I liked the 5L Elinevan NanoOnkens so much that I decided to get another pair of the Mark Audio Pluvia 7.2HD full range 4" drivers and build another pair, for me this time. The alternative copper colored metallic cones were in stock, so I bought those to distinguish from the originals. I will not repeat the build process here as it is identical to the originals. I had sufficient 15mm Baltic birch leftover from the last build to cover a new pair AND add a subwoofer. The NanoOnkens are just 11"x6.5"x7" and the NanoSub is just 13.5"x9"x12", but they all are pretty heavy. This compact, straightforward, and affordable 2.1 system is completely awesome, with the right amp for the NOs (more on that later).
Suffice it to say that the NanoOnkens are heavily braced, fully lined, restricted port, reasonably efficient (87dB), extended range Onkens that sound great. Pluvia 7 second gen high def drivers are sweet from about 80Hz to 24KHz! They are great "full range" drivers, especially in this cabinet, but also want for low end grunt... hence addition of the NanoSub.
I finished the NanoOnkens in COS so did the measuring and full kit listening there (after 72hrs of break in), driven by the Blodgett Theater Integra Research gear. Here's the 2.1 integrated measurement of the new DRC NanoKit in free space (and the NOs themselves). With sub support the NanoKit is solid from 35Hz to 22KHz! Far below are the discrete measurements of the NanoSub and NanoOnkens that initially gave me excitement for the sub described below crushing its NanoOnken support role and great integration dovetail. There is distortion in the sub but it does not rattle me.
Subwoofer Driver & Design... A key to this 2nd Nano kit is the addition of a custom subwoofer. While I've often preferred sealed subs for their tight musical bass, I didn't want the large driver required to get one down to 40Hz (the low note from a standup acoustic bass). So, I chose the 6.5" Tang Band W6-1139SIF and built a tuned port sub; the sealed box for this driver only went to 62Hz. The TB1139 throws a lot of air with 11.5mm Xmax and wide roll rubber surround. And, with a vented fb of 35Hz, it should cover a standup bass fine.
The challenge of venting to get the 35Hz is the length of the bass port needed. A 5cm (2") port would need to be ~15" long in an cabinet with just a Vbox = 11.45L (derived from Small Thiel parameters), and that is a challenge in a small box. I did the math for a full 3" port but this made the port length ~ 100cm (38.7") ~ I will stick with the 2" port version! I also attempted to design a subwoofer around Onken-like rectangular ports but the cabinet needed to be too big for my use... and I've been there once before and abandoned the build. Finally, an alternative to venting is to employ passive radiators instead. Mating the Tang Band to a like Cms/Vas passive radiator was challenging and ultimately didn't even yield a satisfactory model response curve; I eliminated it too. Here are the modeling compares... I'll lose a little low end using my smallish box, but not much.
When designing a cabinet for bass response, size counts, but I still wanted to keep it "Nano." One also needs to account for volume consumed by any amp, ports, and drivers inside the box. With Vamp = 3.795L, Vdriver = 1.108L, Vport = 3.17² * 𝝿 * 31.4 = .994L ∴ Vspk must be at least .994 + 1.108 + 3.795 + 11.54 internally. But I also needed to assure the height accepts the driver and the port flange; and the depth accepts the driver, the amp, and the port I'll run up between them; and the width accepts the driver or amp. So, ultimately I drew a box which internally is 8.25"x11.25"x13" (WxDxH) that yields and internal volume of 19.8 liters (before subtracting the innards' volumes). I then remodeled "my box" with the final cabinet and 35Hz tuned port (shown above).
Subwoofer Parts... I cut the cabinet material from spare 15mm Baltic birch, and had lots leftover for bracing. I used simple black ABS drain pipe parts for the port but I did get a nicer flanged end for the port to the exterior, and the even interior end, to avoid chuffing. I did have to modify the elbow a bit and ABS glue is messy. Port design was tight inside the smallish cabinet I desired, but I got it done; Lp = 31.4cm. I chose a Dayton Audio 100W class AB plate amp and Precision flanged port pieces.
Once I assured the internal fit I disassembled the hardware and glued on the final side. Once dry I'll sand and stain and poly coat before final re-assembly.
I did my usual finishing of sanding, staining in True Black, and coating with 3 layers of polyurethane. Since it's "winter" I did all the finishing inside the warm radiant & water heating closet to assure good curing. I then installed the sub driver, the port, and the amp. The DRC NanoSub came out nice IMO. I might yet "paint" the driver "cone" with some metallic copper design to better mate it to the DRC NanoOnkens.
That's all nice but did it achieve the design objective of righteously covering a standup acoustic bass and integrating with the NanoOnkens well? Yes indeed. After getting a good ~90dB signal from REW to the measurement mic, I set the low pass at several different settings and took measurements. The sub is reasonably flat from 25Hz - 90Hz on its own... very cool. I favored the "orange" low pass cutoff at about 80Hz (clearly the amp continues to pass a signal above that but ok, I understand rolloff). I then checked the integration with NanoOnken measurements in free space just as Eline has them running. GR8 integration. I do hear some chuffing at super-low frequencies below 25Hz, but my material rarely reaches down there. Playing material is different than measuring and the NanoSub is awesome and a perfect compliment to the NanoOnkens.
Now I need to mate the NanoKit with a perfect dac/amp, and find the whole thing a true home. The current temporary home is on the StudyDesk driven by the Topping MX
3S.
