Building The 5L Onkens For Mark Audio Pluvia 7.2HDs ~ Elinevan NanoOnkens 31Aug24

With no new speakers needed, but my not being done with DIY,  I modeled and built a new pair of restricted port bass reflex speakers for a friend; they are 5 liter Onkens. The design is basically the mini Mark Audio Onken for Pluvia 7, mMar-Ken7p ov8, [mini/m Mark Audio/Mar Onken/Ken Pluvia/p 7/7] from D Dlugos from 28Jan16, but the drivers are the updated and still stellar and affordable, Mark Audio Pluvia Seven HD 2nd gen 100mm (4") drivers. I think they look cool in my keen cabinet.

Select... The MA Pluvia 7.2HD drivers are small, very wide full range 20Hz-30KHz, fairly efficient 86dBSPL, magnesium cone drivers which are well regarded in DIY circles ("punching far above their weight/price") in a variety of cabinets. Mark Audio are in the 2nd (maybe even 3rd) generation of the Pluvia 7, with a dimple in the cap. They supposedly do still require a longer, lower volume, break-in time than most drivers, and a decent amp. Mark Audio did a nice package for a pair of Pluvias which included the drivers and gaskets.

Design... The design required a smidge of interpolation as I didn't need the entire planset to build just this simple cabinet. I got it at least approximately right and the sound is fantastic for a very small full range with just a 4" driver. I did buy a new sheet of 15mm Baltic birch for the build (yeah - Russian imports are a 'bit' inflated these day but dang it, the US has nothing to compare), but used less than half of it. I only needed a skosh of 12mm for the port dividers and I found that in my scrap pile.

Model... I modeled the speaker in hornresp (under Wine on macOS) using Mark Audio's Small/Theil parameters for the driver and the cabinet dimensions. The model isn't perfect as Onkens' restricted ports are harder to input in a straightforward way. The bass reflex approximation is fine and showed the speaker would get down to about 77Hz as expected. I don't know why the high end rolls off as it does in the model but the empirical measurement (farther below) shows it flat way beyond my hearing (after a couple days of break in).

Build...  I picked up the 15mm Baltic birch sheet from CO Lumber and had them panel cut 20" from the 5'x5' sheet in order to get it in the car. I took the sheets to the Nest. On the table saw I first cut the 20"piece into "strips" per my cut sheet; then I did the "crosscuts" per the sheet. I next finished the brace pieces with their oddities and used a 4" hole saw to cut the driver openings in the fronts (so much better than my prior jigsaw method). I also properly sized six 12mm port separators from my scraps. At the end of cutting I had the requisite pile of parts.

Gluing began with the port subassemblies for each speaker. Fortunately my table saw cuts in mm were pretty good and stuff fit like a glove. I eased the interior of the fronts around the drivers using a 45° chamfer bit in my router.

Once the ports dried some I installed the front & back & one side to the bottom & top and clamped it all together. I left one side open to add damping material. I installed the upper and lower braces, assuring the fit of the upper with the driver in place dry. I also marked the front of the cabinet for the drivers' #4 5/8" black wood screws.

On the day after, I lined the interiors with 6mm carpet underlayment secured by spray adhesive. I even covered the internal ports at the back ~ it's an aperiodic Onken after all. Once lined, I glued on the 2nd side to each box and clamped them. Once dried, I bevel cut each front side 45° @ 15mm on the table saw. I  also pilot drilled for the driver screws.

Finish... I then sanded the boxes with 120 then 400 using my palm sander; then I wiped them off and used a tack cloth, and vacuumed inside for dust. I picked my favorite true black stain and used pre-stain before and then stained the cabinets. While staining though I set up an "open" driver break in stand. I read a number of times from DIYers and pros alike that these drivers need plenty of break in time at modest volumes before they really open up, or before I should really turn them up. I don't know for sure but I thought I'd get a head start.

After drying a day I brushed on a light coat of satin lacquer, and repeated again. Lacquer was much harder to work with than poly ~ which Lowe's didn't have in satin or even clear semi-gloss. I signed the rear of the speakers with their "spec," their born on date, and my custom rod building brand name, The Rodfather ~ but the lacquer melted it off when I covered over it. I let them dry about five hours. Then I installed the binding posts with pre-attached #20 solid core copper wiring, placed the gaskets on the drivers, soldered the drivers, and then screwed them in place. Nice!

Listen... I took the new speakers inside and set them up in free space in the Nest Office. Using the NAD D3045 and the new Black Ice FX10H, with my Mac as the source,  I listened to some stuff. Very nice. Not much full loud stuff yet so it's really pretty hard to say. I then left the setup running for a some more of days of burn in. On day 3 I listened again through the NAD and my Black Ice ~ smoother. The Black Ice EL84s get some grunt out of the low end ~ amazing. The high end was very present but mellower, a good thing, and the bottom was bigger and better. I kind of understand the recommendation to use a good amp ~ these might fail attached to an entry level Class D but with the NAD and the Black Ice they were excellent and seemed flat beyond my hearing. These drivers have bristling highs for full rangers but of course lack some punch at the low end; the mids are smooth. A full kit using these as mains should include a subwoofer in a 2.1 setup. Still, really nice.

Measure... With ~72hrs of mostly continuous burn in I was more confident of measuring these keen new NanoOnkens. I kept the speakers elevated and in free space in the Nest Office ~ there wasn't appreciable BDS loss; that's great. They sound fantastic and measured very well. They are indeed full range and the mid-highs are awesome but a system could be improved with the addition of a subwoofer as mentioned prior. The Black Ice drives them to achieve some low end, but it's a bit distorted... overall though these guys are super clean. Really pleased ~ highly recommended.

Gifting... Eline came to the Nest for LD weekend; she's a discerning music fan and likes the new speakers I built. I think she was truly thrilled to hear they were indeed hers for her coming birthday. Matt complimented the custom speakers with a gift of the cool NAD D3045 amp. The setup will adorn her living room TV & streaming gear and Eline's phono and vinyl collection. She loves playing classic songs rendered by killer vocalists... then mimics a few notes all night long. Well offered IMO.