Boombox, part 5
Uh, where to begin..? Certainly been lazy with any updates, but quite the opposite with building this ‘thing’ :). Lots of small issues sorted out, plenty of adapting on the fly as well as some amount of re-do, all (finally!) mounting up to a point where the Boombox actually started making noise!
I sure can’t recall the details of even half of all the work I’ve put in, but picking things up from last time, let’s start with the analyzers. I ended up adding a separate 3.3V switch mode DC/DC converter board for them and housing everything inside a small junction box. The analyzer boards used a 10k linear potentiometer for sensitivity adjustment and thus, wiring both to a single stereo potentiometer seemed like a good idea. Too bad I had only a logarithmic potentiometer at hand so as it is for the time being, the adjustment is a bit tricky. Will replace this once I have the proper part.
Briefly summing up the other board mods besides the potentiometer, I angled the microphones at a 90 degree angle (mandatory to fit everything inside the junction box) and wired the second board to use the power switch from the first one. The microphones are right next to the rear 6″ speaker, so I doubt the analyzers will react to anything else than what’s adjusted to sound from this speaker (=BASS!). The 3.3V board is recycled from binned “work stuff”.
With the treble compartment, its top panel was ‘no problem’ whereas the angled one turned out ‘re-do’ all over. Indeed, there was ample space between the 2″ / 1″ speakers for a iPod cradle/dock, but the first design for the angled panel simply proved my 3D dimensioning skills very lacking. Not that all the 2D stuff was in place either.. :). Summing up, I simply forgot to secure ‘odds and ends’ that would’ve actually contributed to me ending up with anything usable right off the bat. Pick up the differences from the following, if you like..:
Whereas the first angled panel was made from 9mm plywood, the second one is 16mm particle board (same as on the top panel). Among helping with many of the “three-dimensional” mechanical issues, the material change also allowed adding a recess for the iPod dock. Despite it slots in with the angled panel firmly enough as-is, I decided to secure the parts together with a short piece of ventilation suspension band.
Besides the speakers, the treble compartment also houses a cigarette lighter jack. This can be used for connecting the Boombox to the electrical system of a car (fuse needs to be added) or for supplying +12VDC to other devices from the car battery. Just to have something for the latter, I ordered a small 1000mA USB power converter. Might come in handy for charging a mobile or such..
In order to fit to the rear 6″ compartment, the reflex tube needed a bit of cutting from its inner end. No idea about whether this affects its performance in some way, but if you do feel free to enlighten me. I cut away small pieces from the top and bottom, should be pretty evident from the picture above. In case you’re wondering about the grille in front of the speakers, that’s something recycled from a door of a old webserver rack and cut to proper sizes.
I also decided to stuff the 6″ compartments with some old pillow fiber fill. I recall reading somewhere that the added material should improve bass response in some way, but without any actual data to back this up (or the interest to run comparison tests) I can only hope that the speakers will be “better” this way. Both 6″ compartments are also sealed airtight with weather/seawater resistant acrylic sealant. Minus the reflex tube on the rear compartment, of course! The treble compartment I left without any: Thanks to the cigarette lighter jack and the iPod dock the compartment is “leaky” anyway so why bother..
Once the sealant dries up (as in, tomorrow) there’s not much anything else left than securely mounting everything to the beer trolley and maybe applying last dabs of paint here and there. Somewhat just in time for my last week of holiday, there’s a fair chance I’ll even get to the “park bit” without having have to wait until next summer :)