SB240 by Hardy
I have now fulfilled a long-treasured dream. A new stereo system. No, not a new device, but a REVOX system from my youth, which was an impossible dream at the time because of my lack of funds. I don’t like the design of today’s newer models. So I bought completely refurbished devices from back then. (For anyone who’s interested: B790, B750 MKII, B77, B760, B215 and B225) And with that, the 50-euro speakers I had bought from a discount store had definitely served their purpose. The sound wasn’t the greatest – lousy would be more accurate.
I had built a couple of speakers about 20 years ago, but I gave them away at some point. So I needed new ones. Because I felt like building something myself again, I started looking online for loudspeaker projects. And what site did I end up on after many hours of research? That’s right – you can imagine which one.
I registered quickly and then read, read, read. Since I didn’t want to start out in the high-price segment, I chose the SB240 for its price-performance ratio. The sound descriptions also helped my decision, although the flowery descriptions are less my thing.
So I headed off to the hardware store to have 21mm MPX birch cut to size. Or should I say hacked off? Angles and dimensions are a whole other story. But with a few extra hours of sanding, I got it under control.
But where could I build the speakers? The basement was out of the question due to a lack of space and bad lighting. So I repurposed my computer and music room as a workshop. The little table had to do as a workbench. There’s not much to say about the gluing process.
I finished it within a week. I also glued in an additional reinforcement. Not that it was structurally or tonally necessary. Just because.
As a replacement for expensive screw clamps with a span of more than 1.2 m, I decided to use a tension belt that cost 6.70 euros. It was a little more trouble to use, but you can’t beat the price.
And now it was time to get sanding. In the apartment? My wife would have killed me. So it was off to the balcony. I spent days dragging the cabinets through the apartment onto the balcony after I got off work. After sanding, I dragged them all back. The gym is kid stuff compared to that.
Once the cabinets were sanded, the question was how to make the cutouts for the chassis. A cabinetmaker quoted me 130 euros to do the cutouts. I thought that was too expensive, so I bought a router and a set of profile cutters. All together they were less than 130 euros. After all, the router wasn’t going to be a one-time investment. I already had the next projects in mind.
The routing template that came with the router only works for a radius bigger than 10 cm, so it was useless for the mid-range and tweeter chassis. So I built my own out of scraps and the guide rails from the original routing template.
The pivot point is an inset M4 inside-edge screw, and is below the contact surface of the router.
The baffle board was cut out in several steps. The connection terminal was also inset in a flash. I also rounded off all the edges of the cabinet with a profile cutter. I rounded off the bass reflex channel too – I thought it just looked nicer.
The router not only covered our balcony in a millimeter of sawdust, the wind also spread it throughout the neighborhood. But apparently we have very tolerant neighbors. Let’s see how their tolerance is when I turn up the amp and let the two SB240s have free rein. Then I separated the last pieces out of the baffle board and the back wall for the connection terminal with the jigsaw.
Since the chassis had now arrived, it was time to solder the crossovers. The crossovers were built onto 2 small 4-mm scrap boards and soldered from the back. All of the technical things were easy for me as a machine fitter. Machine fitters happen to be expert technical builders. -:)
Now that the dusty part of the work was over, I could focus on the surface design. They were going to be black, because it goes with almost every design style. I didn’t want to hide the nice grain and layering of the wood under a coat of paint.
So the cabinets went back out onto the balcony. I didn’t want to get any spots on the carpet. Then I painted the cabinets with a water-based stain and let them dry overnight. The stain makes the wood fibers stand up a little. So then I had to gently sand the cabinets by hand with #320 sandpaper. I removed the sanding dust with a soft brush and then applied colorless antique wax with a rag. After it dries well (according to the wax container), you can polish the surface with a soft cloth. I polished it after 2 hours. I tried to capture the surface in a picture, but it doesn’t come out that well. Now all that was left was installing the chassis and wiring it. But that went pretty fast, too.
Finished? No – in my mind’s eye I could see the bottom 4-6 cm of the loudspeakers getting dented and scratched. The hard plastic of the vacuum cleaner would take care of it. So I went off to the hardware store and had them cut a 0.4m x 2.0m piece of 19mm coreboard into 4 equal pieces. When I got home, I screwed them together in pairs, sanded them, stained and waxed them.
Finally, I put 4 rubber wedges with a diameter of 50 mm and 10 mm thickness between the box and the base. Now it’s done. Since the living-room renovation isn’t underway yet, right now the SB240s are running on a Yamaha AVR in stereo mode. That will change when my new stereo system is set up in the living room.
At this point I would like to thank Loudspeakerbuilding.com for this great assembly kit with its sound, and for the prompt answers to my questionsl.
And where’s the sound description? I said at the beginning that I’m not really about the flowery sound descriptions. For me it’s just the cream of the crop. There’s been enough written about the sound. I don’t have anything significant to add to that..
The loudspeaker assembling kit includes all necessary drivers, components, damping, accessories and the cross over plan and can be ordered at Intertechnik.