It’s been more than 20 years since I built myself a pair of Alto pedestal boxes. And it was just over two years ago that I sold them. I’ve been getting by with a couple of unremarkable Control Ones ever since. Until last spring – while the weather was still cold and dark here – when a good friend brought over an issue of a do-it-yourself magazine. We listened to all kinds of CDs on my freshly restored Harman Kardon, and philosophized about the loudspeakers described in the magazine. There it was again, that feeling that I wanted to build something of my own, to really enjoy music again and even lose track of time so often. Like many of you, I came across this magazine online too, during a specific search, and got hooked.
I decided on the FT6, which I thought was very interesting because of its band-pass filter and compact structure. One Sunday, I sent off an email asking about the FT6. The response came right away: we don’t make the FT6 anymore. But the FT12 is basically its successor. I went back to the magazine and looked up the FT12. Yes, the blue cube looks very compact.And a 3-way band-pass filter? That sounded interesting, not to mention highly promising. Once I had discovered Christian’s ingenious version of the FT12, my mind was made up, and I ordered the assembly kit the same day. The package was delivered just as promptly, by the next Tuesday.
I myself am not quite that fast. Another two weeks went by before I finalized my assembly plan. I was imagining a cabinet that was just as compact as the original box, combined with the wonderful curve of Christian’s FT12. I live in a small half-timbered house with 5-foot-9-inch ceilings in the living room – which has trained me to adopt a humble kind of posture – and with a pitched roof in my “music chamber.” So a pedestal box is out of the question. I sketched some designs on paper and tried to determine the volume of the three chambers. Since integral calculus seemed too complex for finding the parabolic and elliptical areas, an estimate would have to do.
But how was I going to manage the curved side walls? Constructing the sides with six or seven layers of bent plywood was too complicated for me. And the method of forming them with vertically glued wood strips, the way Christian did with his FT12 and Matthias did with the beautiful Duetta Standtop, still didn’t give me the right thrill. Once again, a succinct email helped me out of the fix. The tip was to look for slotted MDF, which is also sold under the name of Topan. To my surprise, our village cabinetmaker had several boards of it in stock.
I took the plans for the baffle board and the three horizontal boards to my woodworking neighbor. He also got the #16 MDF for me, for the assembly. Meanwhile, I had the cabinetmaker cut the slotted MDF to order and glue on some macassar veneer. That saved me the trouble of adding the veneer later once the cabinet was built. The expert waved away my concern that bending the veneered MDF would cause the macassar layer to crack. And he turned out to be right.
The skeleton emerges
The preferred substance for gluing is joint glue. The trimmed boards were easy to fit together, in just two steps. First, I connected the baffle board and rear wall to the lower frame and the lid of the box. Then the two separators were attached inside with glue. By then it felt like I had sweated out more liquid than was in the crate of mineral water weighing it down. The volume separator for the bass and tweeter/mid-range speaker, consisting of a horizontal and a vertical board, did not want to stay in position and kept sliding around. I was finally able to use a clamp to convince the boards to stay in place. The finished skeleton gives you a good idea of what the FT12 will look like.
Sanding, part one
Since I had glued the baffle board and rear wall to the horizontal boards, I needed to sand off the projecting edges on the sides and adjust them to the radii of the sides. It was a welcome excuse to buy myself a belt sander. Equipped with #80 grit, the tool smoothed out the edges in no time, making our terrace look like it had been in a sandstorm. Good thing it was supposed to rain the next day. The transitions with the radii needed more fine motor skills to get them sanded halfway decently. What I found incredibly helpful was lowering my visual standards for the final product, since the three horizontal boards and their radii are not perfectly aligned.
Attaching the first curved layer
I spent a long time pondering the best way to glue the sides onto the skeleton. I researched it online and read other building reports. There is the method with the opposing frames, which Frank perfected with his Minetta. That sounded ingenious. Other people use clamps, wood slats and ratcheting tension belts to hold them in place, but my options were fairly limited, so I had to improvise. I hoped that the jigsaw would magically create something like a frame, with an even radius, from a 40-mm-thick board. But none of them were the same size and the radii didn’t match the actual curves on the box, even though I was working with a drawing template. How was the pressure supposed to be distributed evenly throughout the curved surface? The tension belt method didn’t seem safe to me. The images of the cracked MDF from Frank’s building report had been burned into my brain. But it was the only option I had. I discussed the possibilities with a friend, who told me to attach the first layer of flexible MDF with screws as well as glue. That sounded doable. I fixed the MDF boards in place and drilled another 20 holes with the same core diameter as the 3.5 x 25 Spax, then countersank the holes. But what was that? The MDF was splitting along the lower frame! I was reassured by another email: simply glue the crack together with joint glue (hmm… maybe that’s where the name comes from). I glued on the first layer of flexible MDF with the smooth side facing inward. I applied the glue to the skeleton, placed the board on it and attached it with the screws, starting from the center. The glue that was squeezed out on either sides told me whether or not the pieces were attached evenly.
Up to that point everything had worked well, and I was fairly optimistic. Meanwhile, I had glued the crossovers together, wired them, and anchored them into the cabinet with hot glue. Here, too, I had some help from afar, with a glance at some pictures of my crossovers. I had a healthy respect for gluing on the veneered sides, since I couldn’t attach those with screws. In order to force the veneered flexible MDF to fit the radius, I had to press it on. I did some “dry runs” with tension belts, clamps and a couple of boards, and I made some markings on the edge of the lid and the tops of the side pieces that would need to align in order to make the overhang about the same in the front and the back.
I squeezed joint glue across the surface of the ribbed sides of the first box, and spread it out evenly with a piece of cardboard. Then I leaned the two veneered side pieces against the standing cabinet – veneer facing outward, everybody. :) I quickly tightened the four tension belts with wood caps so that the MDF would lie tightly and evenly along the curve, always making sure the markings at the top weren’t misaligned. The MDF didn’t fit exactly at every spot, but I consoled myself that the joint glue would fill in the small gaps and hold it in place.
After 18 hours, I finally dared to open the package. When I rapped my knuckles on it, it sounded the same all over – a good sign. I did the same with the second box, and then it was back to sanding.
Sanding, part two
Now the front and back overhangs on the side pieces had to be evened out. Once again I went for the belt sander. It was Sunday, and I had the place to myself. To keep from bothering the neighbors, I set up a sanding corner in our 200-year-old vaulted cellar where I could make as much noise as I wanted. It took me five hours to get both of the cabinets sanded smoothly, using #240 sandpaper.
I covered the veneered surfaces with paper. Then I puttied over a few of the more obvious defects. Since I didn’t have much experience with puttying, though, the results were mediocre. The sharp edges of the MDF kept showing through as I sanded. I set up a temporary painting corner in the attic. First I followed the cabinetmaker’s advice and gently sprayed the cabinet with paint, closing the pores in the MDF and creating a foundation layer for the filler. This was followed by three cans of spray filler, which I distributed among the two boxes in several steps. The uninsulated attic was so hot that the spray filler particles dried before they even got to the surface of the MDF – at least, that’s how I explained the numerous “blemishes” to myself. But the blemishes had to go. I took care of them with an orbital sander and #240 grit. Now the recognizable shape of the loudspeaker had a good surface feel, too. The projecting edges and a few other small irregularities were still visible, but that was fine. I wanted to be listening to music by the end of the weekend, so I decided against buying another can of Premium White at Toom. One can would have to do it, and I put it mostly on the baffle board and the lid. I was less careful with the rear wall, for practical reasons.
Sanding, part three
Now it was time to go back to sanding. I only treated a few areas of the painted surfaces with #1500 wet abrasive paper, since this time my focus was on the veneered sides. As soon as the paper was removed, the contrast between the white paint and the dark wood showed up very nicely. I used #240 and #400 sandpaper, mostly by hand. Then I oiled the veneer with linseed oil, which I thought looked pretty good. All that was left was the sound equipment.
Crap, I had cut the provided wires a little too short. Maybe I should have positioned the crossover lower down. For the mid-range speaker, it took a delicate touch to solder the wires onto the solder tabs. A third hand would have been helpful, but in the end it worked out fine. After the chassis, I installed the simple pole-piece clamps, which had been a splurge. I like them better than the black plastic containers. I quickly tapped in the bass reflex tube – oops, I broke it off. The hole diameter was a little too small. Now what??? I remembered the pragmatic approach often mentioned here in the past, and reached for my hot glue gun. It solved the problem by bonding the tube to the baffle board.
In the mind’s ear
A moment of uncertainty. The loudspeakers were connected to the amplifier, CDs at the ready. Would everything work on them? What about Katie Melua? Later! First, Eddie Vedder’s Ukulele Songs. And they sounded great! Vedder has a beautifully deep, gruff voice, and there was plenty of volume. Then came the others. From Dire Straits, Sade, Pink Floyd, Marla Glenn and Supermax (“World of today,” 1977), to Stevie Ray Vaughan, Björk and Mando Diao, all the way through to Sven Väth’s techno classic “The harlequin – the robot and the ballet-dancer,” I listened to all of my CDs. It was a pure joy !!!!!
Thank you for your advice, tips and endless phone calls. Thanks also to those of you in the community, for your creative building reports and the many helpful hints I found in them. I just have one problem now: I could become a multiple offender. It was really fun building the boxes. After all, the little guy wasn’t called the “FirstTime” for nothing, right?