Building a pair of loudspeakers is one thing. Documenting the details of the building process is quite another! Itís hard to say exactly what convinced me to build them myself. Maybe it was just the desire to have something special without spending a fortune on it. Sure, loudspeakers primarily need to sound good, but the eyes are listening too, as they say.
I had always been fond of oval shapes, so I made that the goal of my DIY experiment. I spent weeks surfing the web and reading about do-it-yourself projects, trying to use practical programs to calculate my own cabinet volumes, and I soon realized that building them completely from scratch was not really feasible. So I needed an assembly kit. But before deciding on one or the other, I needed to find out if I could make the shape I wanted with the available resources. Somewhere I found an article about a top-end manufacturer in southern Germany that made its speakers with a layered structure. Interesting!
Since I donít have a CNC router or know anyone who has one, that was out of the question. The only option was to use a saw, I decided. Since the whole thing seemed to be shaping up as a jigsaw project, I did a test with a scroll saw. With a new blade, it handled the 19-mm MDF board perfectly. So it was decided Ė I would be sawing!
The only question remaining: what would I be sawing, exactly?
Anyone doing online research about DIY speakers is bound to come across the LoudSpeakerBuilding.com page sooner or later. The building reports and the results of the projects presented here are fantastic! Itís amazing what people can build in their basements, living rooms and even bathrooms. ;-)† HATS OFF!!!
Since I was interested in a compact loudspeaker, I focused on those assembly kits. The SB18 seemed like the best one for an initial attempt. It was in the Blues Class, but still a reasonable price.
Now that I had chosen the assembly kit, I could start planning the cabinet. I used CAD to determine the new shape and its dimensions, based on the specified volume. Each cabinet needed 21 layers plus the lid and floor.
By now it was October, a little too changeable to be working outside, so I moved myself, my saw and my woodpile into the garden shed for 3 days. Even though I set up my workplace very ergonomically (standing up straight and all that), I have to say I donít recommend all this sawing for people with back problems!!! Once all of the pieces were cut and each one had 6 holes drilled in it, it was time to start assembling them. The individual layers were threaded onto a set of rods and then glued and clamped.
Itís hard to work as precisely with a saw as with a CNC router, and the cabinet walls showed it. I used an orbital sander to smooth the sides. An intermediate attempt to smooth them with spackle was rejected. The thickness of the cabinet walls allowed me to sand everything completely once the lids, floors and pre-cut baffle boards had been glued onto the cabinets.
I didnít scrimp on materials during the gluing process, so they were probably pretty well sealed. Just to be on the safe side, though, I also painted the inside of each cabinet with sealant. Now the raw cabinet bodies were finished.
Since I hadnít heard of the SB18s before now, I decided to stage a test run. The test would show me whether the effort had been worth it so far, or whether I could save myself the trouble of applying the veneer. The crossover, which I had soldered in the meantime, was quickly attached to the chassis; I laid an auxiliary line through the bass reflex tube and out to the amplifier.
Itís probably a little strange to throw in a sound report at this point in the building report. So Iíll limit myself to saying that I was absolutely thrilled, and the SB18s had definitely earned their veneer.
The evening before the planned unveiling came the big shock! One of the cabinets had a crack almost all the way around Ė and it went through the entire thickness of the material. All my attempts to patch up the crack failed, and in fact 2 more showed up. All that work for nothing!! The other cabinet, on the other hand, was perfect. If I hadnít already heard the loudspeakers at this point and recognized their potential, I probably would have quit right then. I think the cracks were due to poor-quality material, and the wood had come from two different sources. I was pretty sure which source was at fault, so I bought the new wood from the ďbetterĒ supplier.
Armed with another stack of wood, fresh saw blades and a thermos of hot coffee, it was back to the garden shed with me Ė this time in freezing cold mid-February. But what must be, must be!
The next steps Ė sawing, gluing and sanding Ė were familiar already, so they went pretty smoothly. It did take a while, though, because of the harsh winter. Finally Cabinet 2.2 was finished, and I put it under ďcrack surveillanceĒ for a couple of weeks. This time, though, I was able to give it the green light, along with the first cabinet.
The SaRaiFo veneer was wonderfully easy to work with, using Pattex high-strength adhesive gel. The veneer has a layer of fleece on the back, which makes it much easier to bend. Because of the rounded back wall, I decided against a terminal. With a simple drilling jig, I drilled countersunk holes one above the other, and installed fully insulated pole terminals.
In terms of sound, I think the SB18 is just great! I am always amazed that so much depth can come out of a compact loudspeaker. Unfortunately I canít really describe my listening impressions very well. The SB18 is just a great speaker. Kudos!!! I canít say whether my modification to the cabinet shape had a positive or negative effect, since I never heard the original model. But it would be interesting to compare them sometime. Maybe someday I will have the chance. I know I didnít reinvent the wheel with this project, and I used techniques that are already well-known here and have been used before. Despite the temporary setback, the effort was worth it. The project was super fun, and it kind of made me want to do more.
SO BE CAREFUL! The SB18 is obviously a gateway drug!
Best wishes, Stefan
p.s. I didnít throw away the cracked cabinet, I found a new use for it!