So after all that talk of efficiency v extension, I figured I’d actually build something. It worked out that I ended up building on both sides of the coin, as the “Extension” build ended up being pretty gigantic. But the review of both approaches is in and it turns out that in some regards efficiency is more pleasant; I used the Faital Pro 5FE100 in a ~8L enclosure tuned to about 45-50 hz with a 3 inch x 15 inch port which I 3D-printed.  It WOMPS. Sounds great, crisp, powerful. Really pushes the “effortless” bass feeling, until you get below resonance and the woofer starts whacking around. It becomes excursion limited quite fast on songs with a lot of low frequency content, and it sounds pretty alarming. This forces my hand in ASP to put in a high pass around 32Hz-20Hz, adding complexity and heartache. But all in all, not a bad design.

As for the extension, which also sounds good, a different set of issues comes into play. I went with the Tang Band W5-1138SMF ~14L tuned to around 40 hz with a PR, and for starters, the thing is fucking gigantic. Despite the apparent size, 40 hz in 14L is pretty damn good, and it definitely has a presence visually and sonically. It sounds large, powerful, and it’s exceedingly hard to push the woofer itself into distortion. However  pushing the low efficiency of that driver is it’s ridiculous excursion capability, which brings an unexpected issue into play: high excursion means a lot of acceleration. A lot of acceleration mechanically means all kinds of shit is moving around, including things coupled to the boombox through the surface it’s on; put the boombox on the counter and all of a sudden the beer bottles on the counter start wiggling around too. Additionally, in the electrical domain, a lot of acceleration means a lot of voltage, which means more batteries.

These factors push the design to seem a lot less effortless than the 5FE100, potentially because the 1138 design seems to promote higher THD. It’s not necessarily a fair comparison, because the ASP, amp, and battery management on the 5FE100 design happens to be a lot better (I built it second, learned from previous mistakes). Normalizing for those factors, though, the smaller size is pretty great as it turns out that there is usually very little content from 40 Hz and below, and because larger boxes tend to be less efficient in terms of materials.


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So for  the KrumpKanon I’m going with the W5-1138SMF, and for Keith’s, the W6 version of the same driver. Why? Because it has the excursion, Fs, and general specs to have solid bandwidth and linearity at loud volumes. Unfortunately, if you look at the models:



The yellow line represents the optimal ported design, while the blue is the optimal 8″ Dayton Audio PR design. The vented design is more efficient, has higher bandwidth, and requires less box volume. However, for a 4″x2.5″ port, opening I’d need 36 inches of port to get the 12L box resonating at 36 Hz. That’s absurd, and what’s more absurd is that at 50W, the airspeed would be ~40 m/s. That’s 90 mph, and the air has to move 90 mph through a folded port 3ft long. I have low expectations for the laminarity of the air flow in that scenario, but an educated guess tells me it would sound like an elephant farting through a muffler.

PR’s it is. With dual 8 inch passive radiators, I could be pretty near the vented design, but a) that’s a ridiculous amount of radiator area for a 5 inch  area, b) that’s 2x the cost, machining, surface area dedicated to the radiator, and c) trying to fit two 8-inch radiators, a 5-inch woofer, and 2 full ranges onto the front of the boom box would be ridiculous. Why not throw them on the back? Well, then the front will look stupid, barren. I want the raw visual and auditory power of a fat fucking 8″ blasting you in the face. But fitting 2 8’s on to the front of a reasonably sized boom box (using the esteemed [boombox name to go here once I find my notes] as a template) would be geometrically dubious.

So at the sacrifice of about 1/3 of an octave of bass, I’m going with a single 8. I hate leaving bass on the table, especially when it’s easy, efficient bass, but given the constraints and my desire for a simplistic design…it’ll have to do. Additionally, and this is the most important part, but, if you look at an analysis of the most popular music being played these days, there’s  little content beneath 40 Hz, and therefore, little need for sound below 40. So I guess 40 Hz it is, and we’ll hope it sounds good. There’s only way to find out.








Probably a lot. Keith says something that’d be good for a house party, as far as portability I was thinking something around the size/weight of the one you made for connor like 10″x20″x10″-ish and somewhere around 15 pounds (I’ve been lifting so weight isn’t too big of a concern)

i guess no more than 25 pounds? i really have no idea.”