Franks SB 417Article byAlpen01 about speaker kit SB 417
Hello, loudspeaker builder community!
It’s high time for me to write my first assembly report. Now that I’ve been enjoying the sounds of my SB 417 for several weeks, I want to let you in on its creation story. It all started in the summer of 2012. I was looking for something to balance out my stressful work life, and I thought back to my childhood and youth. In those days, inspired by a hobby-corner TV show, I had a lot of fun building my own speakers. Now I wanted to revive that hobby, but this time to produce somewhat more sophisticated systems. After some internet research, I ran across Loudspeakerbuilding.com and devoured a huge number of assembly reports.
As my first project, I built two SD315BP subwoofers for our party area and home theater, since the existing PA system was missing the bottom octave in home-theater mode. Unfortunately I can’t contribute any pictures of this project because I was caught up in the excitement of the work and didn’t have the camera handy. After discovering all the low-cost DIY possibilities – which surprised me – I immediately started looking for my next project. I wanted it to be something from the Blues Class so that I could rediscover my extensive music collection. I stumbled across the SB 417, which fit well in our apartment because of its narrow profile. The SB 240 was one size too big for me. Since it’s a long drive to the listing room for me – according to Google Maps, 419 km and more than 4 hours – I decided to buy the SB 417 assembly kits sight unseen (or rather, unheard). I can now say that I wasn’t disappointed!
After a few days, the shipment arrived in late September and I was finally able to get started. I had the MDF cut to size at my local hardware store. To make sure I wouldn’t have to throw away the whole cabinet, I started by cutting the openings for the chassis into the front panels.
Illustration 1: Everything cleanly sketched out
Since I didn’t have a routing template for my router, I built my own simple routing template from wood scraps. First I glued a slat to a board and then drilled two holes at the appropriate intervals, which I used to attach the guide bars for the router with two screws. I sawed a slit in the board so the router head could reach its actual application spot. The guide in the middle of the template was provided by a 4-mm screw that I countersank about 1 cm behind the end of the slit. I was able to create a routing template, using the simplest in-house materials, that can easily cut out even the smallest radius.
Illustration 2: The router using the homemade routing template
The depressions for the chassis were cut into the wood using the router; the jigsaw then cut the actual openings out of the wood. After that came the “test fittings” for the chassis elements. I was lucky – they fit. The extra millimeter I had cut out wasn’t a problem because the coat of paint would make up for it. I did cut out a little too much with the jigsaw for the tweeter, though. I had to fill in those gaps with some wood putty, but I wasn’t sure whether I could still make the tweeter air-tight in the cabinet. In order to make sure that the air set in motion by the bass couldn’t whistle out through the tweeter, I used wood slats and scraps to build a small chamber for the calotte. I vowed to make the cutouts a little smaller for my next project, and to do the rest with a file. Since the volume loss is much smaller than 10%, though, I’m not worried about losing sound quality due to the extra chamber.
Illustration 3: Extra chamber behind the tweeter, made of wood scraps
Once the rough construction of the cabinet was finished, it was time to build the frequency crossover. First I tried to optimize the component positions on paper. After some email correspondence with a couple of suggestions and tips, the crossover layout was decided, and I attached them to wooden boards. The wiring was done on the back side, and the whole thing was then attached to the rear wall of the box using spacers.
Illustration 4: Frequency crossover, Frank’s SB417
Illustration 5: Frequency crossover with spacer in the box
Once the crossovers were in place, I filled the cabinet with Sonofil and glued on the second side wall. Heavy paint buckets provided the necessary pressure. I could hardly wait to put in the chassis elements, and I was anxious for the first listening test. A day later, it was finally time. The speakers stood in our apartment in their rough MDF clothing, and I connected them to my Pioneer VSX -921 at Output B. I turned off all of the bells and whistles that might influence the sound, and the first listening session began.
Now I know what they mean by Blues Class. I have two MB Quart S980s standing in my office, but the SB 417s were better than those speakers in every way. The SB 417s have more pressure and precision in the bass range. The highs are clearer and don’t tend toward sharpness the way the MBs do. The whole stage feels larger and more precise with the SB 417s. These comparisons involve very subtle nuances, or as the SB 417 assembly report so nicely puts it, “you need to have the same background in order to understand the description.”
Even though I resisted the suggestion to come in for an extensive listening test because of the long drive, my enthusiasm wins out here. The SB 417 is a lot of fun, and I really am discovering my music collection all over again.
That could be the end of the assembly report, except that I haven’t talked about the finish for the boxes. Before that step, though, 4 weeks went by. My wife was starting to think that the natural wood color of the MDF looked pretty nice, too. But I wasn’t completely satisfied with the original outfit. Inspired by the Loudspeakerbuilding magazine, I started to think about the look of the boxes. The cabinet for the Little Princess with beech glued onto the sides looked very good – but my cabinets were already finished. The article about the Eton 2U XXL finally gave me the idea for the cabinet design. The front and back sides are painted black, and the sides have pine boards glued on, which would look good with our furniture.
In mid-November I finally had a couple days of vacation to finish my SB 417 project. I took the chassis elements out of the cabinet one more time – good thing I had saved the boxes. Then I sanded and primed the cabinets. There was the usual cycle of sanding and painting. I rounded off the side pieces and adjusted them, then painted them with clear varnish. In addition to glue, I used 6 countersunk screws to attach the side pieces – that made the assembly quite a bit easier.
Illustrations 6, 7 and 8: Sanding and painting, and the rounded side pieces.
Once I had attached the side pieces to the cabinets, I painted the entire cabinet with a layer of clear varnish.
Now the SB 417s have taken up their rightful place in our living room, regaling us with their music. Even if the cabinets aren’t perfect and you can tell it’s a homemade project, I’m happy with the results. For an office guy who doesn’t normally do much carpentry or painting work, I came up with some pretty nice-looking boxes.
I hope you enjoyed my assembly report, and that I encouraged a few of you to try your own projects. My next project is already underway, because the “evil sound cubes” in the TV corner just don’t measure up anymore. I’ve already ordered the Vota 1 and 3 assembly kits.
Thank you again for all your help.
Greetings from the Wilstermarsch region!