boomboxes

I built and sold boomboxes in high school. A bad business, but a good time.

Below is a quick chronicle of my adventures in audio design and its culmination in my endgame: the perfect hi-fi boombox.

teenage audiophile

I was genuinely obsessed with sound in my preteen and early teenage years. I placed speakers literally everywhere I could imagine myself listening to music. Here’s one strange setup: two bookshelf speakers mounted directly atop my bed’s headboard. I fell asleep to Hi Scores every night for a few months. Great sleep, I think I’d usually knock out by Turquoise Hexagon Sun.

Here’s where I did my homework! I’d spend hours a week in complete darkness, closing my eyes, pulling my chair back, and listening to music. Stereo imaging felt (and still feels) like complete magic– there was no better feeling than to give myself completely to the illusion that the bands were in the room with me.

These were really, really nice NHT speakers that I found at a pawn shop in 2011. I still have the included pair of sealed 12” subwoofers in the back of my car!

early experiments

My first-ever boombox, just after completion. My grandfather helped me cut the holes. My eighth-grade self wasn’t yet handy enough to be trusted with a jigsaw.

A pair of early boomboxes from 8th grade.

That’s a Lepai Class T amp on the left– rather underpowered for these terribly inefficient thrift store drivers. Suitcases were decent enclosures, but I never found a satisfying solution to the rattles emnating from the latch mechanisms. These boomboxes were powered by big SLA batteries harvested from old residential router UPSs and made their way to plenty of soccer practices. The boombox on the right likely didn’t have any internals in this pic– before I started selling these things, I’d typically only have the cash for one set of boombox guts at a time. I’d swap the internals between the suitcases depending on which one I wanted to use that day.

A commissioned lunchbox boombox (2012), built for a client in Maryland.

I progressively learned more about electronics design by trying things, failing, and then learning enough theory to understand that thing didn’t work. As my engineering & soldering skills improved, I was eventually able to design devices with the reliability and robustness one would expect from a real product. I took Etsy commissions for custom boomboxes built into bespoke enclosures. By now I’d moved onto better components; this was one of the first devices where I used a 12v lithium battery rather than a big SLA + buck converter.

I eventually landed a spot in a local shop, although I don’t think I ever sold anything there. I sold devices to older friends and took a handful of commissions, but I never sold at prices that would allow me to turn much profit. I fell into most of the common follies that befall hobbyists-turned-entrepreneurs. I was a bit too bashful to find the price that the market would bear, and I mostly just wanted to get enough cash to build my next project. Lessons learned. Alas, my failed business was perhaps the most important thing I’d ever done. I learned that you don’t have to ask people for permission to do things– you can just do them. I learned that making money is quite simple: just build something that people want, and they’ll pay for it. Most importantly, I began to believe that I could do literally anything, so long as I was willing to put in the work.

My endgame: the perfect boombox

A chance enrollment in Cabinetmaking 1 presented a great opportunity for me to try something more ambitious. My boombox business was starting to eat too much of my time (you can look at my 9th grade transcript for evidence), and I started to think about my next venture, a mobile auto detailing business (I’ll write about that adventure another time). But before I retired, I wanted to take the last of my savings and pour it into the project of my dreams: a portable, audiophile-grade boombox.

design

I knew I’d have to punt stereo separation, but I otherwise wanted this thing to be acoustically perfect. I browsed Parts Express obsessively during Spanish class for a few months, but had a hard time making up my mind as to the direction I wanted to go. Should I try building a miniature folded horn, and use fancy Tang Band full-range drivers? How big did I want this thing to be? Should I design a fancy crossover and supplement the main drivers with a small high-excursion subwoofer? I even considered employing a linear array woofer (basically a series of ~6 2.5” woofers in a push-pull setup) before those parts disappeared from the internet (looks like they might be back?).

Fortunately my decisions were made easier by a late-night discovery in the dregs of a hi-fi forum. A Brazilian hi-fi company went bust and a bunch of nice components were liquidated by a Colorado supplier. The Peerless drivers were much, much nicer than anything else I could afford. I found the driver spec sheets, modeled the acoustics in WinISD, and discovered that they would play nicely in a modest ported enclosure. Even better, the kits came with pre-assembled crossovers! I was sold. I forked over my last $150, watched a few Sketchup tutorials, and got busy designing my dream machine.

construction

A few weeks later, my components arrived. I unpacked the box, double-checked the measurements, and lugged my materials into the back of my mom’s car. At this time, I lived outside of the school bus pickup radius and rode along with my mom on her way to work– so I’d typically show up to school at around 6:45am– nearly three hours before class started. It turned out that my cabinetmaking instructor also showed up early, which was great news for my project.

I remember the first day of construction quite clearly: a crisp spring morning, the sun barely peaking over Sunset Mountain. I luggeed boxes of components down the hill, waited for Mr. Randall to unlock the doors, and cracked my knuckles. For a few weeks, I’d spend my early morning sipping coffee and ripping MDF. This was the first time I’d felt genuinely consumed by a project: I’d go to bed thinking about the next steps and wake up knowing exactly what I’d try to get that done that day. It was here that I learned what it feels like to be deeply intrinsically motivated. That was a feeling that school had never really imbued in me, and one that I’d have to wait years to recreate with Polli.

Never will I forgot the joy in my step as I walked to Asheville Woodworking Supply after school to ask for the absolute cheapest veneer they could sell me (it turned out to be Ambrosia Maple). Another time, I begged my mom to drive me to the local Western shop and had them fashion a strap out of the thickest leather I’ve ever seen. I went fishing for scraps in the school shop’s waste pile, found some nice walnut, and built a pretty hinged door for my electronics bay. Finally, I sprayed the whole thing with a few coats of polyurethane. I must admit that I was initially stunned by how heavy the thing was– MDF is denser than the ‘medium’ suggests! Realizing that this device would be portable in the same sense that 2010s gaming laptops were portable, I ditched the idea of a shoulder strap and decided to lean in to making the absolute highest-fidelity ‘portable’ speaker that the world had ever seen.

Now it was time to give my beautiful beast a beautiful voice!

I was on a tight budget! I pilfered the polyfill (used to dampen resonance in the speaker boxes) from a pair of thrifted JBL LX44s. These rather large speakers are still sitting around somewhere on my parents’ property. I remember disliking the sibilance on the titanium tweeters.

A momentous occassion in my shop class- dropping the router in to cut the big holes for the 6.5” drivers. Scary!

Mounting the terminals in my grandparent’s living room after stuffing the boxes with polyfill.

External terminals was a bit of a strange choice, but I wanted to be able to power the device with a proper HiFi amp. Why? I just liked experimenting! I don’t think I ever really believed that amp quality/power levels mattered much, and I wanted to use my boombox as a standard platform to test different equipment.

This potentiometer (DPDT?) confused the hell out of me, and I never quite got my nice aluminum knob mounted properly. I ended up dumping this and using the pot built into my miniDSP.

IIRC, I’d planned to use a Lepai Class T amp, but these went out of production sometime around 2012. I ended up using this beefy 2x100W Class D amp, probably sourced from Parts Express. I’ve probably run 5+ different amp boards in this boombox in the years since.

At some point I accidentally burnt a hole in our living room’s wooden floors with my soldering iron. I banished myself to the front deck for subsequent soldering sessions.

I remember flush-mounting the 3.5mm jack and 4x USB ports being a real challenge. I knew they weren’t coming out once I had them mounted, so I did a try run with everything plugged up before committing. You can also see a smaller Class D amp board I was toying with.

Another dry-run before cutting holes for the ports. I mostly included this pic out of nostalgia for this old tablet. I think it was an Asus EeePad TF101, running a first-gen NVIDIA Tegra chip and Android 3.0 Honeycomb. I remember finding this device impressive, although I preferred the smoothness of my Windows Phone (a Lumia 800). I clearly should have been using Apple products, but I liked to be weird.

Like many, my audiophile journey started with headphones. I’d always wanted a nice headphone amp, but the affordable options weren’t great in 2012. I figured I’d tap the boombox’s DAC + amp to get two birds stoned at once (one of 14y/o Caleb’s favorite lines). Here I am testing my setup with my old ATH-M50s. In one of my first encounters with bullying, a guy stole these out of my backpack in 9th grade gym class and rather boldly wore them around school. I may have won the 9th grade PE award, but my meek teenage self couldn’t muster the courage to snag them back. Thankfully, my 50lb boombox was a bit harder to steal!