it was even somewhat less than that at around 11.7mm in most areas.

The same dado blade was adjusted and used with the crosscut table to cut the notches in the cabinet bracing.

While I knew I had some of the suggested PL Premium coming, I was curious to know if the locally available Liquid Nails was a good substitute. The second "note" on the back of the tube was worrying. I suppose it's telling that an adhesive made specifically for construction isn't a good product for use in tight joints.

When applied, along with the creamy beige were stripes of a darker clear liquid suggesting that the glue had separated while in the tube. I couldn't think of how you might stir or re-mix the contents of the caulk tube before applying, so I just hoped that it wouldn't be a major factor in how the adhesive performed.

I'm using a solvent-based satin finish for the cabinet. Here I'm applying finish to the port slot before assembly.

Assuming that clamping the joint too tightly would decrease the effectiveness of the Liquid Nails as noted on the product, I tried to keep the clamps as loose as practical while still keeping the port divider square. Two biscuits at the joint will undoubtedly assist in keeping the divider secure despite any problems which might arise as a result of clamping pressure.

I used a Jasper jig to cut both round holes in the baffle...

...then used a router table to cut the hole for the wave guide.

Baffle holes cut. I decided to keep the manufacturer's stamp on the front baffle as a badge of shame.

While building the midrange enclosure assembly I noticed that the slots for the #10 biscuits I had been cutting managed to pierce the opposite surface in this instance.

Looking at previous cuts it was apparent that the slots for the #10 biscuits were dangerously deep for the nominal 12mm material. I quickly switched to #0 biscuits.

My final experiment with Liquid Nails will end with the attachment of the midrange enclosure/front brace assembly to the front baffle.

Again, I've clamped securely without too much pressure so there is sufficient adhesive material in the gap to ensure strength in the joint.

With the arrival of my shipment from Speaker Hardware, I've begun gluing up the rest of the box with PL Premium starting with this corner. Having seen pictures that show the adhesive darkening the surrounding wood at the fillet, I pre-finished the outside of the box to prevent the PL from soaking into the wood. This is to keep it from possibly preventing the finish from adhering to the cabinet.

The PL Premium is a smooth, even consistency unlike the Liquid Nails used previously. My observation so far is that when hardened, the PL Premium isn't easily marred by a fingernail like the Liquid Nails is. It seems to dry much harder and stiffer while still remaining somewhat flexible like the Liquid Nails.

To be fair nowhere on the tube do they suggest that PL Premium is a good product for cabinetry. In fact, they mention that the suitability of the product for the given task is the responsibility of the user without explicitly mentioning what applications the product should be used for. While both products seem as though they can handle basic wood joinery only time will tell if they will continue to perform well.

Here is the box joint with the PL Premium glue trimmed off with a wood chisel.

Removing the raised fingers of the box joint with 60 grit sandpaper on a random orbital sander.

I've taken two different types of wood filler and mixed them to match the mystery Malaysian wood, then applied them to the sanded and cleaned box joints. After drying, they were sanded smooth using 120 grit.

A single box joint after filling, sanding and finishing with a solvent based varnish. The last "ply" of the plywood on the right is the PL Premium.

In spite of my best efforts to mask the baffle and surrounds some PL Premium seeped under the tape leaving a brownish grey residue. I used a sharp wood chisel to remove as much of it as possible.

The PL Premium looked even worse after sanding.

Once the finish was re-applied, however, the PL was hardly noticeable.

My woofer and midrange crossover will look a bit different to other builds as they use a different PCB to the one usually supplied. In an effort to get my order out quickly, Leland got boards from Parts Express rather than wait for the out of stock Erse boards to come in.

In the process though, an error was made and I received components for a 15" rather than a 12" woofer. Leland quickly fixed the error and sent out the correct components.

Maybe I'm missing something but it seems to me that PL Premium will make a fine adhesive for the crossover components rather than the hot melt glue or silicone that seem to get commonly used. It will also serve as an accessible sample of product that will be exposed to the same elements over time. If it becomes brittle, dry or gooey over time it should be easily observable here.

At the time of this writing (April 2013) the official "Cheap but Good" crossover schematic for the 12/6 fEARful using the Alpha or Alphalite 6A does not indicate the polarity of the midrange driver. Before you glance at the topology, think '2nd order' then assume the midrange polarity should be reversed, have a look at this forum thread (requires registration/login). Long story short - don't reverse the polarity of the midrange driver.

The tweeter crossover went together just as easily, though I hadn't noticed until I was finished that the official example has the inductor orientations reversed. I had toyed with the idea of using turret boards rather than PCBs but gave up on the idea when it looked as though the board material would be hard to get in the width required for the woofer inductor. It had also escaped my attention that the official tweeter crossover build photo shows the same PCB I used but with turrets!

Because each crossover board was made for a complete high and low pass filter but contains only the corresponding components for one or the other, I was able to move some unused lugs to other parts of the crossover board. Here I've created extra terminals at the input to allow easier daisy chaining of the various crossovers (three in my build) without trying to jam three or more heavy gauge wires into each crimp connector.

I doubled the wires coming into the crossover from the input jack, then doubled them coming out to fan out to the mid and high crossovers.

A wire was included with the Speaker Hardware deluxe kit that was tightly wound and terminated in two uninsulated quick connects. The size of the connectors suggested that the assembly was intended to be used with the midrange driver (they were oversized to use for any of the crossover boards) but strangely, it was nowhere near long enough to reach the port shelf mounted crossover.

I tried to find the same size quick connects locally but couldn't find the exact fit. Maybe something to do with metric vs. imperial sizes.

That same day I discovered that the nylon crossover spacers for the high-pass filter were missing from my order. I spent a day scouring the local mega-hardware store and various electronic shops but turned up nothing suitable. Later I found these plastic feet that were used to pack some woofers from another project.

Maybe not an ideal solution but should work in the short term. Here the high-pass filter is attached to the bottom of the midrange chamber. A piece of foam underneath will keep any resonance to a minimum.

My frustration with my order lead to the first of a series of screw-ups. After routing a recess for the connector dish I decided to freehand the hole with a router, leaving an ugly mess.

Then, while rounding the corners for the protectors with a router, I was careless and caused some tear-out of the plywood. Mind you, this Malaysian ply isn't the strongest wood I've used.

The last mistake was the worst and it looks as though I was too pissed off to shoot a picture. I bought a planer to remove the excess material from the cabinet's back panel which I had deliberately oversized. With my frustration compounding with each mistake, I managed to gouge the back of the cabinet enough to remove one layer of ply at a corner. All in all not a good Sunday afternoon.

Several days later I regrouped and routed a hole for the L-Pad. Again, another hardware shortage - there were only two screws left to mount the L-Pad plate so I stole two screws from the lower corners.

I routed out recesses for the handles (they are not as deep as the plywood is thick) and wondered what the foam gaskets were for. I used them anyway.

I consulted my old Loudspeaker Design Cookbook and saw that I had remembered correctly - normal fiberglass insulation tests better than polyester (referred to in the book under its trademarked brand name) as box stuffing. Perfect because I had a bag of it sitting around.

Then I went down to the local electronics shop and bought two Neutrik Speakon connectors, hooked it up to my Crown XLS1500, put it in bridge mode and now I know. Everything they say about the fEARful is true.

Update Early 2016: For a long time I've been using my fEARful cabinet with a SansAmp Bass Driver Programmable and Crown power amp. But the rackmount Crown not only looked awkward, being wider than the cabinet itself, but has an annoying rattle that I could not manage to track down. Maybe that long plastic actuator for the power switch was the cause?

After getting my Kubicki Ex Factor bass back after a 25 year absence I decided to look for other amplification options and settled on another Tech 21 product, the VTBASS 500. It has quite a different tonal profile to the Bass Driver but with a lot of scope for variation with the Character knob. The Character control goes from a mid dip to peak while its center frequency rises as the control is rotated clockwise - something Tech 21 describes as "...sweeps through decades..." though from memory it covers less than an octave.

I originally built the fEARful to use with digital modelling devices. Its close-to-flat response lends itself to that approach, allowing the modeller to emulate amplifier and speaker responses and reproducing them more accurately than you could expect a normal bass cabinet to do. After trying a Bass V-AMP Pro, Pod X3 and Pod HD I was left wanting. On a whim, I tried the Bass Driver and was hooked; something about the immediacy of analog modelling maybe...