IT HAS BEEN DECIDED

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:

eliseBoxGrabTB1138VentSpecs_PRChoice2.PNG

 

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.

 

 

 

 

 

 

IT WILL BE DECIDED

After modeling 20+ woofers, including the attractive ScanSpeak classic series, the illustrious semi-pro Morel and FaitalPRO designs, and the uncategorizable SB Acoustic woofers, I’ve decided that there are only two viable designs. For the purpose of listening to  party music in party situations (Keith’s BuffBox), I want something like 104 dB at 48-42Hz at max, solid directivity, and about 3dB head room to handle over-compressed music and power compression that comes with party scenarios. For Elise’s use (KuadKrumpKannon), I’m probably going to want something slightly smaller and with slightly less performance. We can go with 100dB 50-40Hz with 3 dB of head room.

That leaves me with two options, the classic crux, the bane of boomboxes, the designer’s dilemma,  the iron law. For a given size, you can either have more bass but lose sensitivity, or have less bass bandwidth but more loudness. The third unspoken option is get both and pay $$$.

One the one hand, I could go for a 2.1 type set up with the boombox-friendly micro-subwoofer designs like the Tang Band 1138-SMF with it’s extreme 45 Hz free-air resonance, it’s lovely 9.25mm linear x-max, 5-something liter Vas and 82 dB sensitivity. Yeah, it sacrifices sensitivity for low Fs+high xMax at a decent cost point, but with 2^6.3 watts power handling we can potentially get to 99 dB at 1m down to 32 Hz in a 15L cabinet. In my experience, having deep reach with slightly less output can be more enjoyable despite not being as overwhelmingly loud. Essentially, I’d give up loudness for an extra  bass half-octave.

Alternatively, I can go for sensitivity over bandwidth. The FaitalPRO 5FE100 is a great example of this, as it maintains decent excursion and could potentially hit low 50’s in a small box while still being 6 dB more sensitive than the 1138-SMF. In fact, it could  hit 103 dB  in a 8L box, for a 51 Hz-3dB points, or and 40 Hz -3dB in a 15L box. It actually could handle producing about 108 dB (that’s at 100W, it can handle 160W) but above and below the port resonance we’d be we’ll out of the linear excursion range of the woofer. It starts to get directive at 1.5 kHz (beam forming begins at f=c/λ which is 2.7 kHz for a 5 inch woofer), so I could easily cross it over with some equally sensitive 1-2.5 inch speakers around 300 hz and call it a day.  Lots of out put, lots of head room, good package. Only two factors to consider: 1) whether it will work with available  passive radiators and 2) What Would Heathor Trainor Think? About the missing half octave?

On the other hand, I could go for a more sensitive design dual-fullrange or dual woofer tweeter with slightly less reach, but I get 3dB off the bat because I’ll have two woofers. The NS4 would be perfect for this but alas, they are gone from the world. The second best thing is the AuraSound NS3-193-8A , and it’s copy cat brothers: Dayton ND90, ND91, ND105, and DS115 are all great candidates for this. But after modeling I found:

  • AuraSound NS3: Great response, pretty design, 50hz in a 4L box. Play nice with passive radiators. All around solid drivers at a good price. Definitely on the table. The only issue is they’re not that sensitive and they don’t hit super duper hard.
  • ND90: good for this application, but still, lots of ripple. -3dB at 40-38 in 9-7.7 liters. Good news is xMech for days, so bottoming out shouldn’t be an issue for these ND series. Doesn’t work
  • Dayton ND91: great for 1-4 liter enclosures. Looots of ripple otherwise, still a lot of ripple.
  • ND105: lots of ripple, needs at least 14L but can get down to 33 hZ  at -3dB, or in 9L, 38 Hz with a bit of extra efficiency in the pass band.
  • DS115: Kind of a middle ground. In 6 liters, could go to 50 hZ -3dB. They look pretty, and with two of them, I could get 104 dB while staying in the linear region.

The downsides to this approach are: raised complexity (I’ll have to fit 2 4th order systems in the same form factor), limited design flexibility (long ports are almost out of the question and passive radiators are harder to fit), potentially greater cost, and of course, half the space which usually ends up meaning less bass.

Here is a graphical explanation of all that jazz ^.

TF ELise session

Transfer Function of Speaker. -3dB point marked in red.

But what do the colors mean? See next photo.

20w legend

Legend of which colors match up with with speaker/box designs.

Transfer functions are great but we want to know the absolute level.

20W comparison

Absolute level. Compare the sensitivity vs the bandwidth of the various drivers. The ND105 manages to be a good combination of both.

But how loud do they really get with linear excursion constraints?

maxSPL Elise session

Maximum (linear excursion) loudness. Note the FaitalPROs (magenta, green, teal) manages massive power handling until the excursion limit kicks in. The previously impressive ND105 (orange) has little-to-no advantage over the 1138SMF (yellow) due to its lower power handling and limited excursion.

So…what to do?

WHAT’S IT GOING TO WEIGH

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.”