Building The BFM Center Channel ~ The Onken-Like NanoCC Rockin' With The NanoOnkens 09Feb25

Blodgett Family Room Center Channel (BFM CC)... Yeah, I haven't built a speaker in a couple weeks so I literally dreamt of a shift to bolster the BFM's new sound ~ try the NanoOnkens in there! It'd be a solid upgrade but I need two things then: 1) a center channel speaker to match and 2) replacement speakers for the Elekit living room tube amp system. This post deals with #1; you'll need to wait for the replacement speakers alluded to by #2. I will say however that in each case, I am a fan of the ~$50 Mark Audio Pluvia 7.2HD full range drivers and bought 3 more of them. Most center channel designs are smallish, especially in height, as they are best placed directly above or below the TV/monitor in a theater build-out. I really like a tight Onken full range sound and the DIY FrugalHorn team (DLugos diagram) drew up a decent, and small, center channel for a variety of MA drivers to mate with those horn designs. Slick, Fb tuned, restricted bass ports, abreast of the Mark Audio drivers. I used that core design to create an Onken-Like NanoCC with a 4" MA Pluvia driver and using leftover 15mm Baltic birch. The new speaker dovetails well in sound and look with the NanoOnkens. I prefer a soundfield built from all the same drivers; it keeps the timbre consistent. I'm replacing some low-end Paradigm bass reflex speakers for the front 3 channels of the BFM system (I've repaired them a couple times already, and replaced the sub). The new NanoCC, and the sub, are behind the acoustically transparent fabric panel below the TV.

NanoCC Design & Cut Sheet... I first took inventory of all the 12mm, 15mm, and 18mm Baltic birch plywood I have. This so I could map out the parts needed against the cabinet raw materials. It's not a classic cut sheet but the process worked so I could use all 15mm for the NanoCC.

I got the parts cut on my table saw and drill press from the leftover 15mm scraps. That includes a front baffle with a 102mm hole for the driver cut with a hole saw and the rear side eased 45° via a router, as well as a brace with holes. Stack of stuff looks "nano" as hoped and took just an hour.

Assembly was pretty quick with just clamps and Titebond 3. From dry fit to final box was 90min. I laid down and aligned the vents as a 2nd step. Acoustical physics analysis on these 9mm ports is not for the faint of heart ~ Onken conviction.

You see the case is heavy and the driver will be braced ~ inert cabinetry is your dearest friend. Never go flimsy on anything... I even glue flute all the seams on the inside to assure security and air seals. I actually learned this best as a kid building custom rockets and needing to assure fins didn't rip off at torque/lift-off. I also dipped into the scrap piles of damping materials when completing the NanoCC. I used 1" wool for key surfaces but stepped to 3/4" for corners and even 1/2"poly between the chambers. All DRC full range builds are heavily damped and super rigid. The cabinet is done but for binding terminals and a driver ~ and perhaps some finish... that "active" stuff is back in COS, where the NanoCC home will be.

Equalizing & Measuring... My first task after installing the new NanoCC and L/R NanoOnken Mains, all based on the MA Pluvia 7.2HDs, was to use the new Onkyo's AccuEQ system to dial in the 3.1.2 array (we have in-ceiling pressence/height speakers in the rear). With an included measurement mic I invoked the automatic measuring system in the Onkyo and let it do its thing for 5min. Always just white noise... no sweeps. Sounds fine ~ far more defined and dynamic than the old speakers, so the upgrade is working well so far. I next measured the NanoCC and the entire NanoOnken-NanoCC-SVS Sub system in place in the Blodgett Fam Rm. The orange below though is just the NanoCC in free space, where it does exhibit baffle diffraction step "loss." However, with the AccuEQ running and the sub engaged, the sweep is down-bending as desired, and sounds quite good. I don't fully understand the wiggles 5KHz-10KHz or the 5-10dB loss 10KHz-20KHz but the room is pretty padded and the measurement are taken kind of off axis (below the mains and above for the center channel) from the speakers' drivers... the speakers are not in ideal locations for listening, but they are out of the way.

The Nano upgrade to the BFM system and driven by the new Onkyo AVR is sharply improved for music and movies.

Update 12Mar25 ~ Finishing the NanoCC... I got after finishing the NanoCC despite it being buried behind a curtain. I chose a Sedona Red for the upper and lower part of the cabinet and my normal real black for the middle near the driver. It's all in an attempt to match the copper cone, and test how future FrugalHorns might look using the same scheme. Hmmm; it looks OK but the lines for transitioning from red to black are hard to keep clean. I kick that decision down the road.