Building the Voigt Pipes

The Voigt pipes stand 72" tall and use Fostex FE166E drivers. These are the same drivers used in the Cain & Cain Abby, which inspired the cosmetic finishing.

These are the plans for a pair of Voigt pipes built by Herbert Jeschke, taken from the single driver website at http://www.melhuish.org/audio/DIYTQ4.html The Voigt Pipe is a Tapered Quarter Wave Pipe enclosure, which is a very old design and not very popular today becasue of its size (if built full length like this one) or the complexity of the cabinet if built as a folded horn. But it's one of the easiest speakers to build if built full length like this.

You begin with two 4' by 8' sheets of mdf or plywood. I chose Baltic birch veneer plywood becasue my friend Paul and I built his Hammer Dynamics enclosures from this material, and the plywood is very attractive with just a coat of varnish. I had built a pair of pipes before using Radio Shack drivers and mdf, which are less expensive, but they didn't look or sound very good so I gave them away.

First you rip the sheet to make it more managable. Leave the remaining sheet a few inches longer than the 71" length for reasons I'll explain later. Then you rip the boards to the desired width. Each enclosure is built from only three boards: the front, the back, and the sides which are split from one rectangular board.

It's surprisingly easy to get two identical triangles from one board. I used another board as a guide for the handsaw. cut along the line, then drew the shape of the first side on the remaining part of the board.

I used some sophisticated tools cause I have them, but all the cutting for this project can be done with an inexpensive circular saw ($40 at Home Depot). Those little battery powered saws are useful for small jobs like this, but their endurance is about one cut, then you have to recharge.

Here's one completed side sitting atop the remaining piece. This is why you start with an overlength board. After you have cut one, you just lay it over the other and cut the bottom of the second triangular board to produce two identical sides. Be very careful handling the sides before the cabinet is assembled; the pointed tops are very fragile.

I don't want any visible screws so I'm using 3/4" stringers to glue the sides to the front and back. Here's the front with the stringers clamped and glued. The next step will be to cut the driver and port holes when the Fostex FE166E drivers arrive.

Finally the 6.5" Fostex FE166E drivers arrived, so I can do the driver cutouts next week.

Each enclosure receives three coats of fast drying semi gloss polyurethane varnish from a spray can. To get a smooth furniture finish the varnished cabinet must sit for 72 hours, after which I will lightly sand it with #220 paper and apply one final coat.

One completed enclosure minus its base, standing beside a Magepan 1.6QR for size comparison. This is a very easy enclosure to build. It could be done with a simple handsaw, a scrollsaw for the cutouts, and a drill.

Each speaker base is a 14X14 piece of 3/4" mdf. I rounded the edges and applied a 1/2" roundover to the front and sides. The discoloration is a 50/50 mix of carpenters glue and water which I painted on to reduce the edges' inclination to adsorb the paint, which I will spray on tomorrow. The best paint I have found for speaker cabinets is Rustoleum Satin Black. Like the varnish on the cabinets, you apply three coats, wait 72 hours, sand, and apply one final coat.

Same base after initial coats of satin black paint

One pipe with its unfinished speaker mounting baffle and port baffle set in place to check fit. The round speaker mounting baffle will be bolted on to enable me to substitute different size drivers by changing to a different baffle. The port baffle is decorative. Both will be painted satin black for contrast with the natural wood enclosure.

The painted port baffles and toilet seats (driver baffles).

Checking the baffles for fit with the driver in place.

The speaker terminals are installed

Looking inside the driver baffle at the stuffing, which is lightly inserted in the top section of the pipe, and the eggcrate foam which lines the area of the back directly behind the driver.

Installing the base. It's best to drill out the screw holes in the base to a diameter slightly larger than the screw, so the thread engages only the cabinet bottom and fits loosely in the base itself. Important note: The center of gravity for these enclosures is NOT at the front-back center of the enclosure; it's much closer to the front. It's hard to tell from this picture, but the back of the base is only 1/2" behind the back of the enclosure. For proper balance the front of the base should extend 4" or more out from the front of the enclosure.

The internal wiring with slip-on terminals. I use these initially to facilitate any final adjustments that require me to remove the driver. Then after everything is finalized I will use a direct solder connection to the driver terminals.

The connectors are slipped onto the driver terminals and the driver is installed.

A closer view of the driver mounted on its satin black baffle,and you can also see the subtle grain of the natural birch finish.

A bullet tweeter is recessed into the back to reinforce the very high frequencies and to provide some ambience with reflected sound off the back wall. These are crossed over at about 12khz using a 1.5uF film & foil capacitor and a very small air core inductor (2nd order crossover) and are attenuated to a relatively soft level. Their effect is barely audible but they do add a more realistic effect to the sound of high cymbals, harpsichords, etc.

OUCH! The only thing that didn't turn out as well as I had hoped was the top of the back panel on both speakers. I had to use a handheld circular saw to trim here, and the veneer got chipped. Fortunately it's on the back so you don't see it.

The "port" really isn't a port at all. It's the mouth of a horn, so this 45 degree reflector really does make sense.

Finally, in the upstairs listening room connected to the Bottlehead Paramours. These speakers are a good match for any 2 watt or greater SET amp.