It's probably more a sign of being a contrarian than anything, but just when the Yamaha NS-10 was hitting its peak of popularity I was busy messing around with Dynaudio raw drivers. Back then they were freely available to the DIY market and I eventually settled on the 17W75XL mid/bass and D-28 AF tweeter in a configuration very similar to that which would later be used in the BM6 passive near-field.
For better or worse, that was my "monitor" setup for the next decade or so and like anything I eventually got used to the sound and could make fairly good judgements by them. Once Dynaudio Acoustics entered the "pro" market I was on to the next thing ;) But after reading the SOS article on the NS-10 I thought I should find out what I was missing a couple of decades ago.
Used systems often come up for sale, though the condition of the drivers is often unknown and the shipping costs are prohibitive. Even though the NS-10 was discontinued a decade ago, parts are available regularly on Ebay. Rather than pay for shipping a particle board box with questionable drivers, I decided to buy new parts and build the simple sealed box myself.
The crossovers are probably the hardest part to find and I was ready to build my own using the schematic given in the widely available instruction manual. However, I noticed that detailed information on the inductors wasn't given, nor were any measurements available on the internet. I mananged to find a pair of new crossovers and took a few notes in case anyone wants to have a crack at making some from scratch:
L1 40mm dia 25mm high core 1.715mH 0.6R DCR
The inductors appear to be wound on powdered iron cores. Keep in mind that the diameters listed are for the flanges; internal diameter measurements would be impossible without unwinding the coil.
I spent a long time looking for an old particle board table or other piece of furniture with that '80s "Japanned" finish but eventually gave up on the idea of duplicating the look of the original. I decided to go with medium density fiberboard rather than particle board mainly for ease of finishing; MDF isn't nearly as thirsty as unfinished particle board and a smooth finish is easier to achieve. The thickness is nominally 16mm and I used simple butt joint contruction. External dimentions are given in the instruction manual.
I was told by the fellow who sold me the crossovers that the original boxes had a brace with a circular cut-out that went between the woofer and the tweeter holes. I used one of those Jasper circle jigs to cut the hole with a router.
After cutting the hole for the tweeter I dropped the tweeter in, lined it up so it was square to the oversized baffle edge and drew the outline with a pencil. I used a straight bit in my router to cut the rabbet freehand. Far from perfect, but cleaning it up with a straight X-Acto style blade made it look a little bit more acceptable.
Fortunately, the woofer is surface mounted. I believe this allows the voice coils to come into closer alignment with respect to the listener.
Though both the table saw and router are Ryobi brand none of the holes in the table saw router attachment feature would fit. I drilled the appropriate positions and used a counter-sink bit to allow the screws to sit flush.
However, it was worth the effort as it allowed better control over cutting the rectagular crossover cut-outs from the rear panel of the box. I advise, as with the baffle, that you cut the hole before installing the rear panel to the box. That way, if you have a problem you can cut a new piece without having to remove it from the box first. Don't ask how I know that.
Next, I drilled holes to accept screws to hold the crossover in place. Then I used a wood bore to countersink the heads of the screws. While my picture shows the closest spaced pair of holes furthest from the right hand edge, the closest ones should be nearest to the right hand edge. Otherwise you'll have to use the "B" crossover for the right side speaker and vice versa.
I've added the color coded wires per the schematic for the woofer and tweeter.
Once all the screw placements had been determined and pilot holes drilled, I sanded the boxes smooth and coated them with a few layers of water based undercoat, sanding between coats.
Using a cheap Malaysian HVLP spray gun, I applied the first coats of British Paints Ritzy Red interior low sheen house paint. The can advised 100ml of water per liter to thin, but this was far too little to ensure it would spray from my home handyman tool, so I just kept adding water until it reached the correct consistency to spray properly. I did not notice any ill effects from adding so much water to the gel-like paint.
To keep the finish protected, I inserted three of the eight speaker mounting screws to create a tripod on the front baffle as the spraying progressed. Once the final coat had dried, I mounted the crossover, stuffed the box with some glass fiber and soldered the drivers to the correct wires shown earlier.
Credit to the guy who started this thread for inspiring the color choice and for showing why buying used systems from Ebay probably isn't the best idea.
L2 28mm dia 20mm high core 591.4uH 0.6R DCR
