SPEAKERS enclosures are fascinating! It’s amazing to think that we can manipulate sound waves and air with mere clever engineering of the boxes (or simply the panels they mount on).
For example, with a simple bass reflex, make a certain box size, get a tube, cut a hole for the tube and the speaker driver, mount them in and voila, you have bass. Make the box bigger and the tube longer and hey presto, more bass.
As a beginner DIY speaker builder with a mechanical engineering background I consider myself to be quite free of the myriad of “traditional” speaker design theories, particularly in choosing materials to build the enclosures. Although I haven’t built many of them, I have all sort of design ideas.
I looked at a pencil made of paper and thought, “paper speaker enclosures, hmm”. I found a company that can machine one-off prototypes from high-grade steel and aluminium, “hmm, bookshelves from a single aluminium billet”.
Before the Formula SAE project was cancelled at my university, I was welding some steel tubing and thought to myself, “steel spaceframe/wood hybrid speaker enclosures”. When my cousin had her wedding at our house and we had a typical nasally sounding PA system for the karaoke, I thought to myself, “why don’t I make a concrete/wood speaker system that match the water feature?”
Honestly, I think the magic is with the speaker boxes. Like the internal combustion engine, we’re pretty much reaching the limits of speaker driver technology. We’ve made pretty much everything, from carbon fibre/Kevlar diaphragms, to plasma, and every combination of magnet and basket material and construction we can think of.
With enclosures, it’s boring. We’ve made speaker enclosures for decades, and we’re coming up with the same old thing! They all look different, but like cars, are they really that different? Same sort of engine, same number of tyres, same sort of configuration, same sort of chassis designs. With cabinets, it’s pretty much MDF and plywood with the same sort of drivers.
In rare cases, aluminium and composites come into play. It’s about time we try something else. Fibreglass with aluminium honeycomb, carbon fibre and stiff rubber sandwich, recycled plastics, paper and carbon, stiff foam sandwiched in fibreglass!
I’ve tried my hands building a transmission line speaker out of hard wood. Wood movement made it a pain to get a very neat fit but I don’t give a s***. Colouration? You bet. Bad? Not bad. Plus, at least it’s not some plastic junk that passes itself off as “extra bass speakers”. Real bass, and real wood is what I delivered. Not even the TV table is real wood, so the speakers are sort of one of the centrepiece of the living room. It’s been a year now and even with the fluctuating humidity and temperature of this country, the speakers are working great. I wasn’t stupid enough to not take any measures of course. There are metal brackets and wooden dowels for bracing. Had to compensate for at least one litre because of that.
Next, I will probably try to machine a baffle with waveguide out of 6061 aluminium, aluminium bracings, and maybe source a 2mm thick aluminium panel for the shaped sides. “Oh it’s going to ring, oh it’s unnecessarily expensive, oh it’s just a fashion statement”, well it probably won’t matter if I do it properly, yes, and yes. Sound is important to me, but I won’t let it get in the way of having fun. I am a person who would rather go, “holy crap, that went beyond what I was expecting!”, rather than, “I followed everything by the book, and this is my reward!” We all got that latter one, at school all the time.
Time to move on and try new things, reward yourself from trying new and risky things. It’s not just the materials, with all the configurations of speaker boxes, then we can really have fun! Transmission lines, horns, bass reflexes, acoustic suspension, sealed, multi-chambers, the lot. We are controlling sound waves and air. I still get a grin whenever I’ve made a bass port that works, even though the working principle is just school grade science. I giggled once I got a parabolic speaker working.
Maybe it doesn’t have to be in a box. Open baffles are wonderful creations, and opens up a world of possibilities in terms of design. They should be the standard for mid-tier home theatre. They sound relaxed and pleasing with dialogues. They require cheaper high Qts speakers, and only a hole through a piece of thick board or panel to be mounted on to. They’re big, but have you looked at other high end systems?
They’re probably the “easiest” thing to engineer for a DIY person, rather than having to make the driver, but it is the most exciting part of a loudspeaker. A speaker driver, no matter how good, cannot hold its own. Whether done by a DIY person or a professional designer, mount them into an enclosure and it could be almost anything you want; a mid-centric speaker for vocals and acoustics, or a speaker with broader range of bass for movies and broader genre of music. Or maybe even a very clean sounding open-baffle with interesting spatial characteristics. Maybe you want it to be a functional yet decorative piece of aural hardware? You decide.