Designer: Dave Burke
Project Time: 8-20 hours
Project Complexity: Hobbyist
Project Cost: $100-$500
The pipes are roughly 71″ high, 5.5″ wide at the top and 9.5″ at the bottom. With careful layout, the entire set can be cut from one sheet of 3/4″ MDF and assembled in one day depending on finish. Andy’s crossover is a simple first order series with L-pad, only 4 parts. The woofer is the venerable Vifa P17WJ and the design calls for the Vifa D25AG or D27TG-35 tweeters. I had a pair of D27’s, but also a pair of PL27TG-35’s on hand. We decided to build with the PL27’s in mind and try to match up with the similar D27’s for a tweaking lesson and a good listen to Andy’s original crossover.
The pipe design served well in all aspects of our requirements, although our particular finish took far longer than we had planned. Between Christine starting a new job and the unusual weather, the finish took over a month and we still have the final clear coats to do. This extra time was used to evaluating different tweeters and crossover topologies. First the two builders assembled Andy’s crossover supplied with the plans. The padding resistor was adjusted for the D27TG-35 tweeters and a test session followed. It was obvious from the first listen Andy had spent a great deal of time and effort on designing the pipes. The sound was open and detailed, however the top end needed to open up slightly for the D27’s. A trial with that crossover and our target PL27’s brought disappointing results. Several adjustments later the D27’s really came to life, but we were no closer with the PL27’s. After consulting with PE Paul who gave us some great insight, we focused on bringing the PL27’s into line. 13 different combinations were tried between 2300-3100hz and our final design ended up at 2450hz. Here’s our final crossover for the PL27TG-35 tweeters.
The following is a pictorial with comments of the building process Christine and Michael followed. Anyone with minimal skills and tools can build these in one day. To construct the pipes they used a circular saw, router, $2 garage sale jigsaw, sander, and an old wooden bed frame and 4″ C clamps as a straight edge and saw guide. All construction was done on our 14′ x 12′ patio behind the garage. With instructions and classes, building the pipes was spread over a 2 1/2-day period instead of 4 to 5 hours. A scale drawing was done after converting the measurements from metric to inches. An order of construction steps was drawn up along with possible finishes for the pipes. The cuts were laid out allowing for the width of the blade cut and including an 1/8″ overhang on the front and back pieces to be flush trimmed with the sides. Front and back pieces were laid out using a centerline to retain an even angle to the top. Sides were laid out with a 90 degrees on the back of the pipe and the sloping angle to the front baffle. The distance from the edge of the saw base to the blade was measured and the blade width added. They measured this distance from the layout lines to clamp down the bed frame section as a saw guide. The last front/back piece was 1/2″ too narrow, so a piece of scrap was trimmed and butt-jointed a full 3/4 of the length by clamping both to a table over a strip of waxed paper. As the glue dried we found the oversize piece and trimmed it up while discussing the “measure 10 times, cut once” idea. After sizing up the cut pieces and doing a dry fit, front and back pieces were chosen and the pipes were glued and clamped. The pieces were glued flush at the pipe base allowing any excess in lengths from the odd angles to overhang the top of the pipe, which would be trimmed later. The sides were clamped to the fronts first allowing the 1/8″ overhang to be flush trimmed. Michael took over as Clamp master having helped on previous projects. It was 114 degrees and the glue was not waiting, so the pipes were glued up in record time. Screws and washers could be used in the absence of a large number of clamps. One construction note is the order we chose over Andy’s recommendations. He advises the woofer and tweeter recesses and cutouts be done to the front baffle and the fill installed before the last piece is glued. This allows the fill in the top half of the pipe to be easily installed and further tuning can be done through the woofer cutout. We elected to do the driver recesses and cutouts after the pipe was glued up and to install the fill from the open end and woofer cutout. I would recommend that the fill should be installed to at least the top 1/3 of the pipe before it’s buttoned up. Wadded up newspaper can be used to keep dust and chips out of the fill. But stuffing the pipe after it is together can be problematic because of the small dimensions at the top. A small end piece is installed before the back is glued and clamped. After it dried, a block and 60 grit sandpaper was used to sand it flush with the sides before gluing the backs on. After a quick safety lesson, the excess glue was sanded off the pipes and the baffle and backs were flush trimmed to the sides with the router. The excess at the tops of the pipes was trimmed using a square as a saw guide and the front baffle as the base. Here I allowed a break in the rules. After routing the driver recesses and cutting a through hole for the woofer with the jigsaw, they were down to their last blade and we needed that for the mouth openings. So out came the RotoZip to finish up. I was glared at for at least a half an hour when the last 2 holes were done in less than 30 seconds. The plans called for the baffle to be cut at the top of the mouth opening and 2 pieces glued to the side edges to finish the baffle. We elected to keep the baffle one piece. The mouth opening was roughed out with the jigsaw and finished with a flush trim router bit. A large piece of Plexiglas was attached to the base of the router to span the opening. A straight piece of scrap was clamped to the pipe forming a guide for the top of the mouth opening. Temporary bases were cut and attached to enable accurate measurements for the reflector piece. UPS arrived much like Christmas in the summer. Michael checked off the list and we were able to test fit the recesses and cutouts. I have to comment on the great service from Parts Express, but to deliver within 30 minutes of gluing the last piece is unheralded service. By the way, I haven’t seen that catalog since Michael got his hands on it. The last piece was the reflector. I had wanted to find the radius of the mouth cross section and install a curved reflector, but that was adding unnecessary complexity to the simple project idea. So we averaged the radius and came up with a reflector smaller than the plans. We decided to try it, and glued it at a 45-degree angle to the centerline of the pipe. With the cabs assembled a hole was cut for the terminal cup below the level of the reflector. Two sheets of felt were glued to the inside back of the cabs behind the woofer and tweeter. The top half of the pipes were stuffed with approximately 12 oz. of poly-fill down to the top of the woofer. A 3-wire harness was assembled and run from a hole through the reflector up a back corner to the speaker cutouts. The entire wire length was hot glued to the back corner to avoid wire rattle and vibrations. Michael and Christine each soldered up crossovers on a 5″ X 4″ piece of Masonite backer board. The crossovers were mounted to the bottom side of the reflector using 4 spots of hot melt glue on the backside of the crossover board and phillips head screws. The finish was left to Christine and Michael, and turned out to be the greatest amount of work. The pipes were sealed and sanded multiple times until a painted finish could be applied. Their original finish was to be a candy blue fading into a candy berrywine with a smoke black base. A trip to the local custom auto paints store left that plan by the wayside. Kustom Kolors candy lacquer was $50 a quart and that did not include the price of reducer or base coat. So on sale candy apple red and base were bought from the bargain bin. The pipes were first sprayed 2 coats of satin flat black lacquer for the smoke black. The tops were masked using low tack fine line tape and given 2 coats of silver base and 3 coats of candy apple. The stripe was again masked with fine line tape and airbrushed with 12-CT gold lacquer. 2 coats of cut high gloss clear were applied over the whole cabs. When the cabs are completely cured (in another 2 weeks) they will be polished out with 3M Perfect-it III finishing glaze and given 4 final coats of high gloss clear. Mouth opening and back are done in flat black industrial lacquer with light texture. The bases were cut from glued 1.5″ slabs and then a 1/2″ 45-degree edge break was cut. They are finished with Minwax colonial stain and 4 coats of Deft high gloss lacquer.
The parts for the pipes were less than $150 plus wood and finish. These speakers are very easy to construct although our finish was far more complex than usual. Typically these can be constructed in one afternoon and finished in veneer or other finishes to taste. They are quite elegant, and have been the all out favorite of the many visitors since the project began. The sound is exceptionally clean and open and prefers a good volume level. Bass is tight and defined and improves with volume, although at light listening levels seems to be lacking. The mids and highs are close to neutral, a shade warm but not forward. This seems to be a quality of many of the Vifa tweeters and the pipes match up extremely well with the P17WJ. Overall, a very good design, and a good project for beginner and experienced alike. Christine and Michael enjoyed the project and have dubbed them the “Snipers.” One final note concerns the base. A heavy base is recommended, and improves the bass performance dramatically. We chose to spike the bases because of our light base material. For a complete set of plans go to http://users.tpg.com.au/users/gradds/ARGOS/taperedpipes.htm. For use with the PL27’s I would suggest trying the crossover above and tweak to your own tastes. Many thanks to Andy Graddon for the great design, and input and ideas throughout the construction process. Thanks also to PE Paul, Lefty, Craig, Wil Kelch, Rob, Chris8 and many others for guidance and general good-natured heckling and prodding.
About The Designer
David, Christine and Michael Burke live in Idaho and enjoy a variety of interests and hobbies, from the highly technical to baking their own cultured sourdough bread. This was Michael and Christine’s first speaker project.
Project Parts List