Ossus Amplifiers - Step 5, 6, 7, and 8 finishing the cabinets

As I sit this morning at my computer working on a second cup of coffee I have here beside me two finished cabinets.

In that picture you see my Gibson Les Paul Smartwood guitar leaning up against my finished products. the amplifier cabinet is on top (the smaller box), and the speaker cabinet is on the bottom. In the background you see my Yamaha CP-80 baby grand piano (It is circa the late 60s/early 70s, just today I spotted one in the music video for the song, "Video Killed the Radio Star," check it out if you don't believe me).
A note to the reader, you can enlarge any picture in my blog postings by clicking on it. Also, my camera seems to be having focus problems, I'm doing my best, but the images have been a tad fuzzy, my apologies.
The speaker cabinet is completely done. Both cabinets are constructed, covered in tolex (the black exterior is a plastic/cloth material with a rough texture customary on equipment designed for concert use), they have their front pieces covered in grill cloth (the cloth is a special design so that sound can easily resonate through while keeping the speaker hidden), they have their rubber feet mounted and they both look great. The speaker cabinet also has its removable castors installed so that it can be rolled from location to location. The Celestron speaker is mounted inside and wired to the input jack in the top center of the rear panel. I used the completed speaker cabinet during yesterday's guitar lesson. My teacher liked the look and sound so much he has asked me to build him one. Quite the compliment. Maybe I can trade lessons for it?

Three more pictures of the finished cabinets. Left there is a closer view of the guitar (for scale, and because it's cool) next to the amplifier and speaker cabinets (top and bottom). Center you see the cabinets from behind. I used traditional looking screws with fancy washers to attach the rear panels to give it that nice standard decorative look. The third picture on the right above is a closer view into the back of the speaker cabinet with the mounted Celestron. If you look you can see the red and black wires from it to the speaker jack in the center of the top panel (there is a dust particle on the camera lens that created a halo next to the jack, ignore that).

Above, to the left, is another view of the rear of the amplifier cabinet. You can see the hole cut at the top to allow the electronics, which get very hot, to exhaust and stay semi-cool for extended life. In the middle is another front view. To the right is a top down view to show how the amplifier is smaller than the speaker so as to fit the chassis. The speaker cabinet needs the extra room for the speaker to resonate. Besides, it would make no sense for the amp to be bigger than the speaker, the same size maybe, but not bigger. It's a personal choice.

These next two pictures show off the underside (bottoms) of the two cabinets. To the left is the amplifier with rubber feet. To the right is the speaker cabinet with both rubber feet and removable castors. Next time I'll position the castors closer to the front and back (as close as possible without being visible). As it is there is a slight chance of tipping over if pushed hard enough. Its a minimal risk, just a small thing to improve next time around.
My recent push to get things going all started a week ago when I was at True Value Hardware on Charles street. I was ordering a step bit to cut holes in the chassis and picking up odds and ends. I needed a stapler to attach the grill cloth to the two boards. I was eyeing a nice stapler when the owner of the place came by and we started chatting. "What are you building this time?" and before I knew it he was impressed with my ambitious goals and offered that I borrow the electric stapler. "Sure, use it then put it back in the box like you found it. Heck, I did that the other day. Its a great stapler." So I left with some random stuff I needed and a borrowed stapler. I don't like keeping borrowed things around, so I felt the need to get going. And so I have.

Just to give you an idea of the process take a close look at the two pictures above. I don't know if I've mentioned before that I don't have a garage, a work shop, or any other normal place to do this kind of work. I have a living room, where I live and work. Every time I wanted to do some work I would haul out all the equipment, set things up, do some work, clean up, put things away, and clean up with my vacuum and sometimes more.The thing you see under the amp sitting on the floor is a piece of plywood, or as I like to call it, my work bench. I'd put that up on a piano stand about a foot off the floor (here it is on the floor as I put on the tolex, wheels, etc) and do my work sitting down. The dust from drilling and sanding had to be managed somehow so I developed techniques to vacuum while I drilled or sanded or anything else so that I always had a nearly perfectly clean working area. This kept the dust to a minimum. If I hadn't done that I would have tracked it all over the place. As it is, my place is perfectly clean each time I stop working, well as clean as it was before I started working.

Once I got the cloth on the speaker front I mounted up the speaker, then I put in the speaker jack and wired things up. I wanted to a) test the connections and b) hear what it was going to sound like so I hooked that up to my existing Bedrock amplifier and turned it up. It sounded great. It was ready to be mounted into the cabinet.
I put the speaker cabinet together after measuring, drilling, counter sinking, and gluing the internal supports in. That took a bit of time. Then I put the pieces of the speaker cabinet together with screws and wood glue. I filled in the counter sunk holes, let it dry, then sanded down the excess putty. The next step was to round the edges with a 1/2" round router bit. That was a pain due to the MDF dust. Then I spray painted all the parts with a flat black paint.
I don't have pictures here, but it was a fun and complex process to cut a properly sized hole in the board for the speaker. It had to be perfect and sized so that there was room to screw things together. I built a jig that attached to my router and the center of the circle out of a piece of scrap wood. Then I used a straight bit, measured one more time, and went for it. Perfect, first try.

I used Dap Weld non-toxic glue to attach the tolex covering. Its important to cut the tolex just right, then carefully position it, check the positioning (twice), practice applying it before applying the glue, then glue it in stages. I used the disposable foam brushes for the glue, get six. Use one, toss it out after you finish up a stage, it will be full of a rubbery cement and its not worth saving. Apply the glue to both the tolex and the wood to be covered at the same time, let it dry a bit (10 min is enough, 5 is okay), then slowly press it into place being sure to check positioning as you go. Press hard enough to remove bubbles and excess glue. Go slow. It pays to be patient at this stage. Don't glue the edges until the glue sets up a bit, use the time to visualize how the tolex will wrap the corner, then wrap on around into the interior of the cabinets. Make sure you think it through, then cut. Remember you only have one shot at this, mess up and you'll be left pealing off the tolex and dealing with a sticky mess and a lot of cleanup. I avoided that, I made one small tolex cutting mistake, but I can live with it. I made another tolex related mistake later because I forced something rather than revising it, again I'll live with it. Its not so visible unless you look for it.

Something I forgot to mention. Before applying the tolex, use a large drill bit to create holes to counter sink the corner pieces. They are formed to sit just below the surface, I didn't do this for the speaker cabinet and I paid the price. I had to use a hammer to flatten them, the screws don't really fit properly, again a minor defect I can deal with. Also make sure you get corner pieces that wrap around at 1 1/2" not 1" (as I did). I had to use a hammer to flatten the wrap, then snips to remove the excess and a file to clean the edges. One more minor mistake that I'll notice, but no one else will. While I'm on the subject, drill the holes for the castors before putting on the tolex too. Again, I didn't and I paid for it later.
The grill cloth went on relatively easily, make sure to double up the edges on the back side when stapling them down. Be careful at the corners, you'll have to cut more than you want to, but don't take too much off. One more lesson I learned at this point is that grill cloth is thick. It'll add at least 1/8 if not 1/4 inch to the edges of the wood making fit hard if your tolerances are too close. This is where I made my second tolex mistake, I forced a piece in and it ripped the tolex. If you look closely on the left of this picture you can find it. Go ahead, try.

Here are a few more shots, by now you know that I'm proud of this work and I'm just showing off. I hope you don't mind.

In other news, I now have the right transformer and guess what, it fits properly. I ordered a step bit (1/8" - 1") to cut the larger holes in the chassis. I've started putting the holes into the turret board using a Dremel mounted on its drill press-like device. I tried installing a turret, but quickly discovered that I was missing something. Turns out that something was the second half to the turret installation tool. I'll try it again soon enough, this time with both pieces of the tool, I bet it'll work this time. My plan is to get things ready to wire up by the end of today, then do the rest this weekend and test it next week. That may be rushing things a bit, but I have momentum now so I might as well keep going.

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