My friend Michael Fidler was having a clearout, and offered a surplus pair of MarkAudio Alpair 10.3 drivers. He imparted to me some of his knowledge in loudspeakr design, and leant a hand in the box modelling to create the speakers herein.
These are full-range speakers with only a single Alpair 10.3 driver directly wired to the output terminals. No crossover, though one might be benefitial to tame their response a bit. I did toy with the idea of adding a tweeter but I was keen to hear a larger full-range design after being impressed by my CHN-50 build some years ago. I also considered buildin ga sealed box which has become my preference, but simulations showed these drivers perform better in vented designs.
We therefore chose a vented design using a pair of slotted ports, , tuned to approximately 48Hz. THe cabinet is roughly sized to a ratio of sqrt2:1:phi, though the last-minute addition of an extra 12 mm to the front baffle means external dimensions are actually 207 x 276 x 440 mm (D x W x H). Internal dimensions are 159 x 240 x 404 mm, approximately 15.43 litres, not including the volume of the port material or the driver. The drivers are centred horizontally on the baffle and 250 mm vertically from the top, putting the driver closer to the ports for aesthetics and allowing space above for a tweeter to be added later.
The speakers were build using scraps of MDF that were cluttering up teh workshop. The veneer is Ayous, chosen because it was the cheapest veneer available and because its straight grain should have made it easier to follow the baffle edges.
The rounded edges presented a challenge to veneer, as they are a 9.5 mm radius. I didn’t have any radiused clamps, or at the time a vacuum bagging setup or suitable press. I discovered that applying two coats of PVA to the cabinet surface and the rear of the veneer, and allowing them to tack, would form an adhesive layer that could be bonded with an iron. Additionally the heat from the iron assisted the veneer in following the rounded edge, mostly without splitting.
The downside to this method is joining pieces. THe iron quickly evaporates any moisture held in the veneer, and causes it to shrink. THus joints that are cut perfectly before heating can separate and require filling. There is no easy way to overcome this besides careful application of the iron, and filling gaps with veneer dust where necessary. Given the choice I would always prefer clamps or a press, but while not a perfect veneering job this method worked surprisingly well.
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