Figuring out a use for ‘50 digital wood joints‘ I posted about earlier sure didn’t take too long.. Simply ‘extremely inspirational’, and I doubt the content provided can be over-advertised ;)
The actual project this time around is a pair of Auratone 5C clones by DaveP @ GroupDIY, complemented by the aforementioned woodworking finesse.
Breaking from my norm of writing multiple work stage posts, I decided to try rolling everything to a single post. Since the bulk of work is pretty much sourced from the internet and around the ‘drawing board’, there’s only build related details to write about. Once I had the part design figured out and CNC’d, the assembly was a snap.
Before diving into the build though, some words about the 5Cs. These are small single-driver loudspeakers manufactured during 1970s which, AFAIK, are still pretty common in studios as ‘single driver reference”. The popularity has to do with the 5Cs having a somewhat emphasized mid-range frequency reproduction, which makes them very usable for checking that your mixdown isn’t cluttered on the mids. This also helps checking that bass instruments actually contain higher harmonics which makes these present ‘in the mix’ if the song is played on systems lacking on the bass reproduction department, like cheap portable radios or TVs.
Given their popularity there are of course a number of modern replicas in the market, like the Behringer Behritone C5As and Avantone Mixcubes. However these both are active speakers (built-in amplifier), and in my opinion, this slightly negates the intended target as ‘amp variable’ is pretty much ruled out of the equation. I doubt I’ll be switching amps a lot, but retaining the possibility to do so is a welcome feature.
Keeping the intended use in mind and knowing I have a tendency to overpopulate the mid-range with my own tunes, the ‘Davetones’ sound much like something that might help me work things on that end. I did consider the Behritones too, since they don’t really cost a fortune. It’s just that ‘all pre-fabricated and no DIY makes Arto a sad boy‘! :,-( *SNIFF*
The drivers DaveP had found are called ‘L69AW‘ and he states them to be, by frequency response, a pretty close match with the ones used in Auratones. The drivers also are magnetically shielded, so placing speakers next to magnetically sensitive devices (like CRT screens) should be ok.
If you, like me, are located outside UK, the biggest downside with these drivers is that they’re only available through Maplin. Conveniently enough, they don’t ship abroad so a bit of local help is needed to get these delivered. In my case, I get to send greets to Andy: Thanks mate! :)
For the enclosure, my idea was pretty straightforward: Make four identical pieces to form the sides and have grooves for for inserting rear and front panels. For the side part, I ended up with the following design after a couple of revisions:
Here, light blue areas are the slots for joining side pieces, yellow ones are the front/rear grooves and white is the piece edge. The piece measures 176*186mm and I chose to dimension cut depths for sheets 18mm thick. For all you imperialists out there, I think that’s about 3/4″. Process the drawing through the CNC and voila:
My initial thought was to use recycled particle board for the panels, but as I had just about the right amount of suitable pine planks I went with those instead. Guess you could call them “vintage” too, as the planks originate from a kitchen shelve my dad built during 1980s! Way later on the shelve ended in my use and, in the recent years, being stored away unused I’ve started recycling the parts for various build projects. This project marks the ‘last of stock’ for these shelve parts, and it gets to continue serving.. albeit as loudspeakers!
As you can see from the above, I had to anyway use particle board for the rear panel. This was because the CNC machine decided to crap out on me during milling, which in turn led to a number of defective panels and leaving me short of materials. As it turned out, the CNC y-axis drive wheel/bar combo had developed some slack, resulting in random skidding and thus “recalibration” occurred mid-program. But whatever, the change in materials isn’t too bad. Rear panel is ‘out of sight, out of mind’ enough anyway :)
With all panels CNC’d I started looking into test-fitting them together. Since its wood were talking about, checking for best-matching pairs prior to adding glue is a must. Whereas the front/rear panels slotted in pretty easily, the tenons instead turned out very tight and required fair amounts of forceful hammering for a good fit. To make them a little less so, I ended up chipping away miniscule amounts of wood from the sides of some tenons. Might not be a bad idea to add something like .1 mm to the slot width to future designs..
.. and this ‘dimensioning fail’ proved true for front/rear panel grooves too, although I noticed this only after adding glue ;). I even secured the opposite panels with bar clamps whilst the glue was drying up, but neither they could squeeze the parts together. The grooves are just too snugly dimensioned, so every edge did not fit in too neat.. and maybe I overdid the amount of glue too! Anyway, should just add a millimeter or two extra depth to the design to accommodate glue. This wouldn’t break the driver/cable terminal center alignment either, thanks to my front panel design handling that by default.
By the way, the double cable terminals I’m using for this project are recycled from some broken amplifier. If seeing them made you think I’m about to go bi-wire, I’m definitely not down with that (british?) silliness! These terminals were just something which I happened to have a pair off.. Plus they do have the 3mm nuts included for easy assembly :)
Once the glue had settled, I gave the front a quick sanding and applied wood filler to hide the gaps. It actually sucks a bit that things came to this, since I was planning to use some wood varnish that’d allow the grain to show through. But the varnish would’ve looked rather crap over wood filler, as all the treated spots end up with a slightly different color tone and also break the grain pattern.. Solid color it is then, and why not go overboard while at it!
Where colors are concerned petrol blue is one of my favourites, and you can bet I was delighted to find a 1 liter can of Sadolin Fashion Extreme Stylish Petrol (wtf!?) wall paint in this color on discount for 5 eur! After applying two layers the rear panel still looked slightly uneven (less absorptive material), but otherwise the finish is pretty smooth. Only minimal brush marks visible up close. Must admit my camera didn’t capture the color tone quite right, as it looks slightly lighter/brighter and blueish in the pictures below than it actually is.
Assembling the speakers revealed one more dimensioning problem. This was a combination of dried up paint blobs, cables and panel thickness: As the driver cable terminals had grown in size (cables soldered in), the driver didn’t fit inside the hole on the front panel anymore. Had the panel material been less thick, the terminals would have (sort of) slotted in over the inner side, when driver is inserted at an angle.
Anyway, I worked around the problem using the quick hack pictured above. A slot for the terminal and paint blobs removed, both chiselled using a drill bit. How clean <3. And there they were:
Material costs for these speakers added up to about 40 eur. This includes speaker postage and the full can of paint, so the actual material costs are somewhat lower. Not too bad at all. Maybe about one eight of the paint got used for this project so it’s easy to guess that the remainder will find its way to future builds.. ;)
I did a quick listening comparison against Alesis M1 Active MK2 speakers, and boy oh boy are these Davetones “mid”. Could just sort of “see” the frequency graph in my mind whilst listening, no real bass nor treble. Should be pretty interesting to put these to use on a real mixing situation. I’m also curious about A/B-ing the Davetones against other speakers (maybe the Avantone Mixcubes) , but I’ll leave this for a later post.. Need to see what I can arrange.
Despite this project was a complete ‘learner’ where CNC’d wood joints are concerned, I’m still just pretty blown away by the whole subject. Will definitely make use of what I learned on the topic later on :). Big thanks to Jochen Gros for sharing the wood joints @ Flexible Stream!